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106 terms

Geology Final Exam

Definition of a River
A flowing body of water
Definition of a Load
What a river carries; made up of particles & dissolved materials
Definition of a Drainage Basin
River with all tributaries
5 Major Drainage Basins
Mississippi, Amazon (South America), Nile (Africa), Yangtze (Asia), Mackenzie (Canada)
Definition of Drainage Divide
Boundary between drainage basins
Definition of Continental Divide
If adjacent drain in different directions off continent
4 Types of Drainage Patterns
Dendritic, Trellis, Radial, Rectangular
Dendritic Drainage Pattern
Gentle slope, uniform materials
Trellis Drainage Pattern
Resistant Ridges
Radial Drainage Pattern
Central Uplift
Rectangular Drainage Pattern
2 directions of structural control
Formula for Discharge
width x depth x velocity
Definition of Hydrograph
Plot of discharge versus time
Definition of Gauging Station
Instrument to measure discharge of a stream
Definition of Basin Lag
Time elapsed between rainfall and peak discharge by river
What Increases Basin Lag
Wetlands, heavy vegetation, convoluted drainage
What Decreases Basin Lag
Paved areas, tiled areas (farming technique), low vegetation areas
Transportation of Particles in Rivers
Suspended, Bed Loads, and Dissolved Loads
Types of Bed Loads Moving Particles in Rivers
Rolling, bouncing, sliding
Channel Types
Straight, meandering, braided
Definition of Flood Plain
Flat valley bottom, normally capped by alluvium, and prone to flooding
Definition of Deltas
Where a river reaches standing water
Definition of Alluvial Fans
If water sinks or evaporates when a river ends and drops sediment. Common in mountainous and desert areas.
Mississippi River Starting Location and Time to Reach Gulf of Mexico
Starts at Lake Itasca in Minnesota. Takes 90 days for it to reach the Gulf of Mexico
Meaning of Mississippi
Percent Divert of Mississippi to Atchafalaya River
Types of Meanders
Extend (bigger), translate (move downriver), rotate (twist), compound (make a circle)
How Canyons Form
When a river is in place and uplift of the surrounding terrain occurs and when precipitation is minimal.
Date, Reason, and Damage From Big Thompson River Flood in Colorado
July 31, 1976. 12 inches of rain in a few hours. Rose from 2 feet deep to 220 feet deep. 144 killed and $35 in damage.
Number of Flash Flood Related Fatalities 1920-1997 in Colorado
Key Elements of Flash Floods
Rainfall Intensity, Duration, Topography, Soil Conditions, Vegetation
#1 Weather Related Killer
Flash Floods
Danger of Flash Floods in Automobiles and On Foot
2 feet of water can float your car and 6 inches can knock you off your feet
Depth of Groundwater
"Water table" down to ~ 10 km
Definition of Zone of Aeration (Infiltration)
Water initially "soaks in" to ground (above water table)
Definition of Zone of Saturation (Percolation)
Where sediment or rock is saturated with water (no air filled pores) (below water table)
Definition of Porosity
Voids (pores) within rocks or sediments
Cause of Porosity
Sorting & arrangement of particles
What Reduces Porosity
Cement (from lithification) and fine grain size
Definition of Permeability
Ability of sediment or rock to transmit fluids
Speed of Groundwater Flow Downhill
Generally ~1m/ day, but varies
Definition of a Shoreline
Intersection between water table and surface
Definition of Cone of Depression
A slope on the water table
What Causes Cone of Depression
Pumping out groundwater
Definition of an Aquifer
A water-bearing layer
Definition of Recharge
When water moves into an aquifer (mostly precipitation)
Definition of Discharge
When water is removed from or leaks out of an aquifer (wells and springs)
Major Aquifer of the Great Plains
Ogallala aquifer
Characteristics of Artesian Systems
1) Interbedded permeable & impermeable layers. 2) Rocks tilted & exposed so water can enter. 3) Sufficient precipitation to keep aquifer filled.
Definition of Springs & Seeps
Where water returns to the surface through leaks
Cause of Ground Subsidence
Groundwater removal
Definition of Glaciers
System of flowing ice that originates on land through accumulation and recrystallization of snow and ice
How a Glacier is Formed
When more snow accumulates each winter than melts in summer
3 Major Former North American Ice Sheets
Cordilleran, Laurentide, Greenland
Fundamental Processes of Forming Glaciers
1) Snow (90% air). 2) Firn (25% air). 3) Glacier Ice (<20% air)
Definition of Valley Glaciers
Narrow tongues of ice in mountainous regions
Definition of Continental Glaciers
Ice Sheets 1000s of meters thick, cover significant % of a continent. Flow outward in all directions. Accumulation area in center.
