Geology Chapter 15

gravity

mountains

earthquake

Gros Ventre Landslide (Wyoming)

Water can easily flow downslope. Water makes the slope material heavier. Water in pore spaces reduces cohesion between particles.

a wildfire oversteepening of a slope adding water to sediments

Solifluction occurs during the Arctic's summer, when the top meter or so of the active layer thaws. Because the resulting meltwater has nowhere to go, it saturates the active layer, causing it to slowly flow.

slide fall flow

A mass movement in which a cohesive block of earth or rock slips downhill relatively quickly in one piece along a zone of weakness is called a

Mass movements that move blocks of materials and unconsolidated materials down a curved surface creating scarps on a slope are known as

When large rocks become dislodged and drop down a steep slope, the mass movement is called a

are very gradual mass movements in which the whole slope moves downhill slowly.

When unconsolidated material moves downslope as a viscous fluid it is called a

Air becomes trapped and compressed beneath the falling mass of debris, which allows the debris to move as a flexible sheet across the surface of the slope.

true

Debris flows generally occur within semiarid areas and tend to be restricted to channels, whereas earthflows most often occur on hillsides in humid areas.

Creep is caused by the repeated expansion and contraction of the regolith, which may be caused by repeated freezing and thawing or wetting and drying. Creep can be recognized by tilted trees, tilted fences, and displaced retaining walls.

Permafrost is permanently frozen ground. If the thermal balance of permafrost is disturbed, ice within the permafrost may melt, causing the ground to slide, slump, or subside.

make the valley walls less steep make the river valley wider

Mass wasting is the downslope movement of rock material driven by the force of gravity. It differs from other erosional processes in that mass wasting does not require a transporting medium.

The river valley is much wider than it is deep.

among rugged, geologically young mountains

Saturation of materials with water Oversteepening of slopes Removal of anchoring vegetation Ground vibrations from earthquakes

Mass wasting and running water produce ______.

angle at which a material assumes a stable slope Typically 25 to 40 degrees for unconsolidated granular particles

has a slope angle steeper than the angle of repose for that material

Forest Fire alters soil: 'Bakes' the ground Can cause top layer to become dry and loose

Type of material involved: -debris, mud, earth, rock Kind of motion displayed: -fall, slide, flow Velocity of movement

In the mountains, mechanical weathering produces angular rock fragments that fall to the base of a cliff. Over time, a talus slope forms.

permanently frozen ground near and in Earth's polar regions