You are possibly looking for Caldera.
A saucer-shaped depression at the mouth of a volcano is called a volcanic caldera. Calderas are formed when a volcano collapses into the emptied magma chamber below, creating a large, basin-like crater.
Crater
The mouth of a volcano is called the "vent." This is the opening through which volcanic materials, such as lava, ash, and gases, are expelled during an eruption. Vents can vary in size and may occur at the summit or along the sides of the volcano. In some cases, the vent can lead to a crater, which is a bowl-shaped depression formed around the vent.
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.
I think its called the 'summit' Crater....
You are asking about the mouth.
Vent .
The opening top of the volcano is called a crater. The super-heated gases and ash billows out of the mouth of hell before the magma erupts out destroying all in its path.
the mouth of the volcano, or caldera.
volcano
the sperm whale has the third largest mouth
depression of the mouth