Study Guide for Unit Two – Plate Tectonics
PART 1: The Theory of Continental Drift is a hypothesis that states that the
continents once formed a large single landmass called Pangaea. Evidence for
Wegener’s theory include a puzzle- like fit of the continents, identical rock types,
identical fossils, and very similar mountain ranges found on different continents
that are separated by a wide ocean.
PART 2:
1. Scientists today use sonar to study the ocean floor. Studying the ocean floor
helps scientists better understand what is happening to our Earth. Scientists
discovered the ocean floor’s topography is not flat like they once believed.
2. The continental shelf is the section of the continental crust that extends
under the water.
3. The continental slope is the steep incline section of the continental crust. It
connects the continental shelf to the abyssal plain.
4. The abyssal plain is a large, flat, almost level region of the ocean floor
covered with thick sediment.
5. The mid-ocean ridge is a long, underwater mountain chain that forms on the
floor of the ocean.
6. The rift valley is a long, narrow crack in the ocean floor in the middle of the
mid-ocean ridge.
7. Seamounts are individual mountains of volcanic material.
8. Ocean trenches are deep valleys or canyons in the ocean floor.
PART 3:
1. Sea floor spreading is the process by which new oceanic crust forms as
magma in the mantle rises through the rift in the mid-ocean ridge and
solidifies (hardens) making new crust. This new crust pushing the older,
colder, denser crust away from the ridge. This movement of the crust away
from the ridge moves the continents with it.
2. The subduction zone is the area below the trench that pulls the cooler, old,
and more dense crust into the mantle. The process of crust being pulled into
the mantle is called subduction.
So, the process of sea floor spreading creates new crust, but the process of
subduction destroys the old crust. Therefore, the overall size of the crust does not
change.
Part 4:
1. The lithosphere is the solid outermost, rigid layer of earth. It is made of the
crust and the upper part of the mantle.
2. The asthenosphere is the soft plastic layer of the mantle that flows very
slowly.
3. Pieces of the “cracked” lithosphere (tectonic plates) float on top of the
asthenosphere. As they float, they are in constant slow motion due to
convection currents in the mantle. The moving of tectonic plates on the
asthenosphere is the theory of plate tectonics.
4. Where these plates meet, events such as earthquakes and volcanoes occur.
The place where plates meet is known as a plate boundary.
Part 5:
Convergent Boundary
Divergent Boundary
Transform Boundary
Diagram
Diagram
Diagram
When two tectonic
When two tectonic
When two tectonic
plates move toward
plates move or pull
plates slide or slip
each other
away from each other
past each other
5. A fault is a crack in the earth's crust resulting from the displacement of the
earth’s crust.
PART 6:
1. Geothermal energy is energy released by heat within the Earth.
2. Energy transferred as electromagnetic waves is called radiation.
3. A renewable resource is a resource that can be replaced at the same rate it is
used.