What is the cooling history of basalt?
Basalt (UK: /ˈbæs. ɔːlt, -əlt/; US: /bəˈsɔːlt, ˈbeɪˌsɔːlt/) is an aphanitic extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon.
Which cooled faster granite or basalt?
Basalt weathers faster than granite because it is not as hard and it’s easier for outside substances to impact and manipulate its structure.
What is the cooling history of granite?
The large mineral crystals in granite are evidence that it cooled slowly from molten rock material. That slow cooling had to have occurred beneath Earth’s surface and required a long period of time to occur. Many of the grains in this rock can be seen with the unaided eye – especially the black grains.
Is basalt a porphyry?
Tholeiitic basalt has fine-grained porphyritic texture, characterized by Pyroxene/Plagioclase phenocrysts (Fig. 2.12) in a fine glassy groundmass.
Is andesite fast or slow cooling?
Andesite and diorite are common rocks of the continental crust above subduction zones. Slow cooling facilitates the growth of large mineral crystals in the rock. Andesite is a fine-grained rock that forms when the magma erupts onto the surface and crystallizes quickly.
Where is basalt most commonly found?
It is found all over Earth, but especially under the oceans and in other areas where Earth’s crust is thin. It formed in the Isle Royale-Keweenaw region because of the Midcontinent Rift. Most of Earth’s surface is basalt lava, but basalt makes up only a small fraction of continents.
Why does basalt cool quickly?
Basalt is extrusive. The magma from which it cools breaks through the crust of the earth and erupts on the surface. Because the magma comes out of the earth (and often into water) it cools very quickly, and the minerals have very little opportunity to grow.
Is basalt heavier than granite?
According to About.com the density of granite ranges from 2.6-2.7 g/cm3 and basalt is 2.8-3.0 g/cm3. Granite contains lots of quartz and feldspar – both fairly light minerals, whereas basalt and gabbro are made of heavier minerals.)
What is the cooling rate of granite?
73%
Igneous rocks are formed by the crystallisation of a magma. The difference between granites and basalts is in silica content and their rates of cooling. A basalt is about 53% SiO2, whereas granite is 73%. Intrusive, slowly cooled inside the crust.
Is basalt a Equigranular?
An equigranular material is composed chiefly of crystals of similar orders of magnitude to one another. Basalt and gabbro commonly exhibit an equigranular texture.
Is granite a porphyry?
In terms of its mineral content this is a typical granite, consisting of pink potassium feldspar, cream sodium feldspar (plagioclase), grey quartz and black biotite mica. This texture, of large well-formed crystals in a finer matrix, is called porphyritic. …
Is pumice fast or slow cooling?
PUMICE – cooled down very fast from lava and has vesicles that indicate that gases were escaping from the rock – microscopic crystals. OBSIDIAN – also cooled down very fast from lava and that is why the glassy appearance with no crystals.
How are phenocrysts embedded in porphyry igneous rocks?
Porphyritic texture is a very common texture in igneous rocks in which larger crystals (phenocrysts) are embedded in a fine-grained groundmass. Porphyry is an igneous rock that contains larger crystals (phenocrysts) in a fine-grained groundmass. K-feldspar phenocrysts in this sample. Width of view 7 cm. TUG 1608-2807.
What kind of texture does a porphyry rock have?
Porphyry is an igneous rock characterized by porphyritic texture. Porphyritic texture is a very common texture in igneous rocks in which larger crystals (phenocrysts) are embedded in a fine-grained groundmass.
What kind of cooling history does an igneous rock have?
Some igneous rocks have a complex cooling history that results in them containing grains of distinctly different crystal sizes. These rocks, with large crystals (known as “phenocrysts”) suspended in a matrix of fine crystals (known as “groundmass”), often have a cooling history similar to the following description:
How are the crystal grains of porphyry formed?
Porphyry deposits are formed when a column of rising magma is cooled in two stages. In the first stage, the magma is cooled slowly deep in the crust, creating the large crystal grains with a diameter of 2 mm or more.