== == Rhyolite, basalt, pumice, obsidian, andesite, dacite, tuff, welded tuff, scoria.
No, not all extrusive igneous rocks contain visible crystals. Some extrusive rocks, such as obsidian and pumice, cool so quickly that mineral crystals do not have a chance to form, resulting in a glassy texture instead.
Some examples of extrusive igneous rocks include basalt, pumice, and rhyolite. These rocks are formed from lava that cools quickly on the Earth's surface, resulting in fine-grained or glassy textures. Extrusive rocks often have small mineral grains due to the rapid cooling process.
The bubbles and pores are from trapped gasses which expanded in the molten material as it neared the surface. They're usually found in extrusive igneous rocks, those that have solidified in the air or on the surface.
Intrusive igneous rocks form beneath the Earth's surface in settings like magma chambers and batholiths. Extrusive igneous rocks form on the Earth's surface from volcanic eruptions, such as at mid-ocean ridges, subduction zones, and hot spots.
The difference between an Extrusive and Intrusive igneous rock is the way in which they cool. An Extrusive igneous rock cools very fast on the surface and is created by lava. Since the cooling process is very fast extrusive igneous rocks have very small crystals (fine grained). On the other hand an Intrusive igneous rock cools very slowly beneath the surface and is created by magma. Since the cooling process is very slow intrusive igneous rocks have very large crystals (coarse grained). In some instances there is also a third type of igneous rock. Technically it is an extrusive rock, but it resembles glass. This glass type of igneous rock forms when magma/lava is instantly cooled.
Some do. These are called extrusive igneous rocks. However a large portion of igneous rocks form beneath the surface. These are intrusive igneous rocks.
Some igneous extrusive rocks include obsidian, basalt, andesite, rhyolite, scoria, pumice, basaltic glass. If you want more, go to page 6 on the Earth Science Reference Tables at the related link.
Underground = intrusive/plutonic aboveground = extrusive/volcanic
Extrusive igneous rocks, some sedimentary rocks
They cool to quickly for crystals to form.
No, not all extrusive igneous rocks contain visible crystals. Some extrusive rocks, such as obsidian and pumice, cool so quickly that mineral crystals do not have a chance to form, resulting in a glassy texture instead.
Extrusive igneous rocks and some sedimentary rocks are formed above ground.
Some other examples are Andesite, Basalt, Rhyolite, and Scoria.
When lava reaches the surface of the Earth through volcanoes or through great fissures the rocks that are formed from the lava cooling and hardening are called extrusive igneous rocks. Some of the more common types of extrusive igneous rocks are lava rocks, cinders, pumice, obsidian , and volcanic ash and dust
== == Rhyolite, basalt, pumice, obsidian, andesite, dacite, tuff, welded tuff, scoria.
Some examples of extrusive igneous rocks include basalt, pumice, and rhyolite. These rocks are formed from lava that cools quickly on the Earth's surface, resulting in fine-grained or glassy textures. Extrusive rocks often have small mineral grains due to the rapid cooling process.
The bubbles and pores are from trapped gasses which expanded in the molten material as it neared the surface. They're usually found in extrusive igneous rocks, those that have solidified in the air or on the surface.