Whenever a volcano acts up, earthquakes are one of the first signs. Why do earthquakes happen under volcanoes anyway? Save this story for later.

Tambora

1. Mt Tambora, Indonesia, 1815 (VEI 7) Mt.
2. Krakatoa, Indonesia, 1883 (VEI 6)
3. Laki, Iceland, 1783 (VEI6)
4. Mt Pelee, Caribbean, 1902 (VEI4)
5. Ilopango, El Salvador, 450AD (VEI6+)
6. Mt Unzen, Japan, 1792 (VEI2)
7. Nevado del Ruiz, Columbia, 1985 (VEI3)
8. Mount Pinatubo, Philippines, 1991 (VEI6)

Two types of volcanically generated earthquakes are volcano-tectonic (VTs) earthquakes and long period earthquakes (LPs). Please visit our volcano seismicity pages to learn about volcanic activity near our Cascade Volcanoes. Volcanic-tectonic earthquakes (VTs) are, simply put, caused by slip on a fault near a volcano.

There are many theories of what can trigger a volcano to erupt. Some are as simple as the buoyancy of magma — it is less dense than the surrounding rock, so it rises until it intersects the surface. This might be high levels of volcanic gases, shallow earthquakes, deformation of the volcano.

Volcanoes form at Earth’s surface whereas earthquakes originate from deeper within the crust. Volcanoes are formed by release of gas and magma. Earthquakes are caused by movement along a fault. Volcanoes lead to the formation of new rock whereas earthquakes simply cause waves which disturb the rock.

Volcanoes are usually less dangerous than other natural hazards such as earthquakes, tsunamis and hurricanes.

Mauna Loa

Tectonic plate movements are the primary cause of earthquakes. Volcanic eruptions can also trigger earthquakes but are often, in turn, caused by tectonic activity….The World’s 10 Most Earthquake Prone Countries.

These eruptions are so energetic that the magma is pulverized into small rock particles, called volcanic ash. The most dangerous features of these events are volcanic ash flows – swift, ground-hugging avalanches of searing hot gas, ash and rock that destroy everything in their path.

Volcanic hazards In this case, magma is shallow, and the heat and gases affect surface and ground water to form vigorous hydrothermal systems. The resulting steam-driven eruption, also called a hydrothermal or phreatic eruption, can happen suddenly and with little to no warning.

Notable precursors to an eruption might include: An increase in the frequency and intensity of felt earthquakes. Noticeable steaming or fumarolic activity and new or enlarged areas of hot ground. Subtle swelling of the ground surface. Small changes in heat flow.

After a volcano erupts, it can damage structures, change landscapes, kill plants or animals, hurt air quality, affect the water and cause climate change.

In theory, there is no limit on the number of volcanoes that could erupt at once other than the number of active volcanoes themselves: while it is thus theoretically thinkable, that all 600 volcanoes (on land) known to have had eruptions during recorded history erupt at once, this is so unlikely that it can be excluded …

The Ring of Fire is a string of volcanoes and sites of seismic activity, or earthquakes, around the edges of the Pacific Ocean.

seven weeks

How often do volcanoes erupt? Some small volcanoes only erupt once in their lives, while other volcanoes erupt multiple times. Kilaeua volcano in Hawaii, which has been erupting continuously since 1983, is the world’s most active volcano.