Chapter 4 Study Guide
Section 1:
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Understand the direct and indirect evidence that the Earth’s mantle is molten:
o Direct – increasing temperatures as depth increases
o Indirect: Seismic waves do not pass through the core. Some waves can move through
solids and liquids. Some can only move through solids. Because these waves cannot be
detected far away, it must mean that the mantle is molten.
Section 2:

Know three types of heat energy transfer:
o Radiation – energy moves as a wave through space (heat radiating from the sun, the
fact that you can feel heat from fire without touching it).
o Conduction – energy is transferred through direct contact
o Convection – heat is passed between molecules of a fluid (air or liquid)
 Heat moves through the mantle because of convection currents
Section 3:

Understand CONTINENTAL DRIFT
o Theory proposed by Alfred Wegener that state there was once a supercontinent called
PANGAEA that broke up and moved due to convection currents in the earth’s mantle.
o
Evidence to support this:
 Fossil – glossopteris found on all continents – means they must have once been
joined. Coal beds found at same level in same area on Europe and North
America. Canadian mountains contain tropical fossils.
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Landform – mountain ranges line up along coasts. South America and Africa fit
like puzzle pieces
Climate – South Africa has geology that shows glaciers once existed there.
Spitsbergen in Arctic Circle has tropical fossils.
Section 4:

Sea – Floor spreading
o Sonar used during WWII showed largest mountain chains in the world exist in middle of
Atlantic Ocean and stretch to all oceans (Iceland is actually top of ridge)
o Ocean floors move like conveyor belts from Mid-Atlantic ridge towards the continents –
pushing them apart
o Subduction occurs where oceanic crust meets continental crust. Oceanic crust is more
dense and slides under continental crust. It eventually melts as it reaches the mantle
and is recycled in the convection currents.

Evidence for this:
o “pillow rocks” look like toothpaste squeezed from tube – can only form when lava cools
rapidly under pressure (from ocean)
o Magnetic strips in crust – molecules line up facing north and south pole in alternating
patterns – means that the earth’s crust is constantly forming throughout history and
moving
o Drilling – oldest rocks on ocean crust are near the coasts, meaning that it moved. If the
crust did not move, all rocks would be same age.
Section 5:
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Plate Tectonics
o Juzo Wilson – describes earth’s crust as large plates pushing and pulling on each other
Plates touch at FAULTS – where most earthquakes occur
Know the types of plate boundaries and forces involved in each:
o
Transform boundaries(shearing):

Divergent Boundaries(tension):

Convergent Boundaries(compression):