Weathering Q&A
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Chaffey College *
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Geology
Date
Dec 6, 2023
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docx
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Weathering Q&A
1.
What are the two types of weathering?
Physical (mechanical) and chemical weathering.
2.
Why is weathering part of the rock cycle?
Rock weathering is part of the rock cycle because breaking down igneous and metamorphic
rocks gives us sedimentary rocks.
3.
What is the aim of physical weathering?
Physical weathering aims to break down rocks into smaller pieces so there is more surface
area for chemicals to attack.
4.
What is lifting Cucamonga Peak while weathering is tearing it down?
The Cucamonga fault uplifts Cucamonga Peak, but weathering is tearing it down.
5.
What causes rocks to explode on mountains during the winter?
Water expands 9% when freezing and can explode rock when it expands.
6.
We used to do Steve Spangler’s experiment in the Chaffey lab. We used dry ice, but what is
he using to cool the elbow pipe?
Liquid nitrogen.
7.
What rock type is found atop Mt. Whitney and Mt. Baldy?
Granite.
8.
What type of rock is found on top of Pine Mountain? (Pine Mountain is between the back of
Mt. Baldy and Wrightwood.)
Pelona schist (metamorphic rock).
9.
What causes granite domes to form?
Pressure release.
10.
Why is unloading the primary physical weathering process for granite?
It doesn’t tend to break into layers like most sedimentary and metamorphic rocks. Granite
forms 2 to 15 miles deep and experiences tremendous pressure from all sides. When faults
bring it up to the surface, the pressure release causes it to pop off rock shells.
11.
What are two synonyms used for pressure release?
Pressure release is also called unloading or exfoliation.
12.
What is another type of weathering destroying Half Dome besides unloading?
Exfoliation.
13.
Why did Twain Harte have to empty their lake quickly?
The dome began to exfoliate, and the popping shells of granite damaged the adjoining
cement dam. They drained the lake to prevent a flood.
14.
What startled the person taking the video of the granite at Twain Harte?
The cracking and popping of the granite.
15.
What vegetable term is the weathering of the granite boulder being compared to?
Onion skin (spheroidal) weathering.
16.
What are the four forces that cause rocks to abrade?
Water (streams and rivers), wind, glaciers, and ocean waves.
17.
What causes stream water to grind down deep canyons if the water is soft?
Streams carry boulders during large storms that can slam into the stream’s bedrock, causing
chipping and breakage.
18.
What type of sediment polished the granite water slide so smoothly?
Sand.
19.
What can sand do to your car windows during a storm driving past Palm Springs?
Sand could cause abrasion to my windows.
20.
Why can’t sandblast a second-story window in a building?
Sand is heavy for the wind to carry, so the greatest sandblasting is usually limited to about 4ft
from the ground.
21.
Why are some boulders out in the desert triangular in shape?
Often, the rocks take on a triangular shape due to the wind shifting directions and attacking
the rock from different angles.
22.
Ice is softer than any most any rock. So, how do glaciers polish, scour, and abrade granite?
Glaciers have sand, gravel, and boulders frozen into their ice, and these rocks scratch, grind,
and polish the bedrock beneath the glacier.
23.
Why does California’s coastline experience such rapid erosion from waves?
They’re made from a softer sediment, which is easier to erode and abrade.
24.
Around Chaffey, what causes some sidewalks to lift and cause a tripping hazard?
Plants/Trees cause physical weathering.
25.
Why do archaeologists try to keep the forest from growing too close to ancient temples?
If these trees aren’t removed, they will eventually level the historic buildings.
26.
What causes a honeycomb structure to develop in coastal sandstone rock cliffs?
Waves spray sea salt onto the coastline, and over time, the accumulating salt grows crystals,
which break apart the rock into a honeycomb pattern.
27.
Why does salt accumulate on the Death Valley floor over time?
The valley floor has been accumulating salt because it has no drainage, and there is extreme
evaporation.
28.
What can the sun do to rocks over time?
Heating and cooling of rocks causes them to expand and contract, and over long periods, this
cycling can break them down.
29.
It can take thousands of years for the sun to cause physical weathering to occur on rock
surfaces. What heat source can cause significant damage to rocks in a few minutes?
Brush fires.
30.
What would be an example of human imprint on the land in the Inland Empire?
Mines, quarries, and road construction are just a few examples of humans altering the
landscape as a form of physical weathering.
31.
What animal is depicted on the petroglyph?
Deer.
32.
What are the two main types of chemical weathering?
Acid attack and rusting (oxidation-reduction reaction).
33.
What are three factors that speed up chemical weathering?
Heat, lots of water, and abundant plants speed up chemical weathering.
34.
What is the most important weak acid that attacks rocks?
The most important acid in weathering rocks and minerals is the weak carbonic acid.
35.
What mineral forms when acids attack silicates like feldspar or biotite?
Acid attack is important in forming clay minerals when acids react with feldspars.
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36.
What causes the chalky appearance of weathered granites?
It often has a chalky appearance on the surface due to clay forming.
37.
Which element causes the iron in rocks to rust?
Oxygen.
38.
What is the chemical symbol for rusted iron?
Fe3+.
39.
What color are rocks with reduced iron, like basalt?
Black.
40.
What is the iron mineral that gives a bright red color to some soils?
Hematite.
41.
What process dislodges minerals and rocks once weathering has taken place?
Erosion.