ENV 151 Study Guide - Quiz Guide: Granite Dome, Spheroidal Weathering, Igneous Rock

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13 Dec 2018
Chapter 4
1. List examples of Earth’s external and internal processes.
External processes weathering, mass wasting, and erosion. Internal processes
mountain building, volcanic activity.
2. From where do these processes derive their energy?
External processes derive their energy from the Sun, while internal processes
derive their energy from Earth’s interior.
3. When a rock is mechanically weathered, how does its surface area change? How
does this influence chemical weathering?
Mechanical weathering increases the surface area of a rock by physically breaking it
down. This leaves more of the surface available for chemical weathering processes.
4. Explain how water can cause mechanical weathering.
Water in its liquid form can cause mechanical weathering if it is running water
by wearing down the surface of the rock. Water can also freeze and cause frost
wedging; as water freezes in rock cracks, it expands, breaking up the rock.
5. How does an exfoliation dome form?
When large amounts of igneous rock that formed deep underground are exposed
by erosion, a process called sheeting occurs, where concentric slabs break loose.
This is partially due to the reduction in pressure the rock is under at the surface.
As the overlying rock is eroding in a process called unloading, it generates an
exfoliation dome.
6. How does biological activity contribute to weathering?
Plant roots can grow into rock fractures and further break it apart. Burrowing
animals may also break down the rock. Other organisms such as fungi and
lichen can produce acids that decompose the rock, and some bacteria also rely on
rocks for nutrients, resulting in rock breakdown.
7. How is carbonic acid formed in nature? What products result when carbonic acid
reacts with potassium feldspar?
Carbonic acid is formed when carbon dioxide dissolves in water. This can occur in
the atmosphere and when water percolates through soil. Clay minerals are the most
common result when carbonic acid reacts with potassium feldspar.
8. Explain how angular masses of rock often become spherical boulders.
Spheroidal weathering occurs as angular rock masses have their joints
extensively invaded by water. Chemical weathering decomposes minerals in the
rock and expands the joints, and rocks are eroded more on corners. The result is
a smooth, rounded rock.
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9. Why did the headstones in Figure 4.9 weather so differently?
They are made of different rock types with different mineral composition.
Different minerals and rocks weather at different rates.
10. How does climate influence weathering?
Temperature and moisture affect chemical weathering rates, with more
humidity and higher temperatures causing higher rates of weathering. Areas
with low freezethaw cycle occurrences also do not tend to see as much, or any,
frost wedging.
11. Why is soil considered an interface in the Earth system?
It is a common boundary where different parts of a system interact; in this case
soil occurs where the geosphere, the atmosphere, the hydrosphere, and the
biosphere all interact with each other.
12. How is regolith different from soil?
Regolith is only broken down rock and mineral matter whereas soil also contains
organic matter, water, and air.
13. Why is texture an important soil property?
Texture is important because it influences the soil’s ability to retain water and
air, both of which are critical to plant growth.
14. Using the soil texture diagram in Figure 4.13, name the soil that consists of 60
percent sand, 30 percent silt, and 10 percent clay.
Sandy loam.
15. Which factor is most influential in soil formation?
16. How might the direction a slope is facing influence soil formation?
If a slope receives more sunlight, such as on a south-facing slope in the Northern
Hemisphere, the soil on it will be warmer and less moist, which will influence the
types of vegetation that can grow in the soil as well as the nature of the soil itself.
17. Describe the following features or processes: eluviation, leaching, zone of
accumulation, and hardpan.
Eluviation washing out of finer soil particles by water trickling through.
Leaching depletion of soluble minerals from upper soil layers.
Zone of accumulation the B horizon, where much of what is washed out of the
E horizon is deposited. Hardpan very compact layer of clay that can form in
the B horizon.
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