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Geology 1050 exam questions
Sample exam questions with answers
Terms in this set (50)
Sketch the Principle of Superposition and define it.
The Principle of Superposition states that the oldest rocks are deeper and ascends to the youngest on top unless the sequences is interrupted. Basically, you can label youngest to oldest on the side and make lines to indicate there are layers. Also, be sure to put oldest at the bottom and an arrow pointing up to youngest. Basically, make it look like what the diagram showed on the 2nd lab.
Define and sketch an unconformity, indicating what part is the actual erosion surface.
Unconformity - An ancient surface of erosion. They break or interrupt a rock unit so the pattern of rocks below it doesn't conform to the pattern above. Make it looks like the diagram on the 2nd lab.
Sketch and define an index fossil.
Index fossil - Fossils that fall within a particular time interval. You can just sketch the trilobite I recently found as an example.
What is the formula for one daughter atom created for every parent atom?
Over time, one daughter atom is created for every parent atom that decays (Po = D + P).
Write the formula to find the ratio of parent to daughter isotopes in a newly cooled rock.
D=#daughter atoms present at time t
Define half-life and write the formula.
The half-life of an isotope is the time it takes for 50% of the original parent atoms to decay (one time unit in our example above).
P=1⁄2Po =Po e^(-λt1⁄2)
Define and sketch erosion.
Erosion is the process where agents (streams, rivers, glaciers, and wind), transport fragments away from the source rock.
What is the difference between sand and silt?
1.) The grain sizes of sand can range from 0.125mm-1mm. Silt is above 0.039mm and can go up to 0.0625mm.
2.) Silt lumps together with other sediments to form mud when a stream slows down.
Define and sketch a poorly sorted sedimentary rock.
A poorly sorted sedimentary rock possess many different grain sizes within a rock. They typically exist in glacial deposits.
Define cross-bedding and sketch a typical environment where you would find it.
Cross bedding refers to (almost) horizontal units that are internally composed of inclined layers. An environment where you can find it is a dune.
Define and sketch a body fossil.
A body fossil is the preserved remains of an actual body (this can even include cells or bacteria). Any sketch with a preserved body in it is a body fossil.
Define and sketch a trace fossil.
Trace fossil - Sedimentary feature(s) the organism made (burrows, tracks, trails). Anything mentioned that is in this defintion's examples and is preserved works for this one.
Define and sketch a marine bias.
Marine bias - Organisms living in ocean are more likely to be preserved due to sediments being in the ocean.
A sketch showing an organism in the ocean living and being preserved after death works in this case.
Define and sketch a skeleton bias.
Skeleton bias - Organisms with hard parts on land are more likely to be preserved. Other parts won't be preserved due to erosion.
A sketch showing a skeleton, teeth, or other hard parts on land underneath the ground works in this case.
Define and sketch Pangaea.
Pangaea is a supercontinent that existed 300 million years ago where all of Earth's current continents were once together.
The sketch of Pangaea should look like the one on Wikipedia.
Define a subduction zone.
When crust collides with another piece of crust. Or, as she put it, when a piece of ocean collides with another piece of ocean. The denser one sinks and the overlaying one goes down a little bit. The other one will be pushed up in this case, and is the reason Mount Everest is getting bigger.
Trenches mark subduction zones and it will eventually go towards the Earth's center and burn away.
Sketch the primary geologic feature seen at a subduction zone.
The geologic feature in question is a trench. Sketch a picture similar to the one seen in slide 19 where the water is and ignore everything else.
Define and sketch one way carbon is removed from the atmosphere.
By burying more carbon expect less carbon in the atmosphere and cools over long periods of geologic time. Specifically, burying organic matter and carbonates locks carbon out of the cycle for a long time, allowing less CO2 in the atmosphere and the Earth will begin to cool.
What is burial promoted by? Define it as well.
Burial is promoted by anoxia, or the absence of oxygen in water that reduces the decay of organic matter.
Define and sketch one way carbon is released from the sediment/rock record.
