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80 Frequently Asked Questions About Earthquakes and Their Answers

It takes a very specific geological event to create an earthquake. Here's how it happens: The ever-present movement of the tectonic plates beneath the Earth's crust causes occasional collisions that release energy, essentially a grinding between two plates. This results in an earthquake. Most quakes tend to occur along fault lines (boundaries between plates) because this is where most movement occurs, plate-to-plate.

The United States Geological Survey defines an earthquake as such: "Earthquake is a term used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip, or by volcanic or magmatic activity, or other sudden stress changes in the earth." Simply stated, this type of disaster involves the events underneath the surface of the Earth that lead up to the quake and the actual quake itself.

Like most natural disasters, quakes require certain environmental circumstances to be in place for them to occur. Again quoting the United States Geological Survey, "An earthquake is caused by a sudden slip on a fault. The tectonic plates are always slowly moving, but they get stuck at their edges due to friction. When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the Earth's crust and cause the shaking that we feel."

There is a very simple bit of advice to remember if you find yourself caught in a quake. This is from the Centers for Disease Control and Prevention, which published findings on the safest way to survive a quake. "DROP down onto your hands and knees before the earthquake knocks you down. This position protects you from falling but allows you to still move if necessary. COVER your head and neck (and your entire body if possible) underneath a sturdy table or desk. If there is no shelter nearby, get down near an interior wall or next to low-lying furniture that won't fall on you, and cover your head and neck with your arms and hands. HOLD ON to your shelter (or to your head and neck) until the shaking stops. Be prepared to move with your shelter if the shaking shifts it around."


Quakes can occur just about anywhere. In fact, almost every state in the United States has recorded incidences of earthquakes occurring. However, some states and regions are more prone to such disasters than others. The ten states in the U.S. that receive the most earthquakes are:

  • Alaska
  • California
  • Hawaii
  • Nevada
  • Washington State
  • Idaho
  • Wyoming
  • Montana
  • Utah
  • Oregon

Earthquakes occur as a natural, though disastrous phenomenon. They are caused by a sudden slip, below the Earth's surface, along a fault line. A fault line is a place where two tectonic plates meet. These plates are slowly moving, and sometimes they grind along each other, causing a shift of rock and a resulting quake to occur.

The Richter Scale is a special measurement designation used to determine the intensity and severity of an earthquake. According to the USGS, "Earthquakes are recorded by a seismographic network. Each seismic station in the network measures the movement of the ground at that site. The slip of one block of rock over another in an earthquake releases energy that makes the ground vibrate. That vibration pushes the adjoining piece of ground and causes it to vibrate, and thus the energy travels out from the earthquake hypocenter in a wave." Earthquakes are measured by their magnitude on a scale of 0 to, essentially, infinity. The highest magnitude earthquake ever recorded ranked at 9.5 on the Richter Scale.

Most small earthquakes only last for a few seconds, but more intense earthquakes can last for several minutes. A quake rarely lasts longer than a few minutes. However, such events can cause massive, even catastrophic devastation in those minutes.

It's not easy to prepare for a quake because such events are not easy to predict. Ready.gov, a government-funded and run disaster preparedness website, says this about preparing for such an event: "Practice drop, cover, and hold on with family and coworkers. Create a family emergency communications plan that has an out-of-state contact. Put together a stash of non-perishable foods, cleaning supplies, and water for several days, in case services are cut off in your area. Secure heavy items in your home like bookcases, refrigerators, televisions and objects that hang on walls. Store heavy and breakable objects on low shelves."

In the United States, the most commonplace for quakes to occur is in California. This is because two tectonic plates meet in California, the Pacific Plate, and the North American Plate. The major fault line that is formed by the plates is called the San Andreas Fault. It's important to keep in mind that, though earthquakes tend to occur in specific regions where tectonic plates meet, quakes can occur at any location and at any time. For example, only eight states in the U.S. have not recorded a quake event (at least not between 1973 and 2003). These are Wisconsin, Vermont, North Dakota, Maryland, Iowa, Florida, Delaware, and Connecticut. As for the remaining 42 states, frequency of quake events ranges anywhere from West Virginia, which has just one quake on record, to Alaska, which has 12,053 earthquakes on record for the 1973 to 2003 recording period.

The "epicenter" (as one would normally think of it) in an earthquake is not called that, though such a term does have its place in quake nomenclature. According to the United States Geological Survey, "An earthquake is what happens when two blocks of the Earth suddenly slip past one another. The surface where they slip is called the fault or fault plane. The location below the Earth's surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the Earth is called the epicenter."

One of the most common natural disasters to occur on Earth, earthquakes can happen almost anywhere, at any time. They are highly unpredictable, as there is no "season" for quakes like there is for many other natural disasters. Quake tremors can occur at any time of the year and at any time of the day or night. They can occur under any weather conditions. They cannot be predicted, at least not more so than a few minutes out from the first tremor. Given how common earthquakes are and their potential for being particularly devastating to established urban areas, it's important to prepare for them and to know how to respond when one occurs.

Possibly, yes. Fracking intentionally causes small quakes, and this process has been linked to larger quakes. A magnitude four quake in Texas some years ago was linked to nearby fracking. Also, detonating a nuclear warhead is another human-created cause of quakes. Detonating such an immense payload causes a seismic shift that is so immense it is comparable to an earthquake. Quoting Michigan Technological University, "The largest underground explosions, from tests of nuclear warheads (bombs), can create seismic waves very much like large earthquakes. This fact has been exploited as a means to enforce the global nuclear test ban, because no nuclear warhead can be detonated on Earth without producing such seismic waves."

While large earthquakes are relatively common in the United States, early warning systems implemented by the United States Geological Survey provide alerts to help Americans take shelter. Furthermore, more durable building methods and well-established emergency response systems help save lives and reduce fatalities during U.S.-based quakes. This is why relatively few Americans die in quakes, compared to other countries that experience similar-magnitude quakes. The most powerful earthquake to strike the United States occurred in Alaska in 1964. This quake was a magnitude 9.2 that struck Prince William Sound and killed 139 people.

The million-dollar question, are quakes increasing in intensity and frequency? In the paper, geophysicist Paul Lundgren of NASA's Jet Propulsion Laboratory in Pasadena, California, said, "We've seen that relatively small stress changes due to climate-like forcings can effect microseismicity. A lot of small fractures in Earth's crust are unstable. We see also that tides can cause faint Earth tremors, known as microseisms. But the real problem is taking our knowledge of microseismicity and scaling it up to apply it to a big quake, or a quake of any size that people could feel, really. Climate-related stress changes might or might not promote an earthquake to occur, but we have no way of knowing by how much." The short answer is that scientists simply do not know if earthquakes will get worse or not. Regardless, individuals and families need to understand how to prepare for an earthquake and what to do should one occur.

The main cause is a shifting of tectonic plates that create a sudden movement of stone beneath the Earth's surface.

What you do after a quake depends on where you are and the type of environment/risks you have around you. According to the City of Portland's official warning system on quakes, "Evacuate if you are in a tsunami hazard zone. Walk inland or to higher ground as soon as it is safe to do so. Do not wait for official notification. Stay away from the coast until officials permit you to return. Check for injuries. Do not move seriously-injured persons unless they are in immediate danger. Check for hazards such as fires, gas leaks, downed utility lines and fallen objects. Clean up any potentially harmful materials spills. Expect aftershocks. Aftershocks following large earthquakes can be large and damaging."

Most scientists maintain that quake prediction is inherently impossible, though some argue that advances in technology could lead to the effective and reliable prediction of earthquakes.

The National Earthquake Information Center locates about 20,000 quakes across the plant each year, or 55 quakes per day.

Approximately 55 significant, notable earthquakes occur on planet Earth each day, but the location of those quakes vary, region to region. For example, California, a quake-prone state in the U.S., experiences about 100 micro-quakes every day. Compare that to other states in the U.S. that may only experience a quake once every several years.

Many organizations provide advice on quakes. The agreed-upon rule of thumb is best put by the CDC: "DROP down onto your hands and knees before the earthquake knocks you down. This position protects you from falling but allows you to still move if necessary. COVER your head and neck (and your entire body if possible) underneath a sturdy table or desk. If there is no shelter nearby, get down near an interior wall or next to low-lying furniture that won't fall on you, and cover your head and neck with your arms and hands. HOLD ON to your shelter (or to your head and neck) until the shaking stops. Be prepared to move with your shelter if the shaking shifts it around."

Earthquakes are unique in that they are a literal shaking of the Earth beneath our feet. Earthquakes are vibrations coming up through the Earth's crust that cause shaking on the surface. Sometimes the shaking feels like it is going back and forth. Sometimes it is entirely erratic and without a pattern.

