A stroke is a brain attack â a sudden interruption of blood flow to part of the brain causing it to stop working and eventually damaging brain cells. The effects can be devastating and may last a lifetime. A stroke is also known as a cerebrovascular accident (CVA). There are several different types of stroke, with different causes. Ischaemic stroke: This is the most common type of stroke, particularly in older people.
Examples of some deep ocean trenches that are subduction zones are off the West coast of South America, in the Peruvian Trench. The Aleutian Trench, in the North Pacific Ocean, and the deepest, most famous one in the world, the Marianas Trench off the coast of the Marianas Islands in the Southeast Pacific.
ocean trenches and ridges. Trench: very deep, elongated cavity bordering a continent or an island arc; it forms when one tectonic plate slides beneath another. Ridge: underwater mountain range that criss-crosses the oceans and is formed by rising magma in a zone where two plates are moving apart.