Deck 8: Precambrian Earth and Life History the Hadean and the Archean Eon

Question 1

The first supercontinent present by Proterozoic time was Vaalbara.

Answer 1

True

Question 2

The Precambrian represents approximately 88 percent of geologic time.

Answer 2

True

Question 3

Over time, Earth's rotation rate has slightly increased.

Answer 3

False

Question 4

Komatiites are common from the Archean eon, although none are produced in modern tectonic environments.

Question 5

Since its formation, the Moon has slowly been moving away from Earth.

Question 6

Continents consist of the portion of land above sea level only.

Question 7

Earth's early atmosphere was very rich in oxygen (O₂).

Question 8

Greenstone belts are dominated by volcanic rocks in the lower and middle parts, and sedimentary rocks in the upper part.

Question 9

Detrital zircon from sedimentary rocks found in Australia yields an age of 4.4 billion years, which indicates that rocks formed on Earth at least 4.4 billion years ago.

Question 10

Earth was a hot, barren, waterless planet during the Archean eon.

Question 11

Greenstone belts are composed of sedimentary and volcanic rocks.

Question 12

Submarine hydrothermal vents commonly are found near mid-oceanic ridges where seafloor spreading occurs.

Question 13

Deoxyribonucleic acid (DNA) is an example of a polymer.

Question 14

The Moon formed after a large object collided with Earth.

Question 15

Precambrian time are subdivided based on numerical dates rather than relative dating.

Question 16

Autotrophs make their own food.

Question 17

Greenstone belts are some of the youngest rocks on Earth.

Question 18

Cyanobacteria (blue-green algae) are an example of a heterotrophic organism.

Question 19

Precambrian shield areas have been tectonically active since the Phanerozoic.

Question 20

Platforms and cratons make up continental shields.

Question 21

The accumulation of an early atmosphere by the release of gases from Earth's interior during volcanism is known as ____.

A) photosynthesis
B) outgassing
C) abiogenesis
D) continental accretion
E) stromatolite

Question 22

How are ocean and continental crust different?

A) Continental crust is basalt, whereas oceanic crust is granite.
B) Continental crust is formed by volcanism, whereas oceanic crust is not.
C) Continental crust is granite, whereas oceanic crust is basalt.
D) Continental crust is dense, whereas oceanic crust is less dense.
E) Continental crust is thin, whereas oceanic crust is thick.

Question 23

What is the primary component of Earth's current atmosphere?

A) carbon dioxide
B) oxygen
C) water vapor
D) nitrogen
E) argon

Question 24

From where does the name "greenstone" in greenstone belts originate?

A) Greenstone belts formed on land.
B) Many of the minerals in greenstone belts are green.
C) Greenstone belts contain the earliest algal fossils.
D) The origins of greenstone belts were first described by the geologist Nathaniel Greene.
E) The type locality for greenstone belts is in Greenland.

Question 25

The high Earth temperatures in the Archean probably played a role in the rapid rate of plate motion.

Question 26

Ultramafic lava flows are significant in the Archean rock record because they indicate that Earth was 90 percent molten.

Question 27

Both the intracontinental rift and back-arc basin model are based on volcanism associated with mantle plumes.

Question 28

The early atmosphere of Earth probably did not contain ____.

A) nitrogen
B) oxygen
C) carbon dioxide
D) carbon monoxide
E) sulfur dioxide

Question 29

The process by which life formed from nonliving matter is known as ____.

A) outgassing
B) photosynthesis
C) continental accretion
D) abiogenesis
E) anaerobic evolution

Question 30

Mound-like structures that represent the remains of photosynthesizing cyanobacteria are ____.

A) greenstone belts
B) stromatolites
C) back-arc basins
D) cratons
E) black smokers

Question 31

Oxygen accumulated in the atmosphere via ____.

A) processes in the ozone hole
B) nucleosynthesis
C) meteorite bombardments
D) differentiation
E) photosynthesis

Question 32

The time in Earth's history before 4 billion years (4000 m.y.) is known as the ____.

A) Hadean
B) Proterozoic
C) Archean
D) Paleoarchean
E) Eoarchean

Question 33

What are the primitive organisms thought to have been responsible for the development of Earth's oxygen-rich atmosphere in the Precambrian?

A) tillites
B) cyanobacteria (blue-green algae)
C) foraminifera
D) diatoms
E) prokaryotes

Question 34

When it first formed, the Sun was 75 times more luminous than it is now.

Question 35

What is the metabolic process in which organic molecules are synthesized from water and carbon dioxide (CO₂), using radiant energy of the sun captured by chlorophyll-containing cells?

A) sexual reproduction
B) paleontology
C) speciation
D) abiogenesis
E) photosynthesis

Question 36

Organisms that do not depend on oxygen for growth are ____.

A) eukaryotic
B) abiogenic
C) abyssal
D) prokaryotic
E) anaerobic

Question 37

Most continents contain large central areas in which very ancient rocks are exposed. These areas are called ____.

A) Precambrian shields
B) platforms
C) continental slopes
D) orogenic belts
E) continental shelves

Question 38

Despite their differences, the terrestrial planets have similar evolutionary trends.