While the 1964 Great Alaska Earthquake was the worst U.S.-based quake, it was only the second-worst earthquake ever recorded internationally. The worst quake ever recorded was in Bi-Bio Chile. It was a 9.5 magnitude quake, whereas the Alaska quake was a 9.2. The Chile quake occurred in 1960.

According to Brooklyn College, the key is in the convergent plate boundaries. According to the college's report: "At convergent plate boundaries, where two continental plates collide earthquakes are deep and also very powerful. In general, the deepest and the most powerful earthquakes occur at plate collision (or subduction) zones at convergent plate boundaries."

Quakes are most likely to occur where two plate boundaries meet. On Planet Earth, that includes places primarily along the rim of the Pacific Ocean, including states and countries along the western Americas, plus China, Japan, Russia, North and South Korea, and various islands along the fringes of the Pacific Ocean.

While there is no scientific consensus that either confirms or denies it, some believe that dogs possess such sensitive hearing that they can pick up the faint scraping and grinding of rocks beneath the surface of the Earth that precede an earthquake.

Seismographs begin alarming us of an earthquake just a few seconds before the actual tremors set in, which is all the warning we usually have before a quake occurs.

Earthquakes are unique in that they are a literal shaking of the Earth beneath our feet. Earthquakes are vibrations coming up through the Earth's crust that cause shaking on the surface. Sometimes the shaking feels like it is going back and forth. Sometimes it is entirely erratic and without a pattern.

Absolutely. In 1960, the largest earthquake ever recorded hit Chile. This magnitude 9.5 quakes caused 1,600 deaths in Chile. Though the earthquake did not occur anywhere near the United States, the earthquake caused a tsunami that traveled across the Pacific Ocean and hit Hawai'i. Thirty-five-foot waves crashed on the island of Hilo and killed 61 people.

Like many other types of waves, quake waves bend when they pass through different materials, which is part of why quake tremors and the direction they travel are so unpredictable.

A fault refers to the fracture along the blocks of crust on either side of two tectonic plate boundaries. A fault line is where most quakes occur.

The Richter Scale is a special measurement designation used to determine the intensity and severity of an earthquake. According to the USGS, "Earthquakes are recorded by a seismographic network. Each seismic station in the network measures the movement of the ground at that site. The slip of one block of rock over another in an earthquake releases energy that makes the ground vibrate. That vibration pushes the adjoining piece of ground and causes it to vibrate, and thus the energy travels out from the earthquake hypocenter in a wave." Earthquakes are measured by their magnitude on a scale of 0 to, essentially, infinity. The highest magnitude earthquake ever recorded ranked at 9.5 on the Richter Scale.

Earthquakes can happen at any time and with very little warning. Experts recommend that if you're already inside when an earthquake strikes, stay inside. Do not run outside or to other rooms during an earthquake. Staying put and seeking cover offers the best chance at avoiding injury. Don't stand in a doorway or near a window. Seek shelter underneath something sturdy, such as a table. If you have children or elderly relatives living with you, help them seek refuge first. Earthquake tremors are usually short-lived. Seek shelter and cover and wait it out.

Aftershocks are complicated. Small, unnoticeable aftershocks can occur for days, months, even years after a major earthquake. But most serious earthquakes produce just a handful of aftershocks that come about shortly after the main tremors recede.

There is no such thing as earthquake weather. It is a myth.

Earthquakes are measured on the Richter scale, a numerical scale used to express the magnitude of a quake. A destructive quake typically has a magnitude of 5.5 to 8.9, with quakes above 8.9 being quite rare and particularly destructive.

Earthquakes and volcanos are both caused by the movement of tectonic plates.

California by far, with Alaska in second place.

According to the United States Geological Survey, "The deepest earthquakes occur within the core of subducting slabs – oceanic plates that descend into the Earth's mantle from convergent plate boundaries, where a dense oceanic plate collides with a less dense continental plate and the former sinks beneath the latter."

Seismologists are Earth scientists who specialize in geophysics. They study the genus and propagation of the seismic waves that create earthquakes.

Yes. A transform plate boundary is simply a type of plate boundary where plates slide horizontally past each other. As the plates rub against each other, huge stresses on the rocks can cause portions of the rock to break, resulting in quakes.

Yes, a volcanic eruption can indeed cause an earthquake, though volcano-caused quakes are usually not as intense as quakes caused by movement along tectonic plate boundaries.

From the USGS, "An earthquake is caused by a sudden slip on a fault. The tectonic plates are always slowly moving, but they get stuck at their edges due to friction. When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the Earth's crust and cause the shaking that we feel."

Three seismographs are needed to locate a quake.

Earthquakes are arguably one of the most destructive natural disasters, often because of the other disasters that they can cause. Earthquakes can trigger landslides and mudslides along hilly terrain, especially in areas with water-soaked soils. Earthquakes can also cause buildings to collapse, disrupting gas, electricity, and telephone service. Earthquakes can also cause fires and even tsunami waves.

Low-pitched rumbles, rattling windows, car alarms, small trembles, crumbling concrete, and a shaking, shifting sound are the noises generally associated with earthquakes.

A quake or tremor that results in a sudden and violent shaking of the ground is the key defining factor of an earthquake.

The highest magnitude is essentially infinite in terms of potential quakes. However, since recording began, the highest magnitude that has occurred was a 9.5 magnitude quake in Chile that occurred in 1960.

When an earthquake occurs, stop, drop, cover, and hold on. This is the immediate response one should take to a quake because one usually does not have much time to prepare for such a disaster.

In this question, "worst" refers to the quake with the highest death toll, even if it was not the highest magnitude quake. According to Our World in Data, the deadliest earthquake ever recorded took place in Shaanxi, China, in 1556. It's estimated to have killed about 830,000 people.

Technically, Yes. However, earthquakes are far more common and likely in some regions than others.

Not one that seismographs have recorded, but it is almost certain that one has occurred in world history.

Geologists use the seismic waves created by an earthquake to measure the quake's epicenter. The epicenter is located by measuring the difference between the arrival time of different types of waves.

Most disasters of this nature last just a few seconds. However, that does not mean one can come out of cover after the initial tremors recede, as aftershocks are quite common in earthquakes. Should a quake strike, one should not come out of the shelter until local responders and authorities say it is safe to do so, unless they live in a tsunamis-risk zone.

Michigan Technological University published an excellent classification system of different magnitude earthquakes. According to their data, a quake event that measures a 5.5 magnitude or higher can cause significant damage.

You can feel anything above a 2.5 magnitude quake, but such quake events usually only cause minor damage.

Seek cover! Drop down low to the ground and try to take cover underneath a stable surface.

A magnitude 4.0 quake can be felt as far as 60 miles away from the epicenter. A magnitude 5.5 quake can be felt 300 miles away from the epicenter. The higher the magnitude of the quake, the further away its tremors can be felt.

Quake tremors travel very fast. The rupture speed of the average tremor is 5,600 to 6,700 miles per hour. For context, most bullets only travel at about 1,700 miles per hour.

The United States Geological Survey defines aftershocks as such: "Aftershocks are smaller earthquakes that occur in the same general area during the days to years following a larger event or "mainshock." They occur within 1-2 fault lengths away and during the period of time before the background seismicity level has resumed. As a general rule, aftershocks represent minor readjustments along the portion of a fault that slipped at the time of the mainshock. The frequency of these aftershocks decreases with time. Historically, deep earthquakes (>30 km) are much less likely to be followed by aftershocks than shallow earthquakes."

There are some simple rules to follow during a quake regarding what not to do. For example, do not run outside or to other rooms during quake tremors. Avoid areas of a building that are right next to exterior walls. Windows, facades, and architectural details are often the first parts of the building to collapse.

There is no such thing as quake season. Statistically speaking, there is an equal distribution of quakes throughout the year and in all types of weather.

If a building collapses during a quake, no floor is a safe floor. However, being on a higher floor increases the chances of survival during such an event. Conversely, being lower to the ground makes evacuation easier after the quake. Simply stated, it's more important to seek cover and protect oneself on whatever floor they are on during a quake than to go looking for a safer floor.

Some animals might be able to sense the initial tremors that come right before a quake occurs. While some scientific papers have been published, the research is still inconclusive and is awaiting peer review.

No. If you are inside during a quake, stay inside. Don't run outside during a quake. Don't run at all during a quake. You are much safer by staying inside and seeking shelter underneath a table.

Such waves are usually called "Seismic Waves."

The best place to seek shelter during a quake is in the center of a room under a sturdy desk or table, not near windows or exterior walls.

According to National Geographic, "A powerful earthquake can cause landslides, tsunamis, flooding, and other catastrophic events. Most damage and deaths happen in populated areas. That's because the shaking can cause windows to break, structures to collapse, fire, and other dangers. Geologists cannot predict earthquakes.”

