Chapter 12 Peterson Final

Falls (Fast Mass Wasting)

type of fast mass wasting characterized by Earth material plum-meting downward freely through air.

Salt Crystal Growth

weathering by the expansive force of salts growing in cracks in rocks; common in arid and coastal regions.

Joint Set

A system of parallel cracks in rock thatcross each other at an angle are sites of concentrated weathering, the spatial pattern strongly influences the appearance of the landforms and landscapes that develop.

Slides

a cohesive or semicohesive unit of Earth material slips downslope in continuous contact with the land surface. Water plays a somewhat greater role

Landslides

large, rapid mass wasting events that are difficult to classify because they contain elements of more than one category of motion or because multiple types of material—rock, soil, earth, debris, and mud—are involved in a single massive event

Angle of Repose

lies between 30° and 34°, varying with the size and angularity of the clasts. Large angular clasts have a _______ _____ __ ______than small, rounded rock fragments.

Unloading

physical weathering process whereby removal of tremendous overlying weight leads to rock expansion and breakage.

Mudflows

rapid mass wasting of wet, fine-grained sediment; may deposit levees and lobate (tongue-shaped) masses. flows faster then earthflows Lahars accompanied the 1980 eruption of Mount St. Helens, and Mounts Rainier, Baker, Hood, and Shasta all have the conditions in place for dangerous lahars to occur

Slumps

rotational slides where a thick unit of unconsolidated fine-grained material sliding downslope on a concave, curved slip plane. undergo a backward rotation as they slide causing what was initially the level ground surface at the top of the ____ to tilt backward most common in wet years and during wet seasons in many regions with substantial relief e.g. Appalachian mtns.

Talus

slope (sometimes cone-shaped) of angular, broken rocks at the base of a cliff deposited by rockfall.

Hydration

water molecules attach to the crystalline structure of a mineral without causing a permanent change in that mineral's composition. The mineral expands when hydrated and shrinks when dehydrated

Differential Weathering (& erosion)

Because erosion removes small weathered rock fragments more easily than large, intact rock masses, areas of diverse rock types undergo _____ ______ Wherever several different rock types occupy a given landscape, some will naturally be more resistant than others to the weathering processes operating there.

Debris-Mud

Debris specifies a mass of sediment composed of a wide range of various grain sizes, at least 20% of which is gravel-sized. Mud indicates saturated sediment consisting mainly of clay and silt, which are the smallest particle sizes.

Freeze-that weathering (ice wedging)

In regions subject to numerous diurnal freeze-thaw cycles, water repeatedly freezing in fractures and small cracks in rocks contributes significantly to rock breakage by

Lahars

Mudflows composed of volcanic ash Serious mudflow hazards exist in many active volcanic regions. Here, steep slopes may be covered with hundreds of meters of volcanic ash that can become saturated when erupted steam cools and falls as rain.

Spheroidal Weathering

Over time, preferential weathering and erosion along crossing joint sets leave rock in the central area between the fractures only slightly weathered, whereas the rock near the fractures acquires a more rounded appearance distinctive, rounded weathered form that develops especially well on jointed crystalline rocks, such as granite

Exfoliation

Removal of outer rock sheets

Climate and Weathering (Water)

Water plays a role in most of the physical weathering processes, but it is essential for all chemical weathering. Chemical weathering increases as more water comes into contact with rocks. Chemical weathering is particularly effective and rapid in humid climates Most arid regions have enough moisture to allow some chemical weathering. Arid regions typically receive sufficient moisture to enable the physical weathering processes of salt crystal growth and hydration of salts. Abundant salts, high humidity, and contact with seawater make salt weathering very effective in marine coastal locations.

Unloading process

a pluton of the intrusive igneous granite can be uplifted in a fault block during tectonism. High elevation helps drive erosional stripping of the overlying rocks, and through this removal of overlying weight--_______ ______ ____--the granite is eventually exposed at Earth's surface.

Avalanche (Fast Mass Wasting)

a type of mass movement in which much of the involved material is pulverized—that is, broken into small, powdery fragments—and then flows rapidly as an airborne density current.

Exfoliation Domes

an unloaded exfoliating outcrop of rock with a domelike surface form. enchanted rock

Weathering

breakdown of rock material at and near Earth's surface is known as

Weathering (Chemical)

decomposes rock through chemical reactions that remove ions from the original rock-forming minerals. ions from a rock either are released into water or recombine with other substances to form new materials, such as clay minerals.

Creep (Slow Mass Wasting)

slow downslope movement of Earth material involving the lifting and falling action of sediment particles.. Most hillslopes covered with weathered rock material or soil the most widespread and persistent form of mass wasting

Mass Wasting (3 classification factors)

1. Nature of Slope Material 2. Angle of Repose 3. Vegetation

Mass Wasting

Gravity-induced downslope movement of rock material that occurs without the assistance of a geomorphic agent, as in the case of a rock falling from a cliff, is known as

Climate and Weathering (Temperature)

chemical reactions proceed faster at higher temperatures. Low-latitude regions with humid climates consequently experience the most intense chemical weathering. In the tropical rainforest, savanna, and monsoon climates, chemical weathering is more significant than physical weathering, soils are deep, and landforms appear rounded. Although chemical weathering is somewhat less extreme in the midlatitude humid climates, its influence is apparent in the moderate soil depth and rounded forms of most landscapes in those regions. the landforms and rocks of both arid and cold regions, where physical weathering dominates, tend to be sharper, angular, and jagged rounded features can remain in an arid landscape as relicts from wetter climates of the geologic past Comparatively low rates of chemical weathering are reflected in the thin soils found in arid, subarctic, and polar climate regimes..

Physical Weathering (Mechanical)

disintegrates rocks, breaking larger blocks or outcrops of rock into smaller clasts. the resulting smaller clasts are more easily eroded and transported than the initial larger ones. the breakup of a large rock into many smaller rocks encourages additional weathering because it increases the rock surface area exposed to weathering processes. Weathering by unloading is especially common on granite