Chapter 14

salt crystal growth

as crystals accumulate over time, they exert a force great enough to separate the grains of the rock Forms alcoves in the base of sandstone cliffs

caves and caverns

caves are natural underground areas large enough for humans to enter... form in limestone because it's so easily dissolved by carbonation. Any large cave formed by chemical processes is a cavern. Generally, form below water table, where later lowering of water level exposes to further development Speleothems from mineral deposits, e.g. dripstones Stalactites from the ceiling and stalagmites on the floor

oxidation

certain metallic elements combine with oxygen and form oxides E.g. rusting of iron to produce iron oxide

tropical karst

cockpits and cones, deeply jointed. Cockpit karst. Tower karsts are resistant cones and towers.

talus slope

cone shaped piles of broken rocks known as talus cones coalesced, resulting from rock fall (falls through the air and hits a surface)

slopes

curved, inclined surfaces that form boundaries of landforms. Forces of erosion must overcome friction and inertia and cohesion of particles to others. Open systems that seek angles of eqilibrium among below forces. Waxing, increasing, slope near the top Waning, concave, slope near the bottom Free face: steep scarp or outcrop that indicates resistant rock Debris slope: receives rock fragments and materials from above. Reflects local climate.

hydrolysis

decomposition of chemical compound by reaction with water. Makes a different mineral in the process. Feldspar + carbonic acid and water à residual clays + dissolved minerals + silica This forms quartz Granular disintegration takes place when minerals in rock are changed by hydrolysis... interlocking crystal network is changed Basalt, mafic, rocks weather faster than granite, felsic.

karst valley

dissolution and collapse, sinkholes coalesce to form valleys, elongated depressions up to several km

frost weathering

expansion of water when freezing... freeze-thaw, breaks apart rocks Important in humid microthermal climates and polar climates, and high elevation climates

joints

fractures or separations in rock that occur without displacement of the rock on either side

scarification

human impacts that move sediment, soil, and rock material Leeching of toxic materials Mountaintop removal is a controversial form of mining done by removing ridges and summits and dumping debris into stream valleys Humans are 10 times more active in shaping the landscape than natural processes!

hydration

involves a new change in structure as water becomes part of chemical composition of the mineral, forming a hydrate. Produces feldspar.

weatheringq

is the process that breaks down rock at Earth's surface and slightly below, either disintegrating rocks into mineral particles or dissolving it into water. Both physical and chemical, weakens rock.

debris avalanche

mass of falling and tumbling rock, debris, and soil travelling at high velocity owing to the presence of ice and water that fluidize the debris

spheroidal weathering

softens and rounds sharp edges and corners of jointed rock as water penetrates joints and dissolves weaker minerals or cementing materials

bedrock

solid rock under loose surface material such as gravel, sand, clay, or soil. Weathering creates a broken up regolith. Bedrock is parent rock for where soil and regolith form. Parent material is the consolidated or unconsolidated material from which soils develop.

angle of repose

steepness of slope at equilibrium, depends on the size and texture of the grains Balance of driving (gravity) force and resisting force (friction and shear)

stable

strength exceeds denudation processes

landslide

sudden rapid movement of a cohesive mass of regolith or bedrock that is not saturated with moisture, large amount falling simultaneously

rotational

surface materials move along concave surfaces

sinkholes

weathering by dissolution of limestone, circular depressions in the ground surface that may reach 600 m in depth (collapse and solution variety)

flow

when moisture content of moving material is high

dynamic equilibrium model

which considers slope and landform stability to be consequences of the resistance of rock materials to the attack of denudation processes, is often used for understanding landforms. When a destabilizing event occurs, a landform or landform system may reach a geomorphic threshold, where force overcomes resistance and the system moves to a new level and toward a new equilibrium state.

