Volcanoes

Volcano Eruption

•A volcano – is an opening in Earth’s crust through which molten rock, rock fragments, and hot gases erupt.

Magma•Composed of silicon and

oxygen compound•Also contains gases,

which expand as the magma rises

•Pressure builds up until the gases blacks out in a violent explosion

Magma

•Magma rises toward Earth’s surface if it is less dense than the surrounding rock.

•Magma chambers – holds magma until it can not hold any more and forces the magma out through an eruption.

Lava

•Lava – is magma that has reached Earth’s surface

Rock Fragments•Ash – tiny rock fragments.

Size of dust to rice grain. Can be carried long distances by wind (even all the way around Earth)

•Block – Can be the size of houses are solid pieces of rock. Fall quickly after eruption

• Cinders – bigger than ash, contain holes and tunnels left by escaping gases

Volcano Shapes and Sizes

•Shapes of Volcanoes depend on Magma Feeding

1.) Most erupt from openings in bowl-shaped pits called craters.

2.) Some erupt from long cracks in the ground

Shield Volcano•Shaped like a broad,

flat dome.•Low silica (flows

easily)

Largest Volcano on Earth and one of the most active!

Name: Mauna LoaLocation: Hawaii Height: 10.5 miles most

is underwater!

Cinder Cone•A steep, cone-shaped

hill formed by the eruption of cinders and other rock fragments that pile up around a single crater. One of the most

famous volcanosName: ParícutinLocation: MexicoHeight: 1.73miles

Composite Volcano• A cone-shaped volcano

built up of layers of lava and layers of rock fragments.

• High silica (flows slower and is pasty)

Deadliest and most destructive volcanic event in the history of the US

Name: Mount St. Helens

Location: Washington, US

Height: 1.58 miles

Monitoring Volcanoes

•Scientist monitor▫Magma movement▫Temperatures at openings, sprins, and lakes on volcanoes

▫Amount and type of gases given off

▫Rising temperatures▫Changes in volcanic gases