A. Weathering: 1.Physical and chemical processes that break down and change the shape of rock on Earth’s surface. a. Physical weathering = mechanical forces b. Chemical weathering = chemical changes weaken the rock 2. Physical and chemical weathering often occur at the same time.
B. What is the difference between weathering and erosion? 1. Weathering breaks down rock and erosion carries the pieces away. 2. Weathering and erosion work together to change Earth’s surface. 3. The result of weathering is sediments, a step in the formation of sedimentary rock.
C. What happens during physical (mechanical) weathering? 1. The rock is: a. broken into smaller pieces b. peeled or cracked c. edges are worn down 2. The rock is the same type, but changed in size and shape.
D. Types of physical weathering 1. Repeated freezing and thawing (melting) of ice/water called ice wedging or frost wedging 2. Plant growth in cracks of rocks 3. Animal action – digging or burrowing 4. Abrasion grinding away of rock by water, wind, ice or gravity. 5. Heating and Cooling – continually rising to high and low temperatures, can cause exfoliation (peeling) of rock layers
Ice wedging – repeated freezing and thawing of ice in cracks of rocks eventually splits the rock. Frost or Ice Wedging
E. Why does water break open rocks when it freezes? 1. Water is the only substance on earth that expands (gets bigger) when it freezes! 2. Explain why ice floats….
Plant wedging – seeds can drop into cracks in rocks and grow… eventually splitting the rock.
Heating/Cooling or freeze/thawing can crack roads
Exfoliation after repeated freeze/thaw, heat/cool or ice wedging
Abrasion – sharp edges get worn down and smoothed by water
Abrasion by wind…like a sandblaster
F. What does a rock look like that weathered in water? 1. Rocks weathered in water are often rounded and smooth because of abrasion in running water. 2. Fact - Water causes more weathering and erosion than another other thing on earth.
G. What do gravity and glaciers do to rocks? Abrasion by gravity and glaciers breaks rocks into jagged pieces.
H. Mountains…compare the 2. Which is more weathered?
The Old Man in the Mountain…. Weathered away! Down fell a face Of a million years counting The king of the mountain And guard of the valley below The last generation The very last era Never to see again 5/3/03
Which layer has been weathered most? Least?
Summary: 1. What types of physical weathering might have contributed to the Old Man’s demise? 2. What climate conditions must exist for ice wedging to occur? 3. Which types of physical weathering could also be considered organic or biological?
Which weathering agents might have changed Cleopatra’s needle?