Ch.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,and biological activity
Describe frost wedging.
When water freezes and expands it enlarges the cracks,after many freeze thaw cycles the rock breaks into pieces
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 activities of organisms,including plants,burrowing animals,and humans
Explain chemical weathering ?
Transformation of rock into one or more new compounds
_______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.
Gravestones made of granite are relatively resistant to chemical weathering,marble gravestones undergo much more rapid chemical weathering
What is regolith ?
weathering produces a layer of rock and mineral fragments
Name the 4 major components of soil ?
Mineral matter,organic matter,water,and air
What are the most important factors in soil formation ?
parent material,time,climate,and slope
Soil varies in composition,___,___,and ___ at different depths
texture,structure,and color
What are three common types of soil ?
pedalfer,pedocal,and laterite
How do human activities affect rates of erosion ?
remove natural vegetation,such as farming,logging,and construction,have greatly accelerated erosion.Without plants soil is carried away more easily by water and wind
What is mass movement ?
Transfer of rock and soil downslope due to gravity
What triggers mass movements ?
saturation of surface materials with water,oversteepening of slopes,removal of vegetaion,and earthquakes
How do geologists classify mass movements ?
based on the kind of material that moves,how it moves,and the speed of movement
When does rockfall occur ?
occurs when rocks or rock fragments fall freely through the air
How do mudflows differ from earth-flows ?
Mudflows are common in semiarid mountains,regions,such parts of Southern California.Earth-flows move relatively slow from about a millimeter per day to several meters per day