Deck 19: Precambrian Earth and Life History

Question 1

What is the basic difference between the Archean and the Proterozoic?

Answer 1

the style of crustal evolution

Question 2

What two processes,which began during the Archean,can account for the introduction of free oxygen into the atmosphere?

Answer 2

photochemical dissociation and photosynthesis

Question 3

What are monomers?

Answer 3

simple organic molecules

Question 4

What are heterotrophic organisms?

Question 5

What are the three major units found in greenstone belts from bottom to top,and what type dominates the lower two-thirds? In the upper third?

Question 6

What are banded iron formations composed mainly of?

Question 7

What do the Ediacaran fauna represent,and why are they important?

Question 8

What does the appearance of red beds in the geologic record indicate about the atmosphere?

Question 9

Why is it believed that cyanobacteria must have been preceded by even simpler organisms?

Question 10

What is an anaerobic organism?

Question 11

What are two examples that demonstrate the difficulty of adopting absolute minimal criteria for deciding whether or not something is alive?

Question 12

Besides the origin of life itself,what was the most significant biological event of the Archean?

Question 13

What are prokaryotic organisms?

Question 14

How does photochemical dissociation of water vapor occur?

Question 15

Briefly explain the difference between the tectonic setting of shield areas during the Precambrian and since the onset of the Phanerozoic.

Question 16

How did Laurentia evolve?

Question 17

Why are ultramafic volcanics rare in rocks that are much younger than Archean in age?

Question 18

What are the two main rock types that characterize Archean shield areas?

Question 19

What is symbiosis?

Question 20

Sandstone-carbonate-shale assemblages are characteristic of sedimentation at what type of plate margin? Describe when they form in the Wilson cycle,and what types of environments they represent?

Question 21

Sandstone-carbonate-shale assemblages comprise ______ percent of the Proterozoic rock record and indicate ____________________ tectonics.

Question 22

The ____________________ forms the core of North America and has been tectonically ____________________.

Question 23

Early gases which had begun to accumulate around Earth during the Early Archean were lost because of a lack of a(n)____________________.

Question 24

The Precambrian comprises what percent of geologic time?

A) 99 percent
B) 88 percent
C) 77 percent
D) 66 percent
E) 55 percent

Question 25

The formation of the Midcontinent rift was ____________________ in time with the Grenville orogeny.

Question 26

The Grenville orogeny occurred between ______ to ______ billion years ago

Question 27

Continents are cored by large areas of exposed ancient rocks called ____________________,which are tectonically ____________________ regions.

Question 28

Early organisms played a role in the accumulation of free oxygen through the process of ____________________,which combines carbon dioxide and ____________________ to make organic molecules,and ____________________ is given off as waste.

Question 29

The assemblage of sandstone-carbonate-shale is probably indicative of ____________________ (in depth)water shelf environment.

Question 30

Evidence for oxygen deficient atmosphere during the Archean includes the presence of detrital ____________________ and ____________________ in ____________________ rocks.

Question 31

Between 1.3 and 1.0 billion years ago,the __________ orogeny occurred in the supercontinent __________.

Question 32

The deposition of banded iron formations primarily occurred about ______ to ______ billion years ago.

Question 33

Sandstone-carbonate-shale assemblages were deposited along _______ continental margins.

Question 34

The ____________________ orogen is the earliest that documents a complete ____________________ cycle of opening and closing ocean basins.

Question 35

What are time divisions in the Precambrian based on?

A) distinct fossil assemblages
B) metamorphic assemblages
C) radiometric age dates
D) time-stratigraphic units
E) none of these

Question 36

Most of the Precambrian is divided into the following two eons _______ and _______,with the earlier part of the time interval being the _______.

Question 37

The process by which gases within Earth are emitted and eventually accumulate into an atmosphere is called ____________________.

Question 38

Continental growth during the Early Proterozoic development of Laurentia was related to ____________________ of ____________________ age cratons.

Question 39

Areas of buried shield rock and younger sedimentary cover are collectively called ____________________,which are tectonically ____________________ and ____________________.

