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Geography Spring Exam 2
Terms in this set (82)
Generally, old, low-elevation heartland region of continental crust; various cratons(granitic cores) and ancient mountains are exposed at the surface. (Often Precambrian rock (> 2 billion yrs.)
Younger sedimentary rocks surrounding continental shields
A migrating piece of Earth's crust, dragged about by the processes of mantle convection and plate tectonics
3 types of stress
tension, compression, shearing
is how rocks respond to stress and is expressed in rocks by folding(bending) or faulting(breaking).
stress causes stretching strain
stress causes shortening strain
stress causes twisting laterally strain
The bending and deformation of beds of rock strata subjected to compressional forces
Arch shaped, upward fold in which rock strata slope downward from the axis, or central ridge, of the fold. ("hill")
A trough-shaped downward fold in which rock strata slope toward central axis of the fold. ("valley"
A state of equilibrium in Earth's crust formed by the interplay between portions of the less-dense lithosphere and the more-dense asthenosphere and the principle of buoyancy.
The process whereby displacements and fracturing occur between two portions of Earth's crust.
Upward-faulted block in a pair.
Downward-faulted block in a pair
means "mountain generating."
two types of crust
one of the two plates sinks under the other creating a subduction zone
A sharp release of energy that sends waves travelling through Earth's crust at the movement of rupture along a fault or in association with volcanic activity
Elastic Rebound Theory
Two sides of a fault appear locked, but with accumulating strain, they rupture suddenly, snapping to new positions relative to each other, generating and earthquake
is the subsurface area along a fault plane, where the motion of seismic waves is initiated.
is the area at the surfacedirectly above the focus
The shock wave sent through the planet by an earthquake or underground nuclear test
instrument used to detect and record the ground motion during an earthquake caused by seismic waves traveling through Earth's interior to the surface
Ground shaking disrupts and loosens the structure of the soil, causing it to flow.
A mountainous landform at the end of a magma conduit, which rises from below the crust and vents to the surface
Pyroclastics(Ancient Greek:pyro="fire" + klastós="broken")
An explosively ejected rock fragment launched by a volcanic eruption: ash, cinder, bombs (more generally called tephra ("ash")).
Rough, jagged basaltic lava with sharp edges. This texture is caused by the loss of trapped gases, a slow flow, and the development of a thick skin that cracks into the jagged surface.
Lava that is more fluid than aa. It forms a thin crust that forms folds and appears "ropy," like coiled, twisted rope
Small and cone-shaped and generally not more than 450 meters in height, with a truncated top
A symmetrical mountain landform built from effusive eruptions*
Low-viscosity basaltic magma and low-gas content, which readily escapes. Lava pours forth onto the surface with relatively small explosions and few pyroclastics
Formed by sequence of explosive eruptions*;steep-sided, conical in shape (sometimes called stratovolcano)
Violent and unpredictable, the result of magma that is thicker (more viscous), stickier, and higher in gas and silica content than that of an effusive eruption
Caldera (from Spanishcaldera, literally "cauldron, kettle")
An interior sunken portion of a composite volcano's crater; usually steep-sided and circular, sometimes containing a lake: also can found in conjunction with a shield volcano.
A general term that refers to all processes that cause degradation of the landscape: weathering, mass movement, erosion, and transportation.
Weathering (breaking down)
The process by which surface and subsurface rocks disintegrate, dissolve, or are broken down (physically & chemically)
Denudation by wind, water, or ice, which dislodges, dissolves, or removes surface materials.
Dynamic equilibrium model
The balancing act between tectonic uplift/the resistance of crustal materials and denudation processes.-Equilibrium condition-Destabilizing event-Period of adjustment-New and different equilibrium condition
The limit up to which landforms change before lurching to a new set of relationships, with rapid realignments of landscape materials and slopes.
Curved, inclined surfaces that bound landforms such as valleys and plateaus
Angle of Repose
The angle at which a slope is inclined and beyond which downslope movement (slope failure) will occur
breaks down rock at Earth's surface and to some depth below the surface, either disintegrating rock and breaking it into particles (physicalor mechanical weathering) or dissolving it in water (chemicalweathering).
