Physical Geography unit 4 review

weathering

process that breaks down rock by disintegrating it into mineral particles or dissolving into water

erosion

the transport of weathered materials to different locations

mass movement

downslope movement of a mass of rock, soil, or sediment under the force of gravity

deposition

weathered materials are added/deposited to a landform or landmass

what is Dynamic equilibrium

the balancing act between tectonic uplift and reduction by weathering and erosion, between the resistance of rocks and the ceaseless attack of weathering and erosion

stable slope

the strength exceeds the weathering and erosion processes (e.g., gentle slope, clay soil).

unstable slope

the slope materials are weaker than the weathering and erosion processes (e.g., steep slope, sand soil).

physical (mechanical) weathering

the process of rock breakage without any chemical alteration

chemical weathering

the actual decomposition of the minerals in rock due to chemical reactions with water

what does more surface area lead to in weathering

more chemical weathering

what are the factors that influence weathering processes

rock composition and structure, climactic conditions, slope orientation, subsurface water, vegetation, time

rock composition and structure (effect on weathering)

Character of bedrock and chemical composition, Joints are fractures within the rock that do not displace either side

climactic conditions (effect on weathering)

Wetter/warmer environments speed up chemical weathering processes

slope orientation (effect on weathering)

Slopes facing away from sun are cooler, moister, and with more vegetation

subsurface water (effect on weathering)

Water table height and water movement influence weathering

vegetation (effect on weathering)

Vegetative cover can protect surface by shielding it from weather and adding stability, It also produces organic acids that dissolve minerals and roots break down rock

time (effect on weathering)

Weathering processes require longer periods

front wedging

Water expands 9% when it freezes, Repeated freezing (expanding) and thawing (contracting) of water is freeze-that cycle breaks rocks apart in the process called frost wedging

thermal expansion

Rock surfaces expand slightly as they are heated by the sun during the day and contract by cooling at night, This causes the outer layer of rock (small fragments and massive slabs)to peel away, In mountainous regions, it is most common at the end of winter

salt-crystal growth

In arid climates, intense heat evaporates moisture from surface of rocks leaving behind dissolved salts as crystals, Salt crystals change 1 - 5% in volume with changes in temperature, Over time, salt crystals grow and exert enough force to break the rock to pieces by separate the individual grains

exfoliation

Most common in high-silica intrusive igneous rocks, rare in others, When deep buried granitic plutons are exposed to the surface (i.e., overlying pressure is relieved), the rock slowly responds with an enormous physical heave, Pressure-release jointing cracks the rock into joints, and separates them int layer resembling curved slabs

spheroidal weathering

Softens and rounds the sharp edges and corners as water penetrates jointed rocks and dissolves weaker minerals, The rock sheds spherical shells of weathered rock like layers of an onion

hydration

the combination of minerals with water; water enters the chemical composition of the mineral

hydrolysis

the decomposition of a chemical compound by reaction with water, producing a different mineral trough the reaction

oxidation

Metallic elements in the minerals combine with oxygen to form oxides (most commonly Iron), Oxidation removes iron and disrupts the crystal structure of minerals, Iron oxides are the main mining source in Marquette Iron Range. Oxidation also seen in soils in humid regions

dissolution of carbonates

Water vapor in the atmosphere dissolves carbon dioxide, forming carbonic acid, Carbonic acid is strong enough to dissolve many minerals (especially limestone) by a carbonation reaction, Rainwater dissolves and washes away the main minerals forming the rock (mostly Ca, Mg, K, and Na)

falls

the detachment and rapid downward movement of a rock.

slides

a unit of material moves along a zone of weakness separating from underlying material

transitional slide

movement along a flat surface parallel to angle of slope

rotational slides

surface material moves along a concave surface

flows

when unconsolidated material moving forms a slurry with water

debris flows

a mixture of water and sediment of all sizes

mudflows

mixture of water and finer materials (clay, mud) forming fluid flow

creep

the persistent, perpetual mass movement of surface soils

watershed

the portion of the landscape in which streams receive their water

interfluves

high ground between valleys hs

sheet flow

thin film of water over surface

continental divides

separate watersheds that empty into different bodies of water surrounding a continent

dendritic drainage

treelike pattern like many natural systems (roots or veins in leaves)

parallel drainage

like dendritic but branches are straighter, aligned with downslope direction

radial drainage

water drains from central peak around a conical feature (dome or volcano) in all directions

rectangular drainage

develops as faulted and folded landscapes guide the water following fractures

trellis drainage

develops in dipping or folded landscapes, influenced by differential erosion

stream discharge

the volume passing a point in a given unit of time

sediment transport

occurs when streamflow propels sediments downstream in general

sediment load

the material carried away by the stream, and the supply is determined by topography, nearby geology, vegetation, and human activity

dissolved load

material that travels in solution, as dissolved compounds

suspended load

composed of fine-grained sediments traveling aloft in suspension

bed load

coarser sediments moved by traction or saltation

meandering stream

a stream that curves

oxbow lake

forms when an isolated meander becomes isolated from the river after a cutoff

floodplain

a flat, low-lying area adjacent to a meandering channel and subjected to recurrent flooding

cutoff

the outside of a meander

point bar

the inside curve of a meander

undercut bank

formed when water flows faster on the outer portion of a meandering curve

natural levees

low ridges of coarse sediments that are formed as by-products of flooding.

how does a cutoff form?

streams erode their outside banks forming a neck of land that eventually erodes

how does a point bar form?

water flow slows down, causing the deposition of sand and gravel carried upon the riverbed

where is water the fastest in a meander

cutoff

where is water the slowest in a meander

the point bar