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Slide 1
Objective: Identify the types of plate boundaries and the land
features and geologic events that each feature makes.
Slide 2
Transform boundaries exist where two plates slide past each
other. No lithosphere is created or destroyed Most transform faults
are found on the ocean floor. Transform Boundary Transform Boundary
Follow this link and draw the transform diagram on page 79.
Slide 3
Alpine fault in New Zealand, which forms the boundary between
the Australian and Pacific plates
Slide 4
the Dead Sea fault, which forms the boundary between the
African and Arabian plates
Slide 5
The San Andreas fault, which lies between the Pacific and North
American plates in California. San Andreas
Slide 6
This occurs most commonly at mid-ocean spreading ridges. At
such ridges, plates move apart and the mantle exposed is melted by
the decrease in pressure, becoming magma. That magma then rises up
to fill in as new oceanic crust. As the plates separate, the
geologic feature known as a rift valley is created. Divergent
Boundary Follow this link and draw the divergent boundary on page
81. Divergent Boundary Divergent boundaries exist where two plates
are moving apart.
Slide 7
Iceland, which sits on the Mid-Atlantic ridge, is splitting
apart on the divergent boundary between the North American and
Eurasian Plates.
Slide 8
East African Rift Valley system marks the boundary between two
plates: the Nubian plate to the west and the Somalian plate to the
east. The rift valley is a classic example of a divergent plate
boundary. Rift Valley
Slide 9
Oceanic-Oceanic Convergence: If the plates moving toward each
other are both made of oceanic crust, one of the plates will move
downward, or subduct, under the other plate. This is called a
subduction zone. A deep trench forms on the ocean floor at the
location where one oceanic plate subducts under another. Also, a
volcanic arc (a chain of volcanoes parallel to the trench)
typically develops above the subduction zone. These volcanoes are
generated as water brought down on the subducting plate melts the
overlying mantle, causing magma to rise through the mantle and
crust, erupting at the surface. Old crust is destroyed at an
oceanic-oceanic boundary. Oceanic-Oceanic Boundary Follow this link
and draw the oceanic-oceanic convergent boundary diagram on page 82
in your IAN. Oceanic-Oceanic Boundary
Slide 10
The Marianas trench and volcanic arc mark where the Pacific and
Philippine plates converge. Marinas Trench The Aleutians, Japan,
and the Philippines are other examples of volcanic arcs that exist
as a chain of islands.
Slide 11
If one plate topped by oceanic crust moves toward another
topped by continental crust, the more dense, oceanic plate will
subduct under the less dense, continental plate and a trench will
develop off the shore of the continent. Old crust is destroyed at
this type of boundary Oceanic-Continental Boundary Follow this link
and draw the oceanic-continental convergent boundary diagram on
page 82 in your IAN. Oceanic-Continental Boundary
Slide 12
Off the coast of South America, along the Peru-Chile trench,
the oceanic Nazca Plate is being subducted beneath the continental
South American Plate. As a result, the Andes, a mountainous
volcanic arc, have developed in South America. The Cascade Range,
where Mt. St. Helens is found, is another example of a volcanic arc
formed by the convergence of oceanic and continental plates.
Slide 13
If both converging plates carry continental crust, neither of
the plates fully subduct. Continental rocks have a relatively low
density and, like two colliding icebergs, usually resist downward
motion. During a collision, the crust is compressed and subjected
to very high temperatures and pressures. The lithosphere thickens
and crustal rocks are folded and faulted. Large amounts of uplift
push rock high into the sky, forming mountain ranges such as the
Alps or the Himalayas. Formation of the Himalayas