Volcanoes can produce devastating destruction. They can create flows of lava that can cover communities at speeds of 450 miles (724 km) and hour. They spew hot ash and boulders in the air to rain down on people. They produce magma and mudslides that slide down the sides of mountains, destroying homes and lives.
When we think of devastation as destructive as this, the most memorable is the eruption that destroyed Pompeii in A.D. 79.
Not all volcanic explosions produce this much destruction. Many people live within the vicinity of active volcanoes and never experience danger. Citizens of Hawaii, for example, are safe even though they live near one of the most active volcanoes in the world.
How much destruction is caused by a volcanic explosion depends on what kind of volcano is erupting. It also depends how much pressure has built up inside the magma.
Have you ever wondered if you would survive an exploding volcano? Chances are, you would, depending on which volcano you’re near. Keep reading to find out which types of volcanoes are the most dangerous.
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The 4 Types of Volcanoes
Volcanoes are grouped into four main types: cinder cones, composite volcanoes, shield volcanoes, and lava domes.
1. Cinder Cone Volcano
We’ll cover this type of volcano first because it’s the simplest. They are formed with particles of congealed lava that come from a single opening called a vent.
Lava below the surface is filled with gas, and when it becomes overwhelmed with gases, the lava is blown into the air through the vent. The lava breaks apart into pieces that harden as they fall. These pieces are called “cinders”, and they fall around the vent opening to create a circular “cone”.
This cone is what forms the typical volcanic “look” as we know it, consisting of a raised ring surrounding a bowl-like crater at the top.
Cinder cones remain small and are usually not more than 1,000 feet (305 meters) tall. They are most commonly found in North America.
2. Composite Volcano
Composite, or stratovolcanoes, are symmetrical, and their sides are very steep. They are much larger than cinder cones, reaching heights of up to 8,000 feet (2,438 meters). The sides of these volcanoes are built from layers of lava, volcanic ash, and cinders.
A volcano continues to grow because it has a tube-like system deep within the earth’s crust. Inside these systems is magma that slowly rises to the surface of the volcano. This is where lava, cinder, and ash material builds onto the volcano.
Like most volcanoes, composite volcanoes have a crater at the peak of the volcano. Unlike cinder cones, composite volcanoes form from vents, often in clusters.
Lava will flow from breaks in the surface of the crater’s walls, or from fissures on the side of the cone. It strengthens the volcano as the lava hardens, forming disks that act as a support structure.
If a composite volcano has become dormant for too long, the volcano will erode. Eventually, the cone will be destroyed. The hard solid magma that is supporting the structure of the cone becomes exposed, and begins to erode away.
Some of the greatest mountains in the world are composite volcanoes. Mount Fuji in Japan and Mount St. Helens in Washington are two of them.
3. Shield Volcanoes
Shield volcanoes are unique because they’re created from liquid lava flows. Shield volcanoes have a central vent at the summit where lava flows in all directions, far from the initial source.
From these lava flows, the volcano is formed, a wide, mildly sloped structure that is mostly flat. The dome of these volcanoes is subtle, and some people refer to them as having a similar shape to that of a shield.
Complete construction of these volcanoes takes a long time, sometimes over a thousand lava flows. As the lava cools, it forms thin sheets over a wide-spread area.
Some of the largest volcanoes in the world have been formed this way. They cover distances of 3-4 miles (5-6 kilometers), with heights reaching upwards of 2,000 feet (610 meters). One of the most famous shield volcanoes in the world is the Kilauea volcano in Hawaii.
4. Lava Domes
Lava domes, also called volcanic domes, are built from small, round masses of lava. These lumps of lava are too thick to flow any great distance. Instead, they pile on top of each other, forming a dome around the vent.
It further grows because the sides of the volcano split. When the surface of the lava cools and hardens, it causes a split. Pieces of the volcano then fall further down the sides.
Some lava domes develop sharp spines-like protrusions around the vent. Others called “couless” are short and steep sides of the volcano.
Domes are generally formed inside the craters or on the sides of larger composite volcanoes. Unlike larger volcanoes, lava domes are usually only a few hundred feet wide and tall.
How Are Volcanoes Formed?
Volcanoes are the source for the creation of over 80% of the surface of the earth. They have sustained the earth. The explosion of their magma has helped form mountains, craters, and fertile soil.
