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Generally, large crystals represent slow cooling rates and small crystals represent fast cooling rates. Crystals need time to form and since extrusive rocks cool very quickly, they have very tiny crystals and some don't even have crystals because the rate of cooling was so fast that crystals didn't have time to nucleate. On the other hand, intrusive rocks cool rather slowly allowing crystals to grow.

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Fast cooling causes smaller crystals to form than when the rocks cools slowly. An igneous rock that cooled quickly is basalt, while a slow-cooler is granite.

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Q: How does the crystal sizes of igneous rocks indicate the rate of cooling and whether the rock is extrusive or intrusive?
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Related questions

Is an intrusive crystal bigger than an extrusive crystal?

Yes. Bigger crystals=Intrusive. Smaller crystals=Extrusive.


How are intrusive rock different from with extrusive rocks?

Intrusive Rocks Intrusive rocks are characterized by large crystal that forms deep underground. Extrusive Rocks They are characterized by fine-grained textures because their rapid cooling at or near the surface.


How does the rate of cooling influence crystal size of igneous rocks and how does that help you to distinguish between intrusive and extrusive igneous rocks?

The longer that magma is able to cool, the larger the crystals will be. Intrusive rocks will have larger crystals than extrusive rocks. For example granite (intrusive) has larger grains than rhyolite (extrusive).


What size crystal do magma make?

it depends on if it is intrusive or extrusive (intrusive is below the earth and extrusive is at or above the earth) intrusive has a bigger crystal because it takes time to cool down.


Is lava intrusive or extrusive?

A pluton is intrusive, meaning that it is below ground. Other words to describe a pluton would be batholith or laccolith.


Why would you except the crystals in a intrusive rock to be larger than the crystals in a extrusive rock?

Minerals formed in intrusive rock cool more slowly than extrusive rock, which is closer to the surface. The longer cooling period allows more time for crystal formation.


What is the difference in crystal growth between intrusive and extrusive igneous rock?

The crystal growth of intrusive igneous is substantially more so than extrusive igneous. Magma cools quicker on the earth's surface, extrusive igneous formed, as opposed to below the crust, intrusive. Therefore the longer it takes to cool the magma, the more the crystal growth.


Which crystal can help identify as igneous rock as intrusive or extrusive?

What is the effect of location on crystal size? Label the location of intrusive and extrusive igneous rocks on the diagram below. Then, illustrate the crystal size of the rock formed at that location in the appropriate callout circles.


Write the difference between extrusive and intrusive igneous rocks?

igneous Extrusive is cool on the outside of the crust and cools quickly before crystal forms igneous Intrusive is cool on the inside of the crust and cools slowly and allowing crystal to form


What type igneous is pumice intrusive small crystal or extrusive large crystal?

It is neither. Pumice is an extrusive highly vesicular igneous rock composed of volcanic glass and very tiny mineral crystals.


Is graphite rock extrusive or intrusive?

GRAPHITE is a native mineral. It is metamorphic and it is effectively the highest grade of coal.


What relative cooling rates of igneous intrusive rocks can be estimated by comparing rocks?

Crystal