Objective: Identify the types of plate boundaries and the
land features and geologic events that each feature makes.
 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
Follow this link and draw
the transform diagram on
next blank slide.
 Alpine fault in New
Zealand, which forms
the boundary between
the Australian and
Pacific plates
 the Dead Sea fault, which
forms the boundary
between the African and
Arabian plates
 The San Andreas fault, which lies between the Pacific and
North American plates in California.
 San Andreas
• Divergent boundaries
exist where two plates are
moving apart.
 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 the next blank slide.
 Iceland, which sits on the Mid-Atlantic ridge, is
splitting apart on the divergent boundary between the
North American and Eurasian Plates.
 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-view video
 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 next blank
slide.
 The Marianas trench and volcanic arc mark where the
Pacific and Philippine plates converge.
 The Aleutians, Japan, and the Philippines are other
examples of volcanic arcs that exist as a chain of islands.
 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
next blank slide..
 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.
 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-view video