Chapter 5: Plate Boundaries and California
Lesson 5.1- Interactions at Plate Boundaries
A.
Stress and deformation result when lithospheric plates
1.
Rocks that are subjected to
a.
at plate boundaries.
temperatures and
become deformed.
When rocks permanently change shape by folding, it is called
deformation.
b. When rocks snap back to their original shapes after stress is removed, it is
called
c.
deformation.
A break or crack in rock is called a
d. A
.
results if the rock on one side of the fracture surface moves
relative to the rock on the other side.
e.
The three forms of stress that
rocks are tension, compression, and
shear.
2.
stress results when plate rock is pulled apart and it becomes
3.
If plate rock is squeezed, the stress of
4.
When plate rock is pushed in opposite directions, the force of
makes the rocks
on it but does not change the
.
stress acts
of the plate.
B. Different types of stress produce different types of
1. Geologists measure the
.
.
of the fault surface to figure out which way the broken
sections of rock have moved.
a. The hanging wall is the block of rock that lies
the fault.
b. The block of rock that lies below the fault is called the
2. Tension forces inside Earth pull rock apart, producing
a. This kind of fault
at an angle.
b. When rock breaks and
along the fault, the
.
faults.
wall slides down the
footwall.
3. In places where the rocks are pushed together, compression produces
4. Where plates slide past each other, shearing stresses produce
a. Strike- Slip faults often are
b.The rocks
faults.
faults.
, not inclined.
each other sideways.
c. Plate boundaries are classified by the way the rocks on either side
.
C. The boundary formed where two plates of lithosphere are moving apart is a
plate
boundary.
1.
occur along divergent plate boundaries.
, dense material below Earth’s crust is forced upward at the mid-ocean
a. Hot
ridges.
b. New seafloor forms as two plates of lithosphere move
.
c. Seafloor located farther from a divergent plate boundary is
because it
cools and becomes denser as it moves away from the center of the ridge.
2.
is the process that pulls a continent apart.
a. A long, narrow
forms when a
b.
slips down.
collects on the floor of the rift valley, pushing the valley deeper.
3. The East African Rift and the Gulf of California are examples of modern continental rift
D. A
.
plate boundary is formed when two lithospheric plates move
toward each other.
1. Where two oceanic plates move toward each other, one of the plates
the other plate and is forced down into the mantle in a process
called
.
a. The colder, older,
slab is usually forced down into the mantle,
forming a
on the seafloor where it bends.
b. High temperature and
in the mantle release
from minerals in
the slab.
c. Water rises from the mantle and causes rocks to
, and
rises to the
surface, forming volcanoes.
2. Sometimes an oceanic plate and a
a. The
less
plate collide at a convergent boundary.
plate always subducts because continental rocks are
than oceanic rocks.
b. The melting of subducted rock produces a curved string of
along the
leading edge of the continent.
3. When two continental plates collide,
form
.
stress forces crust to
and
E. A
plate boundary exists where two plates grind
another, eventually causing
past one
.
1. Lithosphere is neither formed nor
at these boundaries.
2. Oceanic transform boundaries connect pieces or segments of the
3. Continental transform boundaries slice through
a. Large
be
.
lithosphere.
resulting from movement along these faults can
if they occur in populated areas.
b. The
transform
in California is the best studied continental
in the world.
c. Most of California is on the continental
. But a small
part of California, west of the San Andreas Fault lies on the adjacent
plate.
Lesson 5.2- California Geology
A. Transform Plate Boundary
1. Most of California is situated on continental lithosphere of the
.
2. A small part of California, west of the San Andreas Fault, lies on the adjacent
oceanic
.
3. The San Andreas Fault is a transform plate boundary. It is also a zone
of
.
4. The Pacific plate moves northwest relative to the
, at a velocity of
about 3.4 cm per year.
a. The Pacific Plate does not move smoothly, but instead moves in
jerky movements cause
B.
. These
.
Convergent Plate Boundary
1. Just offshore of Northern California, there are
a. These plates, known as the
small oceanic lithospheric plates.
and
, are subducted
beneath the coast. This subduction forms a convergent plate boundary.
b. Melting above this subduction zone produces the volcanic
of the
Cascade Range.
C. California’s Mountains formed from interactions at several
boundaries.
at California’s convergent plate boundaries has been important in forming the
1.
state’s mountains.
2. Granitic rocks form under volcanic mountains where plates
.
a. During mountain building, compressive stresses and heat produces
rocks.
b. The
Mountains formed at a convergent plate boundary from igneous
and metamorphic rocks beneath the surface.
c. The
also formed at a convergent plate boundary from the
subduction of an ancient oceanic plate.
3. Above the subduction zone in northern California, granitic rocks are forming deep in the crust
and
activity produces the
a. Both Lassen Peak and
on the surface.
are active volcanoes in this mountain range.
4. There are some mountains in California that have formed because of
a. The
Eastern California stretches.
stresses.
west o f Death Valley is rising up as the crust in