This is an image of Mt. St. Helens, in Washington, USA.
Click on image for full size
Image from: USGS, courtesy of Volcano World
Volcanoes erupt when magma from deep below reaches the earth's surface. Once the magma reaches the surface, it is called lava and flows out onto the surface. Some really explosive volcanoes spew out lava fragments, dust clouds, and ash. Most volcanoes exist along plate boundaries and are determined based on its violence and frequency. Volcanoes have a cooling effect on weather because the ash remains in the sky and reduces the amount of sunlight reaching the surface.
Extinct volcanoes have stopped erupting, dormant volcanoes erupt rarely, and active volcanoes erupt frequently.
This is a picture of Mount St. Helens, located in Washington, which last erupted in 1980. It had more amounts of ash than lava. This volcano was the result of two plates colliding into each other.
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