Illustrated Volcano Glossary
- VolcanologySmall spherical balls of volcanic ashAccretionary lapilli are small spherical balls of volcanic ash that form from a wet nucleus falling through a volcanic ash cloud. They can flatten on hitting the ground or may roll on loose ash and grow like a snowball. -> See whole entry
- VolcanologyAndesite is a gray to black volcanic rock with between about 52 and 63 weight percent silica (SiO2). Andesites are typical for lava domes and stratovolcanoes.Andesite is an igneous, volcanic rock, of intermediate composition, containing between about 52 and 63 weight % silica (SiO2).
Andesites contain crystals composed primarily of plagioclase feldspar and one or more of the minerals pyroxene (clinopyroxene and orthopyroxene) and lesser amounts of hornblende. At the lower end of the silica range, andesite lava may also contain olivine. Andesite magma ... -> See whole entry
- Volcanology:volcanic ashVolcanic ash is the term for all fine-grained volcanic products (smaller than 2 mm), normally magma or older rock fragmented during explosive eruptions.Volcanic ash has nothing to do with fire, but is a mere definition of grain-size. Ash can range in size from sandy to extremely fine; any fragment ejected by a volcano less than 2 mm in diameter is called ash. It may consists of freshly ejected lava (usually turned into a glass shard because of rapid cooling), older fragmented rock, or small crystals.
Ash is produced by explosive activity when ex... -> See whole entry
- Volcanology:volcanic ash fallVolcanic ash fall is the deposition of ash from the air from eruption plumes emitted during explosive volcanic eruptions.
Related keywords (1):ash