Physical Geography Final New Material

Landforms

Landforms

surface features of the land, balance between internal forces and denudation processes

crustal deformation processes

deformation of rigid rock through tension (stretching), compression (shortening), and shear (twisting)

Rocks under strain may

fold (bend) if ductile, fault (break) if brittle

Fold belts and landforms

folding occurs when convergent plate. boundaries intensely compress rocks and deform them

faults and fault landforms

brittle rocks yield to stresses, normal, reverse, and strike-slip

syncline

a fold that is concave upward

anticline

a fold that is convex upward

normal fault

rocks pulled apart by tensional stress

reverse fault

rocks are forced together by compressional stress

strike-slip fault

offsetting linear features

earthquake occurrence

slippage along fault causes a rapid release of energy that creates a sudden vibration of the earth

fault scarp

a break in the ground caused by an earthquake

focus

the place inside the earth’s crust where the earthquake originates

epicenter

the location on the surface of the earth, above the origin of an earthquake

Hazard

existence of a potentially dangerous situation or event

vulnerability

susceptibility of a community to the hazard

risk

the probability that injury or damage will occur

magnitude

the energy release as the fault ruptures

intensity

severity of shaking at a location, can vary place to place, best indicator of impact

Mercalli scale

damage intensity scale, ranges from I (minor) to XII (catastrophic)

Richter scale

measures the amplitude of seismic waves, logarithmic

Moment magnitude scale

used since 1993, more accurate for large earthquakes, accounts for amount of fault slippage

tsunami

a seismic wave caused by a disturbance

tsunami genesis

ground movement at subduction zones, underwater landslide, undersea volcanic eruption

weathering

a denudation processes of disintegration

erosion

removal transport deposition

erosional agents

flowing water, wind, wave action, ice (glaciation), slope processes (gravity)

Physical weathering

mechanical breakdown of rocks

plant roots

roots can enter crevices and break rock segments apart

frost action

water expands upon freezing, wet, cool environments

salt-crystal growth

water evaporates creating minerals, crystal growth breaks rock, occurs in arid environments

Pressure-Release

Rocks brought near the surface are exposed to lower pressure and expand

exfoliation

layers of rock peel off in slabs or plates

chemical weathering

breakdown through alteration of chemical composition of rock

hydrolysis

water changes the chemical composition of minerals in rock, making them less resistant to weathering

oxidation

some metallic elements, disrupts structure, rocks easier to weather, iron rusting

dissolution of carbonates

water vapor and carbon dioxide create acidic rainwater, minerals dissolve in solution eroded away, limestone and marble

karst topography

sinkholes, disappearing streams, underground streams and caves

joints

small fractures or cracks in rock

rock resistance

different materials have different resistance to weathering

mass movement

downslope movement by gravity, also called mass wasting

rockfall

dry, individual rocks, fast events, forms a talus slope

landslide

a sudden rapid movement of a cohesive mass that is not saturated with moisture

flows

when moisture content is high, earth flow and more fluid mud flow, often caused by heavy rains

soil creep

slow, transport of material downslope, particle by particle

drainage basin

terrain that contributes water to a stream, also called a watershed

drainage patterns

the arrangement of channels, determined by steepness, rock resistance, climate, and hydrology

stream gradient

every stream has a degree of inclination or gradient, affects velocity of flow and energy, may change with tectonic uplift

stream discharge

volume of water per unit time, changes with cross sectional area or velocity

hydrograph

chart displaying change in discharge over time

storm flow

from precipitation that reaches the channel over a short time frame through overland or underground routes.

base flow

from precipitation that percolates to the ground water and moves slowly through substrate before reaching the channel

flooding

overbank flow that is unconfined to a channel

causes of flooding

heavy rains, saturated soils, rapid snowmelt, when a natural or artificial dam breaks or a levee breaks

stage

height of a river above a locally defined elevation

flood stage

full channel

flood control

two approaches to reduce vulnerability: engineering and regulatory

engineering approaches

levees, dikes, flood walls, floodways, channel modification, and dams

regulatory approaches

floodplain zoning, floodplain building codes, floodplain buyout programs, mortgage limitations

hydraulic action

water dislodges and drags rocks

abrasion

rock particles mechanically erode streamed

sediment load

eroded materials delivered to stream

stream capacity

the total load a stream can transport

stream capacity equilibrium

if load is equal to capacity

aggradation

if load exceeds the capacity

degradation

if capacity exceeds the load

what can change stream capacity

slope (greater slope=less capacity) and channel shape and size

stream transport

sediment can be transported three ways: dissolved load, suspended load, and bedload

dissolved load

in solution from chemical weathering

suspended load

are fine-grained particles held aloft by turbulence

bed load

coarser materials are dragged, rolled, or pushed

meandering stream

in gradual slopes, snakelike form, has erosional and depositional features

braided stream

maze of interconnected channels, common in glacial environments, plentiful sediment supply, load greater than capacity

stream gradient

the grade (or slope) of a stream measured by the ratio of drop in elevation per unit horizontal distance

cut bank

occurs when moving water digs out, and washes away the stream bank, below water level.

point bar

crescent-shaped swaths of sand to dot the shorelines of meandering rivers that usually appear along the inner side of a river bend, where the bank wraps around the sandy patch, forming deposits

cut-off meanders

also called oxbow lakes, these are U-shaped lakes that form when a wide meander of a river is cut off, creating a free-standing body of water

floodplain

flat, low-lying areas on either side of stream, frequently inundated by floods, receding water leaves alluvial deposits

alluvial terraces

level areas above a stream, older abandoned floodplains, created from increased erosion and incision

delta

depositional plains that form a triangular shape, decreased velocity at the mouth of a river creates reduced capacity that leads to deposition

eolian processes

refers to the work of wind, like moving water it causes erosion, transportation, and deposition

eolian erosion

two main wind-erosion processes: deflation and abrasion

deflation

removal and lifting of individual loose particles, desert pavement (sediments coverage finer material)

abrasion

the grinding of rock surfaces by “sandblasting”, ventifacts (rocks cut by wind)

dunes

wind-sculptured accumulations of sand formed by deposition

loess

sedimentary deposits of dust, can be deep, makes fertile soils

climatic setting of arid landscapes

evaporation exceeds the precipitation, sporadic convective showers

vegetation cover of arid landscapes

sparse shrubs, much open ground, subject to wind erosion and rain splash, runoff

desert landscapes

intermittent rain + wind, differential weathering, buttes, messes, arches

arroyo

canyon cut by flashy runoff

basins

receive runoff, nutrients from uplands

playa

dry lake beds, only wet after rain even

oceans

cover 71% of the earth, affects climate system, supplies water vapor, important biologically, affects coastal geomorphology

shoreline processes

interface between land and sea, affected by processes from water and land

land side processes

rivers move sediment to shorelines, winds move sand and sediments away from, toward, and along the beach

waves

undulations in the ocean surface caused by winds, help shape coastal landforms

erosion by waves

most coastline erosion is done by waves, swirl away loose pieces of rock, crashing and grinding of sediment (corrosion)

shape of coastline and wave erosion

wave energy concentrated on the headline causes more erosion, resulting in a straighter coastline

sediment transport

waves near the coastline provide energy for moving sediment along the shoreline

tides

daily fluctuations in water level caused by gravitational pull of sun and moon, affect sediment erosion and transportation, ship navigation, fishing, and coastal engineering