Structures and Landscapes
GLS210 Geomorphology Lab
Dr. Lindley Hanson, Dept. Geological Sciences, Salem State College
(lhanson@salemstate.edu)
Erosional landscapes are strongly influence by the lithology and structure of the rocks
being consumed. Lithology determines rock competence, while structure influences
avenues of erosion and overall grain of the landscape.
Goal: In this lab you will learn to recognize and interpret variations in landscapes
attributed to lithology and structure. As with any discipline knowledge of the jargon in
required. During lab and lecture we will be building a glossary of terms through Google
Doc. You will be expected to be able to know and identify features in the glossary.
Objectives:
Upon completion of this lab you are expected to be able to:
1. interpret topography and basic structural elements and alpine landscapes
from satellite images
2. correlate rock strength to lithology
3. identify and define numerous landscape element (see Google Docs glossary)
4. distinguish between tectonic landforms and landforms created by differential
erosion.
Directions: Type your answers in blue. Images must be annotated in powerpoint and
placed back into the document. Upon completion submit through webct.
Time requirements:
Lab time: 6 hours. Homework 4 hours
Requirements:
Google Earth, powerpoint and word
kml files: Panoramio (http://www.panoramio.com/kml/)
Prelab preparation:
1. Before lab research and define at least 10 of the terms listed at the end of this lab.
2. Read:
a. Chapter 5 and 12 in Bloom
b. Chapters 14 and 15 in Jones and Jones
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Laboratory Exercise:
This lab contains two sections. Part I is designed to familiarize you with basic structures
and how they are manifested in the topography. You will also be introduced to features
and landforms associated with different structures. Part II is an interpretive section that
requires that you to interpret aspects of a structure based on elements of the landscape.
Before starting activate Panoramio in the Google Earth Layers Pane. Open the
StructuresLab.kmz file. However keep all folders and layers unselected until needed.
Deselect features you have finished. Too many active layers and folders with slow down
Google Earth.
Part I. Tour of structures and landscapes
Tour the following region through Google Earth and answer the questions. Be prepared
to discuss your answers in class.
A. Horizontal Sedimentary Rocks
Open and view “Horizontal Rocks” folder. Write down your observation and answer
the questions. Double click on the marker to get a description of the area. The
examples in this section lie in the arid and semiarid regions of the West, where resistant
strata are composed of sandstone or massive limestone, and less resistant strata are
either shale or finely-interbedded layers of variable lithologies.
1. Grand Canyon
Activate Terrain mode and fly around the landscape. Note the formation
contacts and their lateral continuity and the dominant drainage basin pattern of
the region. (Refer to pp. 269-271 in Bloom)
a. Identify the Physiographic Province.
b. What is the evidence that the strata are horizontal and vary in their resistance
to weathering and erosion
c. Describe the landscape. What feature(s) or concepts from your glossary are
illustrated here?
2. Canyonlands
a. Describe the landscape. What feature(s) or concepts from your glossary are
illustrated here?
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b. Note the blocks of White Rim Sandstone on the floor of the canyon. What
mass-wasting process is occurring here and why?
c. Note that the jointing is most obvious along the margins of the canyon.
Construct a hypothesis to explain this relationship.
3. Monument Valley
a. Describe the landscape and identify the province. What feature(s) or concepts
from your glossary are illustrated here?
b. Monument Valley and the Grand Canyon contain similar lithologies and
structure. Compare and contrast their landscapes. How are they similar? How
are they different?
c. The Monument Valley buttes (image) are composed of the following
lithologies in ascending order: The Permian Organ Rock Shale forms the
pedestal, the DeChelly sandstone the vertical columns, and the Triassic
Moenkopi (sandstone) Formation and the Shinarump Conglomerate form the
cap. In the space below redraw Merrick butte from this image. Draw in and
label the formation contacts.
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d. On what observations did you base your interpretation?
4. Badlands of South Dakota
The typical topography of the Badlands results from a combination of climate
and geology. The region receives on average 16 inches of rain a year,
temperatures range from an average low of 32 °F during the winter and to 91°F
in July, promoting short grass prairies. Rainfall typically occurs as intense
summer thunderstorms. The poorly consolidated Eocene-Oligocene rocks of
the White River Group lack many of the essential nutrients for plant growth.
The combination of poor vegetative cover, easily eroded strata, which is both
fine grained and impermeable, heightens the effect of runoff to create this highly
dissected landscape.
a. Describe the landscape and identify the province. What feature(s) or concepts
from your glossary are illustrated here?
b. In the Grand Canyon and Badlands NP strata are horizontal yet their
landscapes are noticeably different. Explain why this is so.
B. Inclined Strata
1. Eastern Flank of the Wind River Uplift (marker 1)
a. Describe the landscape and identify the province. What feature(s) or concepts
from your glossary are illustrated here?
b. What is the triangular feature that the place mark is located on? How did it
form?
c. The rule of Vs is discussed in on page 287 of your lab manual. View the
landscape from 6000 ft. State and explain whether or not the rule of Vs
accurately predicts the dip of the strata throughout the view area.
d. What controls the angles of the resequent (or dip slope) and obsequent slopes
along the hogbacks?
