A caldera may form on a volcano.
caldera
arc related caldera
caldera
isit possibly an iceberg or glacier?
No. A caldera is a type of geologic structure formed by the collapse of a volcano.
Caldera
Caldera
Caldera
isit possibly an iceberg or glacier?plateau
That is known as an "intrusion". The magma (lava) is forced under pressure into cracks and fissures within the older rock. There are some good examples of this type of formation in Yellowstone caldera.
a caldera
a stratovolcano with caldera a stratovolcano with caldera