Landforms

logo(1).gif (11000 bytes) A More Revealing Facts of the Earth
Landforms

Crustal movements may cause layers of rocks to be folded.

Compressional forces in the crust push toward each other in opposite directions, bending and folding the rock layers in various ways.

mt.jpg (2429 bytes)

Types of Fold

Simple or Symmetrical Fold

	equal steepness
	2 forces are of equal strength

Asymmetrical Fold

	one limb is steeper than the other
	1 force is slightly greater than the other

Overturned Fold

	one limb pushes over the other
	opposing force is greater

Faulting

-a fracture or break in the earth's crust along a line of weakness

Faulting may be caused either tensional or Compressional forces exerted on rocks either laterally or vertically.

----> compressional <------ <------- tensional----------->

3 major types of Faulting

	Normal Faults ---> caused by tension pulling the crust apart
	Reverse Faults ---> caused by compressional forces in the Earth's crust
	Tear Faults ---> caused by adjacent sections of the crust sliding past each other horizontally e.g. San Andreas Fault in California USA

BLOCK MOUNTAIN (HORST)

~ formed when faulting in the crust due to either tension or compression causes a block of the crust to be uplifted, relative to the depressed crust on either side of it.

A block mountain with a horizontal surface is called a horst. It has 2 pronounced scarps or either called 'overhanging cliff'.

RIFT VALLEY (GRABEN)

~ A rift valley or graben is a long valley, formed by the sinking of land between two roughly parallel faults. e.g. East African Rift Valley

It may be due to tension or compression.

	Normal Fault ~ results in vertical displacement of rocks
	Reverse Fault ~ results in vertical displacement of rocks
	Tear Fault ~ results in horizontal displacement of rocks

This WebPages is done for the competition of ThinkQuest