Download Answer Key for Effects of Plate Tectonics Note-taking

Answer Key for Effects of Plate Tectonics
Note-taking Guide
What are Tectonic Plates?
alters,
solid,
asthenosphere,
tectonic,
surface
The most powerful force that alters the Earth’s surface is the movement of tectonic plates.
Tectonic plates are large, solid pieces of the Earth’s lithosphere that move in different directions
on top of a hotter flowing layer called the asthenosphere.
There are 7 major tectonic plates and some minor ones that make up the surface of the Earth.
Plate Tectonics Theory
interior,
sea floor,
earthquakes,
ocean floor,
Pangaea,
new,
age,
mid-ocean,
moved,
away,
continental drift,
plate tectonic,
geological,
convection,
older
In the early 1900’s, Alfred Wegener, put forward the theory that the continents were once part of
one large land mass called Pangaea.
This theory is called the continental drift theory, and explained why identical animal fossils, like
that of the Mesosaurus, were found on coastlines separated by vast oceans.
It also explained why similar geological features were found across continents like the North
American Appalachian Mountains lining up with mountains in Scotland and Scandinavia.
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But this theory didn’t explain “why” the continents moved. It was only with the ocean floor
explorations of the early 1960s that the continental drift theory was verified.
These explorations led to the discovery of magma oozing up in the middle of underwater
mountain chains, known as mid-ocean ridges, to create new ocean floor. This process was
called sea floor spreading.
Sea floor spreading occurs when tectonic plates move away from each other and create a gap
in the Earth’s crust. Magma rises up and fills this gap, creating new oceanic crust.
The age of the ocean floor is an important piece of evidence that supports sea floor spreading.
New crust is found at the mid ocean ridges and gets progressively older as it moves away from
both sides of the ridge.
The continental drift theory and sea floor spreading, in addition to the discovery that
earthquakes and volcanoes occur most frequently at mid-ocean ridges and specific areas
around the world, led to the development of a new unifying theory called the plate tectonic
theory.
The plate tectonic theory explains how earth works. Heat from Earth’s interior, creates
convection currents which move the lithospheric plates around in different directions, at different
speeds.
Divergent Plate Boundaries
continental,
rift,
divergent,
fault block,
fault,
away,
new
A divergent boundary is the place where two tectonic plates move away, or spread apart, from
one another.
The majority of divergent boundaries are located at mid-ocean ridges where sea floor spreading
takes place and new crust is formed.
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A divergent boundary is also formed when two continental plates move apart; a fault develops
on the Earth’s crust.
Some of the landforms on Earth are created by the movement of divergent plates that cause rift
valleys and fault block mountains.
Convergent Plate Boundaries
asthenosphere,
subduction,
lighter,
convergent,
folded,
denser,
increases,
magma,
towards,
Himalayas,
oceanic,
volcanoes,
trench
A convergent boundary is a place where two tectonic plates move towards, or push against
each other.
When two continental plates converge, they can squeeze together and force the crust upwards.
This leads to the formation of folded mountains. This is how the highest mountain range, the
Himalayas, were formed.
When an oceanic plate converges with a continental plate, the denser oceanic plate slides
beneath the lighter continental plate, into the asthenosphere. This region is called a subduction
zone and the tectonic forces are so strong that a trench or crack can form in the ocean floor.
As the oceanic crust sinks downward toward the asthenosphere, the temperature increases and
the edge of the oceanic plate melts to form magma. The magma can eventually erupt through
Earth’s crust to form volcanoes.
Transform Plate Boundaries
California,
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earthquakes,
slide past,
tectonics,
fault
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At transform boundaries, instead of moving towards or away from each other, tectonic plates
slide past one another. This kind of boundary results in a large fault. An example of this in the
San Andreas Fault in California.
Because tectonic plates are not smooth, a lot of jolting and gnashing occurs while the plates
slide past one another, creating earthquakes.
Plate tectonics has led to a sweeping change in our understanding of Earth and the forces that
shape it.
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