Geology 101 Exam 4

Hydrologic Cycle

Evaporation

liquid water to water vapor

Precipitation

water vapor to liquid water

Sublimation

ice to water vapor

Runoff

process that occurs when precipitation that falls on land runs across the ground surface and enters a stream or lake; forms small rills which will eventually create creeks and streams; promoted by development

Infiltration

when precipitation that falls on land is soaked into the ground and enters a groundwater reservoir

Storage

water is taken out of circulation; usually because it is frozen in glacial ice and snow

Sheet Flow

when runoff initially flows in broad, thin sheets across the ground

Infiltration Capacity

amount of water that run offs versus sinking into the ground; 5 factors for determining: 1) intensity and duration of rainfall 2) how wet the soil was prior 3)soil texture 4) slope of the land 5) vegetation coverage

Rills

tiny channels caused by development of threads of currents; carry water to stream

Two main ways water flows?

Laminar Flow and Turbulent Flow; velocity is primary factor

Laminar Flow

water particles flow in straight-line paths that are parallel to the channel; no mixing; smooth channel at low velocities

Turbulent Flow

water moves in energetic and erratic fashion; characterized by swirling, whirlpool-like eddies; effective in eroding a stream channel and keeping sediment suspended; rough channel at rising velocities

One of major factors in determining velocity is...

the gradient

Gradient of a Stream

the vertical drop of a stream over a fixed distance; vary from one stream to another as well as along the stream course; most streams have preferred profile: high gradient near its headwaters with decreasing gradient as it reaches sea-level

Discharge of a Stream

amount of water flowing past a certain point in a given time of unit; not constant

Stream Anatomy

Tributaries

larger branching channels

Trunk Stream

Main stream; covers greatest part of transport area; broad, flat floodplain; erosion forms cut banks while deposition forms point bars

Headlands

many tributaries; valleys are v-shaped; channels are straight; erosion of substrate

Mouth

stream enters lake/ocean; fan of distributaries forms as sediment load is deposited (delta or alluvial fan)

Longitudinal Profile

head to mouth; usually concave

Watersheds/ Drainage Basin

form source of water in a stream; separated by divides

Drainage Divide

higher land that bounds a drainage basin; separates it from other drainage basins

Dendritic Drainage Pattern

forms where underlying bedrock is uniform and resistant to erosion; controlled by slope of land

Radical Drainage Pattern

streams divide from central area; usually volcanic cones and domal uplifts

Rectangular Drainage Pattern

bedrock is crisscrossed by joints and faults

Trellis Drainage Pattern

forms in areas of underlain by alternating resistant and less resistant rock

Three ways streams rode their channels?

1) lifting loose consolidated particles

2) abrasion

3) dissolution

Three ways streams transport their loads?

1) dissolved load

2) suspended load

3) bed load

Dissolved Load

loads transported in solution; most of dissolved materials supplied by groundwater; amount depends on water chemistry, type of rock groundwater has percolated through, climate

Suspended load

loads transported in suspension (fine sand, silt, clay particles); usually largest proportion of load

Bed Load

loads transported along bottom of channel; particles are too large to be in suspension;

Flooding

levees created during floods and serve to stabilize channel overtime; in subsequent floods, water can cut through levee at crevasse and deposits fine sediment outside of the channel

Stream Erosion and Changing Landscape

Groundwater

flows from regions of recharge to regions of discharge; driven by gravity and water pressure

Zone of Aeration

includes capillary fringe, intermediate belt, and soil moisture zone; water held tightly by surface tension within tiny passages

Zone of Saturation

all open spaces in sediment and rock are filled with water

Water Table

upper zone of saturation; important in predicting productivity of wells; explains changes in flows of streams and springs; accounts for fluctuation of levels of lakes; defined by well depths; moves slowly and at different rates depending on location; piles up beneath high areas between streams; subsides during droughts

Aquifers

permeable rock strata or sediment that transmit groundwater freely; permeable and porous; opposite of aquitard

Springs

occurs whenever water table intersects earth's surface; common reason is vertical or horizontal changes in permeability

Hot Springs

springs that have discharge water that is 10-15° warmer than average annual local air temperature; source of heat from cooling igneous rock or nearby magmatic body; western US

Geysers

intermittent hot springs or fountains in which columns of water are ejected with great force at various intervals; usually associated with active volcano; can reach 100-200 ft

Well

a hole bored into the zone of saturation; small reservoirs into which groundwater migrates and is pumped to the surface; pumping produces cone of depression in water table around well base, can permanently lower water table

Artesian Well

any situation in which groundwater under pressure rises about level of aquifer

Plume of Contamination

sewage and aquifers; follows groundwater flow; movement dependent on geological features

Groundwater Contamination

caused by human products such as pesticides, sewage, fertilizer, gasoline, and chemicals; wells can be contaminated by reversal of groundwater flow in overpumped regions

Caves

usually etched in limestome; has variety of calcite deposits from dripping water (speleothems) such as stalactites, stalagmites, straws, flowstone, etc.

