| Basalt | Andesite | Rhyolite | |
|---|---|---|---|
| Appearance under miscroscope |  |
 |
 |
| Magma properties | High temperature (1,200ºC) Silica-poor Low viscosity Low gas content |
Moderate temperature (800–1,000ºC) Moderate silica content Moderate viscosity Moderate gas content |
Low temperature (750–850ºC) Silica-rich Very high viscosity High gas content |
| Dominant eruption type | Flowing | Flowing and moderately explosive | Very explosive |
| Dominant eruption products | Thin lava flows, forming shields Scoria cones and craters |
Thick, rubbly lava flows Scoria/pumice and ash fall |
Pumice and ash fall Ignimbrite (pyroclastic flow) Lava flows when magma is low in gas |
| Dominant volcano type | Volcanic field | Stratovolcano (volcanic cone) | Caldera |
This table summarises the properties of the three major magma types: basalt, andesite and rhyolite. The photographs show what the cooled magma (volcanic rock) looks like under the microscope.
Using this item
Te Ara - The Encyclopedia of New Zealand
Photographs by Richard Smith, University of Waikato
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Comments
28 March 2014