Earthquakes are unique in that they are a literal shaking of the Earth beneath our feet. Earthquakes are vibrations coming up through the Earth's crust that cause shaking on the surface. Sometimes the shaking feels like it is going back and forth. Sometimes it is entirely erratic and without a pattern. The vibrations of the shifting tectonic plate boundaries are what causes the shaking sensation of earthquakes.

Sometimes, yes. This is not a common or frequent natural event, but it has occurred. Regional earthquakes greater than magnitude six have been identified as a cause point for nearby volcanic events.

Yes. Thousands of earthquakes are recorded on planet Earth each year.

This is a tricky question to answer because the answer is both yes and no. Quoting the United States Geological Survey experts, "A temporary increase or decrease in seismicity is part of the normal fluctuation of earthquake rates. Neither an increase nor decrease worldwide is a positive indication that a large earthquake is imminent. According to long-term records (since about 1900), we expect about 16 major earthquakes in any given year. That includes 15 earthquakes in the magnitude 7 range and one earthquake magnitude 8.0 or greater. In the past 40-50 years, our records show that we have exceeded the long-term average number of major earthquakes about a dozen times."

Quakes cause immense destruction and serious damage to infrastructure. When a magnitude five or above quake occurs in an urban area (with the epicenter of the quake occurring in an urban center), the earthquake can destroy the entire infrastructure of that urban area. Some countries (like the United States) have created advanced technologies and building methods to protect buildings and infrastructure from quakes. Other countries, however, are still at high risk of experiencing serious damage from such disaster events.

Another term for this is "foreshock." A foreshock is a quake that occurs before a larger seismic recording occurs. A foreshock can be a good warning that major quake tremors are just around the corner.

Cities at high risk for quakes are:

  • Tokyo, Japan
  • Jakarta, Indonesia
  • Los Angeles, California
  • Quito, Ecuador
  • Osaka, Japan
  • San Francisco, California
  • Lima, Peru
  • Tehran, Iran
  • Istanbul, Turkey

The entire nation of Japan rests in an active seismic area. Japan records the most quakes of any country.

For the most part, quake events tend to cause fires because tremors damage residential and business gas and electrical lines. That can create natural gas leaks and the downing of power lines, both of which can cause fires.

Not with any kind of predictability or reliability. Quakes come and go. Some years have more quakes than others. However, there is no way of proving if quakes are becoming more common and more intense than they once were.

Unfortunately, no. According to the USGS, "We cannot prevent natural earthquakes from occurring but we can significantly mitigate their effects by identifying hazards, building safer structures, and providing education on earthquake safety. By preparing for natural earthquakes we can also reduce the risk from human induced earthquakes."

It's possible. The USGS has recorded a few instances of serious quakes in Texas, Oklahoma, and other states directly linked to seismic disruptions caused by fracking explosions. From the USGS, "The largest earthquake known to be induced by hydraulic fracturing in the United States was a M4 earthquake in Texas. In addition to natural gas, fracking fluids and saltwater trapped in the same formation as the gas are returned to the surface. These wastewaters are frequently disposed of by injection into deep wells. The injection of wastewater and saltwater into the subsurface can also cause earthquakes that are large enough to be damaging. Wastewater disposal is a separate process in which fluid waste from oil and gas production is injected deep underground far below ground water or drinking water aquifers. The largest earthquake known to be induced by wastewater disposal was a M5.8 earthquake that occurred near Pawnee, Oklahoma in 2016." That's one argument for finding alternative, sustainable, and renewable forms of energy production.


Sources:

https://earthquake.usgs.gov/learn/glossary/?term=earthquake

https://www.cdc.gov/disasters/earthquakes/during.html#

http://www.geo.mtu.edu/UPSeis/why.html

https://www.ready.gov/earthquakes

ttps://www.usgs.gov/natural-hazards/earthquake-hazards/science/science-earthquakes?qt-science_center_objects=0#qt-science_center_objects

https://climate.nasa.gov/news/2926/can-climate-affect-earthquakes-or-are-the-connections-shaky/

https://www.usgs.gov/faqs/why-are-we-having-so-many-earthquakes-has-naturally-occurring-earthquake-activity-been?qt-news_science_products=0#qt-news_science_products

https://earthquake.usgs.gov/data/oaf/overview.php

https://www.usgs.gov/faqs/what-depth-do-earthquakes-occur-what-significance-depth?qt-news_science_products=0#qt-news_science_products

https://www.usgs.gov/faqs/what-earthquake-and-what-causes-them-happen?qt-news_science_products=0#qt-news_science_products

https://ourworldindata.org/the-worlds-deadliest-earthquakes

http://www.geo.mtu.edu/UPSeis/magnitude.html

https://www.usgs.gov/natural-hazards/earthquake-hazards/science/animals-earthquake-prediction?qt-science_center_objects=0#qt-science_center_objects

https://kids.nationalgeographic.com/science/article/earthquake#

https://www.usgs.gov/faqs/can-we-cause-earthquakes-there-any-way-prevent-earthquakes?qt-news_science_products=0#

90 Frequently Asked Questions About Volcanoes and Their Answers

Given that active volcanoes can remain active for centuries and are often unpredictable as to their explosions, it's important to know what they are, the risks of being near one, and how to respond to a volcanic eruption event. According to the United States Geological Survey, such a unique natural formation as this is defined as follows: “Volcanoes are openings, or vents where lava, tephra (small rocks), and steam erupt on to the Earth's surface. Volcanic terrain, however, is built by the slow accumulation of erupted lava. The vent may be visible as a small bowl shaped depression at the summit of a cone or shield-shaped mountain. Through a series of cracks within and beneath the volcano, the vent connects to one or more linked storage areas of molten or partially molten rock (magma). This connection to fresh magma allows the volcano to erupt over and over again in the same location."

Inside the Earth's core, there is a red-hot liquid rock called magma. Volcanoes form when that magma rises to the surface of the Earth and pushes its way out of a vent in the Earth's crust. When the magma reaches the Earth's surface, it cools and hardens. As this happens over countless millennia, a volcano is formed.

A volcanic eruption can last from just a few hours to several years, making it almost impossible to categorize what is considered "normal" in terms of the duration of a volcanic eruption. However, according to the Smithsonian Global Volcanism Program, the median length of time for a single volcanic eruption is seven weeks. An eruption can be fast and sudden or slow and barely noticeable.

Mt. St. Helens is called a “dacite volcano.” It is considered an explosive structure with a complex magmatic system. In fact, the deadliest and most economically destructive volcanic event in U.S. history occurred when Mount St. Helens erupted in 1980. Located in Skamania County, Washington (just 52 miles northeast of Portland, Oregon), the eruption was so violent that the summit of the mountain was completely blown off, reducing the height of the mountain from 9,677 ft to 8,363 ft above sea level. The volcanic event killed 57 people, destroyed 200 homes, and took out 47 bridges, 15 miles of railway, and 185 miles of highway.

(However, there have been other eruptions that were even worse than the 1980 Mt. St. Helens eruption. In 1912, Katmai Volcano in Alaska erupted, a more forceful volcanic event with wider-reaching damage than Mount St. Helens. However, because the region was sparsely populated, there were no human deaths due to the event).


Volcanoes erupt because of pressures occurring below and inside of them. When molten rock called magma rises to the surface, this causes an eruption. As the magma rises, bubbles of gas form inside of it. The result? Runny magma erupts through openings or vents in the earth's crust (often at the peak of the volcano) before flowing onto its surface as lava.

The Yellowstone Caldera, a supervolcano, is located in Wyoming.

It is massive! The huge caldera measures 80 kilometers long, 65 kilometers wide, and hundreds of meters deep. It extends from outside Yellowstone National Park into the central area of the park.

This is a broad, domed structure with gently sloping sides. It looks much like a shield, hence the name. Such a structure is formed by the eruption of fluid, basaltic lava.

Volcanoes usually form at the boundary of the Earth's tectonic plates. That's why, in the United States, most of the country's 160+ active volcanoes are located in California, Oregon, Washington, Alaska, and Hawaii. However, "active" is a loose term. For example, ten active volcanoes in this region include:

  • Kilauea, Hawai'i – Last erupted: 2018.
  • Redoubt, Alaska – Last erupted: 2009.
  • Mount St. Helens, Washington State – Last erupted: 2008.
  • Mauna Loa, Hawai'i – Last erupted: 1984.
  • Lassen Volcanic Center, California – Last erupted: 1917.
  • Mount Hood, Oregon – Last erupted: About 200 years ago.
  • Mount Shasta, California – Last erupted: About 300 years ago.
  • Mount Rainier, Washington – Last erupted: About 1,100 years ago.
  • South Sister, Oregon – Last erupted: About 2,000 years ago.
  • Yellowstone, Wyoming – Last erupted: About 70,000 years ago.

