Well, it depends on where you live. There
are certain areas on the planet where you might want to set up sensors. Most of
those are out in the Pacific Ocean. If your house is in North America, I’m
going to say you’re basically volcano free. Unless you’re on the west coast. And
only a handful of volcanoes have been active in North America in the last 150
years. Here’s why.
How do volcanoes form?
Deep beneath the Earth’s hard crust is a
core of rock so red hot that it has melted. It’s a little like the melted mozzarella
in a cheese stick. Except that in the Earth, the molten rock is swirling and rising
up, unlike the cheese. This molten rock breaks through the crust mostly at natural
seams where continents meet (tectonic plates, actually). That’s why we find
some on the west coast of America.
Earth’s crust is about 30 km thick on the
continents. It would take you just over 6 hours to walk that distance. In some
places on the ocean floor Earth’s crust is thinner, about 5 km thick. At hot
spots in the thin crust, molten rock breaks through and spews out onto the
surface as lava. As the lava cools and builds up on itself over years and years,
it makes a mountain. Because the lava keeps flowing up and out of the Earth in
that mountain, we call it a volcano.
The Hawaiian Islands were formed by lava
bubbling up over many thousands of years and cooling into island-sized mountains.
The tallest of the Hawaiian Islands is actually several hundred metres taller
than Mount Everest, if you measure from its base at the bottom of the ocean.
Scientist believe that the hot spot where lava
is bubbling up stays in one place as the crust slides extremely slowly over top
of it. This is why there is a whole chain of islands in Hawaii. As the crust
moves over the hotspot, a new island starts forming.
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| Lava flows into the sea, growing the big island in Hawaii in 2006. By Jennifer Williams, CC BY-SA 2.0 |
Is it dangerous to live near a volcano?
Lots of people live near a volcano. Does that
sound crazy? I mean, when it erupts, a volcano can spew boiling hot rock chunks
as big as a refrigerator high into the sky. It can send 1200 °C lava flowing
down the hillside for many kilometers. The hot gases and ash that get blown out
with the melted rock can spread clear around the globe, causing destruction in its
path.
When Mt St Helens in Washington erupted in 1980,
it caused a medium-sized earthquake and spread ash all the way around the world
over two weeks’ time. Besides the many bridges, homes and roads that were
destroyed, 57 people were killed by the eruption.
When the Eyjafjallajökull volcano in Iceland erupted in 2010,
planes could not fly in all of Europe for 8 days because of the ash cloud.
Safety officials were afraid the hot ash would damage engines and make the
planes crash. Flights in Europe were grounded because of ash several more days over
a month.
Why do people even live near volcanoes?
The thing is, volcanoes don’t erupt violently
that often. Even the world's most
active volcano is just slowly leaking lava down its sides
and burning surrounding neighborhoods to the ground. That is the Kilauea volcano in Hawaii and it has been erupting constantly for
35 years. But the Yellowstone volcano only erupts
every 700,000 years.
Volcanoes tend to be in very lush
environments. Sometimes the environment is lush because of the volcano and all
the minerals that lava brings to the surface. That may have attracted people’s
ancestors to the area, and they stayed. Some people live near volcanoes because
it is affordable—cheap homes because they risk destruction.
In many cultures, volcanoes are thought to
have spiritual power or importance. They are expressions of the gods, and bring
luck and prosperity as well as destruction. Some people may live near volcanoes
for that reason.
Scientists live near volcanoes so they can
study them. It’s extremely dangerous, and there are many stories of volcanologists dying at
work.
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| A USGS department geologist takes the temperature of a lava flow on Mt. Kilauea in 1984. Public domain. |
Can I visit a volcano safely?
There are about 1,500 volcanoes in the
world that could be active. Only about 500 have erupted in recorded history. In
Hawaii, you can tour the lava tubes created by lava flows. You can visit the Greek island of Santorini
that is still an active volcano with 13,600 people living on it. It has had
very small eruptions that build up its sides over the last 70 years. And there are
at least 1000 others you can climb on. Take a look at the list of volcanoes
and think about which one you’d like to visit.
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| Santorini, Greece, is built on the rim of a very old volcano. You can tour the centre that is an island now. By Pedro Szekely, CC BY-SA 2.0 |
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