Answer: More than 80 percent of the Earth's surface -- above and below sea level -- is
of volcanic origin. Gaseous emissions from volcanic vents over hundreds of
millions of years formed the Earth's earliest oceans and atmosphere, which
supplied the ingredients vital to evolve and sustain life. Over geologic eons,
countless volcanic eruptions have produced mountains, plateaus, and plains, which
subsequent erosion and weathering have sculpted into majestic landscapes and
formed fertile soils.
-- From:
Tilling, 1985, Volcanoes: USGS General Interest Publication.
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U.S. Department of the Interior |
U.S. Geological Survey