Download Plate Project SCRIPT

Project 2: Plate Tectonics
Script
Read part 1: Pangea
1. According to the theory, the surface of the Earth is broken
into large pieces called plates. These plates float over an
inner molten layer. The size and position of these plates
change over time. An example of such movement is the idea
of a super continent called Pangaea that existed millions of
years ago. Evidence suggests that the separate continents we
know today migrated from this one large land mass.
2. The edges of these plates are sites of intense geologic
activity. Earthquakes, volcanoes, and mountain building can
occur when they move against each other.
3. Plate tectonics are a combination of two earlier ideas,
continental drift and sea-floor spreading.
a. Continental drift is the movement of continents over the
Earth's surface and their change in position relative to each
other.
b. Sea-floor spreading is the creation of new oceanic crust at
mid-ocean ridges and movement of the crust away from
the mid-ocean ridges.
Read part 2: intro for Plate Boundaries
1. Many changes and movements in the earth’s crust originate
along Lithospheric plate boundaries.
2. Plate boundaries can be in the middle of the ocean floor,
around the edges of continents, or within continents. There
are several types of plate boundaries, each of which is
associated with a characteristic type of geologic activity.
Read part 3: Divergent boundaries are two plates moving apart
from each other. Also known as spreading boundary, a divergent
boundary occurs where two plates move apart, allowing magma, or
molten rock, to rise from the Earth's interior to fill in the gap.
1. The process by which the plates move apart can also be
referred to as sea floor spreading. At this type of boundary,
new oceanic crust is formed in the gap between two
diverging plates. Plate area is increased as the plates move
apart.
2. Plate movement takes place laterally away from the plate
boundary, which is normally marked by a rise or a ridge. The
ridge or rise may be offset by a transform fault.
3. Presently, most divergent margins occur along the central
zone of the world’s major ocean basins. The Mid-Atlantic
Ridge and East Pacific Rise provide good examples of this
type of plate margin.
Read Part 4: Convergent boundaries are the direct collision of
one plate with another. As seafloor spreading pulls plates apart at
one boundary, those plates push into neighboring plates at other
boundaries. The direct collision of one plate with another type of
plate is called a convergent boundary. Three types of collisions can
occur at convergent boundaries.
1. Oceanic-continental convergence -- One type occurs when a
plate with oceanic crust at its leading edge collides with a
plate with continental crust at its edge. Because oceanic crust
is denser, it is subducted, or forced under the less dense
continental crust. Scientist refer to the region along a plate
boundary where one plate moves under another plate as a
subduction zone. A deep oceanic trench generally forms
along a subduction zone. As the oceanic plate moves down
into a subduction zone, it melts and becomes part of the
mantle material. Some of the magma formed rises to the
surface through the continental crust and produces volcanic
mountains.
2. Continent-continent convergence -- A second type of
collision occurs when two plates with continental crust at
their leading edges come together. During this type of
collision, neither plate is conducted because they both have
the same density. Instead, the colliding edges are crumpled
and uplifted, producing large mountain ranges. Scientist are
convinced that the Himalayas were formed by this type of
collision
3. Oceanic-oceanic convergent -- The third type of collision
along convergent boundaries occurs between oceanic crust
and oceanic crust. A deep ocean trench also forms when one
of these plates is subducted. Part of the subducted plate
melts, and the resulting molten rock rise to the surface along
the trench to form a chain of volcanic islands called an island
arc.
Read Part 5: Transform fault boundaries occur were two plates
are grinding past each other. Transform boundaries neither create
nor consume crust. Rather, two plates move against each other
building up tension and then releasing the tension in a sudden and
often violent jerk. This sudden jerk creates an earthquake.
Example: The San Andreas Fault is undoubtedly the most famous
transform boundary in the world. To the west of the fault is
the Pacific plate, which is moving northwest. To the east is
the North American Plate, which is moving southeast. Los
Angeles, located on the Pacific plate, is now 340 miles south
of San Francisco, located on the North American plate. In 16
million years, the plates will have moved so much that Los
Angeles will be north of San Francisco!