Upload
alyssaduncan
View
2.470
Download
1
Tags:
Embed Size (px)
Citation preview
Tectonic FeaturesILAN ALYSSA RYAN
Tectonic Features•Cuesta•Hogback•Fault Scarp •Shutter Ridge•Sag Pond•Offset Stream Channel•Horst•Graben
Fault Scarp•At the beginning of earthquakes, fault slip starts miles below the earth's surface and then extends outward and upward. Most earthquakes (small to moderate earthquakes, in particular) stop before the fault slip reaches the ground surface, but during large earthquakes the fault slip usually creates a break (or fault scarp) at the ground surface.
Fault Scarp: What to look for•Fault scarps appear as a step in the ground, and can be a few inches to several tens of feet high, but they are extremely difficult to recognize unless they are at least a few feet high.
•With time, the scarp face becomes worn down by erosion and covered by vegetation, making the scarp much less obvious.
Fault Scarp Satellite Images
Fault Scarp Pictures
Fault Scarp Topographic Map
Sources for Fault Scarp:
•http://earthquake.usgs.gov/regional/imw/imw_rito_seco/
•http://www.nbmg.unr.edu/dox/nl/nl14a.htm
Shutter Ridge
•“A shutter ridge is a ridge… along a fault line, blocking or diverting drainage. Typically, a shutter ridge creates a valley corresponding to the alignment of the fault that produces it.” (Wikipedia)
Shutter Ridge Topographic Map
Shutter Ridge Satellite Images
Shutter Ridge Pictures
Sag Pond Topographic Map
Sag Pond
•“A sag pond is a small body of water occupying an enclosed depression or sag formed where active or recent fault movement has impounded drainage. (Sci- Tech Dictionary)
Sag Pond Satellite Image
Sag Pond Picture
Hogback•Homoclinal ridge (shown on next slide)•Composed of steeply tilted strata of
protruding rock•Resembles high, knobby spine between
the shoulders of a hog•Defining characteristic: steep dip slope
greater than 30°•Near symmetric slope on each ridge face.
A cuesta is a homoclinal ridge with a more gentle dip slope.
Hogback Diagram
Process of Formation•Two strata are different types of
sedimentary rock with differing weathering rates
•Softer rock erodes quicker than overlying hard rock
•Softer rock retreats to a point where hard and soft rock strata are adjacent
•Creates cliffs that steepen as the softer rock continues to erode.
http://academic.emporia.edu/aberjame/field/rocky_mt/hogback1.jpg
http://www.cliffshade.com/colorado/dakota_hogback/dak04.jpg
http://www.cliffshade.com/colorado/dakota_hogback/dak04.jpg
Cuesta
•Ridge formed by gently tilted sedimentary rock strata (layers)
•Homoclinal structure•Steep slopes•Rock layers exposed on edges
Cuesta on contour map:
“Cuesta del Burro, Texas”
Cuesta contour map
Offset Stream Channel:Stream offsets are the counterpart to shutter ridges, a sign of lateral movement on strike-slip faults like the San Andreas fault.
Earlier earthquakes clearly helped produce the stream offset, on the San Andreas Fault in Carrizo Plain National Monument.
Offset Stream Channel
HorstA horst is found together with a graben. The graben are the down-dropped blocks and the horst are the unthrown blocks that lie next to the graben.
Flash animation: http://earthquake.usgs.gov/learn/animations/animation.php?flash_title=Horst+and+Graben+Flash+Animation&flash_file=horstandgraben&flash_width=380&flash_height=210
Graben
A graben is a down-dropped block of the earth’s crust resulting from extension, or pulling, of the crust.
Death Valley, California
Death Valley, California
Sources•http://www.thulescientific.com/
MustangRidgeSagPond.jpg•http://edcsns17.cr.usgs.gov/
EarthExplorer/?dataset_name=MAPS_LARGE
•http://www.trails.com/topo.aspx?lat=46.78139&lon=-69.05556&s=50&name=Sag+Pond
•http://blueschist.org/PhotosShutterRidge.aspx