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Granite has a very similar chemistry to rhyolite. However, granite solidifies & crystallises in intrusions deep beneath the surface where the INSULATED environment results in the granite cooling slowly and therefore, having large crystals.
Rhyolite solidifies at the surface, generally directly from volcanic lava, where it cools very rapidly due to lack of insulation from contact with surface temperature rocks & air. As a result of its rapid cooling, it has very small crystals.
by aidan
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Why do some igneous rocks have big crystals or grains and some igneous rocks have small crystals or grains?
Igneous rocks with big crystals or grains form from slow cooling beneath the Earth's surface, allowing time for larger crystals to grow. In contrast, igneous rocks with small crystals or grains form from fast cooling at or near the Earth's surface, limiting the time available for crystal growth.
Name some rocks which have crystals?
All rocks have crystals, or at least crystalline structures. Sedimentary rocks may not have crystals as such, but the individual grains have internal crystal structures. All magmatic and metamorphic rocks have crystals, though they may be too small to be seen without the aid of a microscope. Only possible exception is Obsidian (volcanic glass) which may be amorphous.
Do rocks with small crytals form underground or above ground?
Rocks with small crystals form above ground, because when formed under ground the magma makes the rock cool slower causing more time for the crystals to grow. Above ground the rock cools faster, because the air isn't as hot under ground than above ground.
What is an igneous rock with small crystals?
If you're not looking for anything specific, any extrusive igneous rock will have smaller crystals, if any at all. This is because they cool quickly on the surface, leaving little time for crystals to form/grow.
What type of crystal are formed from in extrusive igneous rocks?
Extrusive igneous rocks form fine-grained crystals due to rapid cooling at Earth's surface, resulting in minerals like basalt, andesite, and rhyolite. These rocks cool quickly, preventing the formation of large crystals typically found in intrusive igneous rocks.
What are Igneous rocks that have large crystals and small crystals?
Igneous rocks with large crystals are called intrusive rocks, formed from magma cooling slowly beneath the Earth's surface, allowing for large crystals to form. Igneous rocks with small crystals are called extrusive rocks, formed from lava cooling quickly on the Earth's surface, resulting in small crystals due to rapid cooling.
Do igneous rocks have small crystals large crystals or no crystals?
Igneous rocks can have both small and large crystals, depending on how quickly they cool. If an igneous rock cools slowly beneath the Earth's surface, it can form large crystals, while rapid cooling at the Earth's surface or in an eruption can result in small or no visible crystals.
Where would you expect to find an igneous rock with small crystals?
You would expect to find an igneous rock with small crystals near the Earth's surface where the rock cools relatively quickly, such as in volcanic eruptions or magma intrusions that do not have much time to grow large crystals. These rocks are known as volcanic or extrusive igneous rocks.
Do extrusive rocks cool quickly?
Extrusive rocks do cool quickly because either the crystals in the rock are very small or there are no crystals at all.
Some WHAT igneous rocks have individual mineral crystals that are too small to be seen without magnification?
Aphanitic igneous rocks have individual mineral crystals that are too small to be seen without magnification. These rocks cool rapidly, resulting in the formation of tiny crystals. Examples include basalt and rhyolite.
Is rhis sentence true or false lava cools quicklyand forms minerals with small crystals?
It is true that lava cools quickly and forms minerals with small crystals.
Why do some igneous rocks have larger crystals but other igneous rocks have crystals so small they have to be seen with a microscope?
Crystal size in igneous rock is dependent on the amount of time spent in cooling from magma or lava. More time means larger crystals. Rocks that have small crystals cooled quickly, so the minerals didn't have time to rearrange and form large crystals before the rock solidified. These small-crystalled rocks are described as aphanitic. Other rocks cooled slowly, so the minerals had time to rearrange and form large crystals before solidifying. These rocks are considered phaneritic. Some rocks cool slowly for a while, and then experience rapid cooling (such as magma that cools slowly inside a volcano, and then cools rapidly when the volcano erupts). Such rocks have large crystals surrounded by tiny crystals. Rocks that form this way are described as porphyritic.
Why do some igneous rocks have big crystals or grains and some igneous rocks have small crystals or grains?
Igneous rocks with big crystals or grains form from slow cooling beneath the Earth's surface, allowing time for larger crystals to grow. In contrast, igneous rocks with small crystals or grains form from fast cooling at or near the Earth's surface, limiting the time available for crystal growth.
Do you think extrusive or intrusive igneous rocks are likely to have larger crystals?
If a rock has large crystals, it is an intrusive rock. Intrusive rocks form underneath the Earth's surface. Magma cools slowly so it has time to form large crystals. An example is granite, where you can see the crystals with your naked eye. Rocks that have small crystals are extrusive rocks. Extrusive rocks are ones that form from lava (blasted out of a volcano) so they cool very quickly, not allowing large crystals to form. An example is obsidian, where you cannot visibly see the small crystals; it just looks like one black, glassy rock.
Do extrustive rocks have small crystals?
Yes, extrusive rocks are rocks that cool rapidly on the surface. Because of the rapid cooling the phenocrysts have little time to grow. Thus resulting in a type of aphanitic texture. Large phenocrysts can be referred to as porphyritic and it is has crystals that are over a certain diameter.
Do igneous rocks have large crystals?
It depends on the cooling rate of the magma. If the magma cools slowly underground, large crystals can form, creating intrusive igneous rocks. If the magma cools rapidly on the Earth's surface, small crystals or glassy textures can result in extrusive igneous rocks.
How do igneous rocks produce big or small crystals?
The small crystals are formed outside the volcano by the cold air... the cold air cools down the igneous rock and the crystals dont have time to join together so the are small. And the big crystals are formed inside the volcano very slowly and that way they have time to join together then there are big crystals that have been formed.
