1. Examples of extrusive rocks include basalt, rhyolite, andesite, obsidian and pumice. 2. Over large areas extrusive rocks lie in flat undisturbed piles on a Cenozoic surface of moderate relief. 3. Torfaj�kull last erupted in 1477 and consists of the largest area of silicic extrusive rocks in Iceland. 4. Over large areas extrusive rocks lie in flat undisturbed piles on a Tertiary surface of moderate relief. 5. Many of the extrusive rocks and some of the Pseudoleucite is an abundant constituent of many of the igneous rocks. 6. Rhyolite is the same as granite chemically; however it is an extrusive rock , whereas granite is an intrusive rock. 7. In contrast, an " extrusion " consists of extrusive rock ; rock formed above the surface of the crust. 8. Because extrusive rocks make contact with the atmosphere they cool quickly, so the minerals do not have time to form large crystals. 9. From 1951 to 1954, Coats was engaged in the search for radioactive granitic rocks, and in field studies of rhyolitic extrusive rocks . 10. Intrusions are one of the two ways igneous rock can form; the other is extrusive rock , that is, a volcanic eruption or similar event.
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