Wednesday, 17 January 2007
09:55:18 PM (GMT)
Did you know that more than 80 percent of the Earth’s surface has come from
volcanoes? And that the sea floor and mountains were formed by countless volcanic
eruptions, while the gases released from volcanoes formed the earth’s atmosphere?
Deep inside Earth, there is a solid mass of rock called the mantle. When rock from
the mantle melts and moves to the surface through the earth’s crust and releases
built-up gases, volcanoes erupt. But why does this solid rock have to melt and come
to the surface?
Very, very high temperature and pressure causes the rock to melt and become liquid
rock called magma. When the magma rises through the denser rock layers and reaches
the Earth’s surface, it is called lava. Imagine how hot it must be!
Volcano Lava Flow
Most volcanoes occur on plate boundaries, or areas where Earth’s shifting plates
meet, split apart, or slide against each other, going in opposite directions, like at
the San Andreas Fault. Do you know what a Hotspot is? As plates move over hotspots,
volcanoes spring up and die down in turn, creating an island chain like the Hawaiian
Islands. There are more than 500 active volcanoes in the world! More than half of
these volcanoes are part of the “Ring of Fire,” which is the area that circles
the Pacific Ocean.
It does sound scary doesn’t it? But Volcanologists– scientists who are volcano
experts–are becoming very clever at spotting the warning signs of an eruption.
Before an eruption, the magma moves into the area beneath a volcano and collects in a
magma chamber. As it comes closer to the surface, the magma releases gases, which
gives us clues about an eruption. The movement of magma produces small earthquakes
and tremors, and gases released near the volcano also offer clues for scientists.
Even then, it is very difficult to predict exactly when a volcano will erupt.
The eruption of Mount Pinatubo in 1992 in the Philippine Islands caused 342 deaths
and more than 250,000 people had to be evacuated to safety!
When the volcano Mount St. Helens in Washington state erupted in 1980, a part of the
volcano collapsed and became a massive landslide covering an area of about 24 square
miles! Before, the mountain was snow-covered and very beautiful, with a forest on it
and at the base of the volcano was Spirit Lake, a clear mountain lake that was very
good for fishing and boating! Volcanologists calculated that the blast started at
about 220 miles per hour but increased to about 670 miles per hour, and was heard as
far away as Montana, Idaho, Canada and California! 57 lives were lost in the
eruption, many buildings were buried and more than 200 homes were destroyed.
Thousands of acres of prime forest, and more than 185 miles of highways and roads
were also destroyed. The damages cost $1.5 billion! Aren’t you glad that you were
Although much of the landscape was destroyed, many small animals, such as rats, frogs
and crawfish managed to survive because they were below ground level or on the water
surface! Isn’t nature is amazing?