Volcanoes are found on every single continent on the planet. About 1,500 volcanoes are still active today.
So, as important as they are to our survival, you may be wondering how volcanoes are formed.
Composition of Magma
Volcanoes are formed from the lava or magma inside them, spilling up from the surface of the earth. What kind of volcano forms depends on the physical properties of the volcano. The major factors that determine how volcanoes develop are these:
- The thickness of the magma
- Very thick and sticky magma form steeper volcanoes
- Thicker magma is more likely to cause explosive eruptions
- How much gas is inside the magma
- The composition of the magma
- How the magma breaks the surface
The creation of a volcano is based on the “eruption” of magma from the center of the earth. Eruption is used in quotations here because not all volcanoes necessarily create an explosion. Some are formed through small spewings of magma from cracks in their surface.
Still, explosions, or flows of magma, create what is called a “caldera”, or the center dome of a volcano.
Before it comes to the surface, magma is found inside a “magma chamber”. The magma chamber is emptied during an explosion. This causes the roof of the chamber to collapse and form a dent within the surface of the earth. Calderas can be quite large, some spanning up to 10 miles (16 kilometers) across.
Calderas can also be formed when a large explosion occurs within a stratovolcano. This causes the tip of the volcano to literally be blown off.
If volcanoes are going to form, they need to be provided with the right conditions. The majority of volcanoes found in the world are found along the edges of tectonic plates. Tectonic plates are large slabs of rock under the earth’s surface. They shift and move, and are responsible for changing the landscape over time.
The collision of tectonic plates creates the formation of mountains and volcanoes.
The formation of volcanoes from these collisions is due to subduction. Subduction is the process of one plate sliding underneath the other as they collide. As this happens, the temperature and pressure surrounding the plates rises. Water is then forced from the rocks. The released water lowers the melting point of the topmost rock, creating magma.
When a large enough source of magma forms within the mantle, it will swell. The Swelling forces it through the surface of the earth. When magma reaches the surface of the earth, the creation of a volcano begins.
Not all volcanoes are formed from subduction, however. Some volcanoes are created from hot spots, or a section of earth with magmatic activity. These generally occur in the center of a tectonic plate rather than its edges. The hotspot will proceed to push its way through the earth’s crust, forming a volcano.
Hot spot volcanoes do not stop after the creation of one volcano. The hot spot changes position, crawling along the tectonic plate. When it finds another place to create a volcano, it does so. In this way, a line of volcanoes can be created rather close to one another. This is how the Hawaiian volcanoes were formed.
Volcanic Eruption Composition And Causes
- Buoyancy of the magma
- Pressure from gases
- New magma entering the magma chamber
Melted rock inside the earth is less buoyant than the surrounding rock. Less-buoyant rock builds up within the magma chamber. Then, it is pushed to the surface. When magma reaches the surface, it is then referred to as lava.
When magma is thin and watery, gases escape from it easily, so it is not likely to be explosive. Instead, it is more likely to just flow from the volcano.
If magma is sticky and thick, gases cannot escape. This causes pressure to build up within the magma and inside the earth. This causes an eventual explosion that is violent, and dangerous.
When new magma enters a magma chamber that is already full, the old magma will need a place to go. As it is pushed out by the new magma, it will eventually reach the earth surface and spill out.
Which Is More Dangerous?
The most dangerous volcanoes are usually found along the boundaries of tectonic plates. Mount St. Helens and Mount Pinatubo are two such volcanoes. Volcanoes formed from hotspots, like those in Hawaii, are usually much less dangerous.
Tephra & Mudslides
When the volcano explodes, it creates “tephra”. These are broken-up pieces of magma that fly through the air. Pieces of tephra can be as small as pebbles to as large as houses.
Leftover tephra from these explosions can cause mudflows. If the eruption occurs during snowfall or rainfall, dangerous mudflows form. They have the capability to bury entire buildings and communities.
Volcanic ash is not the same as the ash we think of when burning wood. It is far more destructive.
Ash from volcanoes is made from fragments of rocks and glass that are extremely sharp and less than 2 mm (0.002 m) in length. As sharp as it is, it’s obviously dangerous to inhale, but it is also extremely heavy. It can land on structures and build up quickly. This causes collapse and power outages.
