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Plate margins and plate tectonics - OCRGlobal earthquake and volcano distribution

Earthquakes and volcanic eruptions affect people all over the world. They are caused by the movement of tectonic plates. There are different types of plate margins where plates interact.

Part of GeographyGlobal hazards

The global distribution of earthquakes and volcanoes

Earthquakes are found along all types of .

[A] Most earthquakes happen along fault lines. [B] Most volcanoes appear on plate boundaries.

Earthquakes caused at plate margins can have either a deep-focus or shallow-focus. The focus of an earthquake is the actual place in the crust where an earthquake is created.

The focus is the underground point on the fault line from which the seismic waves radiate from. The point on the surface directly above is the epicentre.

Shallow-focus earthquakes are more destructive because they make the ground shake more at the surface. For example, the 2021 Haitian earthquake's focus depth was only 10 km. It measured 7.2 on the Richter scale and it did tremendous damage. By contrast, the deep-focus 2022 Peruvian Earthquake, at a depth of 217.8 km, measured 7.2 on the Richter scale but was not intense at the surface.

Hotspots

Hotspots are stationary magma plumes deep in the Earth that create volcanoes on the surface (eg Mount Kilauea in Hawaii).

On a hotspot, magma comes to the surface through cracks in the rocks with great heat and low pressure. Hotspots can be linked to plate margins or may just form on a crustal plate.

A stationary magma plume forms in the mantle. Magma rises to the surface through the crust, forming a volcano. As the crust moves, and island string is created.
[A] Most earthquakes happen along fault lines. [B] Most volcanoes appear on plate boundaries.
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