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The size of the crystals depend on the time it took the rock to cool. Slow cooling rocks have larger crystals because they had a longer time to grow their crystals. For example Basalt is an volcanic extrusive igneous rock that forms from rapid cooling of the magma and are usually located near the surface or on the ocean floor, it has finer crystals not visible by the naked eye. Granite is an intrusive igneous rock that forms from slow cooling of the magma within the earth crust, it has larger crystals.
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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.
Where would you find igneous rocks with larger crystal at the surface or below the surface?
Igneous rocks with larger crystals are typically found below the surface where there is slower cooling, allowing time for crystals to grow. These rocks are known as intrusive igneous rocks and are usually found in the Earth's crust, in regions of volcanic activity or in mountain ranges.
Do phaneritic igneous rocks contain viewable crystals?
By definition, yes. In contrast, aphanitic rocks do not have visible crystals.
What is the best clue to tell in extrusive igneous rocks from in instrusive igneous rock?
Extrusive igneous rocks have smaller crystals due to rapid cooling on the Earth's surface, while intrusive igneous rocks have larger crystals due to slower cooling beneath the Earth's surface. This difference in crystal size can help distinguish between the two types of rocks.
How did igneous rocks form?
Igneous rocks form when magma cools and solidifies either beneath the Earth's surface (intrusive igneous rocks) or on the surface after a volcanic eruption (extrusive igneous rocks). This cooling process can occur slowly, resulting in larger crystals (coarse-grained rocks), or quickly, which produces smaller crystals or glassy textures (fine-grained rocks).
What is the difference in appearance between igneous rocks that have cooled slowly and igneous rocks that have cooled quickly?
Igneous rocks that cooled slowly are intrusive. Igneous rocks that cooled quickly are extrusive. Intrusive rocks form larger crystals, because the crystals have a longer time to grow. Extrusive rocks have small to no crystals, because they had little or no time to grow/form.
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.
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).
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.
Why is a igneous rock appear smooth and glassy?
Some igneous rocks are very smooth and glassy (obsidian) while others have a very rough texture, such as the rocks used on the bottom of a propane gas grill. They are all formed from lava, but the glassy rocks cooled so fast that crystals did not have a chance to form. The rougher rocks cooled more slowly, allowing larger crystals to form--Slower cooling = larger crystals = rougher texture.
What type of rock can be extrusive or intrusive?
Igneous rocks can be either extrusive or intrusive. Extrusive igneous rocks form from lava cooling quickly on or near the Earth's surface, resulting in small crystals. Intrusive igneous rocks form from magma cooling slowly beneath the Earth's surface, resulting in larger crystals.
Where would you find igneous rocks with larger crystal at the surface or below the surface?
Igneous rocks with larger crystals are typically found below the surface where there is slower cooling, allowing time for crystals to grow. These rocks are known as intrusive igneous rocks and are usually found in the Earth's crust, in regions of volcanic activity or in mountain ranges.
How is the size of mineral crystals in igneous rock related to the rate at which they cool?
When igneous rocks cool quickly, they have small crystals and have a texture that may be described as aphanitic. When igneous rocks cool slowly, they have much larger crystals and have a texture that may be described as phaneritic or pegmatitic.
Do phaneritic igneous rocks contain viewable crystals?
By definition, yes. In contrast, aphanitic rocks do not have visible crystals.
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.
What is the best clue to tell in extrusive igneous rocks from in instrusive igneous rock?
Extrusive igneous rocks have smaller crystals due to rapid cooling on the Earth's surface, while intrusive igneous rocks have larger crystals due to slower cooling beneath the Earth's surface. This difference in crystal size can help distinguish between the two types of rocks.
How did igneous rocks form?
Igneous rocks form when magma cools and solidifies either beneath the Earth's surface (intrusive igneous rocks) or on the surface after a volcanic eruption (extrusive igneous rocks). This cooling process can occur slowly, resulting in larger crystals (coarse-grained rocks), or quickly, which produces smaller crystals or glassy textures (fine-grained rocks).
