I was working on my test review multiple choice questions in my textbook and encountered some that I am not sure about the answer. I hope someone can help me so I won't be studying the wrong answers!

Choose the best answer:

1) The geologic time scale is a
a. scale for weighing rocks
b. calendar used by geologist
c. rock record of the earth's past
d. collection of the same kind of rocks
I would eliminate a and d, but I am not sure if the correct answer is b or c...

2) An event that geologists would use in dividing the geologic time scale into smaller units is
a. the eruption of a volcano
b. a change in rock color
c. a change in sediment type
d. the arrival of an ice age
I really have no idea...

3) An important invertebrate in the Paleozoic Era was the
a. ammonite
b. trilobite
c. ostracoderm
d. stromatolite
Is the answer b?
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4) Areas of exposed Precambrian rocks that may represent ancient continents are called
a. shields
b. fossils
c. outcrops
d. cratons
Is the answer a? or d?

5) During the Mesozoic Era, new crust was added to western North America in the form of
a. shields
b. terranes
c. cratons
d. geosynclines
This one I have no idea...

6) The Colorado Plateau was uplifted during
a. Precambrian time
b. the Paleozoic Era
c. the Mesozoic Era
d. the Cenozoic Era
Is the answer d?

Thank you for your help!

Can somebody help me, please?

I was working on my test review multiple choice questions in my textbook and encountered some that I am not sure about the answer. I hope someone can help me so I won't be studying the wrong answers!

Choose the best answer:

1) The geologic time scale is a
a. scale for weighing rocks
b. calendar used by geologist
c. rock record of the earth's past
d. collection of the same kind of rocks
I would eliminate a and d, but I am not sure if the correct answer is b or c...!the geologic time scale is a "relative" time scale based on the position of rocks- best answer is "C"

2) An event that geologists would use in dividing the geologic time scale into smaller units is
a. the eruption of a volcano
b. a change in rock color
c. a change in sediment type
d. the arrival of an ice age
I really have no idea...! answers "a", "b" and "d" have no bearing on the time scale (perhaps "d" in the Quaternary, but not older periods)- so best answer is "c". I don't think any of the answers provided are the best answer to this question

3) An important invertebrate in the Paleozoic Era was the
a. ammonite
b. trilobite
c. ostracoderm
d. stromatolite
Is the answer b?!you are correct

4) Areas of exposed Precambrian rocks that may represent ancient continents are called
a. shields
b. fossils
c. outcrops
d. cratons
Is the answer a? or d?!"a" shields are the Precambrian components of continents, cratons are just stable continental crust, regardless of age

5) During the Mesozoic Era, new crust was added to western North America in the form of
a. shields
b. terranes
c. cratons
d. geosynclines
This one I have no idea...!"b" terranes (shields are precambrians, cratons were not added, and "geosynclines" is an old terminology, used before plate tectonics

6) The Colorado Plateau was uplifted during
a. Precambrian time
b. the Paleozoic Era
c. the Mesozoic Era
d. the Cenozoic Era
Is the answer d?! Precambrian through Tertiary rocks are exposed in the Colorado uplift, meaning it is relatively young- best answer is the youngest era "d" Cenozoic