GEOS 234- Lab Report #6
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Apr 3, 2024
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Earth System History GEOS 234
Unit 6 Lab Geologic Maps and Stratigraphy Mataya Topil 2/3/2024
Summary- This lab involves observing rocks and understanding their formations to get a better idea of the Earth’s history. The maps are an essential tool for geologists to visualize and understand the distribution of rock formations on the Earth’s surface. Through this lab, we look at a map of the Grand Canyon to understand the stratigraphy and geological history of the area. Materials- Computer and Map Procedure-
1.
Explore the map using USGS National Geologic Map Database 2.
Observe and note the map elements such at the title, scale, legend and cross-sections. 3.
Answer the questions based on the map observations. Data- Average Elevation of Plateau Northwest of Widforss Point- 8250 ft
The average elevation of the South rim of the canyon- 6750 ft. Depth of the canyon near the Colorado River- 2500 ft Questions- 1.
Look for the contour on the plateaus north and south of the canyon. What is the average elevation of the plateau northwest of the wildfires point? How does this compare with the
average elevation of the south rim of the canyon? a.
The average elevation of the plateau northwest of Wildforss Point looks to be about 8250ft. The average elevation on the south rim west of Grand Canyon village looks to be closer to 6750ft, making the north rim about 1500ft higher.
2.
Now find the elevation near the Colorado River in the deepest part of the canyon. The label on the contours are more difficult to read over the brown color of the unit in the canyon gorge. What is the depth of the canyon? a.
The deepest part of the canyon has an elevation of 2500ft.
Earth System History GEOS 234
Unit 6 Lab 3.
What is the rock unit cropping out the innter gorge, right next to the Colorado River? What is its age? a.
The formation that intrudes is Zoroaster Granite. This formation is Archean.
4.
Is there any correlation between lithology and topography? That is, do some rocks tend to
weather as cliffs and others as gentle slopes? Why are the reliable cliff formers in the Grand Canyon? a.
Yes. There are some rock formations with much more steep terrain. Examples of these would be Redwall Limestone and Coconino Sandstone. These would be the cliff formers. Formations with gentler slopes include the Bright Angel and Hermit
Shale formations. 5.
What, if any, differences do you see between this profile and the previous example at Uncle Jim Point? a.
Uncle Jim’s point has much steeper cliffs and the profile above here at Shiva Temple has both steep cliffs and gentler inclines.
6.
What rock units in this area are found in depositional contact on the igneous and metamorphic basement rocks?
a.
The rocks that are found in depositional contact on the igneous and metamorphic basement rocks are sandstone and these would be in direct contact with the igneous and metamorphic basement rocks. 7.
How do you interpret the contact between the Zoroaster Granit and the sedimentary rock lying on it? a.
I think that the contact between Zoroaster granite and the sedimentary rock lying on it, would represent an unconformity, showing that there are signs of being displaced or altered by the intrusion. Conclusion- In conclusion, this lab provided valuable insights into the geology of the Grand Canyon region. By studying the geologic map and connecting rock identification with the process of geologic mapping, we gained a better understanding of the stratigraphy and geological
history of the area. The lab also highlighted to importance of field observations in geology and the role of technology in enhancing our understanding of the Earth’s geology. References- https://ngmdb.usgs.gov/Prodesc/proddesc_33640.htm
Earth System History GEOS 234
Unit 6 Lab
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