GEOL1003 exam 1_study guide questions-2
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February 8 2024 GEOL 1003-01, Dr. Philip Bart, Test 1 Instructions. Fill in your name and LSU ID number on your scantron that you brought to class. 45 Multiple choice questions (5 points each): Read each question carefully. Read all the answers. Choose the best answer. Mark your answer clearly on the scantron. Turn in the exam and the scantron. Chapter 11 Archean and Hadean Eons of the Precambrian
1) The Precambrian corresponds to all the time prior to the Cambrian. What is the
oldest Eon of the Precambrian?
A) Proterozoic
B) Archean
C) Hadean
D) Phanerozoic
2) The rock cycle is constantly recycling rock, making new rock from old. Hence, the
older the rock, the more likely that it will experience recycling. On this basis, it is not
surprising that Precambrian-age rocks dating back to the Hadean Eon are rare. Why
is it that scientist think that the radiometric ages of meteorites represent a good
estimate for the age of planets in our solar system?
A) Meteorites represent chunks of mantle and core of small planets that formed at the same
time as Earth
B) Meteorites represent chunks of Earth that were dislodged when the moon struck Earth.
C) Meteorites originate from the same orbit as Earth and hence condensed at the same time
as Earth.
D) Meteorites originate from the Oort Cloud, the hence contain a similar composition to
that of Earth
3) Our solar system is located 2/3 the way out on the Orion-Cygnus arm of the Milky
Way spiral. The Milky Way is but one of 200 billion galaxies in the Universe.
Astronomers have observed that the distance between galaxies is increasing. This
observation is the basis of the Big Bang Theory. What does the Big Bang Theory
state?
A) An early history of meteorite collisions between 4.6 and 3.8 Ga BP led to the formation
of Earth
B) The universe began 13.7 Ga BP by an explosion of all matter that was previously
concentrated at a single point
C) The Solar System began at 4.5 Ga BP when contraction of a solar nebula flattened to a
disk
D) The Earth passed from a molten to solid state in the Hadean Eon at 4.6 Ga as iron sank to
the core
4) The density stratification of Earth into a core, mantle and crust occurred during
the Hadean indicating that Earth passed through a molten state. Some heat was
generated by radioactive decay. What was the other source of heat that put Earth in a
molten state?
A) solar radiation
B) impacts from asteroids and meteorites
C) igneous activity and metamorphism
D) all of the above
5) The first ocean on Earth probably formed during the Hadean Eon. What were the
primary sources of water?
A) groundwater discharge to rivers, which emptied into oceans
B) monsoons in regions where winds blow toward high elevation plateaus
C) dehydration of hydrous minerals
D) volcanic emissions of water vapor and comets that impacted Earth
6) The reason that Archean protocontinents were small is that _________________________.
A) Earth’s interior was not hot enough to make much felsic crust
B) Earth’s interior was so hot that rifting was common
C) the high density of Archean crust caused it to sink into subduction zones
D) the Archean crust was more quickly destroyed by erosion
7)
8)
Chapter 12 Proterozoic Eon of the Precambrian
9) The organisms that form stromatolites are photosynthetic prokaryotes called
cyanobacteria. These organisms proliferated and diversified in the mid-Proterozoic.
The peak in abundance and diversity of stromalolites was at 1.2 Ga BP. Why did
cyanobacteria proliferate?
10) Steranes show that Eukaryotes were around since the Archean at 2.7 Ga BP. The
earliest known fossil Eukaryotes from the Paleoproterozoic included protists called
acritarchs that diversified and became abundant after 1.9 Ga BP. Animal-like
Eukaryotes (protists) formed when amoeba-like prokaryotes engulfed bacterial
cells, which they could not digest. The bacterial cell became a functioning internal
part of the new organism, i.e., a mitochondrion. What evidence supports this view of
how Eukaryotes evolved from the union of two Prokaryotes?
11)
12) Which broad group of organisms was more common during the Proterozoic?
HINT: The Gun Flint Flora of the Lake Superior Region has only this type of organism.
13) The first life was prokaryotic (bacteria and archea) and appeared in the Archean.
Eukaryotic protists appeared later. The rock-record evidence indicates that the
earliest ancestors of all organisms grouped within Kindgom Animalia evolved from
unicellular animal-like protists during the ________________.
