Volcanoes
Created by:  David P.

    The definition of a volcano is "a vent in Earth's surface that often forms a mountain built of lava and volcanic ash, which erupts and builds up" (Glencoe/McGraw-Hill, Glencoe Earth Science).  Most people think that volcanoes are just spread randomly across the Earth, if they are thought of at all.  In fact, active volcanoes are not scattered over the Earth, most occur in belts, especially in the island arcs and mountain ranges bordering the Pacific Ocean.  Theories of sea floor spreading and plate tectonics offer a logical explanation for the location of most volcanoes.
    Maps called topographical maps  reveal the locations of large earthquakes.  They also indicate the boundaries of the 12 major tectonic plates.  For example, the Pacific Plate is bounded by the earthquake zones of New Zealand, New Guinea, the Mariana Islands, Japan, Kamchatka, the Aleutian Islands, western North America, the East Pacific Rise, and the Pacific-Antarctic Ridge.
    Volcanoes can destroy life and help raise life.  The ash spewed from them can smother organisms, while providing rich soil for growing plants.  The hot lava destroys buildings, trees, and just about anything it touches, while creating new land at the same time.
Information from:  www.britannica.com

Mt. Saint Helens:
    Mt. Saint Helens erupted on May 18, 1980.  This volcano is a stratovolcano.  The pressure from all the lava blew the top 1,300 ft. of Mt. Saint Helens.  The ash was blown up into the upper atmosphere.  The blast of the volcano covered 150 sq. miles.  This volcano caused much damage to the state of Washington.  A lake in Washington, called Spirit Lake, is still floating with logs and debris from the volcano.
    The volcano is located at 46.2N, 122.2W.  It is 8,363 feet tall.  The vegetation around the volcano is still growing and the ash still flows.  Even with all these factors, Mt. Saint Helens and the state of Washington is still doing fine.

Pinnacles:
    Pinnacles is a volcano in California.  This volcano is an ancient one though.  Sharp spear like formations dot the land surrounding the volcano, some ranging from 500 to 1,200 feet high.  These are the remains of the volcano.  Actually, the volcano is 195 miles south-west.  This volcano formed 23 million years ago along the San Andreas Rift Zone.  The sliding of the plates moved the spears apart.
    The movement rate of the fault is 1.4 cm/yr.  There is a national park around the volcano.  California is littered with volcanoes and earthquakes.  This is due to the San Andreas Fault.  This is a transform fault, one where two plates slide past one another.

Information found at http://volcano.und.nodak.edu/
Links to Volcano Related Sights

    Volcanoes can cause many hazards.  Among these are burning of buildings, vegetation, and property.  Another hazard is the ash that rains down from the sky.  The ash is put there by the explosion of the volcano.  Sometimes the ash can stay in the air for weeks.  Though this seems harmless, tons of ash can cover houses, cars, and even people, sometimes preserving them in a tomb of ash.  A good example of this is Mt. Vesuvius in Italy.
Hazards of Volcanoes

    Volcanoes erupt because an area in the mantle is hot enough to melt rock.  When it does, the molten rock, or magma, floats upwards.  It collects in large magma chambers, and eventually erupts when the pressure inside the chamber decreases and the gases expand.
Causes of Eruptions

    Believe it or not, volcanoes can be predicted.  There are a few warning signs that a volcano shows that precede an eruption.  Eruptions or steam can be a warning sign, or bulging in a side of a mountain, super heating of springs, as well as other signs.
Signs That an Eruption's Likely to Occur