There are five such structures in the state of Hawaii. Two of them are still active, Kilauea and Mauna Loa.

We normally associate such natural structures with the Tropics and with various islands in the Pacific Ocean. But of the more than 160 active volcanoes in the United States, most of them are in the Pacific Northwest, including northern California, Oregon, Washington State, and Alaska! According to American Geosciences, “There are about 169 volcanoes in the United States that scientists consider active. Most of these are located in Alaska, where eruptions occur virtually every year.”

There are approximately 1,500 such structures in the world, hundreds of which are in the United States.

According to the NOAA, “In geology, a hotspot is an area of the Earth’s mantle from which hot plumes rise upward, forming volcanoes on the overlying crust. In much the same way that plumes rise buoyantly in a lava lamp, plumes of mantle magma (molten rock) are theorized to rise buoyantly from a source within Earth’s deep mantle. When such a plume rises into the shallow mantle, it partially melts and the melt may then rise to the surface where it can erupt as a hotspot volcano. Hotspot volcanism is distinct in that it does not originate from processes that produce the more common submarine volcanism that occurs at boundaries of Earth’s tectonic plates.”

The largest active volcano on the planet, Mauna Loa is a shield volcano. The name is Hawaiian for “Long Mountain.”

There has been a great deal of speculation on this, with some answers being more legitimate than others. Quoting the credible scientists over at the United States Geological Survey, “If another large, caldera-forming eruption were to occur at Yellowstone, its effects would be worldwide. Such a giant eruption would have regional effects such as falling ash and short-term (years to decades) changes to global climate. Those parts of the surrounding states of Montana, Idaho, and Wyoming that are closest to Yellowstone would be affected by pyroclastic flows, while other places in the United States would be impacted by falling ash (the amount of ash would decrease with distance from the eruption site). Such eruptions usually form calderas, broad volcanic depressions created as the ground surface collapses as a result of withdrawal of partially molten rock (magma) below. Fortunately, the chances of this sort of eruption at Yellowstone are exceedingly small in the next few thousands of years.”

Most such structures are found along a belt called the Ring of Fire that encircles the Pacific Ocean. Some, like the hotspots in the Hawaiian Islands, occur in the interior of plates.

Many of the world’s active volcanic structures are located around the edges of he Pacific Ocean, in the Ring of Fire. They can be found along the West Coast of the Americas; the East Coast of Siberia, Japan, the Philippines, and Indonesia; and in island chains from New Guinea to New Zealand.

Like mountains, volcanoes vary greatly in size. The world's largest volcano is Mauna Loa, in Hawai'i. Mauna Loa is about 55,770 feet from its base beneath the ocean to the summit, which is 13,681 feet above sea level. Conversely, the smallest volcanoes in the world look more like large boulders than actual volcanic mountains.

There are about 1,500 active, volcanic structures in the world today.

According to the United States Geological Survey, “Some of the Earth's grandest mountains are composite volcanoes – sometimes called stratovolcanoes. They are typically steep-sided, symmetrical cones of large dimension built of alternating layers of lava flows, volcanic ash, cinders, blocks, and bombs and may rise as much as 8,000 feet above their bases. Some of the most conspicuous and beautiful mountains in the world are composite volcanoes, including Mount Fuji in Japan, Mount Cotopaxi in Ecuador, Mount Shasta in California, Mount Hood in Oregon, and Mount St. Helens and Mount Rainier in Washington.”

Volcanoes are categorized based on the frequency of their eruption. Those that erupt frequently are called "active," and those that have not erupted in many, many years are called "dormant." However, dormant volcanoes could become active again. While there is no scientific consensus on what exactly counts as an active or inactive volcano, the Smithsonian Global Volcanism Program defines a volcano as active only if it has erupted in the last 10,000 years. Using that definition, there are about 500 active volcanoes on Planet Earth here in the 21st century, with more than 160 of them existing in the United States.

Mount Fuji is a Composite Cone, i.e., a stratovolcano. It is a massive mountainous structure and is formed from layers of rock, ash, and lava.

The three types are composite, shield, and cinder cone. There are also supervolcanoes. Following are three quotes from the United States Geological Survey that clearly and concisely define each type:

“Some of the Earth's grandest mountains are composite volcanoes – sometimes called stratovolcanoes. They are typically steep-sided, symmetrical cones of large dimension built of alternating layers of lava flows, volcanic ash, cinders, blocks, and bombs and may rise as much as 8,000 feet above their bases. Some of the most conspicuous and beautiful mountains in the world are composite volcanoes, including Mount Fuji in Japan, Mount Cotopaxi in Ecuador, Mount Shasta in California, Mount Hood in Oregon, and Mount St. Helens and Mount Rainier in Washington.”

“Cinder cones are the simplest type of volcano. They are built from particles and blobs of congealed lava ejected from a single vent. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as cinders around the vent to form a circular or oval cone. Most cinder cones have a bowl-shaped crater at the summit and rarely rise more than a thousand feet or so above their surroundings. Cinder cones are numerous in western North America as well as throughout other volcanic terrains of the world.”

“Shield volcanoes, the third type of volcano, are built almost entirely of fluid lava flows. Flow after flow pours out in all directions from a central summit vent, or group of vents, building a broad, gently sloping cone of flat, domical shape, with a profile much like that of a warrior's shield. They are built up slowly by the accretion of thousands of highly fluid lava flows called basalt lava that spread widely over great distances, and then cool as thin, gently dipping sheets. Lavas also commonly erupt from vents along fractures (rift zones) that develop on the flanks of the cone. Some of the largest volcanoes in the world are shield volcanoes. In northern California and Oregon, many shield volcanoes have diameters of 3 or 4 miles and heights of 1,500 to 2,000 feet. The Hawaiian Islands are composed of linear chains of these volcanoes including Kilauea and Mauna Loa on the island of Hawaii-- two of the world's most active volcanoes.”

The process is complex, but it can be simplified. Inside the Earth's core, there exists a red-hot liquid rock called magma. Volcanoes form when that magma rises all the way up to the surface of the Earth and pushes its way out of a vent that has formed in the Earth's crust. When the magma reaches the Earth's surface, it cools and hardens. As this happens over countless millennia, a volcano is formed.

From the USGS: “Cinder cones are the simplest type of volcano. They are built from particles and blobs of congealed lava ejected from a single vent. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as cinders around the vent to form a circular or oval cone. Most cinder cones have a bowl-shaped crater at the summit and rarely rise more than a thousand feet or so above their surroundings. Cinder cones are numerous in western North America as well as throughout other volcanic terrains of the world.”

Kīlauea, on the Island of Hawai'i, is an active shield volcano. Its most recent eruption occurred in 2018. That eruption created a massive lava flow covering 13 square miles of the island, boiling Hawaii's largest freshwater lake and destroying 700 homes. While Kīlauea is known for its activity and is therefore closely monitored so that residents have time to evacuate before an eruption, it's only a matter of time before this volcano experiences another significant volcanic event.

Impressive and imposing, Mount Rainier is a stratovolcano.

This structure is quite unique. According to the experts at Volcano Discovery, “Present-day Vesuvius is a medium-sized typical stratovolcano volcano reaching a height of 1,281 m a.s.l. It comprises the older volcano, the Somma, whose summit collapsed (likely during the 79 AD eruption), creating a caldera, and the younger volcano, Vesuvius, which since then has re-grown inside this caldera and formed a new cone.”

Yellowstone is a supervolcano. According to one source, “It (Yellowstone) has had three massive eruptions, all of which created calderas. The first eruption occurred some 2.1 million years ago, and the second took place about 800,000 years later.” Though Yellowstone National Park is famous for resting atop a massive volcano, the geysers that reside at the Earth's surface in Yellowstone are not, themselves, volcanic. The big difference between a geyser system and a volcano system is that a geyser emits hot water and steam. In contrast, a volcano emits dust, fine rock particles, larger rocks, and lava.

These structures are build almost entirely from fluid, ongoing, and recurrent lava flows. Flow after flow after flow after flow pours out in all directions from a central summit vent, or from a group of vents, building a broad, gently sloping cone that takes on a flat, domical shape. It has a profile much like that of a warrior's shield, hence the name.

Very hot! The temperature of molten lava coming up out of a vent can vary anywhere from 700 to 1,200 degrees Celsius, or 1,300 to 2,200 degrees Fahrenheit.

