are mafic rocks intrusive or extrusive?
312153
Some examples are: Andesite/dacite (extrusive) and diorite/granodiorite (intrusive). Mafic rocks have low silica content (45-55%). They are usually dark-colored and contain iron and magnesium. Some examples are: Basalt (extrusive) and gabbro (intrusive).
620695
Porphyritic rocks may be aphanites or extrusive rock, with large crystals or phenocrysts floating in a fine-grained groundmass of non-visible crystals, as in a porphyritic basalt, or phanerites or intrusive rock, with individual crystals of the groundmass easily distinguished with the eye, but one group of crystals ...
940381
Basalt is a volcanic or extrusive igneous rock, meaning it has cooled at or near the surface, resulting in rapid cooling and the formation of small crystals. Granite, on the other hand, is a plutonic or intrusive igneous rock, meaning it cooled at depth, much more slowly, resulting in the formation of larger crystals.
845672
Extrusive igneous rock forms when molten rock comes to the surface (lava) and cools quickly to produce fine-‐grained rocks. Intrusive igneous rock forms when molten rock solidifies underground and cools slowly to produce coarse-‐grained rocks.
206632
Aphanitic (a = not, phaner = visible) rocks, in contrast to phaneritic rocks, typically form from lava which crystallize rapidly on or near Earth's surface. When extrusive rocks make contact with the atmosphere they cool quickly, so the minerals do not have time to form large crystals.
353470
When the magma solidifies within the earth's crust, it cools slowly forming coarse textured rocks, such as granite, gabbro, or diorite. The central cores of major mountain ranges consist of intrusive igneous rocks, usually granite.
278834
The Maria are mostly composed of dark basalts, which form from rapid cooling of molten rock from massive lava flows. The Highlands rocks are largely Anorthosite, which is a kind of igneous rock that forms when lava cools more slowly than in the case of basalts.
941110
Rock and Mineral Type Certain types of rock are very resistant to weathering. Igneous rocks, especially intrusive igneous rocks such as granite, weather slowly because it is hard for water to penetrate them. ... Rocks that resist weathering remain at the surface and form ridges or hills.
1287313
['Sills: form when magma intrudes between the rock layers, forming a horizontal or gently-dipping sheet of igneous rock. ... ', 'Dykes: form as magma pushes up towards the surface through cracks in the rock. ... ', 'Batholiths:']
89328
Igneous rocks can become foliated by alignment of cumulate crystals during convection in large magma chambers, especially ultramafic intrusions, and typically plagioclase laths. Granite may form foliation due to frictional drag on viscous magma by the wall rocks.
261247
Igneous rocks are formed from the solidification of molten rock material. ... Examples of intrusive igneous rocks are diorite, gabbro, granite, pegmatite, and peridotite. Extrusive igneous rocks erupt onto the surface, where they cool quickly to form small crystals. Some cool so quickly that they form an amorphous glass.
35373
1) Lava flows are typically finer grained than intrusive igneous rocks. Why? ... Intrusive magma flows onto the Earth's surface and cools very slowly, allowing many small mineral grains to grow. C) The extrusive magma cools quickly so the mineral grains do not have time to grow.
15071
Glassy igneous rocks form when magma cools too fast for mineral grains to grow. Basalt is the aphanitic or fine-grained equivalent of gabbro. Plutonic rocks are intrusive and generally consist of mineral grains coarse enough to be readily visible in a hand sample.
882091
In general, the more felsic the magma the greater the volatile content. So mafic/basaltic volcanoes are fairly quiescent, intermediate/andesitic volcanic eruptions are moderately explosive, and felsic/rhyolitic volcanoes may be extremely explosive.
1127498
Mafic lava creates basalt while felsic lava produces andesitic and rhyolite rocks. ... Either in describing rocks or lava, mafic means that the lava or rock has less silica while felsic implies that the lava or rock has the most silica. 6. Mafic rocks are darker in color than felsic rocks.
1368285
Answer and Explanation: Basalt is not a sedimentary rock. It is actually an igneous rock formed from cooled, melted rocks. In fact, basalt is classified as an extrusive...
515213
Rocks composed mostly of hornblende and intermediate plagioclase feldspars make up the intermediate family of igneous rocks. Intermediate magmas are somewhat more viscous than the mafic magmas. Additionally, they contain somewhat more gas than do the mafic magmas, but not quite as much as the felsic magmas (see below).