GLG 141 Exam 2 (fall 2022, dr. majia, miami university)

1. The law of superposition is what tells us that in a stack of sedimentary rocks that has not been overturned, the _________ are at the bottom and the __________are at the top.

metamorphic rocks; sedimentary rocks

folded rocks; flat rocks

oldest rocks; youngest rocks

weathered rocks; unweathered rocks

sedimentary rocks; igneous rocks

oldest rocks; youngest rocks

2. How can you tell if there is an unconformable contact between two layers of sedimentary rocks?

There will be evidence of missing time, such as a fold in the lower layer while the one on top is not folded

Both layers will be recrystallized due to contact metamorphism

Both layers will be recrystallized due to regional metamorphism

There will be evidence of missing time, such as if the lower layer is made of limestone and gradually turns into the shale layer above

There will be no evidence of missing time between the rocks, such as a limestone capped by a conglomerate

There will be evidence of missing time, such as a fold in the lower layer while the one on top is not folded

3. Construct a geologic history for the diagram below, from oldest rock/event on the bottom to youngest rock/event at the top.

A, B, erosion, C, D, erosion, E, F, erosion

4. You date a rock using a radioisotope with a half life of 2.5 million years. You find that the rock contains precisely 200,000 parent atoms and 200,000 daughter atoms. How old is this rock?

2.5 million years

5. What is believed to be the cause of the Late Ordovician Period mass extinction event? The Permian-Triassic mass extinction event? The Cretaceous-Tertiary mass extinction event?

Late Ordovician: glaciation due to the evolution of land plants/trees and sudden significant sequestration of CO2. Permian-Triassic: massive volcanism, namely the large igneous province of the Siberian Traps. Cretaceous-Tertiary: dinosaurs were likely already in decline, but a massive bolide impact is what likely killed off the non-avian dinosaurs.

How do glaciers form?

rain freezes as it hits the ground in polar regions, progressively building up layers of ice

snow melts during the summertime, flows downhill, and then refreezes into ice, building a glacier

layers of ice build up from the meltwater washing off of mountains

snow builds up in layers and from the weight of overbearing snow, becomes compressed into ice

there is significant amounts of hail in mountainous areas where glaciers form, and the hail condenses into a glacier when it collects in a valley

snow builds up in layers and from the weight of overbearing snow, becomes compressed into ice

Approximately how many years passed between glacial events during the Quaternary Period?

2.6 Ma

800,000 years

500,000 years

100,000 years

20,000 years

100,000 years

8. What happens to Earth's crust underneath thick glaciers? What happens to the crust in that location after the glacier melts?

While a glacier is on top of earth, the crust below sinks further down into the crust, meaning there is less space in between the crust and mantle. When the glacier melts, the weight and pressure are removed and that piece moves back up to where it originally was.

9. Which of the following best describes the relationship between glacial periods or interglacial periods and global eustatic sea levels?

During a glaciation, icebergs float in the ocean in great abundance and raise sea level due to their displacement of water

During a glaciation, the large amount of meltwater flowing out of the glaciers in glacial tunnels contributes to an overall rise in sea level

During an interglacial period, less water is held on land in ice so the sea level rises

During an interglacial period, the ocean water is colder and more dense, so it takes up less space within the ocean basin and sea levels go down

During a glaciation, the glaciers displace so much water in the ocean that the sea levels rise significantly

During an interglacial period, less water is held on land in ice so the sea level rises

10. How do eskers form, and what do they look like? What are the names of the grain sizes in an esker? What is the sorting? What medium (ice, wind, or water) deposited it?

Eskers form when subglacial streams get clogged up with moderately sorted sands and gravels (outwash) carried by the flowing water. When the glacier melts, that ridge/tube of outwash is left out on the landscape.

11. How do erosional vs. depositional glacial landscapes differ from one another? Which type of area is typically better for agriculture, and why?

Erosional and depositional landscapes can both be fairly flat, but erosional landscapes have very thin, patchy soils with bedrock exposed near the surface because the glaciers picked up and removed so much of the overlying material that was once there. All of that material removed from the erosional landscape will then get deposited farther south in the depositional landscape, which means that there will be an abundance of glacial drift dumped there in thick deposits, in which soils can form. Agriculture requires soils for plants, so depositional landscapes with thick soils are much preferred for farming. Agricultural crops cannot grow well in bedrock, which would be a common substrate in the erosional landscapes.

12. Which of the following glacial features are most useful to determine flow directions of the glaciers that were in North America 20,000 years ago?

Kettle lakes

Ground moraines

Glacial lake deposits

Striations

Kames

striations

13. How do end moraines form, and what do they look like? What are the names of the grain sizes in an end moraine? What is the sorting? What medium (ice, wind, or water) deposited it?

End moraines are piles of till that form at the bottom of a braided stream. The end moraines are composed of particles the ice has brought downwards. End moraines are poorly sorted and the grain size is anywhere from clay to boulders.

14. What do humans use freshwater for the most, worldwide?

irrigation

15. Name the five (5) processes that move water through the hydrologic cycle. Which process is most directly responsible for the recharge of groundwater aquifers? Which process is most directly responsible for the buildup of glaciers? In which reservoir is most water held on Earth? In which reservoir is most of Earth's freshwater found?

precipitation, condensation, surface runoff, infiltration, evaporation Infiltration is most directly responsible for the recharge of groundwater aquifers. Precipitation is most responsible for the buildup of glaciers The oceans Glaciers

16. True or False: a watershed is an area of land that drains to a particular stream.

True

17. In which watersheds does Oxford, OH lie?

Four mile creek, The great miami river, Ohio River, Mississippi River

18. What does stream discharge mean?

The volume of water that flows through an area in a particular space and time

19. Imagine you wish to calculate the discharge of the Great Miami River in Hamilton, OH. What three aspects of the river do you need to measure in order to calculate its discharge?