14)
15)
16) Glacial striations, dropstones and tillites of Neoproterozoic ages are found all
over the world. This widespread distribution of glacial deposits has led to the
Snowball Earth Hypothesis. The hypothesis states that Earth entered into a frozen
state on several occasions. The last two events were the Sturtian and Marinoan
events. The evidence (glacial tillites are directly overlain by carbonate rocks, the
types of which are typically deposited in tropical regions) shows that the intense
cold ended abruptly. Large vertical crystals of aragonite (a mineral made of calcium
carbonate) that grew on the seafloor as the inorganic limestone accumulated show
that immediately after the end of the Snowball Earth climate, the ocean was rich in
bicarbonate (an ion associated with weathering of continental rocks by acid rain).
From this evidence, scientists concluded that there was a major release of CO
2
to the
atmosphere that caused abrupt global warming. Apparently, cracks in the ice cover
released the CO
2
that was trapped below the ice. What is the current explanation as
to why Earth froze over during parts of the Neoproterozoic in the first place?
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17) At 1.9 billion years ago, Banded-Iron Formation (BIF), a sedimentary rock,
ceased to be deposited in the ocean. BIF is important because it is THE primary
source of iron-rich minerals used for industrial purposes; so thankfully, Earth went
through this early history that concentrated iron in BIF deposits. Some 1.9 billion
years after BIFs ceased to form, a previous US president placed tariffs on steel (an
alloy of iron with carbon and other elements). What changes brought about the
cessation of BIF production and the coeval subaerial accumulation of Red Beds?
Chapter 13 Proterozoic Eon of the Precambrian
18) Earth formed 4.6 billion years ago and experienced frequent meteorite bombardment for the next 800 million years in an Eon called the Hadean. The decline in meteorite bombardment at 3.8 billion years ago coincides with the start of the Archean Eon. The Archean Eon represents 3.8 billion years ago to 2.5 billion years ago. The earliest evidence of life in the fossil record is found from rocks 3.7 billion years old. In other words, life first evolved 100 million years after bombardments decreased. Earth’s early life consisted of primitive photosynthetic cyanobacteria. These simple organisms are called Prokaryotes to distinguish them from more complex life forms that evolved later. The fossil evidence for cyanobacteria in the Archean includes stromatolite mounds. Stromatolite mounds are found in rock of various ages through the Archean Eon and also in younger rocks assigned to the Proterozoic Eon. The Proterozoic Eon represents 2.5 billion years ago to 545 million years ago. The time since 545 million years ago is called the Phanerozoic Eon. Cyanobacteria still exists today but ever since the start of the Phanerozoic Eon, stromatolites rarely form. Why have stromatolites formed so rarely since the start of the Phanerozoic Eon? 19) 20) Early Cambrian fossils of soft-body animals are known from the Chengjiang Fauna of China. What is the name of the huge swimming arthropod predator that impaled its prey with sharp spines on jointed frontal appendages? 21) 22)
23) 24) Skeletal animals first evolved in the Neoproterozoic and these groups diversified in the early Cambrian. What factor contributed to the success of the animal groups that evolved skeletons? 25) Which of these animal groups had not yet evolved in the early Paleozoic (i.e., the Cambrian and Ordovician Periods)? 26) About 1300 genera of marine invertebrates have been recognized in upper Ordovician rocks. The number declined sharply to about half that number at the end of the Ordovician. The sharp decline was a consequence of an important mass extinction. What caused the end of the Ordovician mass extinction? Chapter 14 MIDDLE PALEOZOIC 27) In the middle Paleozoic, swimming predators included the ammonoids, the eurypterids and fish. Many fish groups evolved by the end of the Devonian. In which order did the fish groups appear in the Silurian and Devonian? 28) 29) 30) Forests did not exist prior to the Silurian. Only large areas of barren rock and soil covered land. One of the most important biohistory events of the Silurian and Devonian was the first-
time invasion of land by plants. The earliest land plants evolved from photosynthetic protists called algae. It is therefore not surprising that the first land plants lived near the edges of water. The first fossil evidence of land plants is found in rocks of Silurian age. What two special evolutionary adaptations of ancestral algae brought about a new group of spore plants? 31) 32) Seed plants evolved in the late Devonian. The seed was an important adaptive break through that involved a new reproductive style than that employed by the ancestral spore-
plant group. What was significant about the adaptive break through represented by the seed?
