Guess the Natural Disaster Between 1980 & 2008: a) # of people killed: 25,197 b) Avg. # of people killed/year: 869 c) # of people affected: 4,080,791 There.

Guess the Natural Guess the Natural DisasterDisaster

• Between 1980 & 2008:a)# of people killed: 25,197b)Avg. # of people killed/year: 869c)# of people affected: 4,080,791• There are 485 active ones on earth.• A third of the activity occurs in Iceland.• The largest one is found in Hawaii.

Volcanoes!

What is a Volcano?What is a Volcano?

A volcano is an opening, or rupture, in the earth’s surface that allows hot magma, ash, and gases to escape from the earth’s interior.

Hawaiian Volcano

Plate Tectonics and Volcanoes Plate Tectonics and Volcanoes are closely linked...are closely linked...

The area surrounding the Pacific Plate has been named “The Ring of Fire.” This ring is home to over 75% of the world’s active and dormant volcanoes.

The Link...The Link...

Ocean Crust

Ocean Crust

Mantle slowly spinning pushing magma to the surface

TrenchMid-Oceanic Spreading

Magma forced up due to friction from plates

Active volcano

Continental Crust

Crust creation spots are found all over the world (dark blue lines). A great deal of energy is released here in the form of erupting magma and black smoke.

FormationFormationMagma escapes

fromthe earth’s surface.

Magma moves and cools due to the air or water being colderThis process continues many, many times creating a new layer each time until a mound, hill, or even mountain-sized shape is created.

Inside a VolcanoInside a Volcano

Magma Chamber

Main Vent

Side Vent

Layers of ash and

lava

Types of VolcanoesTypes of Volcanoes• Volcanoes are classified based on their shape, materials that build them, and how they erupt.

1. Composite Volcanoes• Formed from alternating layers of lava and rock

fragments.• Often form impressive, snow capped peaks.• Erupt rarely and appear dormant between eruptions.• Eruptions are explosive and violent.• Found in convergent areas along plate edges.

Mount Shasta, USAMount Rainier, USAMount Fuji, JapanMount Vesuvius, Italy

2. Shield Volcanoes• Very large with gentle sides formed by runny lava.• Usually formed over hot spots far away from the plate edges or along mid-oceanic ridges.• Eruptions are milder with minimal explosions.

The most famous shield volcanoes form the islands of Hawaii. Seen: Mount Loa and Kilauea

3. Cinder Cones• Steep hill formed above a vent.• The most common landform.• Are not famous for their eruptions; minimal loss of life.• Usually show up in group nearby or on the sides of other volcanoes.• Grows rapidly.

4. Spatter Volcano• formed by lava torn by expanding gas that is thrown.• spatter forms steep sides.

The Dangers...The Dangers...Pyroclastic flows

• mixtures of hot gas, ash, and volcanic rocks that travel extremely fast down volcanic slopes.• one of the most dangerous hazards.

How dangerous?The people of Pompeii could not outrun the pyroclastic flow that occurred during an eruption of Mount Vesuvius in Italy. Archeologists were able to fill voids left in the ash that had hardened and were able to preserve the moulds of people caught in the flow.

The Dangers...The Dangers...Nuée Ardente

• a glowing cloud of ash and pumice.• can fall back to earth before cooling.•“glowing avalanche”• moves at extreme speeds.

The Dangers...The Dangers...Volcanic Ash

• like sharp, glass-like pieces.• damage anything they hit.• ash clouds can interfere with aviation.• ex. Iceland volcano erupts in 2010 and shuts down airports in most of Europe.

The Dangers...The Dangers...Lahars

• mudflows caused by the mixing of volcanic particles and melting ice or snow.• strong enough to push large boulders and trees with it.• most deaths and the destruction are caused by crushing, drowning, or suffocation.

The Dangers...The Dangers...• Blasts – magma builds under the hardened sides. The build-up of gases causes a massive explosion when it finally breaks free. Ex. Mount St. Helen’s, USA.

• Lava – lava flows burn and bury everything they touch. Houses, vehicles, or roads are not safe from the extreme heat. The speed the lava travels at depends on the make-up of the lava.

• Gas – gas is released from the magma. Not only is it highly explosive it is toxic and can suffocate people and animals.

So why would people So why would people decide to live next to or decide to live next to or

nearby these deadly nearby these deadly landforms?landforms?

Advantages of VolcanoesAdvantages of Volcanoes

Geothermal Energy

Volcanoes provide the opportunity for energy extraction, also known as geothermal energy. Heat from inside the earth can be used as energy to power our cities. Its very clean and the resource is almost endless.

Fertile Soil

Despite being deadly during an active eruption, volcanic ash is very beneficial. Over time the ash layer mixes with the soil bringing with it useful minerals. This is converted into very fertile soils. Many of these areas are used for agriculture allowing towns and villages to provide food for it’s people.

Spectacular Scenery

Supports an Economy - Tourism

Important Reminder...Important Reminder...Not all volcanoes are deadly but some can cause great destruction. How do you know? Volcanoes are grouped based on their activity levels.

• Active – erupt regularly.

• Dormant – erupted in historical times but are now quiet. It is possible for them to erupt again.

• Extinct – not likely to erupt because there is no longer a lava supply.

Some of the Most Some of the Most Destructive Volcanoes!Destructive Volcanoes!

Volcano Date Erupted

Number Killed

Cause of Death

Mt. Tambora,Indonesia

April 5, 1815 92,000 12,000 directly from the volcano; 80,000 from starvation afterward.

Karatoa, Indonesia

Aug. 26, 1883

36,417 90% killed by tsunami

Mt. Pelee,Martinique

Aug. 30, 1902

29,025 Pyroclastic Flows

Nevada del Ruiz,Colombia

Nov. 13, 1985

23,000 Mud Flow

Unzen,Japan

1792 14,300 70% by cone collapse, 30% by tsunamiData obtained from: http://www.enotes.com/science-fact-finder/earth/which-volcanoes-have-been-most-destructive

http://www.youtube.com/watch?v=CgpNqrR318Uhttp://www.youtube.com/watch?v=CgpNqrR318U

National Geographic Volcano Footage

Youtube clip: http://www.youtube.com/watch?v=CgpNqrR318U

Pyroclastic Flow – What’s it like to experience one?

Youtube clip: http://www.youtube.com/watch?v=yvG_N7eqMWk

Lahars – Possible to Outrun?

Youtube clip: http://www.youtube.com/watch?v=WEAfXO7q8Xs&feature=related

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