Transcript Movement in Earth Notes

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?
Plate Tectonics
• Wegner introduced the idea of
Pangaea
– A large supercontinent
• Broke apart because of plate
tectonics
– Moving of Earth’s plates
– Causes the land to look different on
Earth
Earth’s Interior
Earth’s Interior
• Crust
– Cool and solid rock
– Divided into continental and oceanic crust
• Mantle
– Hot and liquid rock
• Core
– Divided into inner and outer core
– Outer = hot and liquid metal
– Inner = hot and solid metal
Earth’s Interior
• Continental Crust
– Less dense
– Thicker
• Oceanic Crust
– Beneath the ocean water
– More dense
– Thinner
Plate Tectonics
• Movement happens because
Earth’s makeup
– Lithosphere
• Crust and upper mantle
• These are the ‘plates’
– Asthenosphere
• Mantle just below the lithosphere
• Very liquid and flowing
Plate Tectonics
Plate Boundaries
• Any place plates meet and move is
known as a fault
• Divergent
– Move apart
• Convergent
– Move together
• Transform Fault
– Move along side
Divergent Boundary
• Cause trenches and ridges
• Forms new crust
Convergent Boundary
• Cause trenches, volcanoes, mountains
• Subduction occurs
– More dense
oceanic crust
slides under
less dense
continental
crust
Transform Fault Boundary
• Cause rocks to crack and break
• Causes lots of earthquakes
Evidence
• Magnetic rocks
in the earth
change polarity
Evidence
• Land shapes
• Fossils
• Ancient climates
Tectonic Plates
Earthquakes
• Shaking or trembling caused by the
sudden release of energy
• Usually associated with faulting or
breaking and slipping of rocks
– Occur at boundaries of plates
– Release energy that create seismic waves
• Continuing adjustment of position
results in aftershocks
Movement of Rock
Earthquakes
• Focus
– The point underground where the
rocks start to slip
– Where the earthquake begins
• Epicenter
– Spot on the surface directly above
the focus
Earthquakes
Earthquakes
• Types of seismic waves
– P waves (primary waves)
• Fast moving longitudinal waves
• First waves we detect
– S waves (secondary waves)
• Slow moving transverse waves
• Second waves we detect
– Surface waves
• Rolling wave on the surface of Earth
• Cause the most destruction
Earthquakes
Earthquakes
• Seismology
– Study of earthquakes
– Use a seismograph
Earthquakes
• Seismology
– Three
seismographs
can tell you
the location of
the epicenter
Earthquakes
• Measured using the Richter scale
Earthquakes
Volcanoes
• A vent or hole in the crust
• How a volcano erupts
– Magma collects in a chamber under the
surface
– Pressure builds up as the chamber fills
– Pressure gets so great magma rises to the
hole and comes out as lava
Volcanoes
Volcanoes
• Three types
– Shield
– Composite
– Cinder cone
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
Composite Cone
Volcanoes
• Eruptions alternate between mild and
explosive
• Creates layers of lava and cinders, with
steeper sides
• Magma is thicker, cause most violent
eruptions
• Tallest of all volcano types
Cinder Cone Volcanoes
• Eruptions are rare, but violent
• Most of lava and ash builds up around
vent
• Magma has lots of gas, causing
explosion
• Smallest and most abundant of all
volcano types
Where are volcanoes?
• Occur at convergent plate boundaries
• Oceanic-Continental plates around the
Pacific Ocean
• “Ring of Fire” = location of 75% of
volcanoes
Where are volcanoes?
• Occur at divergent plate boundaries
• Oceanic-Oceanic split, allowing mid-oceanic
ridge to form
Where are volcanoes?
• Occur at hot spots
• In the middle of oceanic plates, magma
comes up from hole
• Form a trail of volcanoes as plate moves
Mt. St. Helens 1980