The deepest part of the Atlantic Ocean is the Puerto Rico Trench off the coast of Puerto Rico
By Shadowxfox , CC BY-SA 4.0, Linkki
The deepest point of the Puerto Rico Trench is 8,648 metres. The trench exists because it is at the border of two tectonic plates: the North American plate and the Caribbean plate. The North American plate is moving towards the west and the Caribbean plate is moving towards the east. The North American plate is partly pushed under sideways be the Caribbian plate.
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There is a risk of earthquakes in the trench and thus tsunamis. A tsunami is caused by a sudden downward shift by a piece of the sea bottom resulting in a tall column of water suddenly moving downwards. The west of Puerto Rico was hit by a tsunami caused by a major earthquake in 1918. The trench is capable of producing earthquakes of a magnitude over 8.0.