Question 40

The Grenville orogen probably resulted from closure of a(n)__________,the final stage in a __________ cycle.

Question 41

Most of the volcanism associated with greenstone belts was ____.

A) subaqueous
B) basalt pillow lavas
C) ultramafic lava
D) subaqueous and ultramafic lava
E) all of these

Question 42

The Precambrian history of Earth is difficult to determine for all but which of the following reasons?

A) There is Precambrian rock exposed only on three continents.
B) Precambrian rock is complexly deformed.
C) Precambrian rock is metamorphosed.
D) In many places the rock is deeply buried.
E) There are few fossils in the Precambrian record.

Question 43

There is chemical evidence that life appeared by ____ and fossils by ____.

A) 3.8 billion years, 2.5 billion years
B) 4.6 billion years, 2.5 billion years
C) 3.8 million years, 3.5 million years
D) 3.8 billion years, 3.5 billion years
E) 4.6 million years, 3.5 million years

Question 44

The increase in atmospheric oxygen during the Proterozoic was related to what?

A) decreased world wide volcanism
B) decrease in size of oceans
C) photosynthesis by bacteria
D) appearance of land plants
E) none of these

Question 45

The heat reservoir of the early history of Earth was generated by all but which of the following?

A) radioactive decay
B) compression of material
C) meteorite bombardment
D) continental collision and accretion
E) none of these

Question 46

Which is the correct sequence of events in the development of a back-arc basin style greenstone belt?
1) granitic intrusion and metamorphism
2)basin opening
3)basin closing
4)extension
5)compression
6)volcanism and sedimentation

A) 2, 4, 6, 3, 5, 1
B) 2, 6, 5, 4, 3, 1
C) 6, 4, 2, 5, 1, 3
D) 6, 1, 2, 4, 3, 5
E) 1, 2, 3, 4, 5, 6

Question 47

Shield areas of continents are found in modern ____.

A) subduction zones
B) continent-continent plate boundaries
C) tectonically inactive regions
D) divergent plate boundaries
E) transform plate boundaries

Question 48

All but which of the following are features of greenstone belts?

A) volcanic and sedimentary rocks
B) key index fossil assemblages
C) granitic intrusions
D) complex folding and faulting
E) abundant chlorite

Question 49

By ____ years ago,much of Greenland,central Canada,and the north central United States formed one large craton.

A) 1.8 million
B) 2.0 billion
C) 1.6 billion
D) 1.6 million
E) 1.8 billion

Question 50

The iron in banded iron formations was primarily in which iron-bearing minerals?

A) iron sulfide
B) iron oxides
C) iron silicate
D) iron carbonate
E) none of these

Question 51

What are small molecules composed of multiple amino acids called?

A) monomers
B) protobionts
C) bacteria
D) proteinoids
E) none of these

Question 52

The large Proterozoic landmass known as Laurentia was composed of ____.

A) Europe, Asia, Scandinavia, NW Scotland
B) North America, South America, Greenland, Baltic Shield
C) North America, Greenland, NW Scotland, Baltic Shield
D) Greenland, NW Scotland, Baltic Shield, Europe
E) Greenland, Iceland, Nova Scotia, Baltic Shield

Question 53

During the Archean,how long was the length of a day on Earth?

A) 36 hours
B) 10 hours
C) the same as the length of a day on modern Earth
D) like the present but there was no day, it was all darkness
E) like the present but there was no darkness, it was all daylight

Question 54

The earliest atmosphere of Earth was ____.

A) the same as the modern atmosphere
B) composed entirely of nitrogen
C) composed of ozone and hydrogen
D) blown into space by solar wind
E) composed of ozone and hydrogen AND blown into space by solar wind

Question 55

What are molecules which are intermediate between inorganic compounds and living organisms called?

A) protobionts
B) proteinoids
C) bacteria
D) amino acids
E) monomers

Question 56

Sedimentary rocks are abundant in the ____ portion of greenstone belts and consist largely of ____ and ____.