33) Animals moved ashore after the evolution of land plants. The first land animals were invertebrates that included millipedes, flightless insects, then scorpions, centipedes and spiders. What was the second group of animals to move ashore? 34) 35) Carbon dioxide in the atmosphere declined sharply during the Devonian. Global climate is very sensitive to the concentration of carbon dioxide in the atmosphere. The associated major reduction in Green House Warming brought about an important climate change, which led to global cooling and glaciation. Why did CO
2
decline so sharply in the Devonian? Chapter 15 LATE PALEOZOIC 36) The two periods of the late Paleozoic are the Carboniferous and Permian. In the US, geologists subdivide the Carboniferous Period into two units called the Mississippian and Pennsylvanian because in those two states rocks of these ages are well represented in the Mississippi Valley and in Pennsylvania respectively. The Mississippian was a time when sea level was so high that most of the North American craton was flooded with a shallow sea. Marine limestones accumulated over most parts of the continental US. The limestones contain fossils of animals that were abundant in the shallow seas. What two animals were abundant in the Mississippian Seas and are found to be important components of Mississippian-age limestones? 37) Burial of plant remains gives the Carboniferous Period its name. No other geologic period contains as many plant fossils. This was a time of enormous plant biomass production and burial in swamps which were extensive. What two Lycopod genera dominated in the Carboniferous coal swamps? 38) All seed plants evolved from an ancestral spore plant. Why did the spore plants decline and the seed plants diversify during the Permian? 39) Large dragonflies existed during the late Carboniferous. Giant arthropods also existed during the late Carboniferous. The large size of these animals indicates that oxygen levels in the atmosphere were higher than today. Why were the oxygen levels high? A) Much dead plant material was being decomposed instead of being buried in swamps. B) Much plant material was buried in swamps and so decomposers extracted far less oxygen from the atmosphere.
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C) The size of biomass increased dramatically which produced a higher flux of oxygen to the atmosphere. D) The number of animals decreased dramatically, hence less oxygen was extracted from the atmosphere. 40) Reptiles evolved from amphibians in the late Carboniferous. The teeth of early reptiles closely resemble those of their amphibian ancestors. The key evolutionary adaptation or break through that separates the reptiles from the amphibians is the amniotic egg. Why was this a significant evolutionary break through? 41) After they appeared in the late Carboniferous, reptiles evolved rapidly and were of many diverse types by the early Permian. The Pelycosaurs were an important group of fin-backed reptiles. The Pelycosaurs included both herbivores and carnivores. What new group of vertebrate animals evolved from the Pelycosaurs during the late Permian? 42) 43) The end of the Permian Period represents the end of the Paleozoic Era. Two extinctions occurred at the end of the Permian, the Guadalupian and Terminal Mass Extinctions. The Guadalupian Mass Extinction eliminated 70% of the marine species. On land, 65% of Therapsid genera and many terrestrial plants were eliminated. In the Terminal Permian Mass Extinction, 80% of all species went extinct. Trilobites, a group that existed for more than 250 million years, were totally eliminated. What caused the end of Permian Mass Extinctions? 44) 45) Plants conduct photosynthesis to produce plant tissue. Upon death, fungi decompose the plant debris. This pair of processes cycles oxygen, carbon and hydrogen in and out of the atmosphere at a particular rate. If plant debris is buried, the CO
2
extracted from the atmosphere to make the plant tissue is instead transferred to the rock record. In other words, the carbon dioxide is no longer participating in a photosynthesis-oxidation cycle. Coal is a rock composed of compressed plant material. Rock of Carboniferous age contains much coal. Beginning with the start of the industrial age in the 1760s, much coal and other fossil fuel that has been locked in the lithosphere for the last 300 + million years has been burned to power modern societies. Burning of fossil fuel is 100% analogous to oxidation reactions done by decomposers. How then has the burning of fossil fuels since the start of the industrial revolution affected the flux of carbon dioxide to the atmosphere?
A) The flux of CO
2
to the atmosphere has stayed the same. B) The flux of CO
2
to the atmosphere has decreased. C) The flux of CO
2
to the atmosphere has increased. D) The flux of CO2 to the atmosphere has not been altered.