Well, isn't that a lovely question. You see, extrusive igneous rocks cool quickly on the Earth's surface, which doesn't give the crystals much time to grow big and strong. Just like how a happy little tree needs time to grow tall and mighty, these rocks don't have that luxury. So, they end up with small, fine crystals that make them unique and beautiful in their own special way.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Extrusive Igneous Rocks. Basalt (Plankey1995 JF)
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.
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.
Lava cools quickly and forms rocks with small crystals. They are called extrusive igneous rocks.
These are extrusive igneous rocks with an aphanitic texture.
Intrusive rock normally has visible crystals. Extrusive igneous rock has small crystals. A black extrusive igneous rock with small crystals could be basalt.
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.
Extrusive igneous rock consists of mineral crystals that are not observable with the naked eye. Obsidian is an extrusive igneous rock (volcanic glass) where there technically are no mineral crystals.