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Is Climate Change Causing More Volcanic Eruptions?
Recent studies show that changes in the climate can have an impact on increasing volcanic eruptions.
The earth has gone through several periods of significant climate change. It has seen the coming and going of various ice ages. During periods of disappearing ice ages, the melting of glaciers increases the frequency and intensity of volcanic eruptions.
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Predicting Future Eruptions
Volcanic eruptions cannot be fully predicted. In fact, it’s impossible for scientists to even predict for sure if a volcano will erupt, let alone the day and time. Predictions have gotten better and scientists can more accurately determine if a volcano is likely to erupt.
Some common signs that may indicate a coming explosion include small earthquakes. You may also see swelling of the sides of the volcano and increased amounts of gas coming from the vents.
Today’s scientists look at the history of each individual volcano to determine a likely time of eruption. They even look at the volcano’s characteristics to predict what kind of eruption it will produce.
Scientists also monitor the volcano for seismic activity and deformations of the ground. These can both be indicators of a near eruption.
Some scientists look at a volcano’s previous eruption history to determine when it may explode next. However, this is not usually a good way to tell a volcano’s activity.
Volcanoes have been around for thousands of years, and we have not been able to study them. We’ve found that volcanoes are not consistent in their behavior.Just because they’ve acted a certain way in the past does not mean they’ll continue to do so in the future.
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Location of Volcanoes Around The World
The majority of the world’s volcanoes are located in the same area. They can be found around the edges of the Pacific Ocean. These edges of the Pacific Ocean make up what is called the “Ring of Fire”.
To give you more of a visual, the Ring of Fire forms a horseshoe shape about 25,000 miles (40,234 kilometers) long. It reaches around from the southernmost tip of South America. It goes across the west coast of North America to the Bering sea to Japan. Then it makes its way to New Zealand.
We learned earlier that most volcanoes form along the boundaries of tectonic plates. A large number of the world’s tectonic plates converge in the Pacific Ocean basin. Specifically, they are found at the edges of the Pacific, Cocos, and Nazca plates.
Earthquakes are extremely common around these plate boundaries. 80% of the world’s earthquakes occur in the Pacific Ocean basin. For the same reason, 75% of the earth’s volcanoes are formed in the same area.
Here is some activity that occurs along the Pacific Ring of Fire that causes volcanoes to form:
- The Middle American Trench has a subduction zone. It’s created volcanoes along Central America
- The Juan de Fuca plate is subducted underneath the North American plate. This formed the Cascade volcanoes
- The Pacific plate is subducted underneath the North American plate. This created the Aleutian Island Volcanoes
- The San Andreas Fault is a transform boundary. Two plates slide past one another, creating friction
Volcanoes In North America
North America is an abundant source of volcanoes. There are 169 volcanoes in the United States considered active by scientists. Many of these are found in Alaska. Others are found in Hawaii and along the Western coast of the country.
The Kilauea volcano in Hawaii is considered one of the most active volcanoes on the planet. It has erupted continuously since 1983.
Below, we’ve included a list of volcanoes in the United States and Canada. They are still considered active or have been active within the last 10,000 years.
- Alaska: 130+ volcanoes
- Arizona: 6 volcanoes
- California: 47 volcanoes
- Colorado: 3 volcanoes
- Idaho: 9 volcanoes
- Nevada: 9 volcanoes
- New Mexico: 12 volcanoes
- Oregon: 60 volcanoes
- Utah: 8 volcanoes
- Washington: 12 volcanoes
- Wyoming: 2 volcanoes
- Canada: 32 volcanoes
The United States has 10 percent of the world’s active volcanoes, more volcanoes than any other country in the world. There have only been two eruptions in the 20th century. These two eruptions include Lassen in 1915 and Mount St. Helens in 1980. Lassen is not even considered active today in the 21st century.
Most volcanoes in the United States and Canada are found along the west coast. They sit on the subduction zones of the Pacific and North American tectonic plates.
Most Destructive Volcanoes In History
Mount Tambora — Indonesia
The deadliest eruption in known history was the explosion of 1815 in Indonesia. The blast of Mount Tambora created a caldera of 4 miles (6 kilometers) long and 3,600 feet (1,097 meters) deep. It also created a plume full of hot ash that spewed 28 miles (45 kilometers) high into the sky.
