Extrusive Rocks (formed from lava):
* Basalt: A dark-colored, fine-grained rock rich in magnesium and iron. It's the most common volcanic rock and is found in shield volcanoes and mid-ocean ridges.
* Andesite: A medium-colored, fine-grained rock with a composition between basalt and rhyolite. It's found in composite volcanoes and continental arcs.
* Rhyolite: A light-colored, fine-grained rock rich in silica. It's often found in explosive eruptions and forms domes and lava flows.
* Scoria: A dark-colored, vesicular (full of holes) rock formed from basaltic lava.
* Pumice: A light-colored, very vesicular rock formed from rhyolitic lava.
* Obsidian: A black or dark-colored, glassy rock formed from rhyolitic lava that cooled quickly.
Intrusive Rocks (formed from magma that cools underground):
* Gabbro: A dark-colored, coarse-grained rock equivalent to basalt.
* Diorite: A medium-colored, coarse-grained rock equivalent to andesite.
* Granite: A light-colored, coarse-grained rock equivalent to rhyolite.
Other types of volcanic rocks:
* Tuff: A rock made from compacted volcanic ash and other fragments.
* Breccia: A rock made from angular fragments of volcanic rock cemented together.
* Agglomerate: A rock made from rounded fragments of volcanic rock cemented together.
The specific types of rocks produced by a volcano are determined by:
* The composition of the magma: Magmas with different compositions (e.g., silica content) will cool and solidify into different types of rocks.
* The eruption style: Explosive eruptions often produce ash, tuff, and breccia, while effusive eruptions produce lava flows and scoria.
Volcanoes can also produce unique rock formations like:
* Volcanic bombs: Large pieces of lava ejected from the volcano that solidify in flight.
* Lava tubes: Channels formed within lava flows as the surface cools and solidifies.
* Calderas: Large depressions formed after a volcano erupts explosively.
So, while volcanoes are known for creating dramatic landscapes, they are also responsible for a diverse range of rock types!
