Geology 535 – Early Earth Evolution

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Geology (GLGY 535-UCAL) Midterm Exam

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Question 1

Majority of the mass in soar nebula is concentrated in... (ID-EEM-15)

A	...the Earth.
B	...the sun.
C	...in the core of the Earth.
D	...in the terrestrial planets.

Question 2

What is Model Age? (ID-EEM-11)

A	It is the time of crystallization.
B	It is the time of separation of isotope from a given reservoir.
C	It is a standard used to calculate type-sections and GSSPs for Geologic Time boundaries.
D	It is the time of primordial soup formation.

Question 3

There are several studies done on age of Earth. The calculated model ages are younger than the crystallization age (absolute age). (ID-EEM-14)

A	False because the model ages are older than the crystallization ages.
B	False because both model and crystallization age are the same. This is how we know the exact age of Earth.
C	Partially true because in most cases model ages are older than the crystallization ages.
D	True

Question 4

___ drives the plate tectonics. Choose the best possible answer. (ID-EEM-39)

A	Adiabatic decompression
B	Surface P-T conditions
C	Orogenic events
D	Interior temperature

Question 5

Modern day Mantle Potential Temperature (MPT) is ____ the Eruption Potential Temperature. (ID-EEM-32)

A	Could not answer the question because it is depend on the type of setting.
B	lower than
C	same as or very close to
D	higher than

Question 6

What is condensation temperature? (ID-EEM-16)

A	It is the temperature which 100% of a given element is condensed out of the nebula gas.
B	It is the temperature which 50% of all the elements are condensed out of the nebula gas.
C	It is the temperature which 50% of a given element is condensed out of the nebula gas.
D	It is the temperature which 100% of all the elements are condensed out of the nebula gas.

Question 7

How is identification of cratons can be economically beneficial? (ID-EEM-07)

A	Majority of food production ("farming") occur in cratonic regions.
B	Majority of the diamond-bearing kimberlites were found in cratons.
C	Majority of precious metals were found in cratons.
D	Majority of oil reserves were found in cratons.

Question 8

The iron sulphide phase in meteorites known as troilites (FeS) contains appreciable concentration of what other element? (ID-EEM-34)

A	Pb
B	Sm
C	U
D	Nd
E	Th

Question 9

The MgO content of an erupted liquid is directly related to the ___ of the liquid arriving on the surface. (ID-EEM-40)

A	closure temperature
B	maximum temperature
C	minimum temperature
D	electron affinity and reactivity
E	liquidus temperature

Question 10

What is the primary factor contributed to core formation in Earth? (ID-EEM-28)

A	Migration of molten Fe alloys along grain boundaries of solid silicates.
B	Heat produced by radioactive isotopes melting the bulk Earth.
C	Chemical differentiation due to rapid exothermic reactions.
D	Gravitational separation of metallic iron from silicates.
E	Differentiation of Fe alloys and silica due to high pressure and temperature conditions.

Question 11

Our Solar Nebula was as hot as 1500 K at one point. As it slowly cooled down, which of the following would you expect to condense first out of the gas cloud? (ID-EEM-25)

A	Silicates
B	Nobel gases
C	Metal oxides
D	Ice
E	Aluminum

Question 12

Which of the following was used by Claire Patterson to determine the age of Earth? (ID-EEM-47)

A	U-Pb dating of meteorites and pelagic sediment
B	Pb-Pb dating of meteorites and pelagic sediment
C	U-Pb dating of ancient zircons
D	Hf-W dating of CAI inclusions
E	Nd model age dating of Isua Supracrustal lithologies

Question 13

Which of the following can be used to establish the depleted of Earth’s mantle through time? (ID-EEM-49)

A	εW and εHf
B	εNd and εHf
C	εNd and εW
D	εNd
E	εW

Question 14

When is the lower intercept of Pb-U concordia-discordia method provide no meaningful values? (ID-EEM-33)

A	If the Pb-loss was episodic/continuous event.
B	If most of the samples plots on the concordia.
C	If there is no upper intercept.
D	If some samples plots on the concordia while others on discordia.

Question 15

The variable patterns of REE abundances are interpreted to be caused by... (ID-EEM-26)

A	...high abundance in refractory elements.
B	...high abundance in volatile elements.
C	...repeated evaporation and condensation.
D	...high condensation temperature.

Question 16

Which of the following is the youngest era in the Archean timescale? (ID-EEM-45)

A	Mesoarchean
B	Paleoarchean
C	Neoarchean
D	Eoarchean

Question 17

According our modern understanding of planetary sciences, where do most meteorites originate? (ID-EEM-37)

A	Moon
B	Asteroid belt
C	Venus
D	Sun
E	Comets

Question 18

When studying Archean Geologic history, you should have a rough idea of the age of Archean cratons. What is a reasonable age range for an Archean craton? (ID-EEM-02)

A	4500 - 4560
B	2500 - 4030
C	542 - 2000
D	3020 - 5560

Question 19

The Hf-W chronometer indicates that the core was formed... (ID-EEM-42)

A	...rapidly.
B	...extremely slowly.
C	...inefficently.
D	...in several stages.

