Geology 1403 Exam 4

hydrologic cycle

The continuous recycling of water from the oceans, through the atmosphere, to the continents, and back to the oceans

gradient

The downhill slope of a river measured as vertical drop/horizontal distance

velocity

The measure of the downstream distance water travels in a given time measured as ft/sec or m/sec
-average velocity increases downstream

discharge

The volume of water in a stream, measured as the volume of water that passes a particular point in a given period of time

bed load

sediment particles transported by a river which are too large to be suspended in the water column

suspended load

The smallest sedimentary particles transported by a stream which are continuously kept suspended above the channel bed

zone of aeration

The portion of the soil or bedrock where the pore spaces are mostly filled with air

zone of saturation

The portion of the soil or bedrock where the pore spaces are mostly filled with water

water table

The surface which separates the zone of aeration from the zone of saturation

aquifer

A permeable layer of rock or sediment transporting groundwater

porosity

The percentage of a material's total volume that is pore space

shoreline

The area between low tide and the highest level on land affected by storm waves

longshore current

Water between the breaker zone and the beach which flows parallel to the shoreline
-along the beach

spit

A finger-like projection of a beach into a body of water such as a bay. (parallel to the shoreline)

tombolo

A projection of the beach from the beach to an offshore island. (perpendicular to the shoreline)
-island offshore

sea cliff

Steep or vertical slopes formed by erosion in the shoreline area

glacier

A mass of ice on land consisting of compacted, recrystallized snow that flows under its own weight
-reservoir in the cycle where water is stored for long periods of time

glacial drift

A general term for all deposits that result from glacial activity

cirque

A steep-walled, bowl-shaped depression formed by erosion of valley glaciers

moraine

A mound-like or linear deposit of glacial till

kettle

Circular to oval depressions left in a glacial outwash plain, often filled with water

saltation

The bouncing or skipping movement of medium sized sand particles

desert pavement

The mosaic of packed together pebbles left behind by the removal by wind of all the fine-grained particles

barchan dune

Crescent shaped dunes which form in areas of limited sand supply. Tips of the dunes point downwind

parabolic dune

Dunes common in coastal areas which are crescent shaped with their tips pointing upwind

running water

most important geologic process modifying Earth's land surface

hydrosphere

consists of all water on earth

what are the characteristics of water flow

-laminar
-turbulent

what is laminar

streamlines are parallel to one another with no mixing

what is turbulent

streamlines are complexly intertwined with mixing
-energetic
-capable of erosion Grand Canyon
-capable of sediment transport Mississippi River

runoff

-downslope movement of water during a rainstorm

what are the types of runoff

-sheet flow or continuous sheet of shallow water
-channel flow or confined to long trough-like depressions

erosional features of streams

-stream terraces
-incised meanders
-water gaps

Load

-dissolved
-solid
-suspended bed

What are the characteristics of channel flow

-gradient
-velocity
-discharge

erosion

removal from a source area of dissolved substances as well as loose particles of soil, minerals and rock
-dissolved substances
-particles

deposition

most of the geologic work of rivers and streams takes placed during floods

alluvial

all processes related to rivers and running water

alluvium

general term for all sediment deposited by rivers

what are the running water depositional settings

-channels
-floodplains
-deltas
-alluvial fans

what are the types of channels

-braided rivers
-meandering rivers

braided rivers

-dividing and rejoining channels
-broad and shallow
-sand and gravel bars
-bed load transport
-arid and glacial environments

meandering rivers

-single channel
-varies in shape from semicircular to asymmetric
-velocity changes across channel
-may cutoff from main channel

what are the parts of a channel

-meandering river
-point bar
-cut bank
-ox-bow lakes

floodplains

low-lying relatively flat areas adjacent to river channels

what are the 3 types of deltas

-stream dominated Mississippi river, LA
-wave dominated Nile Delta, Egypt
-tide dominated Ganges-Brahmaputra Delta, Bangladesh

alluvial fans

fan-shaped desposit formed where a fast flowing stream flattens, slows, and spread typically at the exit of a canyon onto a flatter plain

drainage system

main river channel with all its tributaries

drainage basin

area drained by a river and its tributaries

divide

high ground separating one drainage basin from another

what are the drainage systems

-dendritic or tree branching
-rectangular or right angles
-trellis or parallel main streams
-radial or radiate outward
-deranged or highly irregular

