Download Volcanoes - Unit Launch

Volcanoes
Frequency and Quantity
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There are ~ 550 historically active volcanoes
About 60 erupt annually
The majority are 1) at the edge of continents and
2) underwater
Dormant volcanic
cone in Japan
Mid ocean ridges
Mid ocean ridge
Mid ocean ridge
Rift valley
plate
plate
magma
Mid ocean ridges
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Are continuous underwater mountain ranges
Are formed by rising magma
Cause sea floor spreading
Form a rift valley between spreading plates
Pillow lava at mid
ocean ridge
Land based volcanoes
Mt St Helens one day before eruption
Mt St Helens 4 months after eruption
Another before…
…and 2 years later
Land based volcanoes
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Are more dangerous than underwater types
Form island chains like the Aleutian islands off
Alaska
The Ring of Fire
The ring of fire
The Ring of Fire
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Where the earth’s crustal plates meet, one plate
will often slide under another
As one plate slides under another, it heats up,
mixes with water and the rock melts to form
magma
This less dense magma then rises to feed
volcanoes
A volcano at the edge of a continent
Mid ocean ridge
Sinking plate
?
Melted rock
forming magma
Rift valleys and volcanoes
Outward spreading
Valley forms
here
Rift valleys
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Are formed by plates moving away from each
other
A valley forms by crust sinking between the
diverging plates
East Africa has a large rift valley with volcano
formation
The African Rift Valley
Africa’s rift valley
Rift
valley
Kenya’s Rift valley
Hot Spots
Hawaiian Islands – hot spot
Volcanoes National Park
Hot Spots
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A hot spot is a fixed source of abundant rising
magma
As a plate moves over the hot spot, magma
forms undersea volcanoes; some of which rise
above the ocean surface forming island chains
Loihi Seamount
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A new volcanic cone is forming near Hawaii
It’s top is 1000 m (3000 feet) below the water
surface, and it will break the surface in the next
10,000 to 100,000 years.
Big Island of
Hawaii
Loihi
Map Projections
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How do you project a 3D object on a 2D map?
Mercator Projection
Mercator Projection
Winkel Tripel Projection
Maps of the Earth
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Cartography is the science and art of
graphically representing a defined geographical
area by means of a map.
First off, the earth is round and maps are flat
Map projections are ways of flattening a round
earth into a useful picture; the resulting picture
is distorted
There is always distortion and compromises in
accurately making a map