A crater, caldera. Yellowstone National Park is one big caldera from at least three really big ones. (I've not been there since 1970, but the next one is really going to be a big one...again.)
caldera
If you are talking about the large crater created after a volcano errupts, then it would be a caldera. They are formed after the magma chamber is emptied, when the cone of the volcano collapses to fill the empty space.
mid-ocean ridge
When a volcano collapses a very wide crater is called a caldera.
A circular depression that forms when a magma chamber empties is called a caldera. It is a large volcanic crater made from the collapse of a volcano's mouth.
Underwater mountains that run through an ocean form a mid ocean ridge. They are found all over the ocean, the largest being the Mid Atlantic Ridge.
Its called a "caldera".
volcanic
Calderas form during massive explosve volcanic eruptions. In such eruptions so much material is expelled that it leaves a large empty space under the volcano. The volcano then collapses into this space, forming a giant crater.
seamounts
The chain of volcanic mountains in Central America is called the Central American Volcanic Arc. It extends from Guatemala through El Salvador, Honduras, Nicaragua, and Costa Rica, which are all part of the Pacific Ring of Fire.
Mountains formed by magma that reach the Earth's surface are called volcanic mountains or ridges.
If you are talking about the large crater created after a volcano errupts, then it would be a caldera. They are formed after the magma chamber is emptied, when the cone of the volcano collapses to fill the empty space.
The mid Atlantic ridge.
mid-ocean ridge
When a volcano collapses a very wide crater is called a caldera.
It is known as 'The Ring of Fire' sometimes called the circum-Pacific belt.
A circular depression that forms when a magma chamber empties is called a caldera. It is a large volcanic crater made from the collapse of a volcano's mouth.