Notes-Stress, Faults and Folds
_____________________________ is the bending, tilting, and breaking of the earth’s
crust. Plate tectonics is the major cause of crustal deformation. Crust rides on top of the
mantle. Thicker and heavier crust ___________ deeper into the mantle where thinner
and lighter crust will ____________ higher on the mantle. The up and down movement
of crust is balanced by two pressures. One is the crust pressing ________________ and
the other is the mantle pushing _____. The balancing of the these two forces is called
______________. The up and down movement of the crust to reach isostasy are called
isostatic adjustment. During this adjustment the rocks in the crust are bent causing
deformation. There are ____ basic kinds of stress that the isostatic adjustment causes
_________________________, _____________________, and __________________.
Compression occurs when crustal rocks are squeezed together. Tension is the force that
pulls rocks apart. Here rocks tend to become thinner. Shearing pushes rocks in opposite
directions. Sheared rocks bend, twist or break.
The results of stress are ______________ and _______________. When a rock has
stress put on it and does not break it is called __________________. Folds appear as
wave like structures in rock layers. Some folds are small and can be seen in individual
rocks and some folds are huge and can only be seen from the air. The ____ general types
of folds are __________________________, which are upcurved folds where the oldest
rock layers are in the center, ____________________________ which are downcurved
fold in which the youngest layers are in the center and ____________________________
in which both ends stay horizontal but one side is lower than the other.
Rocks don’t always bend, sometimes they break. When the rock moves and breaks it is
called a _______________. There are several different kinds of faults. There are two
sides to a fault. The side that is above the fault plane is called the
____________________ ___________________. When the hanging wall moves down it
is called a ___________________ fault. Normal faults occur in places where there is
tension or the rocks are being pulled apart. When the hanging wall moves up it is called
a ____________________ fault. Reverse faults are caused by compressional forces. A
low angle reverse fault is called a thrust fault because one side is being thrust onto the
other. The last type of faults are called _____________________ faults. Strike-slip
faults are slide horizontally past one another. If you are looking across to the other side
of a strike-slip fault and that side moves to the left of you it is called a _____________
_____________________ strike-slip fault. Strike-slip faults occur in and around
transform plate boundaries like where we live near the San Andreas fault.