Chapter 5
When does mechanical weathering occur?
When physical forces break rock into smaller and smaller pieces without changing the rock’s mineral composition
Name three physical processes that cause mechanical weathering.
frost wedging, unloading, biological activity
Describe frost wedging.
the mechanical breakup of rock caused by the expansion of freezing water in cracks and cervices
Slabs of outer rock separate like the layers of an onion and break loose in a process called…
exfoliation
What is meant by biological activity?
the mechanical weathering from the activities of organisms: plants, burrowing animals, & humans
____________ is the most important agent of chemical weathering.
water
Can chemical weathering change the physical shape of a rock?
Yes.
What two factors affect the rate of weathering?
rock characteristics and climate
Give an example of a rock characteristic.
cracks
What is regolith?
layer of rock and mineral fragments produced by weathering
Name the 4 major components of soil.
mineral matter, organic matter, water, air
What are the most important factors in soil formation?
parent material, climate, time, organisms & slope
Soil varies in compostion, ____________, ____________, and _____________ at different depths.
texture, structure, and color
What are the three common types of soil?
pedalfer, pedocal, laterite
How do human activities affect rates of erosion?
By removing natural vegetation, such as farming, logging, and construction, humans speed up the effects of erosion
What is mass movement?
the transfer of rock & soil down-slope due to gravity
What triggers mass movement?
saturation of surface materials by water, over-steepening of slopes, removal of vegetation, earthquakes
How do geologists classify mass movement?
based on the kind of material that moves, how it moves, and speed of the movement
When does rockfall occur?
when rocks or rock fragments fall freely through the air
How do mudflows differ from earthflows?
mudflows move quickly
earthflows are relatively slow
Explain chemical weathering.
the transformation of rock into one or more new compounds
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