* Extrusive refers to magma (molten rock) that erupts onto the Earth's surface, typically as lava flows or volcanic ash.
* The rapid cooling and solidification of this magma creates a fine-grained texture in the resulting rock.
Examples of extrusive igneous rocks:
* Basalt: A dark-colored, fine-grained rock commonly found in lava flows.
* Rhyolite: A light-colored, fine-grained rock that can have a glassy texture.
* Andesite: A medium-colored, fine-grained rock that is often found in volcanic arcs.
* Scoria: A dark-colored, vesicular (contains many holes) rock that forms from frothy lava.
* Pumice: A very light-colored, vesicular rock that floats on water.
Key differences between extrusive and intrusive rocks:
* Cooling rate: Extrusive rocks cool much faster than intrusive rocks, resulting in smaller crystals.
* Texture: Extrusive rocks tend to be fine-grained or glassy, while intrusive rocks have larger crystals.
* Occurrence: Extrusive rocks are found at the Earth's surface, while intrusive rocks are found below the surface.
