Have you ever wondered why do earthquakes often happen near volcanic regions?
Generally, the pressure of magma accounts for most earthquakes near a volcano.
The magma finds an escape route through cracks in the rock, creating a small earthquake and renewing the pressure.
As a volcano’s magma chambers slowly fill, the rock above that chamber slowly builds up more and more pressure. The rock slowly gives way to this pressure when the section is full, cracking and releasing the magma into the chamber.
After a time, the process repeats itself. Each time the volcano cracks, it causes an earthquake.
Types of Earthquake
To understand why volcanic regions are prone to earthquakes, it’s best to know the various types and classifications of earthquakes.
Volcanic Earthquakes
Volcanic earthquakes occur when magma moves underground before an eruption.
In 1883, volcanic explosions caused a massive tsunami that struck the shore of Java, and in 1968, Etna volcano’s eruption was accompanied by a swarm of earthquakes that rattled southern Italy.
Tectonic Earthquakes
Tectonic earthquakes occur when rock blocks in the Earth’s crust shift, causing faults.
These shifts can be very small or large, resulting in magnitude 2 or 5 earthquakes.
The 1906 earthquake in California and the 1923 earthquake in Sagami Bay, Japan, were tectonic earthquakes.
Isostatic Earthquakes
Isostatic earthquakes are an example of Earth’s self-stabilizing behavior:
When the tectonic plates that makeup Earth’s surface push up against each other, intense pressure on Earth’s subsurface layer results.
If one of these plates slips, weight is released, and the mantle can flow freely again. This is what causes an isostatic earthquake.
Plutonic Earthquakes
Plutonic rock refers to a broad range of igneous rocks cooled and solidified from magma or molten rock.
Plutonic earthquakes usually occur at depths of 240 to 670 km (150 to 400 miles) and often result from the movement of tectonic plates along deep fault lines.
Earthquakes and Volcanoes Relation
Earthquakes and volcanoes are the results of tectonic plates in motion. Most earthquakes occur between two converging or diverging plates, where one plate moves under another.
As the plates converge, a break in the crust forms over which earthquake-producing stress builds.
Because of this stress, an earthquake occurs when the rock along the fault breaks suddenly.
Diverging plates often produce volcanoes because magma from the mantle rises through a crack between the leaves to form a volcano on land or sea.
Fact: The dynamite used for blasting in dams is a major contributing factor in earthquakes.
Earthquakes and Plate Boundaries
When two plates collide, the heavier will sink beneath the other into the Earth’s mantle.
This creates a mountain range and possibly ignites volcanic activity as well.
When one plate is heavier than the other, it can cause subduction and build a mountain range, but when both plates weigh about the same amount, there is no subduction, and only an earthquake occurs.
So why are volcanoes often in areas prone to earthquakes?
There are times when two plates crush together like cars in a fender-bender, which builds a mountain range with no volcanic activity involved.
During this process, only earthquakes occur.
The Himalayas
The collision of the Indian and Eurasian plates formed the Himalayan mountain range in Asia.
The tremendous strain created by these colliding plates is relieved along transform (strike-slip) faults.
Strike-slip faults are characterized by little or no volcanic activity, mountain building, or earthquake activity.
Note: Earthquakes can be hazardous to nearby populations because they tend to produce destructive earthquakes.
Tsunamis, Earthquakes, and Volcanic Activity
Tsunamis are giant waves that can travel over 600 miles on the open ocean and up to 150 miles per hour along the shore.
Earthquakes along the ocean floor, volcanic eruptions, and landslides are the most common causes of tsunamis.
Water Displacement
An earthquake or volcanic eruption causes the ocean floor to rise, displacing a huge amount of water.
This movement also creates a bulge in the ocean floor, traveling at high speed outward toward the sea surface.
Meteorite impacts, underwater explosions, and even tidal waves due to gravitational changes caused by other celestial bodies (like the moon or sun) may also cause tsunamis in certain circumstances.
Fact: Tsunamis have been known to wipe out entire coastal towns due to their enormous wave height, reaching over 100 feet (30 meters) tall.
Can Earthquakes Cause Volcanic Activity
When studying earthquakes, volcanoes, and why do earthquakes often happen near volcanic regions; scientists often make exciting discoveries.
For example, volcanic areas are more prone to earthquakes, but the inverse is true.
It is, therefore, true that volcanoes sometimes erupt after a big earthquake. They react to stress changes in the Earth’s crust.
The molten rock cools soon after an eruption, and this causes the internal pressure within the volcano to suddenly decrease.
The surrounding rock may then collapse into space, making room for the magma to rise again.
Distribution of Earthquakes
Most of the world’s earthquakes occur in a mountainous region lying about 25 degrees north and south of the equator.
Ring of Fire
An estimated 68 percent of all earthquakes occur within the Pacific Ocean’s “Ring of Fire,” stretching from New Zealand to Chile.
The ring is formed by several tectonic plates that meet in subduction zones.
One plate slides under another and sinks into the mantle, creating volcanic activity and earthquakes.
This “subduction” causes stress to build up on nearby plates, leading to frequent seismic activity.
While most quakes hit Japan and Chile, California has also been hit hard by tsunamis in recent years (e.g., 1942 and 1993).
Mountainous Region
About 21% of the world’s earthquakes occur in a mountainous region that is found in the mid-latitudes across the equator.
This region follows a belt that stretches from Mexico through the Atlantic Ocean, the Mediterranean Sea, and part of India and Asia.
Himalayan Mountains in Asia–which run along the same belt–are also seismically active. These earthquakes are felt throughout India and Asia.
Effects of Earthquakes Caused by Volcanic Activity
Structural Failure after Ground Shaking
Earthquakes can create hazardous conditions, including liquefaction, landslides, and ground shaking.
The ground shaking associated with earthquakes has the greatest destructive potential because the vibrations often cause buildings and other structures to collapse.
Surface Rupture
The main earthquake hazard is the surface rupture of the Earth’s crust.
This can be caused by either vertical or horizontal movement on either side of the fault that has been ruptured.
The ground displacement (the shift in one piece of ground relative to another) can damage structures, roads, railways, pipelines, and other infrastructure.
Fires
Facts about earthquake damage show that fires are the second most common hazard following the actual earthquake.
Electrical and gas lines can be dislodged when the Earth shakings rattle buildings.
Minor vibration may not disrupt these utilities, but a severe shock can release natural gas, then ignited by a nearby spark.
Landslides
When earthquakes occur, nearby areas with weak sandy soils are frequently devastated by landslides, debris, and debris that collide with people and animals, as well as buildings and utility lines.
These landslides can block roads and leave entire communities without power.
Liquefaction
Earthquakes can shake loose soil to such an extent that it turns into a flowing liquid.
This phenomenon is known as liquefaction, and it can undermine the foundations of buildings and other constructed structures, causing them to sink into the ground or dissolve altogether.
Final Thought
The answer to why do earthquakes often happen near volcanic regions lies in the tectonic activities that occur beneath the Earth’s surface, causing disturbances that then create volcanoes.
While earthquakes can be very destructive and devastating, the volcanic activities causing them can be beneficial.
In some places, new lava flow acts as a catalyst for soil enrichment.
For example, regions buried by ash blown from volcanoes over thousands of square kilometers can produce fertile soil beds.
Plants can then take root and eventually have food. Rainfall is the crucial factor; if enough rain falls on the new lava flows shortly after they form, the land recovers quickly.
