global distribution of tectonics

where do earthquakes occur?

majority of earthquakes (about 95%) occur close to or at a plate boundary

what plate boundaries have the most powerful earthquakes?

most powerful earthquakes are usually associated with convergent or conservative plate boundaries

intra-plate earthquakes

those which do not happen at plate boundaries - these are often linked to hot spots or old fault lines

where do volcanoes occur

most active volcanoes occur at or near to plate boundaries, with many (about 75%) occurring around the 'ring of fire' surrounding the Pacific Ocean

what plate boundaries do volcanoes occur at?

convergent and divergent plate boundaries

tsunami distribution

over 70% of tsunamis occur around the Pacific Ocean

• 15% Mediterranean Sea, 9% Caribbean Sea and Atlantic Ocean, and 6% Indian Ocean

what are tsunamis caused by?

tectonic activity 

• most occur due to activity at convergent boundaries

plate boundaries

the locations where the tectonic plates meet

• due to the movement of the plates, these are areas where a range of processes take place

what are the three main types of plate boundary?

• divergent - plates moving apart

• convergent - plates moving together

• conservative (transform) - plates moving past each other or in the same direction at different speeds

divergent plate boundary

convergent plate boundary

conservative plate boundary

what are the three categories of convergent boundaries?

• oceanic - continental

• oceanic - oceanic

• continental - continental (also known as a collision boundary)

hotspots

volcanic eruptions that occur away from plate boundaries

intra-plate earthquakes

these can occur anywhere and the cause is not fully understood but is thought to be:

• tectonic stresses causing ancient fault lines to reactivate

• the plates are moving over a spherical surface and this causes zones of weakness

e.g. the new madrid earthquake in 1812 and the 2011 virginia earthquake are examples of intra-plate earthquakes

volcanic hotspots

these occur over stationary magma plumes (columns of rising magma) in the asthenosphere

• the tectonic plate moves over the plume leading to the formation of a chain of volcanic islands (Hawaii)

• the oldest island is the one furthest away from the plume