Volcanoes

Volcanoes are openings

in the Earth’s surface.

When they are active

they can let ash, gas

and hot magma escape

in spectacular

eruptions.

ash cloud - cloud of ash that forms in the air after some volcanic eruptions. conduit - a conduit is a passage through which magma (molten rock) flows in a volcano. crust - the crust is Earth's outermost, rocky layer. lava - lava is molten rock; it usually comes out of erupting volcanoes. magma chamber - a magma chamber contains magma (molten rock) deep within the Earth's crust. side vent - a side vent is a vent in the side of a volcano. vent - a vent is an opening in the Earth's surface through which volcanic materials erupt.

Where do you find them?

Volcanoes are usually located

where tectonic plates meet

(convergent, divergent and

subduction zones). 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.

Ring of Fire

Formed by the subduction of tectonic plates

When an oceanic and continental plate converge, the more dense,

oceanic plate moves beneath the continental plate. When this

occurs, fluids like water combine with crust and mantle material.

This lowers the melting point of the rock and causes it to melt and

form magma. Because magma is less dense than the surrounding

rock, it will rise and erupt on Earth’s surface forming a volcano.

Volcanoes 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.

As a tectonic plate moves over a stationary mantle plume,

volcanic mountains (like the Hawaiian Islands) form. The

activity of the volcano stops because it has moved away from

the hot spot that supplied it with magma.

Yellowstone, like the Hawaiian Islands, is believed to

lie on top of one of the planet's few dozen hotspots

where light hot molten mantle rock rises towards

the surface.

In addition to subduction and hotspots, rifting

along two divergent oceanic plates (mid-ocean

ridge) can create submarine volcanoes

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!

Olympus Mons is 3 times the size of Mt. Everest!

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.

Mount St. Helens

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

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

Before

After

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