14. Volcanoes are usually
located where tectonic
plates meet. This is
especially true for the
Pacific Ring of Fire, an
area around the Pacific
Ocean where over 75% of
the volcanoes on Earth are
found.
16. They can also form in areas that contain abnormally hot rock
inside the Earth. Known as mantle plumes, these hotspots
are found at a number of locations around the globe with the
most notable being in Hawaii.
17. While we certainly have some big volcanoes
here on Earth, the biggest known volcano in
our solar system is actually on Mars. Its name
is Olympus Mons and it measures a whooping
373 miles wide and 13 miles high!
19. The softened rock is squeezed by all the rock above it, and it
eventually reaches a magma chamber a few miles below the
volcanic vent. As the magma enters cooler surroundings, it gets a
boost from buoyancy. As the magma continues rising, falling
pressure releases high-pressure gas that was trapped inside it, and
the volcano explodes.
20. There are openings in the surface of the Earth.
Hot magma from the mantle is being turned
about under the planet. Eventually, it finds the
escape route, and explodes through the
volcano.
22. On May 18, 1980, a “sleeping giant” woke
up.
• The release of pressure over the magma
chamber created a glowing cloud of gas and
rock debris blew out of the mountain face. The
blast was so strong that all the trunks of trees
neatly aligned to the north. The area
devastated by the direct blast force covered an
area of nearly 230 square miles
23.
24. Shortly after, a second, vertical explosion
occurred at the summit of the volcano, sending
a mushroom cloud of ash and gases more than
12 miles into the air.The cloud of ash darkened
the skies, causing streetlights to come on as far
away as Spokane,Wash., more than 300 miles
away.Ash continued to erupt for more than
nine hours. Ultimately, an estimated 540 million
tons of ash drifted up to 2,200 square miles
settling over seven states
