Table of Contents
How does a dacite volcano form?
Dacite (/ˈdeɪsaɪt/) is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite.
How do you identify dacite?
Dacites consisting mostly of plagioclase and quartz are usually light in color, often white to light gray. Those with abundant hornblende and biotite can be light gray to light brown. The darkest dacites usually contain abundant augite or enstatite.
Is dacite intrusive or extrusive?
felsic extrusive rock
Dacite is a felsic extrusive rock, intermediate in composition between andesite and rhyolite. It is often found associated with andesite, and forms lava flows, dikes, and, in some cases, massive intrusions in the centres of old volcanoes. Dacite is the volcanic equivalent of granodiorite.
What is dacite lava?
Dacite lavas are viscous and tend to form thick blocky lava flows or steep-sided piles of lava called lava domes. Dacitic magmas tend to erupt explosively, thus also ejecting abundant ash and pumice.
What is the definition of dacite?
: an extrusive rock that is sometimes partly glassy and is composed of plagioclase and quartz with biotite, hornblende, or pyroxene.
How fast does andesitic lava flow?
Andesitic lava flows at a rate of a few kilometers per hour, whereas basaltic lava can flow up to 10 km/h. Because of their viscosity, andesitic lavas “rarely extend beyound 8 km from their vents”.
What kind of rock is dacite?
volcanic rock
dacite, volcanic rock that may be considered a quartz-bearing variety of andesite. Dacite is primarily associated with andesite and trachyte and forms lava flows, dikes, and sometimes massive intrusions in the centres of old volcanoes.
Can dacite be red?
Red dacite can be found in Lassen Volcanic at several sites; for example, in the Chaos Crater area at the end of Chaos Crags Trail. Also, along the Devasteted Area Trail you can touch a giant boulder of red dacit at the “Old Giants” interpretive exhibit.
What is dacite made of?
Like andesite, dacite consists mostly of plagioclase feldspar with biotite, hornblende, augite, or enstatite and generally has a porphyritic structure (scattered larger crystals in a fine-grained groundmass); additionally, however, it contains quartz as rounded, corroded crystals or grains, or as a constituent of the …
What type of lava flows the fastest?
Basaltic lava flows
Basaltic lava flows move much faster than rhyolitic lava flows. Also, the amount of gas dissolved in the lava can change the flows ability to flow (viscosity). The rate of material that the vent is spewing out. During some eruptions vast amounts of lava are released and so the flows tend to be faster.
What does andesitic lava form?
Andesite magma commonly erupts from stratovolcanoes as thick lava flows, some reaching several km in length. 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.
What is dacite magma?
Is dacite a mineral?
dacite, volcanic rock that may be considered a quartz-bearing variety of andesite. Dacite is primarily associated with andesite and trachyte and forms lava flows, dikes, and sometimes massive intrusions in the centres of old volcanoes.
What are the four types of lava flow?
There are mainly 4 different types of lava flows. This includes Pahoehoe, A’a, Blocky, and Pillow lava flow.
What is a dacite volcano?
Dacite. Volcanic rock (or lava) that characteristically is light in color and contains 62 to 69 percent silica and moderate amounts of sodium and potassium. Dacite lavas are viscous and tend to form thick blocky lava flows or steep-sided piles of lava called lava domes. Dacitic magmas tend to erupt explosively,…
What is the glossary of dacite?
Glossary – Dacite. Volcanic rock (or lava) that characteristically is light in color and contains 62 to 69 percent silica and moderate amounts of sodium and potassium. Dacite lavas are viscous and tend to form thick blocky lava flows or steep-sided piles of lava called lava domes.
Where is the source of the dacite lava?
The source of the dacite lava was the Nili Patera caldera visible in the southern portion of the lava flow. Small dacite flows can be seen in other parts of the image. The image width is about 10 miles (16 kilometers). Click to enlarge.
Is dacite a porphyritic rock?
It is often porphyritic. Dacite is found in lava flows, lava domes, dikes, sills, and pyroclastic debris. It is a rock type usually found on continental crust above subduction zones, where a relatively young oceanic plate has melted below.