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Vocabulary:
Pangaea: Supercontinent that was evidence of continental drift
Continental Drift: Theory that continents were once together and formed a giant supercontinent.
Suggests t hat continents are in constant motion on surface of the Earth.
Asthenosphere: Not flexible, hard rock layer of the mantle
Plate tectonics: Theory that states Earth’s surface is made of rigid slabs of rock, or plates, that move
with respect.
Lithosphere: Cold and rigid outermost rock layer. Made up of the crust and outermost mantle. Earth’s
tectonic plates are large pieces of lithosphere.
Subduction zone: The area where a denser plate descends into Earth along a convergent plate boundary
Convergent boundary: A plate boundary where tectonic plates collide together, forming mountains
Transform boundary: A plate boundary where tectonic plates move past each other creating tension
Divergent boundary: A plate boundary where tectonic plates dive away from each other
Uplift: The upward vertical motion of Earth’s surface
Folded Mountain: Mountains made of layers of rock that are folded
Magma: Molten rock stored beneath the surface of Earth
Fault-block mountain: parallel ridge that forms where blocks of crust move up or down along faults
Seafloor spreading: Process by which magma pushes to the surface at a ridge creating new earth
Rift Valley: A split in earth’s crust at a divergent boundary
Fault zone: an area of many fractured pieces of crust along a large fault
Ocean trench: A deep, underwater channel created by one plate subducting under another plate at a
convergent plate boundary
Things to know and study
1. Describe Wegener’s Theory of Continental Drift, and the related Theory of Plate Tectonics.
What evidence was used for these theories?
The theory of continental drift suggests that all of the continents were once a part of the
supercontinent called Pangaea. Over time, Pangaea began breaking apart and the continents
slowly moved to their current positions. His evidence included that the continents look like
they could fit together like puzzle pieces, fossils of animals and plants that live on different
continents can sometimes be unique to that continent alone. For example, Lions live in Africa
but not South America. Kangaroos live in Australia but not anywhere else. Since oceans
separate continents these animals couldn’t travel by natural means, however fossils of similar
organisms have been found on several continents separated by oceans making Wegener
believe they were once connected. Examples: Glossopteris, Mesosaurus.
Other evidence includes glaciers and the glacial grooves in rocks showing that glaciers covered
parts of continents that are now warmer climate wise. South America, India, Africa, and
Australia were once closer to Antarctica. Rock clues also supported his theory, for example,
geologists know that rock formations on different continents had common origins and
mountain ranges look as if they would line up/connect. Scientists also know that there was a
volcanic eruption on the Western coast of Africa and the Eastern coast of South America
around the same time millions of years ago- and volcanic rock from the eruption are identical
in both chemistry and age.
Plate tectonics theory: by the late 1960’ s a more complete theory was created stating that
the Earth’s surface is divided into large plates of rigid rock and each plate moves over Earth’s
hot and semi-plastic mantle.
2. Be able to identify the 3 types of plate boundaries: Convergent, Divergent, Transform. How do
each move (ex: push together/pull apart/slide) What land formations/processes occur at each?
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Divergent plate boundaries: Forms where two plates separate. When the seafloor
spreads at a mid-ocean ridge, lava erupts, cools, and forms new oceanic crust. They can
also pull continents apart and form rift valleys. Ex: East African Rift
Transform: forms where two plates slide past one another. As they move past one
another they can get stuck and stop moving. Stress builds up where the plates are stuck
and eventually this stress is too great and the rocks break, suddenly moving apart. This
results in a quick release of energy, resulting in lots of earthquakes
Convergent: form where two plates collide. The denser plate sinks below the more
buoyant plate in a process called subduction. The area where a denser plate descends
into Earth along a convergent plate boundary is called a subduction zone. When an
oceanic and continental plate collide, the denser oceanic plate subducts under the
continental plate. This creates a deep ocean trench, This can also happen when two
oceanic plates collide. When two continental plates collide mountains form.
3. What is the inner core/outer core/mantle made up of?
inner core
outer core
mantle
solid iron and nickel, immense pressure
liquid iron and nickel, rotates around inner core creating a dynamo
effect
molten rock, thickest layer, convective layer
crust
thinnest layer, rock, divided into plates, moves
4. What is the earth made up of? Know the layers of the Earth, and be able to give a fact about
each later.
A. inner core
B. outer core
dynamo effect
C. mantle
D. crust
moves
solid iron and nickel, immense pressure
liquid iron and nickel, rotates around inner core creating
molten rock, thickest layer, convective layer
thinnest layer, rock, divided into plates,
a
5. Where is the Ring of Fire? What is it?
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6. What is the San Andreas Fault? Why do earthquakes occur near it?
Some transform faults can’t be seen at Earth’s surface. For example, the San Andreas Fault in
California is visible in many places. Much of this fault system however is underground. The San
Andreas Fault is not a single fault, many smaller faults exist in the area around the San Andreas
Fault. This area of many fractured pieces of crust along a large fault is called a fault zone.
7. What is the mid-ocean ridge? Why is it important in the process of seafloor spreading? A midocean ridge is where sea-floor spreading takes place. The mid ocean ridge is an underwater
mountain range. New oceanic crust forms along the mid-ocean ridge, and older crust moves
away from the ridge.
8. What are compression, tension, and shear stresses? What kind of landforms do they produce?
Compression, tension, and shear stresses are at work at plate boundaries. Each type of stress
produces different types of landforms.
Compression: largest landforms on earth are created by compression at convergent boundaries.
Types of landforms that form are based on whether the plates are oceanic or continental.
Landforms include ocean trenches, mountain ranges, and volcanic arcs.
Tension: where plates move apart, tension stresses stretch Earth’s crust. Distinct landforms are
produced by tension. This includes mid-ocean ridges, and continental rifts.
Shear: As plates slide past one another shear stresses produce transform boundaries. Landforms
created are not as obvious as the others. These cause transform faults, some form
perpendicular to mid-ocean ridges, and cause fault zones.
9. How do mountains form? Be sure to explain fault-block, folded, uplifted, and volcanic
mountains.
 Folded mountains: form as continental plates collide, folding and uplifting layers of rock,
when erosion moves the upper part of the curst, folds are exposed on the surface
 Fault block mountains: sometimes tension stresses within a continent create mountains.
As tension pulls crust apart, faults form. At the faults, some blocks of curst fall and
others rise. These are parallel ridges that form where blocks of crust move up or down
along faults.
 Uplifted mountains: when large regions rise up vertically with very little deformation
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Volcanic mountains: as molten rock and ash erupt onto the surface of the earth, they
harden. Over time, many eruptions can build hug volcanic mountains such as the ones
that make up the Hawaiian islands.