base level

lowest level to which a stream or river can erode-sea level
-river or stream will adjust to a change in its base level either by eroding deeper or by depositing sediment

graded stream

a stream at equilibrium

valleys

-common
-stream valley or v shaped
-created by erosion of running water downhill

additional erosional landforms

-stream terraces or remnants of old flood plains Snake River, WY
-incised meanders or very steep cliffs cut into rock Colorado River, UT
-water gap or narrow canyone thru rock layers Cumberland Gap

permeability

the capacity to transmit fluids
-rocks may be porous without being permeable

groundwater

water beneath the surface filling open spaces in rocks, sediment and soil

aquiclude

any rock layer with porosity and/or permeability so low that it prevents the movement of groundwater
-precludes

recharge

additions to the zone of saturation
-Florida

what are the groundwater withdrawals

-streams or lakes
-springs
-wells

cone of depression

an area around the well created from pumping water from a well and lowering the water table

artesian system

any system in which the ground water is confined, building up pressure

what is the primary agent of erosion

groundwater

groundwater erosion and transport

-chemical weathering
-ions in solution

surface water erosion and transport

-physical and some chemical weathering
-ions in solution plus solid sediment

what are the features of groundwater erosion

-sinkholes
-karst topography
-caves and caverns

what is the difference between caves and caverns

size
-caves are large enough for a person to enter
-caverns very large caves or cave systems

dripstone

general term for all cave deposits

what are the human impact on groundwater

-over use by lowering the water table
-saltwater incursion
-subsidence
-contamination

examples of geysers

-old faithful
-ca
-iceland

characteristics of shorelines

-narrow and long
-marine processes
-erosion, transport and deposition

3 shoreline processes

-tides
-waves
-currents

tides

move the area of wave attack onshore and offshore twice a day

waves

ultimately responsible for most erosion, transport and deposition in shoreline areas

currents

created by wave motion near shore

waves

created by wind blowing over water from storms

2 types of currents

-longshore
-rip

rip current

narrow surface currents that flow out to sea through the breaker zone
-perpendicular to the shore
-mechanism for mass transport of water out of the breaker zone and back into the deeper water
-extremely strong currents

5 shoreline depositional landforms

-beaches
-spits
-baymouth bars
-tombolos
-barrier islands

beach

deposit of unconsolidated sediment extending from the low tide mark shoreward to a change in topography such as dunes, sea cliffs, or vegetation
-wave energy
-sedimentary materials available

summer beaches

-calm wave intensity
-sandy
-wide berm
-gentle sloping beach face
-smooth offshore profile

winter beaches

-stormy wave intensity
-coarser grained sediment
-small or no berm
-steep beach face
-sand bars parallel to shore

beach sediment

-rivers and streams
-redistributed by longshore currents
-zig zag pattern of sandgrains

baymouth bar

a spit completely closes off the bay

barrier island

long narrow island of sand a short distance offshore, parallel to the coast and separated from the mainland by a lagoon

parts of a barrier island

-beach
-back barrier
-marshy area
-lagoon
-mainland

where do barrier islands form

-gently sloping passive continental margins
-abundant sand
-wave energy and tidal range is low
-east and gulf coasts of the U.S.

how is sediment lost to the shore

-offshore transport by wave action
-wind
-submarine canyons

erosional landforms of beaches

-sea cliff
-wave-cut platform
-wave-built platform
-marine terraces

erosion of sea cliffs

-headlands
-sea caves
-sea arch
-sea stacks

what do erosional shoreline processes do

tend to straighten an irregular coastline over time

depostional coasts

-abundant detrital sediment
-wide sandy beaches
-deltas
-barrier island
ex. east and gulf coasts of U.S.

erosional coasts

-steep and irregular
-lack beaches
-no deltas or barrier islands
-erosional landforms
ex. west coast of U.S.

submergent coast

sea level has risen with respect to land
ex. Chesapeake Bay

emergent coast

land has risen with respect to the sea
ex. S. CA

sea level

is rising worldwide

problems with rising sea level

-flooding
-landward migration of barrier islands
-increased coastal flooding during storms
-saltwater incursion threatens groundwater

ways to prevent or minimize shoreline erosion

-sea walls
-riprap
-sand berms
-beach nourishment

till

sediment deposited directly by ice

glacial ice

sublimates or goes directly from a solid to a gas