Table of Contents
How do you tell basalt from andesite and rhyolite?
- Basalt is an extrusive mafic volcanic rock.
- Andesite is an extrusive volcanic rock with a composition that is intermediate between basalt and rhyolite.
- Rhyolite is an extrusive felsic (silicic) volcanic rock.
What are the differences between basaltic and andesitic rhyolitic magmas?
Basaltic magma is high in iron, magnesium, and calcium but low in potassium and sodium. It ranges in temperature from about 1000oC to 1200oC (1832oF to 2192oF). Andesitic magma has moderate amounts of these minerals, with a temperature range from about 800oC to 1000oC (1472oF to 1832oF).
Is andesite a basalt?
Andesite (/ˈændəzaɪt/) is an extrusive volcanic rock of intermediate composition. In a general sense, it is the intermediate type between basalt and rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende.
Is andesite a rhyolite?
Andesite is an extrusive rock intermediate in composition between rhyolite and basalt. Andesite lava is of moderate viscosity and forms thick lava flows and domes. The word andesite is derived from the Andes Mountains in South America, where andesite is common. Andesite is the volcanic equivalent of diorite.
Is andesite a basaltic?
Basaltic andesite is a volcanic rock that is intermediate in composition between basalt and andesite. It is composed predominantly of augite and plagioclase. Basaltic andesite can be found in volcanoes around the world, including in Central America and the Andes of South America.
What is rhyolite rock?
rhyolite, extrusive igneous rock that is the volcanic equivalent of granite. Most rhyolites are porphyritic, indicating that crystallization began prior to extrusion.
Is andesite a pyroclastic?
Andesite is a gray to black volcanic rock with between about 52 and 63 weight percent silica (SiO2). Andesite magma can also generate strong explosive eruptions to form pyroclastic flows and surges and enormous eruption columns. Andesites erupt at temperatures between 900 and 1100 ° C.
Is andesite less dense than basalt?
Sedimentary rocks (and granite), which are rich in quartz and feldspar, tend to be less dense than volcanic rocks….Rock Densities.
| Rock | Density |
|---|---|
| Andesite | 2.5–2.8 |
| Basalt | 2.8–3.0 |
| Coal | 1.1–1.4 |
| Diabase | 2.6–3.0 |
How is rhyolite formed?
Rhyolite is a volcanic rock. It is fine-grained because it forms by the rapid cooling of magma, usually when it erupts onto the Earth’s surface. When rhyolite erupts quietly it forms lava flows. If it erupts explosively it often forms pumice.