Volcanic eruptions are more common than one might think. Dozens of volcanoes erupt each year in the United States alone, several of which erupt multiple times. Quoting the American Geosciences Institute: “There are about 169 volcanoes in the United States that scientists consider active. Most of these are located in Alaska, where eruptions occur virtually every year. Others are located throughout the west and in Hawaii. Kilauea volcano in Hawaii is one of the most active volcanoes on Earth. It has been erupting almost continuously since 1983.”

There have been at least 404 volcanic eruptions since 1883, almost 200 of which have occurred since the year 2000. But the big question on everyone's minds is this. Will volcanic eruptions become more frequent and more intense in the future? According to the Scientific American, it's likely that volcanic activity will increase as the planet warms. Researchers found that, historically, volcanic eruptions have increased as planet temperatures rose and glaciers melted. As the Earth is currently going through a warming phase, it's safe to assume that volcanic activity will become more common.

It is not. Mount Everest was formed by he clashing of two tectonic plates, the Indo-Australian and Eurasian plates. But there was no volcanic activity involved, hence Mount Everest is jus a very, very tall mountain.

It was Mount Vesuvius that destroyed the city of Pompeii. The eruption took place in A.D. 79, killing about 2,000 people.

Simply put, when molten rock called magma pushes its way to the surface of the Earth’s crust and expels out into the open air, this is a volcanic eruption. In most eruptions, runny magma erupts through openings or vents in the earth's crust before then flowing onto its surface as lava. If the magma is thick, gas bubbles cannot easily escape and pressure builds up as the magma rises. That’s what creates the trademark explosion that volcanoes are known for.

Subduction is simply the collision of continental and oceanic crusts. The oceanic crust melts and migrates upwards, until it ultimately erupts on the surface, creating a volcanic explosion.

There are 20 such structures in the state of California.

There are a little more than 450 such structures in the Ring of Fire.

Such a mountainous structure is formed of hot molten rock, ash, escaped gases, and lava. All of the above solidifies as it cools, following an eruption. What’s left behind is the building blocks for the structure itself.

Most such structures look quite like mountains, but others may look like shields or cones.

Such a geologic feature is a chain of volcanic structures that form above and along a subduction plate. They often spring up in an arc-like pattern, hence the name.

According to the National Geographic, “The Ring of Fire, also referred to as the Circum-Pacific Belt, is a path along the Pacific Ocean characterized by active volcanoes and frequent earthquakes. The majority of Earth's volcanoes and earthquakes take place along the Ring of Fire.”

Volcanoes and mountains are certainly similar. But they are different in that a mountain results from various geological processes (like the movement and collision of tectonic plates). On the other hand, volcanoes form around a vent in the Earth's crust when magma flows up and out of the vent, reaching the surface of the Earth.

When tectonic plates collide, volcanoes often form. This usually occurs when a thin, heavy oceanic plate “subducts,” or moves under, a thicker continental plate of heavy, solid rock. Then, when enough magma builds up in the magma chamber, it forces its way up to the surface and then erupts, often causing volcanic eruptions.”

Simply put, such structures change the surface of the Earth by allowing molten rock (magma) to escape from inside the Earth, come to the surface, and from various rock formations and even mountains.

The temperature of lava flow is usually about 2,000 degrees Fahrenheit. In other words, very, very hot!

There are about 1,500 such structures that qualify as active.

It is mineral-like, but not a true mineral. This is mostly because it’s composition is too complex and intricate to be classified as a single mineral.

Indonesia has the most by far. With over 13,000 islands within its boundaries, many of them formed by volcanic activity, this country has the most such structures of any country in the world.

Such an eruption has both warming and cooling effects. For example, released ash and sulfur dioxide have a cooling effect, because such particles reflect sunlight. However, such structures also release CO2, causing a warming effect.

This is another term for volcanic activity or phenomenon.

Kilauea is the most active by far! It is almost always erupting to some degree.

Vesuvius is considered the most dangerous. It’s eruptions are very explosive and sudden, and while it has been dormant since 1944, about 3 million people live within close proximity to it, suggesting the possibility for a great deal of destruction were it to erupt again.

Ojos Del Salado is the tallest, in the Andes Mountains, coming in at 22,615 feet above sea level.

According to the National Geographic, “Volcanic ash is a mixture of rock, mineral, and glass particles expelled from a volcano during a volcanic eruption. The particles are very small—less than 2 millimeters in diameter. They tend to be pitted and full of holes, which gives them a low density. Along with water vapor and other hot gases, volcanic ash is part of the dark ash column that rises above a volcano when it erupts.”

They are wider because of the difference in how they are formed. Composite structures are formed by upwards and outwards explosions, whereas shield structures are formed by constant, steady, ongoing lava flow.

Yes, particularly along the East African rift.

Yes. Because volcanic activity causes vibration within the earth’s crust and interior layers, this can set off earthquakes.

Eruptions can have a warming effect, as co2 is released into the atmosphere during an eruption.

There are four basic types: composite, shield, super, and cinder cone.

Magma, lava, gases, and ash.

The word is Latin in origin. According to the USGS, “The word ‘volcano’ comes from the little island of Vulcano (with a U) in the Mediterranean Sea off Sicily. Centuries ago, the people living in this area believed that Vulcano (with a U) was the chimney of the forge of Vulcan – the blacksmith of the Roman gods.”

An extinct volcanic structure, a dormant one, and an active one are all different and unique. According to Volcano Discovery, “An active volcano is a volcano that has had at least one eruption during the past 10,000 years. An active volcano might be erupting or dormant. An erupting volcano is an active volcano that is having an eruption. A dormant volcano is an active volcano that is not erupting, but supposed to erupt again. An extinct volcano has not had an eruption for at least 10,000 years and is not expected to erupt again in a comparable time scale of the future.” And can inactive volcanic structure become active again? Yes! A volcano can go for millions of years without erupting and then suddenly become active again.

Both plate boundaries and convergent plate boundaries can cause volcanic activity.

It is highly fertile because it is composed on many non-crystalline minerals, such as allophone. In simple terms, these minerals create strong bonds with organic matter, and that leads to the accumulation of organic matter in the soil.

There are two crucial ways to respond to a volcanic eruption, and how you react to such a natural disaster will depend on the type of volcanic eruption.

  • If the volcanic eruption involves ash fall but not lava flow, it's important to stay inside.
  • If the volcanic eruption involves lava flow, it's important to leave the area immediately.

Before and during a volcanic event, listen to the advice of local officials. They will tell you if you should take shelter in your home or if you should evacuate. If the eruption does not involve lava flow, stay indoors and:

  • Close all windows, doors, and fireplace or wood stove dampers.
  • Turn off all ceiling fans and all heating and air conditioning systems.
  • Bring pets and livestock into closed shelters and keep them there.

During an eruption, wear goggles and an N-95 respirator if they are available to you. If your eyes, nose, or throat become irritated from volcanic gases and fumes, move away from the area immediately. If you are caught outside during an eruption, seek shelter indoors. During volcanic activity, stay apprised as to what local officials and emergency responders are saying. If officials initially tell you to shelter inside but then change the recommendation later on to evacuate the area, follow their instructions immediately, as that likely means the volcanic event changed to one that involves dangerous lava flow.

Such is simply an opening, varying in size, out of which can escape magma, lava, gases, and volcanic debris.

Olympus Mons is the largest by far, located on Mars. According to NASA, “The largest of the volcanoes in the Tharsis Montes region, as well as all known volcanoes in the solar system, is Olympus Mons. Olympus Mons is a shield volcano 624 km (374 mi) in diameter (approximately the same size as the state of Arizona), 25 km (16 mi) high, and is rimmed by a 6 km (4 mi) high scarp. A caldera 80 km (50 mi) wide is located at the summit of Olympus Mons. To compare, the largest volcano on Earth is Mauna Loa. Mauna Loa is a shield volcano 10 km (6.3 mi) high and 120 km (75 mi) across. The volume of Olympus Mons is about 100 times larger than that of Mauna Loa. In fact, the entire chain of Hawaiian islands (from Kauai to Hawaii) would fit inside Olympus Mons!”

This is relatively infrequent, but yet, volcanic activity can cause impulsive disturbances in the ocean, displacing a great volume of water and causing a tsunami as a result.

Yes they do.

They are formed by volcanic activity on the seabed, often near the boundaries of tectonic plates.

This is partially dependent on the speed of eruption. While the United States Geological Survey has systems in place to detect volcanic eruptions, volcanic activity can still occur very quickly, with a volcano going from inactive to active overnight. One example of rapid volcanic activity was Paricutin, a volcano that appeared in a Mexican cornfield in 1943. Within a week, it was five stories tall! Ultimately, lava cools and hardens following an eruption. But how long it takes to do that is dependent on how rapidly and with how much intensity the volcano is erupting.

Such a structure is called a Submarine Volcano.

