Obsidian is formed from very rapidly cooling lava.
obsidian
cool rapidly
Obsidian cools relatively quickly compared to other volcanic rocks. This rapid cooling occurs when lava cools swiftly upon exposure to air or water, preventing the formation of large crystals. As a result, obsidian has a glassy texture and lacks a crystalline structure, which distinguishes it from other igneous rocks.
Obsidian
In reference to the cooling of magma into rock, basalt is formed from rapid cooling.
obsidian
cool rapidly
Obsidian cools relatively quickly compared to other volcanic rocks. This rapid cooling occurs when lava cools swiftly upon exposure to air or water, preventing the formation of large crystals. As a result, obsidian has a glassy texture and lacks a crystalline structure, which distinguishes it from other igneous rocks.
Obsidian and Pāhoehoe lava
They cool to quickly for crystals to form.
Igneous rocks that cool quickly on the Earth's surface are called extrusive or volcanic rocks. Examples include basalt, obsidian, and pumice. These rocks have fine-grained textures due to their rapid cooling.
Obsidian
In reference to the cooling of magma into rock, basalt is formed from rapid cooling.
cool too quickly for mineral grains to form, resulting in a non-crystalline structure.
Examples of igneous rocks are pumice, obsidian, basalt, and rhyolite.
They are formed when either a sedimentary rock or a metamorphic rock are exposed to high heat and turn into magma and then cool quickly.
Yes extrusive rocks are fine grained because they cool down at a faster rate.