geologic time relative dating
DESCRIPTION
Interpreting Earth’s Rocks to Determine Its Past History. Geologic time Relative dating. Geologic Time. Relative Dating - sequence of geologic events in a region (order of past events) How do we know how old something is?. Law of Superposition. Oldest layer on bottom (if undisturbed). - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/1.jpg)
Interpreting Earth’s Rocks to Determine Its Past History
![Page 2: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/2.jpg)
Geologic Timechapter 18
• Relative Dating - sequence of geologic events in a region (order of past events)
• Not quantitative
![Page 3: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/3.jpg)
http://www.angelfire.com/az3/mohgameil/Layering4.jpg
Law of Superposition
• Oldest layer on bottom (if undisturbed)• Only works for SED rocks
Younger
Older
![Page 4: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/4.jpg)
Law of Superposition
In horizontal rock layers, the oldest and first formed is on the bottom. 5 is the youngest
because it is on the top, closest to the surface.
![Page 5: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/5.jpg)
http://www.calstatela.edu/faculty/acolvil/sediment/superposition.jpg
The Grand Canyon
![Page 6: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/6.jpg)
Principle of Original Horizontality
• Sediments are originally deposited as horizontal (or near horizontal) beds (ONLY FOR SED ROCKS)
Folding happened AFTER rocks were deposited
![Page 7: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/7.jpg)
folded rock layers = compression by tectonic activity
![Page 8: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/8.jpg)
Cross-Cutting Relationships(overlap law)
• An igneous intrusion (or fault) is younger than the rock layers that it cuts across.
fault
oldest
These are younger than
the surrounding
rock
youngest
![Page 9: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/9.jpg)
Cross-Cutting Relationships
6 is younger than1, 2, or 3 because it cuts across them!
![Page 10: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/10.jpg)
1
12
2
3
3
4
5
![Page 11: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/11.jpg)
Which came first?
A
CB
DE
Order the rock layers above from oldest to youngest.
![Page 12: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/12.jpg)
Which came first?
The first layer deposited and the oldest is D, followed by C, A, B, and E.
DD
DC
CA
B
B
E
![Page 13: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/13.jpg)
Law of inclusions
• The inclusion (xenolith) is older than the rock it is in
• Snickers bar
![Page 14: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/14.jpg)
James Hutton: The father geology (1726-1797)
Uniformitarianism: processes acting on earth today (volcanism, erosion, plate tectonics, glaciation, etc.) have done so in the past IN THE SAME WAY!
“The present is the key to the past.”
![Page 15: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/15.jpg)
Unconformities = “Missing Time”
• Represented by squiggly lines on cross sections
![Page 16: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/16.jpg)
Angular unconformity
![Page 17: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/17.jpg)
Angular Unconformities
• Folded layers below horizontal layers.
angular unconformity
(rock layers have been eroded away)
rock layers are eroded
new horizontal layers are deposited
![Page 18: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/18.jpg)
F E D C B A
Angular Unconformity
sedimentary rocks above and below unconformity surface with rocks below tilted at an angle
![Page 19: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/19.jpg)
Granite
sedimentary rock layers
Cambrian
Precambrian
Nonconformity – younger sedimentary rocks rest on older igneous rocks
![Page 20: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/20.jpg)
Nonconformity
![Page 21: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/21.jpg)
![Page 22: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/22.jpg)
Disconformity
DISCONFORMITY:Missing rock layers (sedimentary)
Very hard to pick out
![Page 23: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/23.jpg)
Disconformities
![Page 24: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/24.jpg)
Let’s Play….Name the UNCONFORMITY!
![Page 25: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/25.jpg)
Siccar Point, Scotland
![Page 26: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/26.jpg)
![Page 27: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/27.jpg)
![Page 28: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/28.jpg)
http://www001.upp.so-net.ne.jp/fl-fg/06-02.htm
![Page 29: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/29.jpg)
![Page 30: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/30.jpg)
![Page 31: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/31.jpg)
Resources• http://courses.geo.ucalgary.ca/glgy209L03/docs/Lecture15_GLGY209_six.pdf• http://perth.uwlax.edu/faculty/stoelting/Intro/Guides/Images2/law_of_superposition_b.jpg• http://www.science.sjsu.edu/scied/255/ppt/superposition/img025.jpg• http://www.gpc.peachnet.edu/~jsummero/Cross-cutting-a.jpg
• http://www.gc.maricopa.edu/appliedscience/gjc-nsf/images/CRH0204.JPG• http://maverick.gc.maricopa.edu/appliedscience/gjcweb/geomap/images/ang.unconf.jpg• http://www.geog.ouc.bc.ca/physgeog/contents/images/hutton.jpg• http://www.bigbendpaleo.com/Photo%20Gallery/Big%20Bend%20Region,%20Texas/Big%
20Bend%20National%20Park%20-%20Syncline%20-%20Javalina%20Creek%20-%2020%20June%201995.jpg
• http://geoimages.berkeley.edu/GeoImages/Johnson/Images/Large/CD3/028.jpg• http://www.vvdailypress.com/travel/rainbow/images/rock.jpg• http://academic.emporia.edu/aberjame/struc_geo/folds/fold06.jpg• http://www.geology.pitt.edu/images/folds.jpg• http://faculty.evansville.edu/de3/b39902/PPoint/Geologic%20Time/img007.jpg• http://www.photo.net/photo/pcd2882/grand-canyon-region-aerial-85.3.jpg• http://www.cowanstark.com/horsehoe-bend.jpg• http://home.flash.net/~alanm52/Cross_cutting.jpg• http://www-class.unl.edu/geol101i/images/igneous%20images/Black%20Canyon%20Gunn
ison.jpg• http://freespace.virgin.net/craven.pendle/stratigraphy/unconformity.jpg
![Page 32: Geologic time Relative dating](https://reader034.vdocuments.net/reader034/viewer/2022051517/56815a66550346895dc7b0f9/html5/thumbnails/32.jpg)
• http://comp.uark.edu/~sboss/siccar.jpg• http://www.pittstate.edu/services/scied/Teachers/Field/Camp/Us67-1/us67cut.jpg• http://maverick.gc.maricopa.edu/appliedscience/gjcweb/geomap/images/MW8-11.jpg• http://www3.uakron.edu/geology/Foos/parks/rmgcan2.html• http://www.ldeo.columbia.edu/edu/dees/ees/ies2/slides/disconformity.gif• http://geology.lssu.edu/NS102/images/figure%2009-06.gif• http://www.crienterprises.com/C-Assets/J-Hanifa-Unconf-W-Birk.jpg• http://www.uoguelph.ca/~sadura/stgref/stg32b.gif• http://www.geo-outdoors.info/images/eye_protection.jpg• http://enterprise.cc.uakron.edu/geology/natscigeo/Lectures/time/gtime1.htm