Geology 535 – Early Earth Evolution

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Geology (GLGY 535-UCAL) Midterm Exam

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Question 1

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 there is no upper intercept.
D	If some samples plots on the concordia while others on discordia.

Question 2

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

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

Question 3

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

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

Question 4

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

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

Question 5

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

A	Eoarchean
B	Paleoarchean
C	Neoarchean
D	Mesoarchean

Question 6

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

A	It is the time of separation of isotope from a given reservoir.
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 crystallization.

Question 7

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

Question 8

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	closure temperature
C	liquidus temperature
D	maximum temperature
E	minimum temperature

Question 9

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

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

Question 9 Explanation:

Specifically microfossils.

Question 10

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	Nobel gases
C	Silicates
D	Ice
E	Aluminum

Question 11

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

Question 11 Explanation:

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

Question 12

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

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

Question 13

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

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

Question 14

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	3.69 Ga
D	4.56 Ga
E	3.55 Ga

Question 15

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

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

Question 16

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

Question 16 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 17

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

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

Question 17 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 18

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

Question 19

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

A	Al
B	S
C	Mg
D	Pb
E	Cu

Question 19 Explanation:

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

Question 20

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

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

Question 21

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

A	10
B	5
C	1000
D	150

Question 22

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

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

Question 23

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

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

Question 24

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

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

Question 25

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

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

Question 26

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

A	Sm
B	O
C	Hf
D	Lu
E	Si

Question 27

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

Question 28

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

A	Shale
B	Loess
C	Sandstones
D	Limestone

Question 29

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	75% of all Ordinary Chondrites contains CAIs and AOAs.
D	Ordinary Chondrites are the most common type we have today.

Question 30

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

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

Question 31

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	True
D	Partially true because in most cases model ages are older than the crystallization ages.

Question 32

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

A	Comets
B	Sun
C	Moon
D	Asteroid belt
E	Venus

Question 33

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

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

Question 34

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

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

Question 35

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. three
D	I. three II. two
E	I. two II. five

Question 36

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 37

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

A	Sandstones
B	Limestone
C	Shale
D	Loess

Question 38

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	Very high condensation temperature.
C	Silica content of the original source of the elements.
D	Volatility of the elements.

Question 39

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

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

Question 40

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

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

Question 41

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

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

Question 42

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	The raised rim is more susceptible to weathering.
B	Plate tectonics may have destroyed the original structure.
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 42 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 43

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

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

Question 44

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

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

Question 45

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

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

Question 46

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

A	U
B	Pb
C	Nd
D	Sm
E	Th

Question 47

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

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

Question 48

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

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

Question 49

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

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

Question 50

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

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

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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