today’s list____________ ch15: rock deformation 1)mapping geologic structures 2)how rocks get...
Post on 20-Dec-2015
233 views
TRANSCRIPT
![Page 1: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/1.jpg)
Today’s list____________Today’s list____________
Ch15: Rock Deformation
1)Mapping geologic structures
2)How rocks get deformed
3) Folds
![Page 2: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/2.jpg)
Study questions____________Study questions____________Ch15: Rock Deformation· What type of tectonic forces makes a normal fault? A reverse fault? A strike slip fault?
What is the difference between brittle and ductile deformation?
What are the strike and dip angle of a deformation?
What is the shape of an anticline, syncline, and what is the relative age of rocks exposed?
What type of deformation is the San Andreas Fault? The mid-ocean ridge?
![Page 3: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/3.jpg)
1) Mapping geologic structures
Deformational processes create faults, folds, joints
rock structures
Visible when rock beds are exposed at surface
out crops
![Page 4: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/4.jpg)
1) Mapping geologic structures
Strike and dip
TSP 15.8
![Page 5: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/5.jpg)
1) Mapping geologic structures
Strike and dip
Strike
Dip
Compass bearing of a rock layer relative to North
Angle of tilt of a bed from a horizontal plane
Fig.11.4
![Page 6: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/6.jpg)
1) Mapping geologic structures
N 75 E
![Page 7: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/7.jpg)
2) How rocks become deformed
Confining pressure: force equal in all directions
Differential stress: force not equal in all directions
![Page 8: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/8.jpg)
2. Brittle deformation rocks crack/fracture
3. Ductile deformationrocks flow
Shallow in crust Deeper down
2) How rocks become deformed
Response to differential stress
1. Elastic deformation – the rock returns to nearly its original size and shape when the stress is removed
![Page 9: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/9.jpg)
2) How rocks become deformed
Fault definition: a fracture where displacement has occurred: rocks on either side of fault have moved relative to each other.
![Page 10: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/10.jpg)
Fault definition: a fracture where displacement has occurred: rocks on either side of fault have moved relative to each other.
2) How rocks become deformed
![Page 11: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/11.jpg)
JointsJoints
Fractures where no slip has occurredFractures where no slip has occurred
Not same as a fault! Not same as a fault!
Why?Why?
Slip happens on faults!Slip happens on faults!
![Page 12: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/12.jpg)
2) How rocks become deformed- brittle materials
Compressive forces:shortening
Differential stress: force not equal in all directions
![Page 13: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/13.jpg)
2) How rocks become deformed- brittle materials
Tensional forces:stretching
Differential stress: force not equal in all directions
![Page 14: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/14.jpg)
Shearing forces:shearing
2) How rocks become deformed- brittle materials
Differential stress: force not equal in all directions
![Page 15: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/15.jpg)
2) How rocks become deformed - brittle materials
![Page 16: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/16.jpg)
2) How rocks become deformed - brittle materials
Rift valleys are the result of tensional forces in the crust, creating a series of normal faults.
The downfaulted blocks result in a Rift Valley.
Fig. 11.13
![Page 17: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/17.jpg)
2) How rocks become deformed - brittle materials
St. Andreas fault is an example for a strike-slip fault
Because it is a plate boundary, it is also a transform fault
Fig. 11.10
![Page 18: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/18.jpg)
Fault System Example : San Andreas
![Page 19: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/19.jpg)
2) How rocks become deformed- ductile materials
Compressive forces:shortening
Differential stress: force not equal in all directions
Shearing forces:Shearing/bending
Tensional forces:stretching
![Page 20: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/20.jpg)
3) How rocks fold
series of wavelike undulations of once-flat rock layers
many sizes: microscopic to 100’s of meters
compressive stresses: shorten+thicken crust
![Page 21: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/21.jpg)
3) Folds
Anticlines fold upward… Synclines fold downward…
Fig. Story 11.16
![Page 22: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/22.jpg)
horizontal and plunging anticline
3) Folds
Plunging fold:
axis of fold penetrates intothe ground
Fig. 11.16
![Page 23: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/23.jpg)
![Page 24: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/24.jpg)
![Page 25: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/25.jpg)
Plunging anticlines and synclines
See Fig. 11.17
![Page 26: Today’s list____________ Ch15: Rock Deformation 1)Mapping geologic structures 2)How rocks get deformed 3) Folds](https://reader035.vdocuments.mx/reader035/viewer/2022062308/56649d4a5503460f94a27662/html5/thumbnails/26.jpg)
3) Folds
Types of folds
Other deformations
Symmetrical, asymmetrical, overturning, plunging…..
dome - circular upwarping (anticlinal structure)basin - circular downwarping (synclinal structure)
Fig 11.19