karst topography

Areas characterized by solutional channels underground Limestone formation must contain 80% or more calcium carbonate Complex patterns of joints in limestone needed for water routes Aerated zone must exist between ground surface and water table Vegetated cover to supply organic acids that enhance dissolution process

dynamic equilibrium

As physical factors fluctuate in an area, surface constantly responds in search of equilibrium. Every change produces compensating actions and reactions. 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.

internal and external processes

Endogenic processes build initial landscapes. Exogenic processes develop sequential landscapes of low relief, gradual change, and stability. The internal and external countering processes act on landscapes simultaneously at different rates. e.g. giant sculpture is endogenic, but acid rain weathering is exogenic

geomorphic cycle

Equilibrium stability Destabilizing event Period of adjustment Development of a new and different condition of equilibrium

geomorphologic concept

Geomorphology is the science of landforms including origin, evolution, form, and spatial distribution of landforms. Denudation is any process that wears away or rearranges landforms. The principle denudation processes are weathering, mass movement, erosion, transportation, and deposition.

shear failure point

In any mass movement, gravity pulls on a mass until the critical shear-failure point is reached. The material can fall, slide, flow, or creep.

factors of weathering

Joints Climate Slope of orientation: controls sun exposure. Slopes facing away from the Sun tend to be cooler, moister, and more vegetated. Noticeable in middle and higher latitudes. Subsurface water: position of water table and water movement influences weathering Vegetation: produces organic acids, from decay or organic matter, that can contribute to chemical weathering. Plant roots can break up rocks and stabilize soil. Time is the final critical factor of weathering

slope

material loosened by weathering susceptible to erosion and transportation Forces of erosion must overcome other forces If the angle is steep enough for gravity to overcome frictional forces or if impact of raindrops or wind dislodges material, then erosion of particles and transport downslope can occur Slope is stable if its strength exceeds the weathering and erosions processes Unstable if materials are weaker than weathering and erosion

unstable

materials are weaker than denudation processes

translational

movement along a planar surface parallel to the angle of slope

physical weathering

or mechanical weathering, refers to the breakup of rock into smaller pieces with no alteration of mineral identity. Chemical weathering is the chemical decomposition of minerals in rock. It can cause spheroidal weathering.

creep

persistent, gradual mass movement of surface soil. Individual particles are lifted.

snow avalanche

rapid, gravity-driven mass of snow that is moving down slope Driven by changes in snow crystals which induce variation in the mechanical properties of snowpack Typically starts at a single point and extends laterally Also changes in the density of the snow --> that isn't a good slope to ski on! Check profile of snow pack Rapid temperature changes lead to isothermal conditions. What sets it off? New snow, wind, precipitation, structure/stability, rapid temperature changes Refreezing of water that had melted during the day (top melt infiltrates the bottom) heats the surrounding snowpack This snowpack is isothermal, has the same temp Normally, isothermal snowpack is around 0 degrees Celsius Any additional energy with trigger melt Once in motion: flowing, airborne Algae grows on the snow. Dust acts as a substrate, shown on the top of snow. Brown in color. This dust then changes the albedo of the snow. Algae contributes to this change. What used to be highly reflected will now decrease. Now the rest is being absorbed. Going to heat up that snowpack and contribute to melt.

karst topography

refers to distinctively pitted and weathered limestone landscapes. Sinkholes are circular depressions caused by weathering of limestone landscapes

exfoliation

rock peels or slips off in sheets instead of breaking up into grains Creates arch and dome shaped features on the exposed landscape - largest weathering features in area extent Pressure is released from removal of overlying rock Separates joints into layers resembling curved slabs or plates, thinner at the top of the rock structure and thicker at the side Also force of gravity at a curved surface?

geomorphology

the science that analyzes and describes the origin, evolution, form, and spatial distribution of landforms. Processes of landmass denudation involve weathering, mass movement, erosion, transportation, and deposition.

carbonation

water vapor dissolves readily in carbon dioxide... strong enough to dissolve many minerals, especially limestone Calcium carbonate + carbonic acid and water à calcium bicarbonate