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How are volcanoes and earthquakes interrelated?

Both volcanoes and earthquakes occur due to movement of the Earth’s tectonic plates. They are both caused by the heat and energy releasing from the Earth’s core. Earthquakes can trigger volcanic eruptions through severe movement of tectonic plates. Similarly, volcanoes can trigger earthquakes through the movement of magma within a volcano. Therefore, one aspect of how are volcanoes and earthquakes interrelated is the cyclical relationship where earthquakes cause volcanic eruptions and magma movement causes earthquakes.

Earthquakes and volcanic eruptions in itself are dangerous natural phenomena which poses risk to humans. Furthermore, tsunamis are an equally deadly secondary effect caused by underwater disturbances such as earthquakes, volcanic activity, landslides, underwater explosions or meteorite impacts which pose significant danger to human lives.

What are tectonic plates and how do they explain volcanoes and earthquakes?

The outer layer of the Earth is made up of solid rock, called lithosphere. The lithosphere is broken up into 17 major separate pieces that fit together like a bad jigsaw puzzle. A piece of the puzzle is called a tectonic plate. The plates are horribly placed, with overlapping pieces, gaps, and are forced to fit with each other even when they don’t. Because the tectonic plates don’t go well together, it creates earthquakes and volcanic activity when two plates collide, diverge or slide past each other.

Tectonic Plates
tectonic plates Image: United States Geological Survey
public domain

There are three types of boundaries caused by tectonic plates on Earth: first, transform boundaries when two plates slide or grind past each other. Transform boundaries are horizontal movements of plates and do not create or destroy plates. Second, divergent boundaries when two plates create a gap in between each other. Divergent boundaries create ocean basins when plates move apart from one another. Third, convergent boundaries when two plates crash towards each other and overlap to form a subduction zone.

Tectonic plates are extremely large and can encompass both land and ocean. These tectonic plates interact with one another because of the Earth’s internal heat. This heat causes movement of material beneath the Earth’s crust and releases energy in the form of earthquakes and volcanic eruptions. Interactions between the tectonic plates occurs in three main places: first, oceanic-continental convergence, where the continent meets the ocean. Second, continental-continental convergence, where two continents meet. Last, oceanic-oceanic convergence, where two oceans meet.

So, how are volcanoes and earthquakes interrelated? Both volcanoes and earthquakes are caused along the boundaries of tectonic plates due to their movements and interactions.

How dangerous are volcanoes and earthquakes to humans?

How many deaths there are and how severe a natural disaster is depends on the interactions we have as humans with our environment. A strong earthquake can be completely overlooked if it happens in the middle of land where hardly any people live in, for example in December 2003, when a 6.5 magnitude earthquake in Central California killed two people. Consequently, a similar earthquake in a densely populated metropolitan area can cause many deaths, injuries and destruction of property, for example, a 6.6 magnitude earthquake in Bam, Iran killing 30,000 people, injuring 30,000 more and destroying 85% of property.

The same goes for volcanic eruptions, if an underwater volcano erupted in the middle of the ocean, it would have little impact to humans living far inland. However, if the volcano had been dormant for a significant amount of time and humans started populating the land close to the base of a volcano it would be devastating should it ever erupt. Further, indirect consequences of a volcanic eruption can have a greater impact than the eruption itself. For example, volcanic ash can induce climate change that have serious agricultural, economic, and sociological impacts on people’s lives.

Read these articles to learn more about the structure of the volcano and the internal structure of the volcano.

To find out more about where the next volcano will erupt in Australia, read this article.

Tsunamis as a result of earthquakes or volcanic activity

Tsunamis are giant waves that occur when a large volume of water is displaced. The most common causes of underwater disturbances that lead to tsunamis are earthquakes and volcanic eruptions, especially because most volcanoes are underwater. Although tsunamis can also be caused by landslides, meteorite impacts and underwater explosions. Tsunami waves travel extremely fast, with wave speeds reaching up to 900 km/h in deep water. The waves get taller the closer they reach the shoreline because of rapidly decreasing depth of the sea floor, and slow down to 20 – 50 km/h.

tsunami Image: Sadatsugu Tomizawa
creative commons