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Identifying Unconformities and other structures
e. Paleozoic strata unconformably overlie highly metamorphosed Precambrian
rocks. Move due west of the marker until you locate the unconformity. With the
measuring tool determine approximately (to the nearest .5 miles) how far west
the unconformity is from the marker. Name the type of unconformity this is.
Answer_ miles
f. What other structures do you see in the metamorphic core of the Wind Rivers?
Signs of Alpine Glaciation
g. Was this mountain range ever covered by alpine glaciers? ____ Cite any
evidence if present.
h. Double click on the Wind River Lakes marker, and then on the Wrangell-St
Elias Range. Compare these two landscapes and discuss the formation of the
elongate lakes formed on the western flank of the Wind River Range.
2. Comb Ridge, Utah
a. Describe the landscape and identify the province. What feature(s) or
concepts from your glossary are illustrated here?
b. What evidence is there that the strata west and east of the escarpment are
horizontal?
c. From the base up why does the obsequent slope change from gentle to
steep?
C. Faults
1. The Garlock Fault is a predominantly strike slip fault that extends from the San
Andreas Fault to Death Valley.
a. What geomorphic feature is formed over the fault?
b. Explain why such features form along strike slip faults faults.
2. The Owens Valley Fault is the western-most normal fault of the Basin and
Range. The scarp marking the fault line reflects the relative motion between the
western and eastern block.
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a. Based on the topography and the information given about determine the
direction of dip for the fault.
b. In general, can you tell the dip of a fault from the slope of the fault scarp?
Explain.
D. Jointed Terrains
1. Zion National Park, Utah
a. Describe the landscape. What feature(s) or concepts from your glossary are
illustrated here?
2. Arches National Park, Utah
a. Describe the landscape. What feature(s) or concepts from your glossary are
illustrated here?
3. Black Hills, South Dakota
a. Like the Wind River Range in Wyoming the Black Hills is an Laramide
uplift. Look closely at the Panoramio images. Is the rock exposed here
sedimentary, igneous, or metamorphic? Describe the landscape.
b. Zoom out and look at the overall fold structure of the Black Hills uplift. What
is it?
c. Look at the immediate area around the marker. Is there any evidence that this
area was affected by alpine glaciation?
E. Folds
1. Southern Iran: Tectonic Landforms
a. Structural and topographic basin: Using the image below place five strike
(one on each side in in the middle) and dip symbols around the structure
showing the strike and direction of dip of the beds. Draw the fold axis with
arrows indicating directions of plunge. Indicate where the oldest and
youngest strata are. Identify the fold and label any other observed
geomorphic landforms.
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b. Southern Iran: fold 2. On the image complete the following. Draw three
strike and dip symbols (flanks and hinge). Indicate the fold axis and locate
the oldest and youngest strata. Identify the fold and label any other observed
geomorphic landforms.
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Part II. Interpretive exercises
A. Grass Valley, Nevada
a. Describe the landscape. What feature(s) or concepts from your glossary are
illustrated here?
b. Determine whether Grass Valley a full graben or half graben? Discuss how
you came to this conclusion.
B. Southern Appalachians – Vicinity of Gate City Kentucky
Study the topography and the Geology of Gate City map overlay. . (Legend) Do not
select the Structure-Sections overlay. A description of the geologic formations is given in
the Appendix. Complete the following:
1. Describe the landscape and identify the Physiographic Province. What feature(s)
and/or concepts from your glossary are visible here?
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2. Refer to the features indicated by place marks:
a. Fold A Identify the obsequent and resequent slopes and determine whether
this fold is an anticline or syncline and the direction of plunge and cite your
supporting evidence.
b. Fold B Identify the obsequent and resequent slopes and determine whether
this fold is an anticline or syncline and the direction of plunge and cite your
supporting evidence.
c. Fault (Marker 3) In addition to folds, this region is cut by numerous faults
that all dip to the southeast and are contemporaneous with folding. Is this fault
a thrust or normal fault? Discuss your evidence. Hint: follow the trace of the
fault east and note the age of the beds on both sides.
d. Would you consider the scarp formed along the fault a fault scarp, fault-line
scarp, or something else? Does it vary along strike? Explain.
e. Marker 4. Identify the drainage basin pattern of the region around this
marker and the structure of the underlying sedimentary rocks? In which
Appalachian Province is this located?
f. Describe the topography of the formations listed below. (Do they form
lowlands or ridges? Is the topography variable, indicating a variety of
interbedded lithologies?)
Clinch Sandstone (Scl):
Sevier Shale (SSv):
Newman Limestone (Cn):
Marysville Limestone (Cambrian m):
Lee Conglomerate (Cls):
Russell Formation (Cambrian rl)
g. Hypothesize the origin of the very prominent ridge indicated by marker 5
and discuss your logic. (Check your answer by activating the structure section.)
h. The Cumberland Gap (Marker 6) is a water gap formed by a stream flowing
across the grain of the landscape. List and describe three hypotheses developed
to explain the origin of streams that traverse the regional structure.
1.
2.
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3.
3. The basins and domes in Iran are considered tectonic landforms, however the ridges
and valleys in the Appalachian Province are not. Explain the difference.
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