Question 39

Hot mineral-rich seawater is ejected from ____.

A) volcanic arc systems
B) convergent boundaries
C) submarine hydrothermal vents
D) SPAHs (sulfur, phosphorus, and hydrogen) vents
E) subduction zones

Question 40

You are hiking in eastern Canada over a surface composed of very old igneous and metamorphic rocks. In geologic terms, you are most likely walking across a(n) ____.

A) continental shelf
B) platform
C) orogenic belt
D) shield
E) continental rise

Question 41

During the process of ____________________, rising magma from a subducting plate or mantle plume accumulates beneath a continent.

Question 42

____________________ organisms need no oxygen to survive.

Question 43

Why does Earth have water?

A) photosynthesis
B) large concentrations of sedimentary rocks
C) torrential flooding in Earth's early history
D) enormous tidal forces in early Earth history
E) outgassing and comet impacts

Question 44

What are the two tectonic models postulated for greenstone belt evolution?

A) back-arc marginal basin and continent/continent collision
B) continent/continent collision and intracontinental rift
C) intracontinental rift and back-arc marginal basin
D) subduction and mid-ocean ridge
E) subduction and continent/continent collision

Question 45

Collectively, the shield and platform of a continent are known as a(n) ____________________.

Question 46

Earth's first atmosphere likely consisted of ____________________ and ____________________, the most abundant gasses in the universe.

Question 47

Areas of buried shield rock with younger sedimentary cover are known as ____________________.

Question 48

____________________ organisms rely on external sources of nutrients.

Question 49

The newly-formed Earth's atmosphere was very different from Earth's current atmosphere because it had ____.

A) an abundance of mercury vapor
B) an enormous amount of carbon dioxide, resulting in very hot temperatures due to greenhouse effect
C) virtually no oxygen, a necessary component for the existence of animal life
D) an enormous amount of methane and ammonia, which was never lost by the atmospheres of the outer planets
E) virtually no nitrogen, the major component of today's atmosphere

Question 50

The nucleus or foundation of a continent is a(n) ____.

A) stromatolite
B) greenstone belt
C) Permian province
D) craton
E) orogenic belt

Question 51

What is one characteristic of Archean rocks?

A) paleomagnetism
B) numerous outcrops
C) medicinal properties
D) diverse fossil content
E) earliest fossils of life on Earth

Question 52

Geologists believe that ____________________ are the remains of reef structures from one of the first photosynthesizing organisms.

Question 53

Which event did not occur in the Hadean (4.6-4.0 bya)?

A) formation of oceans
B) extremely bright Sun
C) formation of Moon
D) accretion of Earth
E) formation of core and mantle

Question 54

The ____________________ forms the exposed part of the craton in North America.

Question 55

The three intervals, from oldest to youngest, of Precambrian time are the ____.

A) Hadean Eon, Archean Eon, and Proterozoic Eon
B) Archean Era, Hadean Era, and Proterozoic Era
C) Proterozoic Eon, Hadean Eon, and Archean Eon
D) Hadean Era, Archean Era, and Proterozoic Era
E) Archean Eon, Hadean Eon, and Proterozoic Eon

Question 56

Early atmospheric gases were emitted because of ____________________.

Question 57

The earliest crust was probably ____.

A) rich in precious metals
B) composed of felsic igneous rock
C) composed of ultramafic rock
D) very similar to the one of today
E) composed of basaltic rock

Question 58

Why does Earth have plate tectonics?

A) denser oceanic crust (relative to continental crust)
B) thicker oceanic crust (relative to continental crust)
C) relatively rapid cooling
D) convection currents and released heat deep within the mantle
E) active volcanoes (in the past and present)

Question 59

____________________ refers to the formation of life from non-living matter.

Question 60

What are two possible energy sources for the synthesis of organic molecules?

A) UV radiation and magnetism
B) radioactive decay and lightning
C) radioactive decay and UV radiation
D) lightning and UV radiation
E) lightning and magnetism

Question 61

Why is the early rock record of the Precambrian rocks more difficult to interpret than the rock record of the Phanerozoic Eon?

Question 62

What are two reasons that Earth lost its first atmosphere of hydrogen and helium?

Question 63

Discuss the origin of early Earth's hydrosphere.

Question 64

Discuss the origin of Earth's earliest granitic crust. What processes were important in forming this crust?

Question 65

Describe and discuss the early atmosphere of Earth. What was its most likely composition? How was it different from the present atmosphere and why?

Question 66

Explain why Mercury, Venus, and Mars lack plate tectonics.

Question 67

Describe prokaryotic cells and discuss the role they played in early Earth.

Question 68

Early in Earth history, the Sun was less luminous, which should have caused Earth to be much colder and all water to be frozen. Yet all evidence points to the presence of liquid water on Earth. Give two explanations that could resolve the "faint young sun paradox."

Question 69

Describe and discuss the difference between a craton and a shield.

Question 70

Discuss the characteristics and formation of greenstone belts. Why are these rocks important in explaining early Earth history?