The primary way carbon is released from the sediment/rock record into the atmosphere is by burning the material that has carbon in it.
How do you identify statements are falsifiable and what isn't?
1.) It has to be possible to test the idea and prove it false.
2.) A supernatural idea is untestable (and it isn't falsifiable).
Define a fact and give an example.
Confirmed observations; can change if ability to observe improves.
Example: Earth revolves around the sun.
Define a theory and give an example.
A well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses; allows us to model or predict.
Example: The theory of plate tectonics.
Contrast a fact and theory.
A fact is a confirmed observation. A theory is the end goal of science that can incorporate facts in order to explain some aspect of the natural world.
The examples from earlier work, but below are the two she used.
Fact example: Sandstone is made up of sand grains that are cemented together.
Theory example: Populations of organisms change over time because the most fit individuals are more likely to pass their particular traits on to the next generation
What is an unconformity and what geologic process is needed for it to form?
Gaps in the rock record and are anctient erosion surfaces. Erosion is needed in order for an unconformity to form.
Why can fossils be used to provide relative dates for rocks in which they are found?
Fossils can be used to provide dates for the rocks in which they are found because certain organisms only existed within a certain period of time and are fossilized and are known as index fossils.
What are the two characteristics that make a good index fossil?
1.) Correlation: Being able to correlate different rock layers with each other that had the same fossils around a similar time.
2.) Stratigraphic gap: A missing period of time indicated by another fossil species correlated around the same time as the other, that can infer sea level fell or erosion occurred.
Use the stratigraphy techniques learned in the lab to practice and re-mark the order of the diagram. Mark any unconformities. Then, list the order the events must have occurred in order to produce these rocks.
Look at your old lab and compare it to the answers you printed out from the new lab.
Does the rate of decay of a radioactive element remain constant, decrease linearly over time, or decrease as a curve over time?
The rate of decay remains constant over time since half-life only halves the radioactive atoms.
The ratio of daughter to parent isotopes in a rock D/P is 75/25. The half-life for this isotope system is 50 million years.
200 million years. You take the original amount by adding the D and P isotopes, which is 100. Keep dividing by 2 until you get 25. Then multiply the half-life by each step you took (or the amount of halves you applied).
You use radiometric dating to determine that the age of a rock is 92 million years. What happened 92 million years ago, exactly? That is, what event is being dated?
The event is the Cretaceous period.
Given: Sandstone, conglomerate, siltstone, shale...Reorder these from largest to smallest grain size. Which rock formed in the highest current energy, and how do you know?
The rock that formed in the highest current energy is shale since it has the smallest grain size due to being carried by high amounts of erosion (a stream from the examples).
Charles Lyell is celebrated for making uniformitarianism a central idea in geology. Briefly describe the idea of uniformitarianism (also known as the uniformity of process or actualism), and give one specific example of how geologists use uniformitarianism to understand some aspect of Earth's past.
The fundamental physical and chemical principles that humans observe operating today operated throughout the Earth's history.
Example: Sea level rising and falling in order to understand what once existed as land and what doesn't.
For each of the following sedimentary environments, describe the characteristic sedimentary rocks and features that are associated with them: Desert, River, Lake.
Desert - Evaporates and dunes.
River - Channel-shaped deposits and floodplain muds.
Lake - Finely-layered muds, terrestrial fossils.
For each of the following sedimentary environments, describe the characteristic sedimentary rocks and features that are associated with them: Glacier, Shallow Tropical Sea, and Ocean.
Glacier - Poorly sorted sediments and glacial grooves.
Shallow Tropical Sea - Sand and mud or carbonates (often with fossils).
Ocean - Limey sediment accumulation in shallow water.
Your great-aunt Agatha thinks it would be cool to have her cat Fluffy fossilized when he dies. Explain to her what would generally be required for this to happen. Then, more specifically, suggest two different ways in which Fluffy's soft part anatomy might be preserved in a fossil.
The organism what have to be buried. For the soft parts to be preserved it would have to be buried quickly, or it would have to be preserved in an area that lacks oxygen.
