Law of SuperPosition

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Law of SuperPosition

• Geologic Time

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Super what??!?!

• Superposition Younger rock layers are on top of
  older rock layers.
• Used with the other principles of stratigraphy to
  study rock layers and layering.
• Stratigraphy Branch of geology concerned with
  the study of the formation, composition, ordering
  in time, and arrangement in space of stratified
  rocks. USGS
• Nicolaus Steno (1669)

http//stloe.most.go.th/html/lo_index/LOcanada8/80
1/2_en.htm
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Principles of Stratigraphy

• superposition - in a vertical sequence of
  sedimentary or volcanic rocks, a higher rock unit
  is younger than a lower one. "Down" is older,
  "up" is younger. 
• horizontality - rock layers were originally
  deposited close to horizontal. 
• Original lateral extension - A rock unit
  continues laterally unless there is a structure
  or change to prevent its extension. 
• cross-cutting relationships - a structure that
  cuts another is younger than the structure that
  is cut. 
• inclusion - a structure that is included in
  another is older than the including structure. 
• "uniformitarianism" - processes operating in the
  past were constrained by the same "laws of
  physics" as operate today
• http//www.talkorigins.org/faqs/dating.html

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Inclusion
Original lat. Ext.
Cross Cutting
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Animations

• Disconformity http//duedall.fit.edu/wholeearth/
  PHysical20geology20animations/0012.swf
• Geologic history
• http//www.wwnorton.com/college/geo/earth2/content
  /chapter_12/animations.asp12_1

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Rock Layer Formation

• Sedimentary igneous rock that is broken down by
  weathering into fine particles. Compressed over
  time by its own weight and weight of layers above

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Rock Layer Formation

• Igneous formed from liquid hot magma that cools
  above or below the earths surface.

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Were are fossils found

• Sedimentary rock -- yes, Most fossils are found
  in sedimentary rocks as an animal dies it gets
  buried by sediment , perhaps along a river or
  lake bed, and the organic parts of the animal are
  replaced by minerals in the water/sediment that
• Igneous rock -- nope, Fossils arent found in
  igneous rock because remember that igneous rock
  starts out as molten lava and if an animal were
  to be covered by it then it would melt or burn
  away.

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How old are fossils?

• 2 Generic Methods
• Absolute
• Several methods.
• (radiometric) Measurement of the decay rate of
  isotopes.
• Carbon 14 5730 years Dates organic material
• Potassium Argon 50,000 to 2 billion years ago
  Dates volcanic material
• Relative
• Uses igneous rock above or below sedimentary rock
  to determine age.

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• Which layers are Sedimentary/Igneous?
• S 1,2,3,4,5,7,8,11,12
• I 10,8,6
• Which layers are older?
• 1 - 12
• What is a possible history for this area?
• 1-5 area was covered by an ocean
• 7 - Oceans recede, area appears to be covered by
  large amounts of plant life
• 9 small to mid size animals appear
• 11,12 larger animals appears

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Resources

• http//www.usgs.gov/
• http//jersey.uoregon.edu/mstrick/AskGeoMan/geoQu
  erry13.html
• Wiki Sedimentary -- http//en.wikipedia.org/wiki/S
  edimentary_rock
• http//www.talkorigins.org/faqs/dating.html
• http//www.pbs.org/wgbh/evolution/library/03/3/l_0
  33_01.html
• http//pubs.usgs.gov/gip/geotime/time.html lt-
  curvy geotime
• http//www.kidsgeo.com/geology-for-kids/0030-geolo
  gic-time.php
• http//stloe.most.go.th/html/lo_index/LOcanada8/80
  1/3_en.htm
• Geology an introduction to physical geology ,
  Chernicoff Whitney, ISBN 0-13-147464-1 , Page
  20
• Geology an introduction to physical geology ,
  Chernicoff Whitney, ISBN 0-13-147464-1 , Page
  234