Remote Sensing Lab, Part A
Patterns of Erosion
Background
The purpose of this lab in to develop an
understanding of how
fluvial (= river) erosion
and
the “fabric” of rock below the surface
interact
to produce landforms
Fabric
The earth’s crust is composed of numerous
different kinds of rock, often in close
proximity.
Some rocks weather and erode faster than
other
The most easily erodable get washed away
fastest, and tend to form valleys
The most resistant rocks get washed away
slowest, and tend to form the highlands
Fabric due to sedimentary layers
Very interesting landforms are formed when
sedimentary layers are eroded, because its very
typical for soft and hard rock layers to alternate
(e.g. soft shale and hard sandstone).
Many interesting cases occur, depending upon the
configuration of the layers, which can be flat
laying, dipping, folded and faulted.
Exampe 1. Eroded edge of
flat-lying sediments
Example 2. A high angle fault that creates a
steep fault scarp.
Example 3: A low angle fault. Note that the
steep slope is not directly due to faulting.
Resistant rock
Resistant rock
Resistant rock
easily erodable rock
Example 4: Dipping sediments lead
to parallel ridges and valleys
valleys
ridges
Note that ridges are asymmetric in
shape. One side is steep, one side
gentle. This shape is called a
hogback.
Interaction of dip and folding
makes
for really beautiful
landforms
Erode Me !
Example 5: Dome and
Example 6: Basin
Folded Sediments, where the folds dip (=plunge) into the earth
Example 7: Syncline
(downwarped sediments)
Example 8: Anticline
(upwarped sediments)
Instructions
For each five areas:
1. Three images are provided for each area:
Image 1: Location of the study area (its right in the middle)
Image 2: The study area itself
Image 3: The study area with the yellow line AB crossing it.
Find the study area on Google’s satellite map feature and use it to
view the area. Examine it at a variety of zoom levels.
2. Identify the main rivers and their direction of flow. Be careful not to
confuse roads with rivers (but keep in mind that roads can follow
river valleys).
3. Identify what parts of the region are topographically high and
topographically low. Both the pattern of rivers and shadows can
help.
Instructions, continued
4. Make a full-page sketch of the area. Include rivers,
valleys, canyons, ridges and a scale in kilometers.
Identify the high ground and the low ground.
5. Which of the example landforms best approximates
the landforms in the area? Site specific evidence.
6. Sketch a profile through the earth along line AB that
shows what you think that the rock layers are there.
Identify which layers are most and least erodable.
7. Describe briefly how the landforms might change as
more erosion occurs.
Area 1. In Wyoming
Area 1.
A
Area 1.
B
Area 2. In the Indian Subcontinent
Area 2.
Area 2.
A
B
Area 3. In Alaska
Area 3.
Area 3.
A
B
Area 4. In Eastern North America
Area 4.
Area 4.
A
B
Area 5. In Pakistan
Area 5.
Area 5.
A
B