AIM: How are volcanoes formed?

Do Now: Look at the 2 pictures below, which one is a volcano? What are some clues that

lend you to your decision?

Notepack # 10

Review - 3 types of plate boundaries

Convergent – moving together

Divergent – moving apart

Transform – sliding past one another

What is a volcano?• Volcano are areas of the Earth’s surface

through which magma makes it way through the crust to the Earth’s surface.

• The word, “Volcano” comes from the Roman word Vulcan, which means “fire”

What are some famous Volcanoes?

Don’t Copy!!

• Mt Vesuvius near Pompeii

79 AD

What are some famous Volcanoes?

Don’t Copy!!

• Mt Kilauea

• Mt St. Helen

Present

What are some famous Volcanoes?

Don’t Copy!!

• Mt St. Helen

1980

What are some famous Volcanoes?

Don’t Copy!!

• Krakatau

1883

What’s inside a volcano?

• Beneath the volcano is the Magma Chamber.

• The Magma Chamber is filled with molten (melted) rock that comes up from the Mantle.

• Magma inside the volcano is always under pressure. When the pressure gets too great, an eruption will occur to release this pressure.

Crust

Magma

Chamber

What’s inside a volcano?

• Down the center of the volcano is the vent.

• During an eruption, this vent fills with magma, (now called lava), transports it out of the volcano.

• Once the lava reaches the top of the vent, it slides down the side of the volcano. When the lava cools, it turns into rock causing the volcano to grow taller and wider.

Vent

What’s inside a volcano?

• Because the magma is under pressure, sometimes small vent break through the side of the vent making secondary vents.

• If these smaller vent go across layers of rock, it is called a dike.

• If the vent stops between layers, allowing magma to get sandwiched between layers, it is called a sill.

Dike

Sill

Magma

Vent

Dike

Crater

Ash

Lava

Sill

Cone

Types of Volcanoes

• There are three types of volcanoes:

– Shield Volcanoes

– Cinder Cone Volcanoes

– Composite Volcanoes

Types of Volcanoes

• Shield Volcano

a) Built from layers of lava which cool into solid rock.

b) Non-explosive eruptions

c) Not very steep, but can be big

d) Hawaiian Islands are shield volcanoes

Types of Volcanoes• Cinder Cone Volcano

a) Built from pyroclastic material (ash)

b) Almost no cooled lava on its sides

c) Moderately explosive, short eruptions

d) Small in size, steep slopes

Types of Volcanoes

• Composite Volcanoes

a) Most common type

b) Explosive eruptions and lava flow

c) Built from pyroclastic material (ash) AND lava

Volcanoes

Quiet

lava

flows

• http://www.youtube.com/watch?v=90XFpu-65JY&feature=relmfu

• http://www.youtube.com/watch?v=_-nBMsKj_c4

• http://www.youtube.com/watch?v=JmPuy-pqIQE&feature=related

Volcanoes

Mt. St. Helen before the explosive eruption

Volcanoes

VolcanoesTime lapse of the eruption

Volcanoes

Mt. St. Helen after the eruption

Materials that come from Volcanoes• There are many things that can come out of a

volcano:

• Lava is magma that reaches the surface of the crust. Affects are very localized

• Pyroclastic Ash is a mixture of tiny rocks and dust that form huge clouds. Affects are localized and regional.

• Pyroclastic Ash can be very thick and block out sunlight destroying crops.

• The ash can settle on local land, burying towns.

• Ash also can suffocate the area, making it hard to breathe.

Materials that come from Volcanoes (cont)

• Volcanic gases- Very hot and poisonous ( CO2, HCl, SO2, HF) Affects are localized, regional global- Greenhouse effect.

• These gases can raise global temperature as solar heat is trapped in the atmosphere.

• http://www.youtube.com/watch?v=vPRoTQYXwuY

• http://www.youtube.com/watch?v=ssa3S1Lx36Y&feature=related

Where are volcanoes located?

Where are volcanoes located?

• Usually located near plate boundaries.

• Convergent subduction zones is where most of our land volcanoes are located (and the most dangerous).

• Divergent plate boundary is where fissure, sea-mount, and shield volcanoes occur.

• The biggest volcanoes on the Earth are located over top of hot spots.

Pacific Ring of Fire

• The Ring of Fire is a zone of frequent earthquakes and volcanic eruptions that encircles the basin of the Pacific Ocean.

• 90% of the world's earthquakes and 81% of the world's largest earthquakes occur along the Ring of Fire.

Pacific Ring of Fire