Speed of Glaciers
~ 1 cm to 1 m/ day
Speed of a Glacial Surge
~ 200 m/ day
Definition of a Cirque Glacier
Occupies a bowl shaped depression
Definition of Zone of Accumulation
Where snow accumulates
Definition of Zone of Ablation
Where snow melts or is removed from glacier
3 Major Continental Glaciers
Northern Canada (Baffin island), Greenland, Antarctica
Work of Glaciers
Erosion, transportation, deposition
Types of Glacial Erosion
Plucking (picks up rock and soil) and abrasion (ice polishes, scratches, and grooves bedrock using rocks)
Difference Between Glacier Load and River Load
Glaciers carry rock and sediment completely in suspension and glaciers do not sort or round particles
Types of Glacial Deposition
Till (deposited directly from glacier), Outwash (deposited by streams near a glacier), Loess (windblown silt), Erratics (unpredictable deposit - a boulder differing from surrounding bedrock)
Landforms Formed by Valley Glaciers
Cirque, Tarn, Horn, U-shaped and hanging valley, fjord
Definition of a Cirque
Bowl shaped depression on mountainside carved by a glacier
Definition of a Tarn
Lake in a cirque after glacier is gone
Definition of a Horn
Peak carved by glaciers (ex. Matterhorn, Italy)
Definition of a Hanging Valley
Carved by glacier flowing downhill
Definition of a Fjord
Flooded glacial valley
Landforms Formed by Continental Glaciers
Moraines, kettle lakes, eskers, and drumlins
Definition of Moraines
Layers or hills of till deposited directly by the glacier
Types of Moraines
End moraine (at edge of glacier) and ground moraine (at base of ice)
Definition of Kettle Lakes
Formed by melting of stagnant ice buried by till or outwash
Definition of Eskers
Sinuous ridges, river deposits, 25-100 m wide
Definition of Drumlins
Tapered Hills, usually in 'fields', 1-2 km long
Timing of Known Major Ice Ages
1 more than 2,000,000 years ago, 4 during Pleistocene (10,000 years to 2,000,000 years ago)
Name of current Ice Age
Holarctic-Antarctic Ice Age
Hypotheses for Ice Ages
Astronomical, Atmospheric Changes, and Plate Tectonic/ Ocean Currents
Explanation of Astronomical Hypothesis for Ice Ages
Variation of solar radiation (~ 3%), variation in Earth's orbit (eccentricity, tilt, precision), Interstellar dust cloud dimming sun
Explanation of Atmospheric Changes for Ice Ages
Change in greenhouse content (CO2 is strangely low and temperature is low)
#1 Greenhouse Gas
Water vapor
Explanation of Plate Tectonic Hypothesis for Ice Ages
Position of plates, circulation of oceans, and resultant precipitation patterns all effect temperature
Definition of Fossil Fuels
Remains of plants and animals trapped in sedimentary rocks form Paleozoic - ~Mid-Tertiary
Bacteria and Plankton Fossil Fuels
Oil and natural gas (liquids)
Plants Fossil Fuels
Percent of Coal Made Up of Organic Material
Conditions to Make Coal
Swamps; stagnant and oxygen poor. Compaction (~10:1), water removed
US Locations of Coal
Appalachians, Rockies, Dakotas
Best Coal Type
Higher "Grade" Coals Forms From
Higher % of Carbon
Amount of Peat to Make ~ 5m of Antracite Coal
Definition of Carbon Sequestration
Take CO2 and pump it back into ground
Time and Location of First Commercial Wells
1847: Pittsburgh
Percent of Natural Gas Made of Methane
Sources of Natural Gas
Oil fields, coal beds, swamps, landfills, cattle, and sewage
What is Oil?
Mixture of hydrocarbons and organic molecules. 83-87% carbon and 10-14% hydrogen
Percent of Oil Converted to Fuels
84%, rest used as fertilizer, drugs, plastics
Formation of Oil
1. Marine Strata (trapped micro-organisms form residues). 2. With heat (solid organic material becomes liquid within "source rock"). 3. Migration (may escape to surface). 4. Accumulation (trapped)
Definition of Oil Shale
Not really oil or shale; mine rock, heat, get oil-like substance
Amount of Oil Used to Get Fuel Out of Oil Shale
~ 40 L/Ton
Location of Biggest Deposits of Oil Shale
Potential Benefit of Oil Shale
2000 Billion Barrels