What is the skeleton bias? Why is it a problem for scientists studying ancient ecosystems?
The skeleton bias means that organisms with hard parts are more likely to be preserved. This is a problem for scientists studying ancient ecosystems because soft parts or that aren't fossilized will decay or go away via erosion.
Briefly describe, and give an example, of two different methods we can use to work out how a fossil organism lived.
1.) Comparison with living relatives (fossil clams look a lot like living clams).
2.) Functional studies
(pointy teeth = predator, streamlined = fast swimmer)
Optional: 3.) Detailed observations of the fossils
Briefly describe three lines of evidence that Alfred Wegener and Alexander Du Toit used to argue that the southern continents (South America, Africa, India, Australia, and Antarctica) used to be attached to each other.
All possible options:
1.) The geographical fit of the continents
2.) Shared distinctive rock bodies
3.) Shared fossil plants and animals
4.) Glacial deposits and markings
Given a diagram showing a cross-section through the Earth, label a place where sea floor is being created and a place where sea floor is being destroyed.
A place where the sea floor is being created would be right above the plate that is subducting. The one that is being destroyed, is the lower part of the subducting plate that is touching the mantle.
Make a cross-section sketch of an ocean-continent subduction zone. Label the ocean plate, the continent plate, and the trench. Draw arrows to show the direction in which each plate is moving. Indicate in the sketch where you expect volcanic activity to take place. Where is a place on earth today where this type of subduction is happening?
An example of what this would look like, is on the 20th slide of pptx 7. The land past the trench is the continent plate, the plate underneath the trench would be the subducting ocean plate. The ocean plate would be have an arrow pointing underneath the continent plate and the continent plate arrow pointing towards the subducting ocean plate. The Himalayas were formed this way.
Compare and contrast the type of mountain range you would expect to find at an ocean-continent collision and a continent-continent collision.
An ocean-continent collision mountain range would produce a coastal range of volcanic mountains. A continent-continent collision would produces a large interior mountain range with NO volcanoes.
Describe the steps involved in a process that takes carbon from the atmosphere and puts it into the sediment/rock reservoir. (There's more than one possible pathway.)
All possible options:
a.) Photosynthesis-respiration. Uptake by rocks in weathering. Organisms use carbon from the ocean/atmosphere to construct organic matter and shells of calcium and carbonate, CaCo3.
c.) Stored oil, gas, coal, and kerogen.
A rock sample has relatively more carbon-13 atoms than the standard value. Is its δ13C value positive or negative?
The δ13C value will be positive.
As organic matter is buried, does the ocean become relatively more enriched or depleted in carbon-13? Why?
If burial increases, the ocean becomes more enriched in carbon 13 because of anoxia preventing bacterial decay.
If the rate of burial of organic matter increases, what happens to the amount of CO2 in the atmosphere? How would this change affect global temperatures?
The amount of CO2 in the atmosphere decreases when the rate of burial of organic matter increases. The global temperatures would cool then.
Describe a human activity that increases CO2 levels in the atmosphere.
A human activity that increases CO2 levels is burning material with carbon in it, such as dead leaves or coal.
Describe three different specific lines of evidence we have that global warming is occurring today.
All possible choices:
-Atmospheric CO2 is over 40% higher today than in 1800
-Temperature increase of about 0.85oC (1.5oF) since 1880
-Last decade was warmest on record
-Global ice sheets and snow cover have decreased, permafrost is thawing, arctic sea ice has shrunk
-Globally, sea level rise of 19 cm since 1900
Describe three possible consequences of global warming.
All possible choices:
-Increased severity of storms and coastal flooding
-Flooding/drowning of low-lying cities & countries
-Loss of wetlands / contamination of drinking water supplies
-Drought and crop failures in interiors
-Change in plant ecosystems / extinction of plant & animal species
-Increase in infectious disease and malnutrition rates
-Release of even more CO2 from thawing peat bogs
What evidence is there that South America and Africa once touched each other?
There were fossils of the same species existing on the edges of both continents facing towards each other.