volcanoes 12 1 notes 08 09
Post on 14-Jan-2015
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What are volcanoes?
• How many active volcanoes in the world?– Over 600
• What is the world’s most active volcano?
• Vocab words:– Vent– Magma chamber– Crater– lava
Why does magma move towards the surface?
• Magma is less dense than surrounding rock.
Where does magma form?
Volcanic Vent
• The opening of a volcano where the magma escapes to reach the earth’s surface
Craters
• The steep walled depression around a volcanoes vent
How do Volcanoes Form?
heat and pressure changes the rock to melt forming liquid magma
Magmas less dense than rock, forced slowly towards earth’s surface
Effects of Eruptions
• Floods• Lava Flows• Ash, rock, chemicals in the air (acid rain)• Burning• New land masses• Destruction• Mud Flows
Kilauea in Hawaii
The Hawaiian name "Kilauea" means "spewing" or "much spreading," in reference to the lava flows
• Most Recent EruptionContinuous since January 3, 1983
• Number of Historical Eruptions 61
Effects of Eruptions
• Ash – harmful to life, buildings, roads
• High temperatures – can ignite wood
Mt Spur, Alaska
Montserrat
Montserrat 1995 - 2004
• Pyroclastic flow – hot volcanic gas and ash moving in a cloud directly over the Earth’s surface
• Acid rain – results when sulfur gases from volcano mix w/ water in the atmosphere– Harmful to vegetation and aquatic life
Where do volcanoes occur?
• They often occur when Earth’s tectonic plates:– Move apart – divergent boundary– Move towards each other – convergent
boundary– At “Hot Spots” – where crust of Earth is
thinner than normal
Divergent boundary
Iceland
Mid-Atlantic Ridge
Hekla
• Hekla is located in Iceland
• last erupted on February 20, 2000
• At a divergent plate boundary
• composite volcano• began erupting in
1819
Iceland
Iceland
Convergent boundary
Mt St Helens
Soufriere Hills on Montserrat
• Example of a convergent boundary responsible for volcanism
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