The Global Environment - Unit 1 (Lithosphere)

Uniformitarianism

Assuming that what happens today probably happened before, both gradual and catastrophic, will happen again

Numerical age

Dating of rock, measure of decay

Lithosphere

“Rigid layer,” crust and upper mantle

Asthenosphere

“Plastic layer,” convection zone, within the mantle

Magnetism

Generated by fluid material of outer core

Plate Tectonics

Lithosphere is divided into floating plates migrating over the mantle

Convection currents

Upwelling and downwelling forces, movement of solid and liquid materials

Continental drift

Dynamic global landmass, once were all connected, may be again one day

Seafloor spread

Ocean expands, moving the plates

Mid-ocean ridges

Where new earth crusts originate

Subduction

One plate descends beneath another, denser plate below

Superposition

Rock formation at the bottom is the oldest, newest at the top

Crust

Top layer, variation (mountains, ocean)

Mantle

Both upper and lower, temperature gradient, heat migrates outward (geothermal heat)

Core

Dense, solid material (iron)

Residual heat

Decay of radioactive materials

Continental crust

Lower density

Oceanic crust

Higher density

Igneous rock

Formed from molten material

Sedimentary rock

Formed from compaction or chemical processes

Metamorphic rock

Altered by heat and pressure

Ridge push

Magma-formed mid-ocean ridges

Slab pull

Cooling plates sink, pulling other material down with

Convergent plate boundaries

Collision zones

Divergent plate boundaries

Rifting apart

Transform plate boundaries

Sliding, shifting fault lines

Exogenic

Driven by solar radiation and gravity, geomorphology

Endogenic

Driven by heat and radioactive decay, geology

Stable formations

Mountains, continental cratons

Active formations

Active movements (folding, faulting, etc.)

Volcanic landforms

Surface accumulation of molten rock

Craton

Nucleus of a continent, crystalline rock on which the continent “grows”

Continental shield

Large region where the craton is exposed at the earth surface, often by erosion

Terranes

Pieces of younger crust that becomes attached to the plates through plate motion

Tension

Stretching

Compression

Shortening

Shear

Twisting/tearing

Deformation

Rock strata are compressed

Folding

Result of compressional stress and shortening

Anticline folds

Arch-shaped, forward fold

Syncline folds

Trough-shaped, downward fold

Monocline folds

Large folds (similar to carpet laid over a stair step), often result of faulting

Dome

Heavily eroded convex uplift, oldest strata in the center

Basin

Uplifted, eroded syncline, youngest strata in the center

Warping

Produces bends greater in extent than folds (magma upwellings, hotspots)

Isostatic adjustment

Uplift or sinking of the lithosphere in response to weight at the surface

Orogenesis

Tectonic activity, produces mountains

Earthquakes

Sharp release of energy from crustal plate collisions

Elastic Rebound Theory

Strain accumulates until rock breaks, releasing elastic energy

Focus

Where earthquake starts

Epicenter

Area at the surface directly above the focus

Foreshock

Smaller event preceding the main event

Aftershock

Can mirror quake intensity

Volcano

Central vent or pipe through which magma rises from the asthenosphere and upper mantle

Pyroclastic

Rock and other material ejected violently during eruption

Aa

Rough basalt with sharp edges, a thick skin over slowly cooling lava

Pahoehoe

Shiny and smooth basalt that resemble coiled, twisted rope (underwater eruptions)

Cinder cone

Small, cone shaped hill made of pyroclastic material

Caldera

Large, basin shaped depression when a volcano collapses

Effusive eruptions

Vast outpourings of low-viscosity lava

Shield volcano

Built of effusive eruptions, resembles a shield of armor

Mass movement

The downslope movement of a body of material propelled by the force of gravity

Denudation

The rearrangement and wearing away of landforms over time, result of exogenic processes

Dynamic Equilibrium

Balancing act between stable and unstable systems, in a state of constant change

Weathering

Breaking down rock by disintegrating it into mineral particles or dissolving it into water

Physical weathering

Disintegration of rock without any chemical alteration (freeze/thaw processes), results in increased surface area

Chemical weathering

Changes in the chemical makeup of rock material, results in material being more erodible

Factors influencing the weathering process

Rock composition and structure, climate, slope orientation, subsurface water (water table), vegetation

Thermal expansion

Objects warmed by the sun expand, then contract when cooled (at night)

Exfoliation

Outer layers of exposed rock peel or slip off in sheets as pressure is released, exposes harder materials beneath

Hydration

Combination of water with a mineral, little chemical “damage,” but does include structural changes

Hydrolysis

Chemical reaction of a mineral with water, material breaking down

Oxidation

Metallic elements combine with oxygen, susceptible to further weathering

Dissolution of carbonate materials

Dissolves minerals by carbonations (limestone and marble)

Differential weathering

Combination of physical and chemical processes, materials weather at different rates, results in irregular appearances

Karst topography

Areas with limestone formations, bumpy surface, underground channels (caves, sinkholes, disappearing/losing streams, aquifers)

Slope orientation

Controls the amount of precipitation and wind, microclimates

Mass wasting

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

Dynamic equilibrium model

Slope is stable if forces promoting motion are balanced by forces opposing motion

Angle of repose

The maximum slope angle at which material remains in place

Oversteepening

Slope exceeds angle of repose due to erosion or removal of toe support

Rock falls

Detached rocks abruptly fall, talus slopes

Rotational landslide

Material moves as a unit along a weak zone, concave weak zone

Translational landslide

Material moves as a unit along a weak zone, parallel to slope angle

Debris flows/avalanche

Mixture of water and debris, unconsolidated material, ranging from fast to slow

Earth flow

Unconsolidated material, mixture of water, debris, and soil, relatively slow

Mud flow

Unconsolidated material, mixture of water and finer sediment, relatively fast

Creep

Individual particles disturbed by expansion/contraction (freeze/thaw, moist/dry, solifluction), very slow

Erosion

Hydraulic action: flowing fluid loosens, lifts, and breaks up rock. Abrasion: moving materials tumbles into and grinds each other

Transportation

Movement of eroded materials, load dependencies: velocity and size

Water erosion

Material: dissolved, suspended, and bed load. Movement: solution, suspension, traction (stopping), saltation (skipping)

Wind erosion

Wind moves particles via drag, only works on dry materials, wind speed and particle size matters

Deposition

Resting place for eroded materials after transportation

Dunes

Depositional landform, shape and size result of: direction and strength of wind, consistency of wind, sand supply, vegetation

Loess

Depositional landform, homogeneous deposits of win-blown dust

Snowline

Lowest elevation where snow remains year-round

Firn

Granular, compacted snow in transition to glacial ice

Accumulation zone

Uppermost area of glacier, where accumulation of snow is greater than loss from ablation

Ablation zone

Glacier loses mass due to melting, sublimation, and other processes

Terminus

The “end” of the glacier, usually the lowest point