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That's because of the cooling speed. When a magma or a lava cools, it forms crystals. The longer these crystals have the time to form, the larger they will be. However, at the surface, the lava cools relatively fast (at least, compared to magma that stays inside the earth). The crystals in the rock that forms that way don't have a lot of time to form, so don't grow big.
Wiki User
∙ 13y ago
Wiki User
∙ 14y agoThey have small crystals because ...they from out side the volcano ... so the lava does not have much time to cool !!!
Wiki User
∙ 11y agoSince it is erupted on the surface, lava cools pretty quickly. Too quickly for large crystals to form.
Wiki User
∙ 10y agoQuick cooling inhibit the the growth of large crystals.
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Does lava have large or small crystals?
Rocks formed from lava (known as extrusive igneous rocks, because the lava comes to the surface) can be any size - large or small. However, the density of the rock and the size of the crystals making up the rock is informative. Less "thick" (viscous) lava will produce higher-density rocks. The more silicon is contained in the lava/rocks, the thicker it will be. Thinner lava contains more iron and less silicon. The faster a lava cools, the smaller the crystals in the rock will be. By using crystal size in minerals, geologists can determine how fast the lava cooled, which helps to determine the type of eruption and the surface conditions when it occurred.
What is the name of A dark rock with small crystals formed on the surface of the earth?
Most generally, an igneous rock with small crystals formed from the cooling of lava on the surface of the Earth would be classified as basalt.
Is shale a volcanic rock with small crystals made when lava cools?
No. Shale is a sedimentary rock formed from mud.
Would you list intrusive rocks under rocks that form above the ground or below?
Intrusive rocks are Igneous rocks that have been formed underground. Igneous rocks are formed by the cooling of lava/magma. Igneous rocks are divided into two categories- intrusive and extrusive. Intrusive is when the magma cools slowly beneath the Earth's surface, which causes large crystals to form. When lava cools above the Earth's surface, it is called extrusive. Extrusive rocks have smaller crystals compared to intrusive, the difference always being noticable.
What type of rock is formed from molten lava?
When molten magma cools and crystallizes, it becomes a hard rock called igneous rock. Different magmas have different compositions and so produce different igneous rocks. If the magma cools beneath the earth's surface, it cools slowly. Rocks formed like this are called intrusive rocks, and have large crystals, e.g. granite, gabbro, dolerite. If magma comes to the surface (in a volcanic eruption) it cools rapidly. Rocks formed like this are called extrusive rocks, and they have small crystals, e.g. basalt, obsidian, pumice. Igneous rocks have interlocking mineral crystals. The crystals are arranged randomly throughout the rock. Igneous rocks are mostly non-porous.
Does lava have large or small crystals?
Rocks formed from lava (known as extrusive igneous rocks, because the lava comes to the surface) can be any size - large or small. However, the density of the rock and the size of the crystals making up the rock is informative. Less "thick" (viscous) lava will produce higher-density rocks. The more silicon is contained in the lava/rocks, the thicker it will be. Thinner lava contains more iron and less silicon. The faster a lava cools, the smaller the crystals in the rock will be. By using crystal size in minerals, geologists can determine how fast the lava cooled, which helps to determine the type of eruption and the surface conditions when it occurred.
If the lava cools quickly the crystal are what?
If lava cools quickly, the minerals don't have as much time to form crystals, so the crystals do not become very large. Igneous rocks that cooled quickly and have small crystals are described as "aphanitic" igneous rocks.
What rock cools on the surface?
Lava cools quickly and forms rocks with small crystals. They are called extrusive igneous rocks.
What type of rock forms when lava cools very quickly?
igneous with small crystals. Extrusive igneous rock forms from the solidification of lava. Rocks such as rhyolite, pumice, obsidian, and basalt. Igneous rocks are formed by magma (inside the earth) or lava (outside earth) that cools and hardens. Extrusive rocks are rocks thathave exited the earths surface.
What is the name of A dark rock with small crystals formed on the surface of the earth?
Most generally, an igneous rock with small crystals formed from the cooling of lava on the surface of the Earth would be classified as basalt.
Where does Igneous rock form below or above?
Igneous rocks are formed from the cooling of lava/magma. (Lava is magma that has been moved from beneath the Earth's surface to above.) They can be formed above or below the Earth's surface- when formed above is called 'Extrusive Igneous rock' and when formed below is 'Intrusive Igneous rock'. When a rock is extrusive, it forms small crystals. When it is intrusive, it causes large crystals to form.
Why would granite have larger crystals than igneous rocks formed from lava cooled above the earth's surface?
Because crystals in granite had more time to form
What rocks are formed after lava dries out?
Igneous rocks are formed from the cooling and solidification of magma or lava.
What is the rate of cooling in reference to magma and lava?
The rate of cooling is the speed at which magma or lava crystallizes. When the speed is slow it results in big crystals. When the speed is fast it results in small crystals.
Why would granite rock have larger crystals than igneous rocks formed from lava cooled above the earth's surface?
Because crystals in granite had more time to form
What does lava that cools quickly form?
fast cooling lava -small crystals or no crystals
What lava that cools quickly form?
fast cooling lava -small crystals or no crystals