Question 20

There are several criteria in classification of refractory elements. What is the most important parameter in refractory elements? (ID-EEM-17)

A	Type of reactivity and radioactivity of elements.
B	Silica content of the original source of the elements.
C	Very high condensation temperature.
D	Volatility of the elements.

Question 21

What is the oldest known radiometric date for Chrondrites as of October, 2014? (ID-EEM-38)

A	3.69 Ga
B	4.23 Ga
C	4.56 Ga
D	3.55 Ga
E	3.69 Ga

Question 22

Which of the following statement best describes the studies done on surface compositions of the Earth's crust? (ID-EEM-31)

A	Seismic evidence shows only two parts of the crustal sections; Middle and Lower. The Upper section is distinguished by elemental studies.
B	Major element data are consistent from study to study.
C	Over 50% of the data on major elements falls considerably outside of the range found by Eade and Fahrig's Canadian Shield Average.
D	Trace element data are consistent from study to study.

Question 23

In discordant analysis, the upper intercept provide what valuable information? (ID-EEM-13)

A	The closure conditions.
B	Crystallization age.
C	Initial isotopic ratio.
D	The time of formation.

Question 24

Which of the following is useful for estimating the abundance of soluble elements in the upper crust? (ID-EEM-43)

A	Loess
B	Sandstones
C	Shale
D	Limestone

Question 25

Why do we prefer to date zircons? (ID-EEM-10)

A	They are the most abundant mineral in cratons.
B	They have a very high closure temperature.
C	They have hardness of 5 in Mohs scale and therefore resistant to weathering.
D	It is easier to determine the isotopic compositions of zircons.

Question 26

What does the mass spectrometer actually measure? (ID-EEM-09)

A	Density of isotopes.
B	Ratios of parent to daughter isotopes.
C	Alpha, beta and positron decay of isotopes.
D	Weight and electrical charge of each isotope.

Question 27

Shield areas in continents are characterized by which of the following features? (ID-EEM-44)

A	Large variations in heat flux within a smaller area
B	Lower than average heat flux
C	Heat flux higher than in oceanic domains
D	Higher than average heat flux

Question 28

Archean cratons have a deep lithopheric root. Most roots of these cratons exceed ____ km. (ID-EEM-06)

A	5
B	1000
C	10
D	150

Question 29

Aristarchus lunar creator has typical characteristics of an impact creator. We found that the raised rim areas of the creator has been "eroded" or "disfigured". It is most likely caused by which of the following processes? (ID-EEM-01)

A	Plate tectonics may have destroyed the original structure.
B	Solar radiation and flares may have burnt out the thin and tall rim section.
C	Later impacts may have destroyed the raised rim.
D	The raised rim is more susceptible to weathering.

Question 29 Explanation:

Since moon does not have an atmosphere, you can rule out weathering. There are no plate tectonics. Therefore NASA scientists concluded, the only reason the raised rims are damaged because of later impacts that destroyed the original structure.

Question 30

Which of the following element used in isotopic age calculations also plays a major role in zircon crystal lattice? (ID-EEM-24)

A	Lu
B	Si
C	Hf
D	Sm
E	O

Question 31

Two isotopic systems of U-Pb were compared using isochron technique. One system had a large ratio of daughter isotopes compared to the parents. Which of the following statement is correct? (ID-EEM-18)

A	The system with large number of daughter isotopes ratio most likely have been an opened system at some point.
B	The system with large number of daughter isotopes ratio most likely have a shallower isochron.
C	The system with large number of daughter isotopes ratio most likely have a steeper isochron.
D	The system with large number of daughter isotopes ratio most likely have been undergone crustal or magmatic contamination.

Question 31 Explanation:

While it is possible, it is difficult to determine the state of a system using isochrons (open/close). It is also possible that the system may have be opened at some point. But, still it cannot be inferred simply by an isochron. Therefore, the only logical answer is the slope of the isochron itself. You have to apply the knowledge to answer this question.

Question 32

Given the following profile of a typical komatiite flow facies, where would you sample to estimate the composition of the original magma? (ID-EEM-29)

Facies	Profile	Zone
A1	Chilled flow top	Spinifex zone
A2	Random spinifex
A3	Plate spinifex
B1	-	Cumulate zone
B2	-
B3	-

A	B2
B	A1 in the chilled flow top region.
C	A3 in the plate spinifex region.
D	B1
E	Anywhere within the cumulate zone.
F	Anywhere within the spinifex zone.

Question 32 Explanation:

The highest (top) layer cool down faster hence preserving most of the geochemical properties of the original magma.

Question 33

Shot-lived isotopic systems are not suitable for studying which of the following situations? (ID-EEM-30)

A	To estimate timing of melting and crystallization sequences.
B	To estimate condensation temperatures of materials from Solar Nebula.
C	To estimate relationships between cogenetic samples.
D	To analyze relatively short processes that occur for 300 million years.
E	To analyze metal-silicate-sulfide differentiation.

Question 33 Explanation:

A typical short-lived isotopic system last for less than 100 million years. Therefore these systems cannot be used to analyze processes that takes longer than 100 Mya.

