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Arches National Park Geology Tour provides an extensive, visually rich description of the geology of Arches, by Deborah Ragland, Ph.D. See our DVD collection.
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

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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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA