Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Earth Systems 3209 Unit: 4 The Forces Within Earth Reference: Chapters 4, 15, 16, 19; Appendix A & B

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Forces and Factors that affect Deformation Unit 4: Topic 3.1 Focus on...  defining crustal deformation, force, and stress.  outlining and describing three types of deformation.  identifying and describing the forces that cause deformation.  identifying and describing the factors that affect deformation.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Terminology associated with Crustal Deformation: Crustal Deformation is associated with Internal Forces within Earth! Crustal Deformation  General term that refers to all changes that occur to the original form and/or size of a rock body.  It may also produce changes in the location and orientation of rocks.  Most crustal deformation occurs along plate tectonic margins.  Plate motions and the interactions along plate boundaries generate tectonic forces that cause rock units to deform.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Terminology associated with Crustal Deformation: Force  anything that tends to put stationary objects in motion or change the motion of moving bodies. Stress  is defined as the amount of force applied to a given area.  Two types of stress; 1) Uniform – equal stress in all directions. 2) Differential – varying stress in different directions. Strain  causes an irreversible change in the shape and size of a rock body. Original configuration is not retained during deformation.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Types of Crustal Deformation: Differential Stresses: Compressional  stresses that shorten a rock body are compressional in nature Tensional  stresses that elongate a rock body Shear  stresses that cause sections of a rock body or two separate rock bodies to slide past one another

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Types of Crustal Deformation:  When rocks are subjected to stresses greater than their own strength, they begin to deform, usually by folding, flowing, or fracturing. 3 types of deformation: 1)Elastic Deformation - recoverable 2)Brittle Deformation - permanent 3)Ductile Deformation - permanent

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Types of Crustal Deformation: 3 types of deformation: 1)Elastic Deformation  stress is applied gradually and when the stress is removed the rock will return to nearly its original size and shape.  elastic deformation is recoverable after stressing.  earthquakes result from stored elastic energy.  once the elastic limit is reached it either flows (ductile) or fractures (brittle).

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Types of Crustal Deformation: 3 types of deformation: 2)Brittle Deformation  stress is applied gradually and when the rocks strength is exceeded the rock will behave like a brittle solid where it will fracture and the rock will not return to its original size and shape.  occurs near the surface where temperature and confining pressures are lower.  brittle deformation is permanent.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Types of Crustal Deformation: 3 types of deformation: 3)Ductile Deformation  stress is applied gradually and when the rocks strength is exceeded the rock will flow in solid state and produce a change in the original size and shape without fracturing.  occurs at great depths beneath Earth’s surface where temperature and confining pressures are higher.  ductile deformation is permanent.  An example would be similar to a penny placed on a railway track and flattened by a passing train. Metal is permanently changed.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Factors that Affect Crustal Deformation:  The factors that influence the strength of a rock and thus how it will deform include; 1)Temperature 2)Confining Pressure 3)Rock Type 4)Time

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Factors that Affect Crustal Deformation:  The factors that influence the strength of a rock and thus how it will deform include; 1)Temperature  the colder the Earth materials, the more brittle the deformation will be.  the warmer the Earth materials, the more elastic or ductile the deformation will be.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Factors that Affect Crustal Deformation:  The factors that influence the strength of a rock and thus how it will deform include; 2)Confining Pressure  confining pressure will only result in elastic or ductile deformation at varied depths beneath Earth’s surface.  brittle deformation typically occurs on the surface when there is no confining pressure from above.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Factors that Affect Crustal Deformation:  The factors that influence the strength of a rock and thus how it will deform include; 3)Rock Type  all rock types can be deformed.  however, sedimentary rocks could be more easily deformed since they are softer.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Factors that Affect Crustal Deformation:  The factors that influence the strength of a rock and thus how it will deform include; 4)Time  rapid deformation tends to result in brittle deformation.  slower deformation over longer periods of time tends to result in elastic or ductile deformation.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Example 1: Which factors would cause a rock to deform by brittle deformation ? TimeTemperature (A) ShorterColder (B) ShorterWarmer (C) LongerColder (D) Longer Warmer

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Example 2: Which type of stress and faulting occurs at divergent plate boundaries? StressFaulting (A) shearnormal (B) shearreverse (C) tensionnormal (D) tensionreverse

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Your Turn... Take the time and complete the following questions... (Solutions to follow) Question: Which rock type is most easily deformed by stresses in Earth’s crust? (A)igneous plutonic (B)igneous volcanic (C)metamorphic (D)sedimentary

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Solutions... Question: Which rock type is most easily deformed by stresses in Earth’s crust? (A)igneous plutonic (B)igneous volcanic (C)metamorphic (D)sedimentary

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Summary... Overview of Points covered:  Crustal deformation is a direct result of stresses put on rocks.  3 types of stress include; 1) Tensional, 2) Compressional, 3) Shear  3 types of crustal deformation include; 1) Elastic, 2) Brittle, 3) Ductile  Factors affecting crustal deformation include; 1) Temperature, 2) Confining Pressure, 3) Rock Type, 4) Time