Download Earth*s Structure

Earth’s Structure
Earth has three main layers.
•Crust
•Mantle
•Core
•Layers are different
because of their
chemical composition
Crust
•We live on top of here.
•Thinnest layer: <1% of Earth’s
mass
•Continental and oceanic
•Minerals and rocks found here
Mantle
•Under the crust
•Makes up most of Earth’s mass: about
67%
•Denser than the crust
•Sometimes mantle rock pushes to the
surface (magma)
Core
•Center of Earth
•About 33% of Earth’s
mass
•Made of iron and nickel
Physical Structure of Earth
•Lithosphere- crust and rigid upper mantle; tectonic
plates
•Asthenosphere- soft rock of the mantle; how
tectonic plates move
•Mesosphere- between outer core and
asthenosphere
•Outer core- completely liquid; iron and nickel
•Inner core- solid and dense
Copy the picture.
Outline:
Crust- brown
Mantle- red
Core- orange
Lightly color Earth’s
physical divisions.
Use a different color
for each.
Pangea Theory
•All continents originally one land mass:
Pangea 245 million years ago
•Wegener’s Hypothesis: continental driftsingle land mass broke up many times
over the years and moved to where they
are now
Tectonic Plates
•Pieces of the lithosphere
that can move
•Sit on top of
asthenosphere
Tectonic Plate Boundaries
•Convergent- plates collide
Ex: continental-continental; continentaloceanic; oceanic-oceanic
•Divergent- plates separate
Ex: sea-floor spreading
•Transform- plates slide past each other
Ex: San Andreas Fault in CA
Subduction occurs at
convergent
boundaries
with oceanic
crust.
Continental-Continental collisions
can sometimes form mountains.
Sea-Floor Spreading
•Happens at mid-ocean ridges (underwater
mountain chains)
•Sea-floor spreading: new oceanic
lithosphere forms when magma rises to the
surface and becomes solid
•This happens because tectonic plates spread
apart
What can happen at boundaries?
•Convergent- earthquakes,
volcanoes, mountains
•Divergent- earthquakes,
volcanoes
•Transform- earthquakes
Deformation: Stress on Rocks
•Compression- forces squeeze rock; occurs at
convergent boundaries
•Tension- forces stretch rock; occurs at
divergent boundaries
•Folding- rock bends because of stress
Faults
• Rock layers can break with stress
• Faults- where rocks break and slide past each
other
• There’s always a fault at a transform boundary
(ex: San Andreas)
• Faults can be at other places (ex: New Madrid
runs through Memphis)
Earthquakes
•Seismology- study of earthquakes
•Seismic waves- energy waves that travel
away from earthquakes
•Body waves (P and S)
•Surface Waves- travel slowly and are very
destructive
P Waves
•Pressure/primary waves
•Travel through solids,
liquids, and gases
•Fastest
•First waves detected
S Waves
•Shear/ secondary waves
•Second fastest
•Stretch rock sideways
•Cannot travel through liquid/
bend around the outer core
Volcanoes
•Magma rises because magma is less
dense than the rock around it
•Occur at mid-ocean ridges, subduction
zones, and hotspots
•Hotspots are not at plate boundaries
Seismographs determine:
•Magnitude: the size of the earthquake
(Richter Scale)
•Depth: how deep the earthquake was
•Location: where the earthquake
occurred