A) bottom, argillite, graywacke
B) upper, argillite, graywacke
C) middle, argillite, graywacke
D) top, argillite, limestone
E) bottom, argillite, limestone.

Question 57

The Archean atmosphere could be described as what?

A) oxygen rich
B) nitrogen rich
C) ozone rich
D) oxygen deficient
E) carbon dioxide rich

Question 58

What factor(s)led to the enormous scale of banded iron deposition during the Proterozoic?

A) abundance of dissolved iron in seawater
B) increase in photosynthesizing bacteria
C) chemical affinity of iron to combine with available oxygen
D) all of these
E) none of these

Question 59

All organisms are composed mostly of all but which of the following?

A) oxygen
B) nitrogen
C) calcium
D) carbon
E) hydrogen

Question 60

Which factors likely played a role in the development of early life?

A) presence of carbon, hydrogen, nitrogen, and oxygen
B) ultraviolet light
C) lightning
D) ultraviolet light and lightning only
E) all of these

Question 61

The oldest eukaryotes in the fossil record are at least how old?

A) 2.0 billion years old
B) 1.2 billion years old
C) 1.0 billion years old
D) 3.4 billion years old
E) 5.0 billion years old

Question 62

Pegmatites are associated with ____ rocks and contain ____,____,and ____.

A) greenstone belt volcanic, copper, lead, zinc
B) greenstone belt volcanic, rubidium, beryllium, lithium
C) granitic, lithium, zinc, gold
D) granitic, lithium, beryllium, rubidium
E) sedimentary, gold, chrome, platinum

Question 63

The Sudbury Basin is one of the richest mining areas in the world because it

A) is a banded-iron formation.
B) is a meteorite impact site.
C) is a layered intrusion.
D) is a stromatolite.
E) all of these

Question 64

The Ediacaran fauna include representatives of the modern phyla ____.

A) Proterozoa, Annelida, and Arthropoda
B) Annelida, Arthropoda, and Cnidaria
C) Proterozoa, Porifera, and Cnidaria
D) Coelenterata, Annelida, and Cnidaria
E) Coelenterata, Proterozoa, and Porifera

Question 65

Sandstone-carbonate-shale assemblages occur along continental rift margins and intracratonic basins.

Question 66

Rocks associated with the Wopmay orogen document the oldest complete Wilson cycle.

Question 67

Subunits within the shield are delineated by radiometric ages and structural trends.

Question 68

Sandstone-carbonate-shale assemblages are restricted to the Proterozoic.

Question 69

The rate of plate motion was probably slower in the Archean.

Question 70

The boundaries of subunits or smaller cratons within the shield are based on topographic expression of different rock types.

Question 71

Ophiolites are abundant in Archean age rock sequences.

Question 72

In the back-arc basin model for greenstone belt evolution,metamorphism and deformation are closely tied to basin opening.

Question 73

The Grenville orogeny was the culminating event of the amalgamation of Laurentia.

Question 74

Which of the following might be considered advantages that multi-celled organisms have over single celled organisms?

A) They can grow larger.
B) Specialized cells are more efficient.
C) Cells can be replaced, thus they live longer.
D) Specialized cells for reproduction aid in population growth.
E) all of these

Question 75

The enormous amount of banded iron formation deposited during the period of 2.5 to 2.0 billion years ago signifies a transition from oxidizing to reducing atmosphere on Earth.

Question 76

Banded iron formations are composed of almost 99 percent silica with only minor iron impurities that give a streaked or banded appearance.

Question 77

The presence of thick sections of carbonate and sandstone indicates that Archean continents had well-developed shelf environments.

Question 78

The rapid rate of plate motion was probably the most important factor in rapid continental growth in the Late Archean.

Question 79

Archean and Proterozoic greenstone belts formed in similar tectonic settings.

Question 80

Archean age rocks are important sources for all but which of the following commodities?

A) chrome
B) gold
C) platinum
D) lead
E) nickel