Andesite is an extrusive igneous rock, meaning it was formed from cooled and solidified lava. It's typically gray to dark gray in color and has a fine-grained texture.
While andesite is the dominant rock type, you can also find other volcanic rocks in and around the volcano, such as:
* Dacite: Another extrusive igneous rock, but slightly richer in silica than andesite.
* Basalt: A dark-colored extrusive igneous rock, often found as flows within and around the volcano.
* Tuff: A rock formed from compacted volcanic ash.
The composition of Mount St. Helens' rocks is a result of its geological history and the specific conditions of its magma chamber.
