Forces in the earth s crust earth comm understanding your environment pages 43 47
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Forces in the Earth’s Crust Earth Comm : Understanding Your Environment, pages 43-47. Earth and Space Science. I. Forces in the Earth’s Crust. Natural forces fold, tilt, and move rock layers  These actions are called deformation Can cause layers of rock to be folded, break,

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Forces in the Earth’s Crust Earth Comm : Understanding Your Environment, pages 43-47

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Forces in the earth s crust earth comm understanding your environment pages 43 47

Forces in the Earth’s CrustEarth Comm: Understanding Your Environment, pages 43-47

Earth and Space Science


I forces in the earth s crust

I. Forces in the Earth’s Crust

  • Natural forces fold, tilt, and move rock layers

    These actions are called deformation

  • Can cause layers of rock to be folded, break,

    and move


There are three types of forces that can deform rocks

There are three types of forces that can deform rocks.


1 tensional forces

1. Tensional forces

– Forces which stretch / pull parts of the rock in opposite directions


2 compressional forces

2. Compressional forces

– Forces that squeeze together parts of the rock


3 shear forces

3. Shear forces

– Forces that try to cause materials to slide past

each other


Forces in the earth s crust earth comm understanding your environment pages 43 47

  • They can act alone or as a combination

    * If any of these forces are greater than the material’s strength, the material will deform

    (bend, break, stretch, compress, twist, etc.)


A folding and faulting

A. Folding and Faulting


Temperature plays a key role as to what type of deformation occurs

Temperature plays a key role as to what type of deformation occurs

  • Low temperature  rocks are brittle and

    break easily

    - deform by fracturing / faulting

    - generally the rocks in the upper crust are

    cooler in temperature


Temperature plays a key role as to what type of deformation occurs1

Temperature plays a key role as to what type of deformation occurs

  • High temperature  rocks tend to deform by changing in shape continuously instead of breaking

  • Generally the rocks in the lower crust are warmer in temperature


Forces in the earth s crust earth comm understanding your environment pages 43 47

  • Folding is an example of how rocks can change their shape continuously without breaking


Speed of deformation plays a key role

Speed of deformation plays a key role

if force builds up slowly = folding is more likely

if force builds up quickly = faulting is more likely


Fault

Fault

  • A crack in the lithosphere which can allow rock bodies to move past each other

    can be caused by shear forces, compressional forces, and/or tensional forces or a combination


Folding

Folding

  • A bend in a layer of rock, usually due to deformation

    - usually caused by compressional forces

    - very common in layered rocks such as sedimentary


Forces in the earth s crust earth comm understanding your environment pages 43 47

* These processes occur over long periods of time and cannot be directly observed in nature


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