You need the width and depth of the river, and then you need the speed of the water flowing through that point too

20. Water that is moving at a very high velocity will most likely cause ___________ of sediment on the stream bottom.

Erosion

Transportation

Deposition

None of these

All of these

erosion

21. Water that is moving at a very low velocity will most likely cause ___________ of sediment on the stream bottom.

Erosion

Transportation

Deposition

None of these

All of these

deposition

22. What is the typical gradient of braided streams?

steep slope

23. Describe the discharge of braided streams.

irregular/ highly flucuating

24. Which of the following describes discharge of most meandering streams?

Highly fluctuating

Relatively constant

Highly sloped

None of these

All of these

relatively constant

25. Which letter represents the cut bank on the photo below? What is the dominant process (erosion, transportation, or deposition) in this location?

B erosion

26. Which letter represents the point bar on the photo above? What is the dominant process (erosion, transportation, or deposition) in this location?

A deposition

27. Given the dataset in the chart below, complete the rank and recurrence interval columns. The equation for recurrence interval is RI=(n+1)/m, where n=number of years on record and m=rank of each flood. What is the recurrence interval of the year 2010 flood?

Year Discharge (in cfs) Rank (m) Recurrence Interval (RI)

2010 20,000

2011 15,000

2012 17,000

4

28. In your own words, explain what a "100 year floodplain" is.

A 100 year floodplain is an area that has a 1% chance of having a flood every year that on average is likely to occur once every 100 hundred years

29. What is the probability of Hamilton, OH experiencing a 100 year flood next spring (spring of 2023)?

1%

30. If Hamilton experiences a 100 year flood next spring, what is the probability of Hamilton experiencing a 100 year flood the next spring (spring of 2024)?

1%

31. What are the two distinct reasons why flooding in the American Midwest is currently getting worse?

More land surfaces are being paved over and otherwise made impermeable, so more water is becoming runoff and less water is able to infiltrate. This sends all the water to streams all at once, resulting in more flooding. In addition, climate models suggest the Midwest will be receiving more rain in the future, particularly during intense rainfall events during which there will be much more water draining to stormwater runoff systems.

32. Despite a severe drought in which no rain has fallen in over a month, the streams in Oxford still have some water flowing in them. Why is this?

The water is base flow sourced from the groundwater aquifer

33. To be an effective aquifer that holds and transmits water easily, a layer of sediment underground will ideally have what qualities?

High permeability and high porosity

34. Under what circumstances will groundwater flow "uphill", against the forces of gravity?

The rocks are folded extensively due to compression, so water will move through them differently

If the rocks are faulted via extension, they are thinner and will accumulate water in their high points

If water is hot enough, it will rise up in the magma chamber and metamorphose the surrounding rocks

If the rocks are hot enough, they will become buoyant and flow upwards with the associated groundwater

If a low pressure area exists above, the water will flow upward to it

If a low pressure area exists above, the water will flow upward to it

35. Why is the water from unconfined aquifers more likely to be polluted?

Because there is no protective, non-porous "confining layer" protecting the aquifer from pollutants up on the land surface

36. Cones of depression are caused when:

groundwater is polluted by ores and fossil fuels underground

faults break up the rocks, causing hydrocarbons to flow upward to the surface

groundwater moves too slowly through the aquifer, creating cone-

shaped air pockets around the well

the groundwater becomes too thick to flow up the well quickly

water is extracted from the aquifer faster than it can flow to the well

water is extracted from the aquifer faster than it can flow to the well

37. The water that comes through our taps on Miami University's Oxford campus is sourced from an aquifer made of _____________.

Unconsolidated sands and gravels deposited by the river

38. What are the most common type of water problems in the American Midwest, and what are the best ways to mitigate them?

Water quality issues, particularly from non-point source pollution like nutrient runoff from fields/lawns, soil and sediment erosion from fields and development construction sites, and bacteria washing into rivers from human developments, livestock farms, residential lawns, etc. These factors can (and are, in some places!) being mitigated by applying less fertilizer and catching it before it can reach our waterways; by promoting no-till farming and allowing buffer zones between steam systems and river ways.

39. What are the most pressing water issues in Namibia? What are some ways they are being mitigated?

Water scarcity is the most pressing issue in Namibia. They are recycling their old water and reusing it.

40. True or false: All water on Earth is "reclaimed" water.

True

41. What are the five major factors of soil formation?

41. Parent material, relief/topography, climate, organisms, time

42. Which factor(s) of soil formation will likely change if Ohio's climate warms and gets wetter as predicted over the next several decades? Explain.

42. Climate, then (indirectly) organisms that will likely come about as part of a climatic change and biome shift.

43. Soils formed in glacial deposits or alluvial (river) deposits are examples of _______________ soils.

43. Transported

44. Soils formed in broken down bedrock are _______________ soils.

44. Residual

45. How will soil fertility be affected by processes that remove soil organic matter from the soil, such as frequent tilling/cultivation, and why?

45. Lowering the soil organic carbon will make soils less healthy for plants, and also more likely to erode and less capable of holding onto the water.