Scientists use seismographs to measure the tremors that begin shortly before a volcanic eruption occurs.

It is a mixture of rock, mineral, and glass particles. The particles are small, usually less than two millimeters in diameter. It is very irritating to the throat, lungs, eyes, and nose, so people who are near an eruption should take cover or evacuate and do everything they can not to breathe the ash.

It is called extrusive rock or igneous rock.

Not really. Mountains can be formed by volcanoes, and volcanic activity can change mountains, but a mountain cannot suddenly become a volcano. However, volcanoes are actually types of mountains.

Yes, sometimes. It usually takes a large earthquake, but this has been known to occur.

These are created when a narrow stream of hot mantle rises up from deep inside the earth and melts a hole in the plate, all so that the magma can ooze upwards. The Hawaiian Islands are an example of such a formation.

According to one source, “The Richter scale measures earthquake strength. Volcanoes have a similar scale called the Volcanic Explosivity Index (VEI).... It measures how much volcanic material is ejected, the height of the material thrown into the atmosphere, and how long the eruptions last.”

They are usually thousands of feet deep, with their bottommost sector being difficult to find.

It usually takes millions of years for such structures to form.

There are six such structures that we know about, in the world today.

Such an event is an electrical discharge caused by a volcanic eruption, rather than by an ordinary thunderstorm. It comes about as a result of colliding, fragmenting particles of volcanic ash. Such ash generates static electricity, leading to electrical discharges in the form of lightning.

There are 12 states that have active volcanoes. They are as follows:

Alaska: 141

California: 18

Oregon: 17

Washington: 7

Hawaii: 5

Utah: 4

Idaho: 4

New Mexico: 3

Arizona: 2

Nevada: 2

Colorado: 1

Wyoming: 1

In the Ring of Fire.

They are often located in the Ring of Fire, along the borders of the Pacific Ocean.

Though most volcanic activity that occurs each year in the United States is not that extreme, there is the potential for massive destruction from a volcanic eruption. Fast-moving lava can kill people, and falling ash can make it difficult to breathe. Lava can destroy homes, roads, livestock, farms, and infrastructure. Volcanic eruptions can also cause fires and earthquakes, leading to famine and immense loss of local resources and the capacity to sustain human life.

Not only does Alaska have a huge number of volcanic mountains, but many of the state’s volcanic structures are active! Alaska contains over 130 volcanoes and volcanic fields. The volcanoes in Alaska make up well over three-quarters of U.S. volcanoes that have erupted in the last two hundred years.

Yes! There are several. Currently, only two of them are active, Mount Erebus and Deception Island.


Sources

https://www.usgs.gov/natural-hazards/volcano-hazards/about-volcanoes

https://www.americangeosciences.org/critical-issues/faq/how-many-active-volcanoes-are-there-united-states#

https://www.britannica.com/place/Yellowstone-Caldera

https://www.volcanodiscovery.com/volcanoes/faq/active_erupting.htm

https://www.usgs.gov/volcanoes/mount-st-helens

https://avo.alaska.edu/volcanoes/about.ph

https://www.bbc.co.uk/newsround/44100737

https://www.usgs.gov/volcanoes/yellowstone/questions-about-yellowstone-volcanic-history

https://oceanexplorer.noaa.gov/facts/volcanic-hotspot.htm

https://www.usgs.gov/faqs/what-would-happen-if-a-supervolcano-eruption-occurred-again-yellowstone?qt-news_science_products=0#qt-news_science_products

https://pubs.usgs.gov/gip/volc/types.htm

https://www.volcanodiscovery.com/vesuvius.html

https://www.nationalgeographic.org/encyclopedia/ring-fire/

https://www.nationalgeographic.org/encyclopedia/volcanic-ash

https://www.usgs.gov/media/audio/where-did-term-volcano-com

https://mars.nasa.gov/gallery/atlas/olympus-mons.html

90 Frequently Asked Questions About Tsunamis and Their Answers

A: The National Ocean Service defines them as such: "Tsunamis are giant waves caused by earthquakes or volcanic eruptions under the sea. Out in the depths of the ocean, tsunami waves do not dramatically increase in height. But as the waves travel inland, they build up to higher and higher heights as the depth of the oceaan decreases. The speed of tsunami waves depends on ocean depth rather than the distance from the source of the wave. Tsunami waves may travel as fast as jet planes over deep waters, only slowing down when reaching shallow waters. While tsunamis are often referred to as tidal waves, this name is discouraged by oceanographers because tides have little to do with these giant waves."

A: While more common in the Pacific Ocean, such a wave can strike any coast at any time, putting all coastal regions at risk. They occur as a direct result of a violent eruption or earthquake under the surface of the ocean. According to the National Ocean Service, about 80% of such waves are caused by earthquakes. But they can be caused by volcanoes, landslides, certain types of weather, and even asteroids or comets colliding with the ocean.

A: When a large and sudden displacement occurs in the ocean (think a large earthquake below or near the ocean floor, or a volcanic eruption, or converging tectonic plates), the force of such a disruption creates waves that radiate outward in all directions from their source. This is what makes such waves so unpredictable and volatile. For example, an earthquake in one corner of the Pacific Ocean can cause a massive wave to strike a coastline thousands of miles away.

A: From a disaster preparedness standpoint, there is very little that one can do to "prepare" for such an event. The best advice is:

1). Outfit yourself in such a way that you have as much warning as possible before a wave strikes. For example, invest in an emergency radio that picks up the NOAA weather report, an automated, 24-hour network of F.M. weather radio stations that monitor weather hazards.

2). Even more importantly, have an evacuation route planned. Remember, if you live in a coastal area, you may not have much warning before a wave strikes. Even if you do get an alert on your radio, cell phone, or T.V., you may only have a few minutes to evacuate. So gather up your family, leave your possessions behind, and follow your evacuation route. Seek high ground and travel inland, if you can.

There's no "battening down the hatches" and waiting out such a wave. You must get away from the coast as soon as possible.


A: As touched on earlier, such waves can occur anywhere there is an ocean coast. However, they are most likely to happen in the Pacific Ocean and near Indonesia, as the Pacific Rim bordering the ocean has many active submarine earthquake zones.

A: It does not necessarily look like a traditional wave, with curling, cresting movement. Rather, most massive wave events will look like a wall of water moving forward or just a steadily, rapidly rising water level.

A: The speed and force depend quite a bit on the depth of the ocean. If one forms in very deep water, it can move extremely fast, over 500 mph. And because the wave moves within the water, mariners out at sea will not usually notice as one passes beneath them. The immense force of the water and the rising water level is not typically noticeable until it reaches shallow water and coastal areas.

A: Not last for very long. Most last for five minutes to two hours. However, just because water levels from a recede after a wave hits does not make it safe to return to a coastal area. Large events may involve more than one wave/water level rise, and some have even been recorded as lasting for several days. That's why it is important not to return to a tsunami site until after emergency response officials have said it is safe to do so.

A: The 1958 Lituya Bay Earthquake and Megatsunami was the largest by far. This was a massive wave that climbed almost 200 feet above sea level up the shore and more than 1,700 feet inland, caused by a severe earthquake and landslide in the region. (See the Sources section under "Earthquake Alaska" for an excellent article on this mass destruction event!)

A: Though rare, some have been recorded as reaching more than 100 feet in height, a mega wave that surges inland, far beyond where waves usually break on the shore. However, most such waves are usually relatively short in height (10 feet high or so), which unfortunately hides their danger and destructive force.

A: Thousands of miles. Such wave events can travel across an entire ocean's span before reaching landfall. Perhaps the most famous example of this was a devastating earthquake in a coastal region of western South America, yet which caused a massive wave event to strike Hawaii, thousands of miles away.

A: There are usually 2-3 such waves that occur per year.

A: The word means "harbor wave" in Japanese.

A: No, mainly because earthquakes are usually what cause such wave events, and earthquakes themselves cannot be predicted more than a few seconds or short minutes before they occur.

A: According to one scientific paper on such an event, "Most tsunamis are caused by large earthquakes on the seafloor when slabs of rock move past each other suddenly, causing the overlying water to move. The resulting waves move away from the source of the earthquake event."

A: One of their unique attributes is how different they are from wind-driven waves. While a wind-driven wave (like one caused by a hurricane) only travels along the topmost layer of the ocean, a tsunami moves through the entire water column, from the ocean floor to the ocean surface. This is why such an event will often appear like a massive water ripple rather than a wave.

A: Seek higher ground, and move away from the coast. Flee away from the coast and above the ocean level.

A: Most waves are usually around ten feet high, but they have been recorded as reaching thirty feet high or higher, and they can travel up to 1,000 feet inland, sometimes climbing up entire hillsides in doing so.

