Transcript FOLDS and FAULTS

FOLDS and FAULTS
Stresses in the Earth’s Crust
Stress can be Compressional,
Tensional, or Shear
Compressional stress pushes matter (rock layers) together
Tensional stress pulls matter (rock and dirt layers) apart.
Shear stress is rotational, the stress is parallel to a face of the material
2 Basic Types of Folds
1- Anticline:
when layers are folded upwards in what looks
like an arch. The layers are symmetrical (look
alike) on either side of its center.
Caused by Compressional Stresses
2 Basic Types of Folds
2- Syncline
This is when the rock layers are folded
downward.
Caused by Compressional Stresses
A Third Type of Fold
Overturned Folds: anticlines and /or synclines
that have also undergone secondary forces
Caused by Compressional Stresses followed by Shear Stresses, or Compressional
Stresses from a different direction from the original force.
FRACTURES and FAULTS
Breaks in rock are put into two categories
• Fractures:
When there is no movement along either side
of the rock break.
• Faults:
When either side of the rock break moves in
opposite directions
3 Types of Faults
1- Normal Fault: One side of the fault has slipped down
in comparison to the other side.
Normal Faults are caused by layers being pulled
apart, by TENSIONAL stresses.
Gravity causes one side to slip down.
3 Types of Faults
2- Reverse Fault: One side of the fault has slipped up
in comparison to the other.
When layers are pushed together, by
COMPRESSIONAL forces, this kind of fault occurs.
stress
3 Types of Faults
3- Lateral or Strike-Slip Fault: Two layers of rock
are shifted horizontally or parallel to the fault
plane.
These faults are created by SHEAR forces
Images from:
http://www.williamsclass.com/SixthScienceWork/FoldFault/FoldFaultGeologyNotes.htm#Fault