The explosion was ranked as a “super-colossal” eruption. It was rated a 7 on the Volcanic Explosivity Index, the second highest rating. The explosion was so intense that the sound was heard 1,200 miles (19,312 kilometers) away.
10,000 people were killed from the initial explosion, but its destruction didn’t stop there. Volcanic ash filled the air, blocked the sun, and cooled the earth. The event was so dramatic that it was known as the “year without a summer”.
The harmful particles of ash caused people to develop disease. The cold temperatures made people starve. As a result, 82,000 more people died.
Mount Vesuvius — Pompeii, Roman Empire (Italy today)
Mount Vesuvius lives in what is now known as Naples, Italy. It is a stratovolcano that completely buried the towns of Pompeii and Herculaneum of the Roman Empire in A.D. 79. It killed thousands of people in a matter of hours. The volcanic ash was so thick that it preserved bodies and structures throughout the town.
This volcano is considered one of the most dangerous in the world. 3 million people currently live near it, and the volcano last erupted in 1944.
Mount St. Helens — Washington State, United States
Mount St. Helens is less than 100 miles (161 kilometers) from Seattle, Washington. It is one of the most active volcanoes in the United States. In May of 1980, it exploded with a blast that killed 57 people and caused damage over tens of miles. 520 million tons of ash were blown to the east. It caused complete darkness in Spokane Washington, a town 250 miles (402 kilometers) from the volcano.
Is There A Volcano Under Yellowstone National Park?
In short, yes, there is a volcano under Yellowstone National Park. It is a supervolcano known as Yellowstone Caldera or Yellowstone supervolcano, capable of producing destruction were it to ever erupt again. But will it ever erupt? Should we be worried?
How It Formed
Yellowstone’s volcano is made of rocks from the Precambrian period. These date to about 4.6 billion to 541 million years ago. The Cenozoic era came next which includes the last 66 million years of history. Mountains, volcanoes, glaciers, and faults began to form around the area of Yellowstone.
16.5 million years ago, volcano creation exploded. Volcanoes began popping up along the borders of Nevada, Oregon, and Idaho. About 2.1 million years ago, the North American plate began to shift. This moved the Yellowstone area closer to a shallow source of magma.
Magma remained close to the surface of the Yellowstone area. Two separate magma chambers formed near the surface of Yellowstone. These chambers were made out of partially molten and solid rock.
The First Explosion
The area saw an increase in earthquakes because of the expansion of the earth’s crust. This expansion was caused by the rise and fall of the magma. This increased stress in the earth’s surface created more earthquake activity and new faults.
Once the faults reached the magma chamber, the faults began to ooze magma. With this oozing came the escape of gases, causing the volcano to erupt in a massive explosion. The eruption produced a lot of volcanic ash along with pyroclastic flow.
The rock began to collapse and created Yellowstone’s first caldera. The explosion was so large that volcanic ash covered 5,790 square miles (1.5 square meters) of land. It reached as far as what is now Missouri.
Two smaller eruptions occurred 1.3 million years ago and 631,000 years ago. They created the two more recent calderas. 80 eruptions have occurred since then. They created the West Thumb of Yellowstone Lake, and partially filled the caldera floor and surrounding landscape.
Will the Yellowstone Supervolcano Erupt Again?
A significant amount of ground deformation has been recently noted. The deformation runs along the caldera between Old Faithful and White Lake in the Pelican Valley.
Surveys performed in 1985 noticed an alarming amount of ground lift in the caldera. The land had expanded over 3 feet (0.9 meters). Since then, it went through a few phases of lifting and sinking. Eventually, it reached an uplift of 10.6 inches (27 centimeters) between 2004 and 2010. The caldera has since begun to sink again.
Although these changes have been significant, it is not necessarily cause for alarm. Calderas can go through periods of lifting and sinking for thousands of years without an eruption occurring.
It is extremely likely that Yellowstone’s volcano will produce another devastating eruption. However, it’s not likely to happen anytime within the next several hundred years. More likely, an eruption will occur several thousand to millions of years from now.
The most likely scenario we could experience in our lifetime is a slow lava flow. It would trickle across the landscape over a period of months or years. In this event, people and animals will have time to evacuate and relocate before any major damage is done.