Sinkholes

caused by collapse of caves

Karst Topography

landscapes that have been shaped by dissolving power of groundwater; punctuated by sinkholes; lack surface drainage; limestone dissolves under soil

Causes of Floods

torrential rains rapidly dumping large amounts of water, long period of continuous rain (ground saturated), rapid snowmelt along large drainage basin, failure of dam or levee

Regional Floods

disasters in slow motion; result from unusually heavy rains and/or snow melt throughout a season over a broad area

Flash Floods

occur very rapidly; affect only small areas; result from intensive rain events or dam failures; most dramatic in desert areas; little warning

Flood Frequency Curve

shows maximum annual discharge for a stream plotted against probability of occurrence; based on data collected over many years; stages are discussed as 10-year, 50-year, and 100-year with 10%, 5%, and 1% likelihood of occurance in any given year

Bathymetric Profile

A map of the ocean floor that shows the ocean depth by using sonar signals; continental shelves, slopes, rises, abyssal plains, and mid-ocean ridges

Global Ocean Circulation

dependent on temperature and salinity; cold water sinks to the bottom at poles and creeps towards equator; warmer seas- circulation induced by evaporation and produces denser and more saline water, freezing of water increases salinity, rainfall decreases it

Coriolis Effect

effect of Earth's rotation on the direction of winds and currents; causes surface ocean currents generated by wind to not flow parallel to wind; flow in circular paths called gyres; northern hemisphere= clock-wise and deflected to right, southern hemisphere= counter clock-wise and deflected to left, equator= western

Waves

Wave Height

measured vertically from trough to crest

Wavelength

measured horizontally from crest of one wave to crest of next

Wave Period

time required for one full wave to pass a fixed position

Wave Height, Length, and Period determined by...

wind speed, length of time wind has been blowing, and the distance wind has traveled over open water (fetch)

Waves moves in...

circular motion; passing wave is transmitted down into water column

Breakers

waves breaking into foam as they approach or dash against the shore

Refraction of Waves

refracted towards headlands; erodes headlands and deposits material on beaches

Erosional Wave Features

wave cut cliff, sea arch, sea stack

Wave Cut Cliff

cliffs created by erosion

Sea Arch

erosional hole in a headland; caused by wave action and erosion

Sea Stack

towers of bedrock that have been isolated by concentration of erosional effects of refracted waves

Depositional Features

tombolo, baymouth bar, spit

Tombolo

ridge of sand connecting headland area to island immediately offshore; depositional feature

Baymouth Bar

a sandbar that completely crosses a bay, sealing it off from the open ocean

Sand Spit

where the coastline indents landward, beach drift stretches beaches out into open water to create

Rip Current

form when strong wind and waves force excess water up onto the beach, water accumulates to a critical point and flows all together down a beach and escapes offshore

Longshore Current

caused by water and sand grains carried up the beach at a zig-zag angle

Barrier Islands

depositional feature; ridges of sand that run parallel to the coast, separated by lagoon

Most beaches in general are...

ephemeral (not permanent), change seasonally and cyclically

Hard Stabilization Features

most human attempts to combat beach drift and other forms of beach erosion have been futile; jetties, groins, breakwaters, seawalls

Jetty

serve to keep the entrance of harbors and bays free of shallow sand, however erosion is typical adjacent to the jetties

Groins

increase sand deposition in the region directly upcurrent but increase erosion rates in the region directly downcurrent; small jetties

Breakwaters

a barrier built out into a body of water parallel to coast; protect a coast or harbor from the force of waves; create calm area for boats; lead to greater deposition of sand, displacing water

Sea Wall

built between beach and area of development; successful at protecting property, but lead to erosion of the entire beach

Beach Renourishment

taking sand from offshore or other adjacent areas and putting it on beaches to prevent loss from erosion; successful; expensive and not permanent solution

Glaciers

A large mass of recrystallized ice on land that shows evidence of being in motion or of once having moved

3 Types of Glaciers

alpine, continental, piedmont

Continental Glaciers

(ice sheets) large, broad, slow-moving glaciers that cover large portions of continental areas; flow because of pressure applied by the weight of ice at their source areas

Alpine Glaciers

(valley) restricted to valley areas at high

elevations; resemble rivers of ice; moves down slopes

Piedmont Glaciers

exit the confines of a valley and spread out laterally over a broad and relatively flat area; occur where alpine glaciers encounter a broad flat plain and spread out

Two Ingredients for Glacier Formation

1) low temperature (high elevation or high latitude)

2) snow compressed into ice

Granular Ice

50% air

Firn Ice

20-30% air

Glacial Ice

20% air as bubbles trapped in ice

Movement of Glaciers

glacial ice in zone of accumulation flows down-slope; move as a result of amount of snow accumulating compared to the amount of glacier melting at the toe

Anatomy of a Glacier

zone of accumulation, zone of ablation, snow line, terminus,

Zone of Accumulation

Area of net snow addition

Zone of Ablation

Area of net ice loss

Snow Line

The elevation above which snow remains all year long

Terminus

end of glacier

Mountain and continental glaciers produce a variety of...

distinctive erosional and depositional

features

Cirques

Bowl-shaped basin high on a mountain