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Chapter 5
Deformation of the Crust
Section 5.1
 Some
changes in the earth’s crust
occur because of changes in weight
of some part of the crust.
 When parts of the crust become
thicker and heavier, they will sink.
 If they become lighter and thinner, it
will rise.
Section 5.1
 The
balancing of the mantle pushing
up and the crust pushing down is
called isostasy.
 The up and down movements of the
crust is called isostatic
adjustments.
Section 5.1
 Isostatic
adjustments are constantly
happening.
 The wearing away of rocks can
reduce the height and weight of a
mountain.
Section 5.1
 Rivers
can carry large amounts of
mud, gravel, and sand into an ocean
and pile up.
 Adjustments can also be found
where glaciers once covered the land
Section 5.1
 Crustal
stress occurs when plates
collide, separate, or rub together.
 Strain is a change in the shape or
volume of rocks because of the
stress of being squeezed, twisted, or
pulled apart
Section 5.1
 Compression
occurs when crustal
rocks are squeezed together
 Tension pulls rocks apart
 Shearing pushes rocks in opposite
directions
Section 5.2
 Folding
of rocks occurs when rocks
are permanently deformed but no
broken
 3 types of folds
 Anticlines are upward curved folds
where the oldest layer is in the
center. Like a hill
Section 5.2
 Synclines
are downward folds where
the youngest layer is in the center.
Like a valley
 Monoclines are folds where both
limbs stay horizontal
Section 5.2
 Rocks
do not always fold.
 They often break from the stress.
 If there is no movement in the break
it is called a fracture.
 If there is movement it is called a
fault.
Section 5.2
A
fault plane is the surface of a fault
where motion occurs.
 The hanging wall is the rock above
the fault plane
 The footwall is the rock below the
fault plane
Section 5.2
A
reverse fault causes the hanging
wall to move up.
 A thrust fault is almost horizontal
 A strike-slip fault is where the rocks
are moving horizontally
Section 5.3
A
mountain range is a group of
adjacent mountains with the same
general shape and structure
 A mountain system is a group of
adjacent mountain ranges
 A mountain belt is a group of
mountain systems
Section 5.3
 Mountains
can form when
Continental crust collides with other
continental crust or with oceanic
crust.
 Mountains can also form when
oceanic crust collides with oceanic
crust.
Section 5.3
 The
highest Mountains Ranges in the
world are made of folded mountains
that usually are made when 2
continental plates collide.
 Volcanic Mountains form when
molten rock erupts to the surface.
Section 5.3
 The
northern oceanic crust of the
African plate, which is the seafloor of
the Mediterranean Sea, is still
subducting beneath the continental
crust of Eurasia.
 Eventually the Mediterranean Sea
will become smaller and smaller and
disappear.