Feature formed from layers of ash and lava

A volcano is tall, cone-shaped, and made up of alternating layers of lava and ash. A wide, gently sloping mountain formed by thin layers of lava that pour out of a vent and harden on top of previous layers is known as a volcano. Ash, cinders, and bombs build up in a steep pile to form volcanoes.

I thought it was ash cinder and magma ... then the layer under that is bedrock as its formed under the ocean where constant volcanic heat forms the rock ... plus a bomb explodes when its atoms get accelerated and when gunpowder gets how you gonna have bombs in lava