1.5) According to these web pages: https://www.nps.gov/goga/learn/education/cher

Question

1.5) According to these web pages:

https://www.nps.gov/goga/learn/education/chert-faq.htm

https://pubs.usgs.gov/bul/b2188/b2188ch3.pdf

Chert in the Marin Headlands (and elsewhere!) is best described as a(n):

Select one:

a. clastic sedimentary rock

b. chemical or biologic sedimentary rock

d. igneous plutonic rock

e. metamorphic rock

1.6) Chert is a rock that tells us about the geologic history of San Francisco. According to the web pages provided above, where did the chert form?

Select one:

a. It formed at the bottom of the ocean, when the plate was near the equator. It was then transported here by plate movements.

b. It formed at the bottom of the ocean at a time when the plate was fairly near to San Francisco.

d. It formed at the bottom of the ocean when the plate was near southern California. The plate then moved here along a transform fault (e.g., the San Andreas).

1.10) Which of the following statements best describes a volcanic igneous rock?

Remember that rocks can consist of bits that aren't minerals... for example: teeth, bones, glass, coal, etc.

Select one:

a. It cooled slowly, so it is coarse grained (has large-sized crystals).

c. It cooled so quickly that no crystals formed (it is a glass).

d. A and B

e. B and C

1.12) Now a question about Geologic Time... Which relative dating principle states that sedimentary layers lower in a sequence are older than the sedimentary layers overlying them? Be sure to read and watch the videos to learn these ideas!

Select one:

b. Principle of cross-cutting relationships

c. Principle of inclusions

d. Principle of superposition

1.25) Given the Principle of Original Horizontality, what event must have occurred following deposition to produce the non-flat-lying stack of rock layers in the picture below?

Select one:

b. They float to the surface due to low density.

c. They are uplifted or exhumed by vertical movement on faults.

d. Natural gas pushes them up gradually.

Explanation / Answer

1.5 Classic sedimentary rock

1.6 It formed at the bottom of the ocean, when the plate was near the equator. It was then transported here by plate movements.

1.10 It cooled slowly, so it is coarse grained.

1.12 Principles of superposition

1.25 They are uplifted or exhumed by vertical movement on faults.

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