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Graded Assignment
SCI112A: Earth Science | Unit 4 | Lessons 7 and 8: Laboratory: Interpreting Geologic History
Name: Ayana Ortega
Date: 1/4/16
Graded Assignment
Lab Report: Interpreting Geologic History
Answer the questions below. When you are finished, submit this assignment to your teacher by the due date for
full credit.
In this laboratory experiment, you will write a narrative history of a rock section found in the Grand Canyon. You
will describe and explain the events starting with the Vishnu Schist forming and ending with the unconformity
above the Redwall Limestone in the Mississippian. Your description should include environmental changes.
Example:
1.

Sea level lowered, and the Esplanade Sandstone was deposited in a beach environment.

Erosion, and the sea level rose.

Hermit Shale deposited in a deeper sea.

Sea level drops, returning the area to a beach environment where the Coconino Sandstone was
deposited.
Interpret the bottom half of the cross section below. Start with the Vishnu Schist and end with the Redwall Limestone.
(16 points)
Correct order:
1.
Vishnu Schist
2.
Zoroaster Granite
3.
Bass limestone
4.
Hakatar Shale
5.
Igneous intrusion
6.
Shinumo Quartzite
7.
Dox Sandstone
8.
Tepeats limestone
9.
Bright Angel Shale
Score
10. Muav limestone
11. Temple butte limestone
12. Redwall limestone
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Page 1 of 5
Graded Assignment
SCI112A: Earth Science | Unit 4 | Lessons 7 and 8: Laboratory: Interpreting Geologic History
Proper environmental changes:
Erosion occurs after the Zoroaster granite, before the bass limestone.
Temple butte limestone is formed in a shallow sea and erosion occurs before the Redwall limestone is laid down.
:
(6 points)
2. There is one of each type of unconformity in this diagram. Name at least one of each of them
by indicating the layers that they are between.
Score
Nonconformity:
Answer: The unkar Group shows angular unconformity because the layers are turned at angle.
Angular unconformity:
Answer: Specifically the angular unconformity occurs between the Cambrian and Precambrian rocks. The Dox
sandstone, Shinumo quartzite, Hakatar shale, and bass limestone have been filled. An angular unconformity
occurs between the Cambrian and Precambrian rocks. The Dox sandstone, Shinumo Quartzite, Hakatar Shale,
and Bass limestone have been filled.
Disconformity:
Answer: The disconformities are marked irregular lines between the sedimentary rocks layers.
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Copying or distributing without K12’s written consent is prohibited.
Page 2 of 5
Graded Assignment
SCI112A: Earth Science | Unit 4 | Lessons 7 and 8: Laboratory: Interpreting Geologic History
Your Score
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Copying or distributing without K12’s written consent is prohibited.
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Page 3 of 5
Graded Assignment
Symbol
SCI112A: Earth Science | Unit 4 | Lessons 7 and 8: Laboratory: Interpreting Geologic History
Name
Environment
Sandstone
Beach or nearshore environment
Limestone
Forms in warm shallow seas
Shale
Igneous Rock
(Granite)
Deep sea
Formed when rocks melt and then recrystalize
Metamorphic Rock
(Schist)
Formed when rocks are severely deformed without melting; in
this cross section, the Vishnu Schist represents the original
surface in the area
Igneous intrusion
Magma melting and rising from deeper levels
Hint: How can you tell the difference between an intrusion and rocks melting in place? Rocks melting in place
usually appear as a large mass, whereas intrusions seem to have risen up from a source.
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Copying or distributing without K12’s written consent is prohibited.
Page 4 of 5
Graded Assignment
SCI112A: Earth Science | Unit 4 | Lessons 7 and 8: Laboratory: Interpreting Geologic History
© 2006 K12 Inc. All rights reserved.
Copying or distributing without K12’s written consent is prohibited.
Page 5 of 5