Tectonic activity and plate boundaries - EdexcelGlobal distribution of earthquakes and volcanoes
Earthquakes and volcanic eruptions affect people all over the world. They are caused by the movement of tectonic plates. Tectonic hazards can destroy buildings, infrastructure and cause deaths.
The Earth's surface is made up of two types of crust:
oceanic crustThe surface of the Earth's crust found underneath the oceans, forming the ocean floor. - found underneath the oceans. It is denser than the continental crust and can be subductionWhen one crustal plate is forced beneath the other.
continental crustThe surface of the Earth's crust found underneath large land masses. - found under land masses or continents. It is generally older than oceanic crust and is less often destroyed
Earthquakes are found along all types of plate boundaryThe region where two or more tectonic plates meet. It is a zone of intense seismic activity. (or margins) as shown on this map.
Volcanoes are also mainly formed at plate boundaries. There are some important exceptions. for example the Hawaiian Islands, which are entirely volcanic in origin, formed in the middle of the Pacific Ocean, more than 3,200km from the nearest plate boundary.
This is explained by the 'hotspot' theory, that there are fixed spots in the mantle where magma rises to the surface. As the crust moves over these fixed spots, volcanoes are created, eventually forming a chain of volcanoes.