| |
USGS Photo Glossary: caldera |
 | | The caldera is 10 km in diameter and 500-1,000 m deep. |
 | | A caldera is a large, usually circular depression at the summit of a volcano formed when magma is withdrawn or erupted from a shallow underground magma reservoir. |
 | | Calderas are different from craters, which are smaller, circular depressions created primarily by explosive excavation of rock during eruptions. |
| volcanoes.usgs.gov /Products/Pglossary/caldera.html (340 words) |