Download What is physical weathering?

Lesson 8
Aim: What is physical weathering?
IV. Weathering: breaking down rocks
Physical Weathering (a.k.a. mechanical weathering)
- Physical weathering breaks down rocks without changing their composition
1. Frost Action
a) When water freezes, it expands about 9 percent
b) In places where T constantly goes above and below 32°F (here!):
- water seeps into cracks in rocks, concrete, roadway
- water freezes and expands, making cracks larger
- repeats until pieces break off
c) At high altitudes: large rocks are exposed, in spring and summer
the temperature drops below freezing every night. Result: boulder
field- large areas of broken rock. If cliff: collects at bottom
d) Causes roads to warp, pushes rocks to surface each spring, creates
potholes, cracks concrete
Q: Why is it important to remove plants growing in concrete?
2. Plant Action
- Soil and water get into the cracks in rocks and concrete
- Plant seeds and spores fall into cracks, grow
- First: moss and lichen. When they die, soil more fertile.
- Then: weeds
- Roots grow, breaking rock apart
3. Pressure Unloading
- Rock deep under the crust is under pressure, creates joints (cracks)
and strain (line of weakness) in the rock.
- Pressure (weight of material above) keeps the rock from splitting
- Rock comes to the surface: due to earthquake, erosion (material
worn away: water? wind? etc.), landslide, frost action, etc.
- Sudden removal of pressure causes rock to split
V. Chemical Weathering: objects on Earth's surface react with an agent
and change into a new substances
DNQ: Why do some people fall on the sidewalk? DI
EARTH SCIENCE 1 DO NOW
1. What are sediments?
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2. What are three major ways of turning rocks into sediments?
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3. Why are we interested in learning why rocks becoming sediments?
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EARTH SCIENCE 1 CLASSWORK
1. a) Why do the Park Department turn off water to unheated restrooms and water fountains?
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b) What are some ways to winterize an unheated vacation home in Vermont?
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2. Why are plants undesirable in the concrete joints or near a building?
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3. What may happen if people take apart the pyramid or the stonehedge?
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4. Weathering
a) What is physical weathering?
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b) What is chemical weathering?
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c) How do physical and chemical weathering compare?
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5. a) How many seismic stations is required to locate an earthquake epicenter?
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b) Explain your answer for the minimal number of seismic stations?
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EARTH SCIENCE 1 H.W. 4-8
READ: EARTH SCIENCE Pages 149-151
1. Define weathering
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2. Physical Weathering
a) What is frost action?
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b) How do boulder fields form?
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c) Why would there be no frost action in Antarctica, even though there is
ice all year around?
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d) Why are there pieces of rock at the bottom of a cliff face?
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e) Why must you pull weeds out of the concrete in front of your house?
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f) What is pressure unloading?
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