Download Land Form Patterns: Tectonic Faults

Unit 1: Land & Water Forms
World Geography 3200/3202
Outcomes
 In this lesson you will:
 1.1.6 Explain how tensional forces create a normal fault.
(k)
 1.1.7 Explain how compressional forces create reverse
and overthrust faults. (k)
 This lesson corresponds to the information contained
in the "Mountains Formed by Faulting" section found
on page 14 of your text.
Fault Lines
 Fault lines are basically great cracks in the earth’s
crust created when plates are
compressed against each
other.
 The break or crack may
be slight or may run deep
into the Earth’s crust
 The length of the fault may
be short or may extend
hundreds of kms.
Faulting
 Faulting is instrumental in mountain building
 Geologists have analyzed the precise ways in which
plates are changed by faulting & have developed four
main types of mountains
1. Normal Fault Mountains
 Caused by: tensional forces.
 Occurs when: A plate on one side of the fault drops
down lower than the plate on the other side
Fault Block Mountains
 Sometimes two normal faults occur parallel to each
other
 In some cases the broken plate between the faults
drops as the broken plates move away from each other
forming a rift valley
 In case when many layers of the Earth's crust are
moved vertically upward between two parallel
fault lines, Fault Block Mountains result.
 The vertical force is caused by the Earth's internal
pressure.
Reverse Fault Mountains
 When simple rock layers around a fault push
against each other instead of pulling away, one
block can be pushed up over the other
 This results in the creation of a Reverse Fault
Mountain caused by compressional forces where
plates move together at the fault.
Overthrust Faults
 when the plate that suffers the fault has already
undergone folding, & its folded layers are then
pushed up & thrust over layers on the fault’s other
side, an Overthrust Fault occurs.
Faulting: A Review
 Q. What name is given to large cracks in the earth's crust?
 A. FAULT LINES
 Q. What name is given to faults formed by tensional forces?
 A.NORMAL FAULTS
 Q. What name is given to faults formed by compressional forces?
 A. REVERSE FAULTS
 Q. How do overthrust faults differ from regular reverse faults?
 A. THEY WERE FOLDED BEFORE FAULTING