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Changing Earth
Movement in Earth
Questions to Answer
• How does the movement of
tectonic plates affect the Earth’s
surface?
• How does the transfer of energy
relate to earthquakes and
volcanoes?
• How do humans prepare and
respond to natural events?
Earth’s Interior
I. Earth’s Interior
A. Three major layers of the Earth
• 1.Crust – outermost & thinnest layer
– Cool and solid rock
– Divided into continental and oceanic crust
• 2.Mantle – middle layer
– Hot and liquid rock, 80% of Earth’s volume
• 3.Core – center layer of earth
– Divided into inner and outer core
– Outer = hot and liquid metal (iron & nickel)
– Inner = hot and solid metal
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Earth’s Interior
• 1.Continental Crust
– Less dense
– Thicker, deepest beneath mountains
• 2.Oceanic Crust
– Beneath the ocean water
– More dense
– Thinner
B. Plate Tectonics
• 1. Alfred Wegner introduced the idea
of Pangaea (noticed coastlines fit together)
– A large supercontinent
• 2. Broke apart because of plate
tectonics –theory that Earth’s surface is made of
large moving plates
– Moving of Earth’s plates
– Causes the land to look different on
Earth
Plate Tectonics
• 3. Movement happens because
Earth’s makeup
– a. Lithosphere
• Crust and rigid upper mantle
• These are the ‘plates’, 7 large pieces &
several small pieces (tectonic plates)
– b. Asthenosphere
• Mantle just below the lithosphere
• Very liquid and slowly flowing
Plate Tectonics
C. Plate Boundaries
• 1.Any place plates meet and move
is known as a fault (crack in Earth)
• Three Types of Plate Boundaries
• a. Divergent Boundary
– Move apart
• b. Convergent Boundary
– Move together
• c. Transform Fault Boundary
– Move along side (scrape past each other)
2. Divergent Boundary
• Cause trenches and ridges (mid-oceanic)
• Forms new crust, magma rises between• Rift valley- most studied- Mid-Atlantic Ridge
3. Convergent Boundary
• Cause trenches, volcanoes, mountains
• Subduction occurs
– More dense
oceanic crust
slides under
less dense
continental
crust
4. Transform Fault Boundary
• Cause rocks to crack and break
• Causes lots of earthquakes
D. Evidence
• 1. Magnetic rocks
in the earth
change polarity
Evidence
• 2. Land shapes
• 3. Fossils
• 4. Ancient climates
Tectonic Plates
II. Earthquakes and Volcanoes
A. Earthquakes
• 1. Shaking or trembling caused by the
sudden release of energy
• 2. Usually associated with faulting or
breaking and slipping of rocks
– a. Occur at boundaries of plates
– b. Release energy that create seismic
waves
• 3. Continuing adjustment of position
results in aftershocks
Movement of Rock
Earthquakes
• 4. Focus
– The point underground where the
rocks start to slip
– Where the earthquake begins
• 5. Epicenter
– Spot on the surface directly above
the focus (greatest damage here)
Earthquakes
Earthquakes
• 6. Types of seismic waves
– a. P waves (primary waves)
• Fast moving longitudinal waves
• First waves we detect
– b. S waves (secondary waves)
• Slow moving transverse waves
• Second waves we detect
– c. Surface waves
• Rolling wave ( & ) on the surface of Earth
• Cause the most destruction, collapse of buildings
Earthquakes
Earthquakes
• 7. Seismology
– Study of earthquakes
– Use a seismograph
Earthquakes
• a. Seismology
– Three
seismographs
can tell you
the location of
the epicenter
Earthquakes
• 8. Measured using the Richter scale
Earthquakes
B. Volcanoes
• 1. A vent or hole in the crust
• 2. How a volcano erupts
– a. Magma collects in a chamber under the
surface
– b. Pressure builds up as the chamber fills
– c. Pressure gets so great magma rises to
the hole and comes out as lava
Volcanoes
Volcanoes
• 3. Three types- determined by type of eruption
– a. Shield
– b. Composite
– c. Cinder cone
1. Shield Volcanoes
• Eruptions are mild and occur frequently
• Creates buildup of a gently sloping
mountain
• Magma is very runny and long flowing
• Largest of all volcano types
2. Composite Cone
Volcanoes
• Eruptions alternate between mild and
explosive
• Creates layers of lava, ash, & cinders,
with steeper sides
• Magma is thicker, cause most violent
eruptions
• Tallest of all volcano types
3. Cinder Cone Volcanoes
• Eruptions are rare, but violent
• Most of lava and ash builds up around
vent –”cone”
• Magma has lots of gas, causing
explosion
• Smallest and most abundant of all
volcano types
C. Where are volcanoes?
• 1.Occur at convergent plate boundaries
• Oceanic-Continental plates around the Pacific
Ocean
• “Ring of Fire” = location of 75% of volcanoes
Where are volcanoes?
• 2. Occur at divergent plate boundaries
• Oceanic-Oceanic split, allowing mid-oceanic
ridge to form
Where are volcanoes?
• 3. Occur at hot spots
• In the middle of oceanic plates, magma
comes up from hole
• Form a “trail” of volcanoes as plate moves
• seamount – volcanoes forming under water
• Mantle plumes
Mt. St. Helens 1980