Question 34

Steeper the Isochron, ___ the system. (ID-EEM-12)

A	higher the uncertainties in
B	younger
C	larger the diffusion into
D	older
E	larger the diffusion out of

Question 35

Which of the following statement is false about Ordinary Chondrites? (ID-EEM-22)

A	85% of all Ordinary Chondrites are observed falls.
B	Most of the Ordinary Chondrites have petrologic types from 3 to 6.
C	Ordinary Chondrites are the most common type we have today.
D	75% of all Ordinary Chondrites contains CAIs and AOAs.

Question 36

At the very beginning, solar nebula is made up of 71% what component or gas? (ID-EEM-36)

A	Helium gas
B	Rocks and dust particles
C	Water vapor
D	Hydrogen gas

Question 37

Which of the following statement is correct about cratons? (ID-EEM-04)

A	Within the creaton, platforms are areas where basement is overlaid by sediments and sedimentary rock.
B	Shield is a made up of several smaller creatonic nuclei.
C	There are only two places on Earth with creatons; Africa and North America.
D	Within the creaton, shield are areas where basement is overlaid by sediments and sedimentary rock.
E	The geochemical composition of creatons are homogeneous.

Question 38

Typically, what is the duration for a radioactive isotopic system? (ID-EEM-08)

A	4 half-life cycles.
B	8 half-life cycles.
C	13 half-life cycles.
D	14 half-life cycles.
E	5 half-life cycles.

Question 39

Where did we find the oldest known terrestrial Geologic martial on Earth? (ID-EEM-41)

A	Kaapvaal, South Africa.
B	Isua Formation, Greenland.
C	Jack Hill, Australia.
D	Western Canada Sedimentary Basin, Canada.

Question 40

Which of the following contains the most refractory phases in chondritic meteorites? (ID-EEM-48)

A	Chondrules
B	Metallic portion of the matrix
C	Nebula
D	Matrix
E	CAI’s

Question 41

What are CI chondrites? (ID-EEM-27)

A	The most common chondrites that falls under petrologic Type 3.0 to 3.1
B	They are part of the differentiated group.
C	A type of chondrites with high abundance of silica and can be used to measure differentiation time period.
D	The most primitive chondrites that falls under petrologic Type 1.0

Question 42

A overall positive εHf value indicates... (ID-EEM-35)

A	...a crustal source.
B	...a system that has underwent gradual isotopic gain.
C	...a mantle source.
D	...a closed system.
E	...an open system.

Question 43

Which of the following represents a normal order of condensation from a solar nebula gas as temperature decreases? (ID-EEM-46)

A	Metal oxides, silicates, volatiles
B	Any chemical group based on radial distance from the sun
C	Volatiles, silicates, metal oxides
D	Silicates, metal oxides, volatiles

Question 44

Which of the following is useful for estimating the abundance of soluble elements in the upper crust? (ID-EEM-50)

A	Limestone
B	Shale
C	Sandstones
D	Loess

Question 45

Chondrites have been classified into __I__ classes/types and the most common class/type, Ordinary Chondrites have __II__ groups/subtypes. (ID-EEM-21)

A	I. two II. four
B	I. two II. three
C	I. three II. two
D	I. three II. three
E	I. two II. five

Question 46

Which of the following element most likely the one to condensed out of the solar nebula first? (ID-EEM-20)

A	Mg
B	Al
C	Pb
D	Cu
E	S

Question 46 Explanation:

You should know this without memorizing all the refractory elements because CAIs in Chondrites.

Question 47

A overall negative εNd value indicates... (ID-EEM-19)

A	...a closed system.
B	...an open system.
C	...nothing because there is not enough information provided to answer the question.
D	...a mantle source.
E	...a crustal source.

Question 48

The Ediacaran GSSP is primarily based on what type of evidence? (ID-EEM-03)

A	Fossil evidence
B	Sm-Nd dating
C	U-Pb dating
D	Refractory elemental abundance

Question 48 Explanation:

Specifically microfossils.

Question 49

Which of the following observation on differentiation is true? (ID-EEM-23)

A	During differentiation of Earth, large portion of silica sank into the core of the Earth.
B	Differentiation occurs at a extensive rate on larger plants.
C	All meteorites are not differentiated because they are failed planets.
D	Differentiation is highly dependent on the pressure conditions.

Question 50

What is the simplest method to determine relative age of a luna crater? (ID-EEM-05)

A	Combination of geochemical and physical analysis of rocks from center and outer rim of the creator.
B	Size and shape of the creator.
C	Geochemical analysis of rocks from the center of the creator.
D	Overprinting of craters with respect to each other.

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Credits: Based on the excellent class notes provided by, Dr. Rajeev Nair during Fall 2014.
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This class covers rapidly evolving subject matter. Due to cutting-edge research into Early Earth, there is a very high possibility that some of the questions may not be relevant to your current understanding. Please use this quiz with caution.

Sanuja Senanayake

Geology 535-University of Calgary

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Geology (GLGY 535-UCAL) Midterm Exam

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Geology (GLGY 535-UCAL) Midterm Exam

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