A: The biggest such wave event was a wave that crashed 1,720 feet inland in Libya Bay in Alaska in 1958.

A: Yes, it's possible. Hurricanes can cause ocean sediments to move about, which could trigger an undersea landslide, which could then cause a massive wave event to form.

A: Yes. Dozens of such wave events have crashed upon the shores of California.

A: The National Oceanic and Atmospheric Administration has a special DART program (Deep-ocean Assessment and Reporting of Tsunamis). This system locates waves as soon as they occur within the deep ocean using buoys and other deepwater equipment to monitor sea-level changes and forces moving through the water.

However, though some measurement and graphing systems have been proposed, there is no current, universally accepted method for measuring the severity of such events. And that's mostly because the severity will be entirely different based on where it strikes. For example, a wave may cause utter devastation in a coastal city just a few miles away from the earthquake source. But, conversely, that very same wave may not cause much damage at a coastal city several hundred miles away from the source.

As a general rule, most oceanographers measure such waves either by the severity of the damage they cause (if that damage is mostly uniform, strike-point to strike-point) or they measure the event by the height of the wave created by it.

A: This varies considerably, but flooding can extend inland by as much as 1,000 feet.

A: Such is a massive wave, a veritable wall of water that moves towards the coast and inland, sometimes travels 1,000 feet or more inland.

A: Most such wave events are caused by earthquakes and are therefore not easily predicted.

A: Yes. Hundreds of such wave events have hit the U.S. However, there have not been many deaths, at least not compared to natural disasters in the Pacific Ocean near Asia, Southeast Asia, and the Indian Ocean.

A: Approximately two such wave events occur each year.

A: Yes. This is not as common as earthquakes causing such events, but volcanoes can cause massive wave crashes.

A: Yes, but such events are very, very rare. Almost all massive wave events that occur in the United States occur on the west coast.

A: Unlike hurricanes that are hazardous within the ocean and approach land, a massive wave event only becomes dangerous when it comes near a coastal region. As the wave enters shallow water, it slows to 20 to 30 mph. Then, three things occur that make the wave disastrous:

The wavelength decreases.

The heigh increases.

The currents intensify.

Because such a wave involves a sudden rush of water from the ocean up onto the coast and further inland, it can cause immense damage to human life, property, and entire, local economies. For example, it can destroy boats in harbors and shallow water; it can ruin cars parked near the coast, and it can even flood, damage, and destroy buildings.

Such a wave may only be 10 feet high, but the force of the rushing water can pick up and move virtually anything in its path, including entire houses and smaller buildings. Furthermore, some waves have been recorded as reaching 100 feet high or more, which causes them to act as a massive wave and a surging rise in ocean water level, all at the same time.

A: No. Such a wave does not occur like a tidal wave, or windblown wave does, and it would be foolish and potentially lethal to try and surf a tsunami wave.

A: The water sucks back out into the open ocean, often dragging cars, trees, buildings, and people with it.

A: It's highly unlikely that this would occur, but large lakes have been known to experience smaller versions of oceanic tsunamis.

A: Yes, it's possible, has occurred before, and all undoubtedly happen again.

A: Yes. Hawaii has experienced a significant percentage of all such wave events that have occurred in the United States.

A: There may be a noticeable earthquake, a loud roaring sound, and the coastal water will likely seem to suck away from the coastline before coming back in force.

A: According to one research paper, "A subduction zone is a boundary between tectonic plates that are part of the Earth's shell. These plates descend or subduct under an adjacent plate. Sudden movement of the plates causes them to stick and generate an earthquake. The overriding plate gets squeezed as it sticks to the subducting plate. This pushes the leading edge down and the rear area bulges upward. Slowly building stress over centuries the movement continues. When an overriding plate breaks free and rises seaward the seafloor rises and lifts the water above it creating an earthquake along the subduction zone. A tsunami is generated. As the bulge end of the plate collapses it thins out and lowers coastal areas. The tsunami races off in two different directions, one, growing in size towards landfall nearby, the other to a distant shore."

A: That depends entirely on the location of the wave. As for the event that forms it, it can happen in an instant. But the crucial factor as to the speed of a forming wave is how close people are to the source point of the wave. For example, suppose a coastal city or populated area is just a few miles from the source point. In that case, the wave could arrive in a matter of minutes, giving locals little time to prepare or evacuate.

Conversely, a coastal area that is hundreds or thousands of miles away from the source point could still be severely affected by the wave, but locals may have several hours to evacuate.

A: This varies, event to event, but most such events have several waves in them.

A: Convergent plate boundaries are the type of place boundary most commonly associated with such wave events.

A: Usually, an earthquake is what causes such an event.

A: 1964 was the year of the last serious wave event in Oregon.

A: Yes. According to the USGS, "Tsunamis can be generated on impact as a rapidly moving landslide mass enters the water or as water displaces behind and ahead of a rapidly moving underwater landslide."

A: Yes. Particularly marine life that lives close to shore. Entire ecosystems can be destroyed and removed by such a wave event.

A: Yes. More than two dozen such wave events have been recorded as striking San Diego since recording began in 1806.

A: Weather scientists use seismographs to record such wave events.

A: That depends on how close the coast is to where the earthquake occurs. If the earthquake occurs very close to a coastal area, a massive wave may crash upon that coast within minutes. However, serious earthquakes out in the open ocean can cause massive waves that travel thousands of miles and take hours to reach the shore.

A: Unlike as is the case with many other natural disasters, it does not make sense to shelter in place if a massive wave is heading your way. Rather, seek higher ground, and move inland. Of course, moving inland is always ideal. But if you cannot move inland, seek higher ground where you are.

A: Such wave events do come in different shapes and sizes, though they should not be confused with tidal waves. Although both are sea waves, a tsunami and a tidal wave are two very different and unrelated phenomena. A tidal wave is a shallow water event caused by the gravitational interactions between the Sun, Moon, and Earth. In addition, tidal waves can be influenced by wind.

On the other hand, Tsunamis are ocean waves triggered by a massive event underneath the ocean's surface. One of the key differences between the two is that a tsunami involves a sudden rise in the ocean's water level up onto a coastal area. In contrast, tidal waves usually do not do this.

A: NOAA has listed the following signs as being strong indicators of an approaching, mass wave event, including a strong earthquake that causes difficulty standing, a rapid rise or fall of the water along the coast, a load ocean roar, and the rapid departure of coastal mammals and birds.

A: Do NOT stay near the coast or on the beach to watch the wave come in. Seek high ground, and try to move inland as far as possible.

A: All of the coastal regions of the United States are at risk for such waves. Large wave events have struck American coasts, and they will undoubtedly occur again. Here are a few from relatively recent history:

In 1946, a tsunami with a wave height cresting between 33 and 55 feet struck Hawaii, killing 159 people.

In 1964, a magnitude 9.2 earthquake in the Gulf of Alaska generated a tsunami that caused damage and loss of life in Alaska, Hawaii, California, Oregon, and Washington.

A 1929 magnitude 7.3 earthquake in the Grand Banks area of the Caribbean Sea caused a small tsunami that caused minor damage as far north as South Carolina.

A: Yes! Some scientists believe dogs can sense such wave events, and coastal birds have repeatedly been spotted fleeing the beach right before such a wave occurs.

A: No. Such a wave event does not just occur on the surface of the ocean. It also occurs throughout the entire depth of the ocean, particularly as the ocean gets shallower.

A: We cannot prevent such wave events from occurring, but we can better prepare for them and respond to them when they do occur.

A: Did you know that 40% of the world's population lives within 100 kilometers of an ocean coast? Though massive wave events might not be as common as other disasters like earthquakes, tornados, or hurricanes, tsunamis have the potential to affect countless lives and create incomprehensible damage. Tsunamis are a legitimate concern for billions of humans on all continents of our planet. They're a constant disaster threat that poses a serious risk for those who live in coastal regions. That's why it is important to know what they are and how to prepare for them. Humans who live in coastal regions must innovate better, safer, and more efficient evacuation plans or build and develop coastal cities on higher ground to adapt to them.

A: Scientists use seismographs to study such wave events and the earthquakes that create them.

A: Virtually anything. Cars, boats, humans, animals, trees, other plants, even entire buildings and homes can be destroyed.

A: If you are not near a high-risk coastal area, you can donate to organizations that help support victims. If you live near a coastal area, you can receive first responder training and volunteer in the relief efforts if such a wave event ever strikes your area.

A: Such a wave event is much like a tidal wave, only much more forceful, hence the distinction. But as the wave approaches the shore, the force of the wave pulls the water in front of it back into the wave, building force and making the wave even more powerful.

A: Yes. Such waves do not always look like traditional tidal waves. But they do have a crest.

