FAULTSFAULTSABIN V . ARKKATTUABIN V . ARKKATTU

In geology, a fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement along the fractures as a result of earth movement.

Large faults within the Earth's crust result from the action of plate tectonic forces, with the largest forming the boundaries between the plates, such as subduction zones or transform faults.

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Mechanisms of faulting

Because of friction and the rigidity of the rock, the rocks cannot glide or flow past each other.

Stress builds up in rocks and when it reaches a level that exceeds the strain threshold, the accumulated potential energy is dissipated by the release of strain, which is focused into a plane along which relative motion is accommodated—the fault.

DeformationDeformation

The process by which the shape of a The process by which the shape of a rock changes because of stressrock changes because of stress..

There are There are two types of stresstwo types of stress that occur that occur in rocks:in rocks:

CompressionCompression TensionTension

Compression Compression Compression occurs when Compression occurs when rock is rock is

squeezed.squeezed.

Compression Compression happenshappens when two when two plates collide plates collide at a convergent at a convergent boundary.boundary.

Compression occurs and Compression occurs and forms forms large mountain ranges.large mountain ranges.

Compression/ Mountain Compression/ Mountain BuildingBuilding

The Himalayas, for example, were raised by the compression that accompanied collision of the Indian plate with the Eurasian plate. Another example is Europe's Alps and Jura mountains which were also formed by horizontal compression, generated in their case by collision with the African plate and the Eurasian plate.

TensionTension

Tension occurs when an Tension occurs when an object is stretchedobject is stretched.. Tension Tension occurs when plates move away fromoccurs when plates move away from

each othereach other at plate boundaries. at plate boundaries. At the Mid-Atlantic ridge the seafloor is At the Mid-Atlantic ridge the seafloor is

spreading at a rate of about 3cm per year. The spreading at a rate of about 3cm per year. The frequency of earthquakes at a mid-ocean ridge frequency of earthquakes at a mid-ocean ridge will depend on how much tension is happening will depend on how much tension is happening at that point. The more tension means the at that point. The more tension means the more seafloor spreading, resulting in a higher more seafloor spreading, resulting in a higher frequency of earthquakes at a particular mid-frequency of earthquakes at a particular mid-ocean ridge. ocean ridge.

FaultsFaults

Some rock layers break when stress is Some rock layers break when stress is applied to them.applied to them.

The The surface along which rocks breaksurface along which rocks break is is called a called a faultfault..

The The blocks of crustblocks of crust on each side of the on each side of the fault are fault are called fault blockscalled fault blocks..

A A fault hasfault has a a foot wall and a hanging wall.foot wall and a hanging wall.

FootwallFootwall

Footwall

You could walk up this face of the fault, on foot, hence the name footwall.

Hanging WallHanging Wall

You could hang from this wall.You could hang from this wall.

Hanging Wall

This is a normal fault. Notice how the rock layers are the same at the red lines.

Hanging wall and Hanging wall and FootwallFootwall

3 Types of Faults3 Types of Faults

Normal FaultNormal Fault Reverse FaultReverse Fault Slip-Strike FaultSlip-Strike Fault

Normal FaultNormal Fault

Rocks are Rocks are pulled apart because of pulled apart because of tensiontension..

In a normal Fault, the hanging wall slides down the footwall.

FootwallHanging wall

Reverse FaultReverse Fault

In a reverse fault the hanging wall is pushed upward due to compression.

Strike-Slip FaultStrike-Slip Fault

Opposing forces cause rocks to move horizontally. Earthquakes occur along these faults.

San Andreas Fault, CaliforniaSan Andreas Fault, CaliforniaStrike-Slip FaultStrike-Slip Fault

3 Most Common Types 3 Most Common Types of Mountainsof Mountains Mountains exist because tectonic Mountains exist because tectonic

plates are continually moving plates are continually moving around and colliding with each around and colliding with each other.other.

There are There are 3 types of mountains3 types of mountains, , named for how they form:named for how they form:

FoldedFolded Mountains Mountains Fault-BlockFault-Block Mountain Mountain VolcanicVolcanic Mountain Mountain

Folded MountainsFolded Mountains FoldingFolding is a process in which the Earth's plates are pushed together is a process in which the Earth's plates are pushed together

in a roller coaster like series of high points and low points.in a roller coaster like series of high points and low points. Folding Folding bends many layers of rocks without breaking them.bends many layers of rocks without breaking them. The The Appalachian Mountains and Rocky Mountains of the United States, Appalachian Mountains and Rocky Mountains of the United States, and the Alps of Europe are examples of mountain ranges that were and the Alps of Europe are examples of mountain ranges that were formed by folding. formed by folding. Folded Strata (Layers)Folded Strata (Layers)

Fault- Block MountainsFault- Block Mountains Mountains sometimes form when many layers of the Earth's crust are Mountains sometimes form when many layers of the Earth's crust are

moved vertically upward at fault lines by pressures caused by plates moved vertically upward at fault lines by pressures caused by plates colliding. Fault lines are great cracks in the crust. The mountains that are colliding. Fault lines are great cracks in the crust. The mountains that are formed in this way are called formed in this way are called fault-block mountains. fault-block mountains. The Sierra Nevada The Sierra Nevada mountains in California and Nevada, and the Grand Teton range of mountains in California and Nevada, and the Grand Teton range of Wyoming are examples of fault-block mountains.Wyoming are examples of fault-block mountains.

Fault block mountains form when tension causes large blocks of crust to drop down relative to other blocks.

Volcanic MountainsVolcanic Mountains

Volcanic mountains are forms when Volcanic mountains are forms when magma erupts from a divergent boundary magma erupts from a divergent boundary and hardens. and hardens.

Many volcanic mountains exist under the Many volcanic mountains exist under the sea.sea.

Some volcanic mountains rise above the Some volcanic mountains rise above the surface of the ocean to from islands, surface of the ocean to from islands, Hawaii for example.Hawaii for example.

Hawaiian IslandsHawaiian Islands

SummarySummary Faulting has a major influence on the way Faulting has a major influence on the way

the earth looks. Mountains form and the earth looks. Mountains form and disappear over time, as well as large rift disappear over time, as well as large rift valleys and other features. This has an valleys and other features. This has an impact on where and how we live. impact on where and how we live.