Geology 535 – Early Earth Evolution

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Geology (GLGY 535-UCAL) Midterm Exam

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Question 1

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

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

Question 2

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

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

Question 3

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

A	Al
B	Mg
C	S
D	Cu
E	Pb

Question 3 Explanation:

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

Question 4

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

A	Nd
B	Th
C	Sm
D	U
E	Pb

Question 5

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

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

Question 6

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

A	Si
B	Sm
C	O
D	Lu
E	Hf

Question 7

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

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

Question 8

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

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

Question 9

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

Question 10

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

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

Question 11

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

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

Question 12

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

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

Question 13

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

A	Sandstones
B	Limestone
C	Loess
D	Shale

Question 14

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

A	Eoarchean
B	Paleoarchean
C	Mesoarchean
D	Neoarchean

Question 15

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

A	10
B	1000
C	5
D	150

Question 16

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

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

Question 16 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 17

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

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

Question 18

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

A	It is the temperature which 50% of all the elements are condensed out of the nebula gas.
B	It is the temperature which 100% of a given element is 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 19

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

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

Question 20

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

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

Question 21

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

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

Question 22

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

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

Question 23

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

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

Question 24

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

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

Question 25

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	542 - 2000
C	2500 - 4030
D	3020 - 5560

Question 26

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

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

Question 27

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

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

Question 28

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

Question 28 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 29

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

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

Question 30

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

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

Question 31

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	Metal oxides
B	Silicates
C	Nobel gases
D	Ice
E	Aluminum

Question 32

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

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

Question 33

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

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

Question 34

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

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

Question 34 Explanation:

Specifically microfossils.

Question 35

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 36

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

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

Question 37

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

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

Question 38

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

Question 38 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 39

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

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

Question 40

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

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

Question 41

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

Question 41 Explanation:

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

Question 42

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

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

Question 43

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

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

Question 44

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

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

Question 45

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

A	Venus
B	Sun
C	Comets
D	Moon
E	Asteroid belt

Question 46

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

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

Question 47

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 48

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

A	Shale
B	Sandstones
C	Limestone
D	Loess

Question 49

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

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

Question 50

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

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

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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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Standing on the shoulders of giants