A: If you are at home, DO turn off all water, gas, and electricity and flee to higher ground. Do NOT go down to the beach to watch the wave come in.

A: They are categorized and recorded by the magnitude of the largest wave in the set, whichever one that happens to be.

A: Drastically. The base of such a wave can completely change the topography of the seafloor. It erodes the seafloor sediments and can completely devastate the "benthic" layer or the sea bottom ecosystem.

A: Seek higher ground as quickly as possible while moving away from the water's edge.

A: While such wave events have the potential to be extremely devastating, the silver lining (if there is any) with this natural disaster is that they are relatively infrequent. Major tsunamis that have the potential to cause serious damage usually occur once every 10-12 years on average, with smaller, less destructive events having the possibility to occur more frequently.

As for the future, it is thought that climate-induced sea level rises will make tsunamis worse. It is unclear if tsunamis will become more frequent in the future. Still, many scientists believe that rising sea levels will only exacerbate the destruction wrought by waves, as levees and break walls are already overtaxed.

A: While these are not as common as other natural disasters like floods, earthquakes, tornadoes, and hurricanes, tsunamis do happen. There have been about two dozen recorded tsunamis that have occurred in the last decade.

A: If you are aware that a wave is inbound, the best thing is to evacuate immediately and seek higher ground. Do not stay near the coast. Instead, flee away from the coast and seek higher ground as soon as possible.

A: Recovering from a tsunami is sometimes a slow and arduous process, given how much damage can be caused by them. Some basic tips include:

Avoid disaster areas the may still be dangerous.

Avoid debris in the water.

Check yourself and others for injuries and seek first aid.

Assist in rescue efforts, but only in such a way that does not put yourself in danger.

Stay out of buildings with water in them, as the waves can cause floors and walls to crack and collapse.

A: Preventing or reducing wave damage is a science in and of itself. Washington University offers a full college course on the subject. Citing their information, there are four key ways to prevent and reduce damage:

"1. Avoid Inundation Areas: Site Buildings or infrastructure away from hazard area or locate on a high point.

  1. Slow Water: Forests, ditches, slopes, or berms can slow down waves and filter out debris. The success of this method depends on correctly estimating the force of the tsunami.
  1. Steering: Water can be steered to strategically placed angled walls, ditches and paved roads. Theoretically, porous dikes can reduce the impact of violent waves.
  1. Blocking: Walls, hardened terraces, berms and parking structures can be built to block waves. The house and household in a wide community context such as whether it is a majority or minority situation, the conflict situation and ownership issues."

A: Some scientists think so. A warming planet is likely to lead to a range of events, including more frequent earthquakes, volcanic eruptions, giant landslides, and wave events.

A: No. Although both are sea waves, they are distinctly different. According to the United States Geological Survey, "A tidal wave is a shallow water wave caused by the gravitational interactions between the Sun, Moon, and Earth ("tidal wave" was used in earlier times to describe what we now call a tsunami.) A tsunami is an ocean wave triggered by large earthquakes that occur near or under the ocean, volcanic eruptions, submarine landslides, or by onshore landslides in which large volumes of debris fall into the water."

A: It's unlikely that a single nuke could cause a massive wave, but a line of explosions denoted off the coast could indeed create a destructive tsunami.

A: Yes. Other weather events and world factors can cause tsunamis, like a landslide or a volcanic eruption.

A: Yes! Shockingly enough, yes. According to one weather expert, "Tsunamis, also known as tidal waves, are almost exclusively believed to be an event that occurs in the world's oceans and seas. Generally, a tsunami is caused by an Earthquake, volcanic eruption, or other underwater explosions such as landslides, glacier movement or even meteorite impacts. But tsunamis on the Great Lakes, known as 'meteotsunamis', can also happen. These are described as a rather unfamiliar phenomenon, but they have actually been happening often over the years."

A: The answer is quite disgusting. According to the India Water Portal, "The earthquake and the tsunami is a natural phenomenon. BUT the black water is manmade! The black colour is putrefying sewage that accumulates on the ocean floors off the coast line of the continents where humans inhabit. The black tsunami illuminates a painfully unnoticed reality that the great majority of the people on our planet ignore. Storm water, domestic faeces and industrial sewage have been discharged into our rivers, lakes and oceans for more than two thousand years. The Romans discharged contaminated water into rivers and oceans. The black mud spreads to cover the beds of oceans, lakes, rivers and manmade channels. These become aquatic death zones created by man."

A: An orphan tsunami is a tsunami wave event that occurs, but the scientists who study it cannot accurately find or determine the parent earthquake that caused it. It is a mystery event, essentially.

A: To be classified as such a natural disaster, a wave has to meet the following qualifications, according to NOAA, "A tsunami is a series of waves caused by earthquakes or undersea volcanic eruptions.... Tsunamis are giant waves caused by earthquakes or volcanic eruptions under the sea. Out in the depths of the ocean, tsunami waves do not dramatically increase in height."

A: The fear of tsunamis, or waves in general, is called "Cymophobia."

A: According to NOAA, "Most tsunamis are caused by earthquakes on converging tectonic plate boundaries. Since 1900, over 80% of likely tsunamis were generated by earthquakes. However, tsunamis can also be caused by landslides, volcanic activity, certain types of weather, and—possibly—near-earth objects (e.g., asteroids, comets) colliding with or exploding above the ocean."

A: "Tsunami" is a Japanese word. According to Washington University, "Tsunami is a Japanese word with the English translation, 'harbor wave.' Represented by two characters, the top character, 'tsu,' means harbor, while the bottom character, 'nami,' means 'wave.' In the past, tsunamis were sometimes referred to as 'tidal waves' by the general public, and as 'seismic sea waves' by the scientific community. The term 'tidal wave' is a misnomer; although a tsunami's impact upon a coastline is dependent upon the tidal level at the time a tsunami strikes, tsunamis are unrelated to the tides. Tides result from the imbalanced, extraterrestrial, gravitational influences of the moon, sun, and planets. The term 'seismic sea wave' is also misleading. 'Seismic' implies an earthquake-related generation mechanism, but a tsunami can also be caused by a nonseismic event, such as a landslide or meteorite impact."

A: In total, there have been 72 recorded wave events that have hit the United States since 1737, with a total of 548 deaths. Virtually all of these have occurred in the Pacific Ocean, with most regions affected being Alaska and Hawaii. The most recent wave to hit the United States was a landslide in Icy Bay, Alaska. No fatalities occurred.

A: According to data compiled by NOAA and the Global Historical Tsunami Database, "Tsunamis that cause damage or deaths near their source occur approximately twice per year. Tsunamis that cause damage or deaths on distant shores (more than 1,000 kilometers, 620 miles, away) occur about twice per decade." In summary, massive wave events are uncommon, but they are deadly.

A: The Pacific Ocean has the most recorded instances of tsunami waves, particularly near Indonesia. This is because the Pacific Rim borders the Pacific Ocean and has many active submarine earthquake zones. However, more recently, tsunamis have been recorded in the Mediterranean Sea region and are expected in the Caribbean Sea.

A: Tsunamis, in rough English translation, means "harbor wave."

A: Scientists use seismographs to measure the strength, intensity, speed, and size of tsunamis.

A: They are called as such because, unlike tidal waves, tsunamis can cause mass deaths when they reach land.

A: Tsunamis are classified by their strength and intensity. According to the experts, "A small movement from a convergent boundary will produce a tsunami of weak to moderate strength, while a major movement from the same boundary will produce a tsunamis of significant magnitude. Tsunami are usually named for the landmass they impact, or city or town they inflict damage upon. The recent Fukishima tsunamis that impacted Japan was named for the nuclear reactors that were overrun with salt water from the ocean. Footage of the tsunamis show it reaching far inland, destroying houses, fields, and part of the Japanese population that lived there. While at sea, it is hard to gauge the strength of a tsunamis, as there is more room for the water to swell in."

A: According to the data, most tsunamis cause a sea rise of no more than 10 feet. However, a tsunami wave can reach heights of 30 feet or more. Keep in mind, though, 40% of the world's population lives in coastal areas. Just in the United States alone, 127 million people live near sea level. This is why tsunamis are so dangerous. Though a tsunami wave may only cause a sea-level rise of 10 feet, that 10 feet of rise and the fact that a wave can travel up to 1,000 feet inland can be devastating for human habitation.

A: Very deadly! Not only are tsunamis deadly in the initial rush of water that comes surging up onto the land, but when the water recedes into the ocean, it can drag people out into the open water and drown them.


Sources:

https://oceanservice.noaa.gov/facts/tsunami.html#

https://www.un.org/esa/sustdev/natlinfo/indicators/methodology_sheets/oceans_seas_coasts/pop_coastal_areas.pdf

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