Bedrock(parent rock: source material)
the rock of the Earth's crust that lies below soil and regolith, and is sometimes exposed at the surface as an outcrop.
Partially weathered rock overlying bedrock, whether residual or transported
The unconsolidated material, that is the basis of soil development
Factors Influencing Weathering Processes
rock composition and structure (jointing), climatic conditions, subsurface water, slope orientation, vegetation
Rock composition and structure
Minerals, Hard/soft, broken/unbroken, soluble/insoluble
(fractures without displacement)
Climatic conditions (precipitation & temperature)
warmer: faster chemical decomposition-colder: freeze-thaw
N, S, E, W: exposure to the sun, wind, precipitation
position of the water table and water flow
Can protect rock from rainfall, but . . .Roots, organic acids, and decay
Physical Weathering (mechanical weathering)
The breaking up and disintegrating of rock without any chemical alteration.
types of physical weathering
exfoliation, frost wedging, thermal expansion
Frost wedging (or freeze-thaw action)
Water expands as much as 9% when froze
(salt crystal weathering)
Daytime heat (expansion)/nighttime cooling (contraction
Exfoliation (pressure-release jointing)
Mechanical forces enlarge joints in rock into layers of curved slabs or plates, which peel or slip off in sheets
Decomposition and decay of the constituent minerals in rock through chemical alteration of those minerals
A chemical weathering process in which the sharp edges and corners of boulders and rocks are weathered to thin plates that create a rounded, spheroidal form
A chemical weathering process involving water that is added to a mineral, which initiates swelling and stress within the rock, mechanically forcing grains apart as the constituents expand.(does NOT form a new chemical compound)
Chalk: a soft, white,porous,sedimentarycarbonate rock (calcium carbonate (CaCO3) (an alkali that neutralizes acids) is composed of calcium and oxygen combined with carbon. Industrially important source rocks limestone,chalk,marble,andtravertine.)
a salt (the product of a base and acid reacting and both becoming neutralized), made up of calcium and oxygen combined with sulfurCaSO4·2H2O.
(Greekhydro-, meaning 'water', +lysis, meaning 'to unbind')A chemical weathering process in which minerals chemically combine with water; a decomposition process that causes silicate minerals in rocks to break down and become altered.
A chemical weathering process in which oxygen dissolved in water (combines with) certain metallic elements from oxides (e.g., "rust" of iron in a rock or soil (ultisols, oxisols)
A chemical weathering process in which weak carbonic acid (water and carbon dioxide) reacts with minerals that contain calcium, magnesium, potassium, and sodium (especially limestone), transforming them into carbonates
The effects of different resistances in rock, coupled with variations in the intensity of physical and chemical weathering
Pitted, bumpy surface topography
Well-developed solution channels (dissolved openings and conduits) underground
Requires limestone with 80% CaCo3
Aerated zone between surface and water table
Vegetation to provide organic acids
Nearly circular depression created by the weathering of karst landscapes with subterranean drainage
Mass Movement (a.k.a. Mass wasting) ("landslide")
The downslope movement of a body of material (soil, sediment, or rock) propelled by the force of gravity.
Mass movements are classified based on
speed and moisture
Free-falling movement of debris from a cliff or steep slope.
Formed by angular rock fragments that cascade down a slope along the base of a mountain; poorly sorted, cone-shaped deposits.
Material moves as a unit along a zone of weakness that separates the slide material from more stable underlying material. Intermediate is rate of movement and water content. Translational Slides, Rotational Slides (Slumps)
A type of mass movement that flows downslope in a slurry of unconsolidated material, specifically a mixture of water and sediment that is mainly gravels, boulders, and other rock fragments coarser than sand, but also includes mud, silt, and sand.
Fluid downslope flows of material of smaller size and higher water content than a debris flow
A high-speed flow of rock and debris, sometimes fluidized by ice in steep mountain regions.
A persistent mass movement of surface soil where individual soil particles are lifted and disturbed by the expansion of soil moisture as it freezes or by grazing livestock or digging animals.
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