Faults and Land

Formations

Tectonic Movement

The Earth’s surface consists of moving tectonic plates that exert large forces on one another.

Some types of rock tend to crack under stress. These cracks are called faults. Faults come in all lengths, from a few centimetres to hundreds of kilometres. Other times the rocks can bend which allows them to become folds.

Faults

The movement of the rock in a fault may be vertical,

horizontal, or a combination.

Normal Faults

Normal faults occur when

rocks are under tension—that

is, when the rock is pulled

apart. In a normal fault, one

block of rock usually slides

down the fault face, leaving

the other block at a higher

elevation.

Normal Faults

In a normal fault the

land mass that is pulled

away is called the

hanging wall and the

stable land mass is the

foot wall.

The force that does this

is a tension force

pulling the land masses

apart.

Reverse Fault

Reverse faults occur when

the rock is under

compression—that is,

when the rock is pushed

from opposite directions.

Typically, one block slides

up the fault face, leaving

the other block lower

down.

Reverse Fault

A land mass is pushed up and often over a second land mass. In this situation the land mass being moved over is the hanging wall and the stationary one is the foot wall.

The type of force that does this is a compressional force.

Strike-Slip Faults

A strike-slip fault occurs

when two pieces of

crust slip sideways past

each other. Sudden

movements may occur,

which can cause

devastating

earthquakes.

Strike-Slip Faults

In a strike slip fault the

two land masses are

moving past each other.

A shearing force is

responsible for moving

the land masses.

Folding

Rocks that resist faulting when

stressed tend to change shape. The

buckled layers that form in these

rocks are called folds. Folds can be

of any scale. The simplest type of

fold is called a monocline. Other

types of fold result from more

complicated movements of the

Earth.

Folds

Where rock layers form a

series of folds, some parts

of the folded strata get

pushed downwards, while

other parts hump

upwards.

Anticline and Syncline

The downwardly deformed part of a fold is called a syncline. The

upwardly deformed part of a fold is called an anticline.