Assignment 4 This covers Unit IV Geologic Time in the textbook (Chapter 8).

Matching (3 points)

1)      Match each item with the correct description (there will be one unused description).

catastrophism

amber

uniformitarianism

index fossil

A)    a fossil organism that is restricted to a certain brief stretch of geologic time, but was widespread and abundant during its time on Earth- Index fossil

B)     the notion that we can understand the geologic past by focusing on present day processes and physical laws; geologic change may be slow or gradual- Uniformitarianism

C)     an unconformity in which younger sedimentary layers overlie older metamorphic or intrusive igneous rock (sedimentary layers sit on an erosion surface)

D)    the defunct notion that the Earth is only a few thousand years old, and that all geologic change is accomplished rapidly through violent events-catastrophism

E)     fossil tree sap- Amber

MULTIPLE CHOICE.  Choose the one alternative that best completes the statement or answers the question. (3 points each)

Numbers 2, 3, and 4: Examine the figure above that shows the sequence of strata in three Colorado Plateau national parks (page 282 in textbook).

2) Which unit(s) are shared by Grand Canyon National Park and Zion National Park?

A) Moenkopi and Chinle

B) Toroweap and Kaibab

C) Kaibab only

D) Kaibab and Monekopi

Answer; D) Kaibab and Monekopi

3) If the Wingate Sandstone was deposited in the Triassic period, the Navajo Sandstone in the late Triassic through early Jurassic, and the Carmel Formation in the Jurassic, a visitor to Bryce Canyon National Park shouldn’t expect to find any strata older than the ________ period.

A) Permian

B) Triassic

C) Tertiary

D) Cretaceous

Answer; B) Triassic

4) Since the Moenkopi Formation was deposited at the end of the Permian period and the very beginning of the Triassic, and the Navajo Sandstone was deposited at the end of the Triassic and into the Jurassic, what is the age of the Chinle Formation?

A) Triassic

B) Jurassic

C) Permian

D) Cambrian

Answer; A) Triassic

5) “This rock is fifteen million years old,” is an example of ________.

A) the principle of cross-cutting relationships

B) superposition

C) a numerical date

D) a relative date

Answer; C) a numerical date

6) Which of the following geologic observations would NOT bear directly on working out the sequence of geologic events in an area?

A) a well-exposed dike of basalt in sandstone

B) an unconformity between a granite and sandstone

C) inclusions of sandstone in a granite pluton

D) the feldspar and quartz contents of a granite

Answer; D) the feldspar and quartz contents of a granite

7). A worm would stand a poor chance of being fossilized because ________.

A) worms contain no carbon-14

B) worms live in the shallow ocean

C) worms have no hard parts

D) worms were very rare during the geologic past

Answer; C) worms have no hard parts

8) Using the known rates of radioactive decay to date the crystallization of certain minerals is known as ________ dating.

A) relative

B) fossil assemblage

• C) conventional

D) radiometric

Answer; D) radiometric

Fill in the blank. Write the word or phrase that best completes each statement or answers the question. (2 points each)

9) A lava flow includes fragments of limestone in it. Which rock unit is older, the lava flow or the limestone? _____LIMESTONE___

10) A sandstone is found to overlie a shale. The shale contains a volcanic ash layer that has been radiometrically dated to 84 million years ago. Both the shale and the sandstone are cut by a pluton of gabbro that has been dated to 60 million years old. How old is the sandstone layer? ____BETWEEN 84 AND 60 MILLION YEARS OLD____

11) The amount of time it takes for half of the remaining radioactive isotopes to decay is the _____HALF-LIFE___ of a isotope system.

12) A group of fossils found together in a given rockbed is called——FOSSIL ASSEMBLAGE

13) All else being equal, in a horizontal sequence of sedimentary rock layers, each higher bed is younger than the bed below it. This idea is the principle of __SUPERPOSITION______.

14) The process by which geologists identify and match sedimentary strata and other rocks of the same ages in different areas is _______CORRELATION_.

15) When radioactive potassium-40 decays, the stable daughter isotope ____ARGON-40____ is produced.

16) A(n) _____DISCONFORMITY___ is an erosional unconformity with parallel beds or strata above and below.

#9-16 Vocabulary (extra words and/or phrases are included, not all will be used)

• correlation
• superposition
• alpha decay
• Curie point
• half-life
• carbon-14
• argon-40
• uranium
• inclusion
• dike
• sill
• disconformity
• marble
• lava flow
• limestone
• younger than 60 million years old
• between 84 and 60 million years old
• older than 84 million years old
• penguin
• pigeon

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