Rhyolite how is it formed

If rhyolitic magma is rich in gases, it can erupt explosively which will solidify quickly forming pumice. Certain times extremely porous rhyolite lava flows occur and such flow allow degassing and subsequent collapse of lava which forms obsidian.

Rhyolite can be considered as the extrusive equivalent to the plutonic granite rock, and consequently, outcrops of rhyolite may bear a resemblance to granite. Due to their high content of silica and low iron and magnesium contents, rhyolite melts are highly polymerized and form highly viscous lava. They also occur as breccias or in volcanic plugs and dikes. Rhyolites that cool too quickly to grow crystals form a natural glass or vitrophyre, also called obsidian.

Slower cooling forms microscopic crystals in the lava and results in textures such as flow foliations, spherulitic, nodular, and lithophysal structures.

Some rhyolite is highly vesicular pumice. Eruptions of rhyolite are relatively rare compared to eruptions of less felsic lava. Only three eruptions of rhyolite have been recorded since the start of the 20th century: at the St. Eruptions of granitic magma can produce rhyolite, pumice , obsidian, or tuff. These rocks have similar compositions but different cooling conditions.

Explosive eruptions produce tuff or pumice. Effusive eruptions produce rhyolite or obsidian if the lava cools rapidly. These different rock types can all be found in the products of a single eruption. They are usually reddish-purple, and sometimes gray. They are very hard to break with a hammer and contain quartz and feldspar crystals. The mystery of the origin of rhyolite rocks in San Diego can be explained keeping in mind the concept of geologic time, and earth processes that take place over millions of years.

Red rhyolite rocks found today on San Diego beaches actually had their origin over miles away in the mountains of Sonora, Mexico. How did they end up here? The minerals form when lava cools so quickly that gas becomes trapped, forming pockets called vugs. Water and gases make their way into the vugs. Over time, gem-quality minerals form. These include opal, jasper, agate, topaz, and the extremely rare gem red beryl "red emerald". Actively scan device characteristics for identification.

Use precise geolocation data. Select personalised content. Create a personalised content profile. Measure ad performance. Select basic ads. Create a personalised ads profile. Select personalised ads. Apply market research to generate audience insights. Measure content performance. Develop and improve products. List of Partners vendors. Share Flipboard Email. Anne Marie Helmenstine, Ph. When rhyolite erupts quietly it forms lava flows.

If it erupts explosively it often forms pumice. Rhyolite forms from magma that contains lots of silica quartz and is the fine-grained equivalent of granite. Discover the unique landscape of the British Isles with our interactive Geology Toolkit, featuring a geology timeline, rock analyser, rock cycle, landscape features and safety tips. We invite you to discuss this subject, but remember this is a public forum. Please be polite, and avoid your passions turning into contempt for others.

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