Chapter 9 - ESC1000 Flashcards
What is the hydrological cycle?
The unending circulation of Earth’s water supply. The cycle is powered by the Sun and is characterized by continuous exchanges of water among the oceans, the atmospheres, and the continents.
What is evaporation?
The process of converting a liquid to a gas.
What is infiltration?
The movement of surface water into rock or soil through cracks and pore spaces.
What is runoff?
Water that flows over the land rather than infiltrating into the ground.
What is transpiration?
The release of water vapor to the atmosphere by plants.
What is evapotranspiration?
The combined effect of evaporation and transpiration.
How is the hydrological system balanced?
The amount of evaporations is equal to the amount of precipitation.
Over the oceans, evaporation exceeds precipitation, yet sea level does not drop. Explain this.
Balanced is achieved because 36,000 cubic kilometers of water annually makes it way back from the land to the ocean.
Describe the hydrological cycle?
Water evaporates from the ocean and accumulates in the atmosphere as water vapor, eventually it precipitates back into the ocean or the land, if it precipitates on the land it can infiltrate underground, runoff back into the ocean, or evaporate/transpire from the surface.
What are the 5 factors that determines if the water runs off rather than soaking into the ground?
- The intensity and duration of the rainfall.
- The amount of water already in the soil.
- The nature of the surface material.
- The slope of the land.
- The extent and type of vegetation.
What is a drainage basin?
The land area that contributes water to a stream. Also called watershed.
What is a divide?
An imaginary line that separates the drainage of two streams; often found along a ridge.
What is headward erosion?
The extension upslope of the head of a valley due to erosion.
What is a river system?
Entire drainage basin of a river.
What are the 3 zones a river system can be divided?
- Sediment production
- Sediment transport
- Sediment deposition
What is the zone of sediment production?
The zone where most sediment is derived and is located in the headwater region of the river system.
What is the zone of sediment transport?
Network of channels referred as the trunk streams.
What is the zone of sediment deposition?
Area where sediment is deposited. Most sediment accumulates at the river mouth to form a delta.
What are the 4 type of drainage patterns?
Dendritic pattern, rectangular pattern, radial pattern and trellis pattern.
What is a dendritic pattern?
A stream system that resembles the pattern if a branching tree.
What is a radial pattern?
A system of streams running in all directions away from a central elevated structure, such as a volcano.
What is a rectangular pattern?
A drainage pattern characterized by numerous right angle bends that develops on jointed or fractured bedrock.
What is a trellis pattern?
A system of streams in which nearly parallel tributaries occupy valleys cut in folded strata.
What is laminar flow?
The movement of water particles in straight-line paths that are parallel to the channel. The water particles move downstream, without mixing.
What is turbulent flow?
Movement of water in an erratic fashion, often characterized by swirling, whirlpool-like eddies.
What contributes to the stream’s ability to erode its channel?
Turbulence because it lifts sediment from the streambed.
What is an important factor of turbulence?
Velocity. As velocity increases, the turbulence as well.
What 3 factors affect flow velocity?
Gradient, discharge and channel shape, size, and roughness.
What is gradient?
The slope of the stream, generally measured in feet per mile.
How does the channel shape, size and roughness affect flow velocity?
The shape, size, and roughness affect the amount of friction.
What is discharge?
The quantity of water in a stream that passes a given point in a period of time.
What are intermittent streams?
Streams that exhibit flows only during wet periods?
What are ephemeral streams?
Streams in arid climates that carry water only after a heavy rainstorm.
What is longitudinal profile?
What is pothole?
A circular depression in a bedrock stream channel created by the abrasive action of particles swirling in fast-moving eddies.
What are the 3 ways streams transport their load of sediment?
Dissolved load, suspended load, and bed load?
What is dissolved load?
The portion of the stream’s load that is carried in solution.
What is suspended load?
The fine sediment carried within the body of flowing water.
What is bed load?
Sediment that is carried by the stream along the bottom of its channel.
When does precipitation of dissolved load occurs?
When the chemistry of the water changes.
What are the 2 factors that controls suspended load?
- The stream’s flow velocity.
- Settling velocity of each sediment grain
What is settling velocity?
The speed at which a particle falls through a still fluid. The size, shape, and specific gravity of particles influence settling velocity.
What is saltation?
Transportation of sediment through a series of leap or bounces.
What are the 2 criteria used to describe the stream’s capability to carry solid particles?
Capacity and competence.
What is capacity?
The total amount of sediment a stream is able to transport.
What is competence?
A measure of the largest particle a stream can transport; a factor that is dependent on velocity.
What is sorting?
The process by which solid particles of various sizes are separated by moving water or wind. Also, the degree of similarity in particle size in sediment or sedimentary rock.
What is alluvium?
Unconsolidated sediment deposited by a stream.
What are the 2 types of stream channels?
Bedrock channel and alluvial channel.
What are bedrock channels?
They are stream channels that cut into the strata and typically form in the headwaters of the ricer where streams have steep slopes.
What are alluvial channels?
A stream channel composed of loosely consolidated sediment (alluvium).
What are the 2 types of alluvial channels?
Meandering channels and braided channels.
What is a meandering channel?
A channel that transport much of its load in suspension and generally moving in sweeping bends called meanders.
What is the cut bank?
The area of active erosion on the outside of a meander.
What is a point bar?
A crescent shaped accumulation of sand and gravel deposited on the inside of a meander.
What is a cutoff?
A short channel segment created when a river erodes through the narrow neck of land between meanders.
What is an oxbow lake?
A curved lake produced when a stream cuts off a meander.
What is a braided channel?
A stream channel consisting of numerous intertwining channels.
What is a stream valley?
The channel, valley floor, and sloping valley walls of a stream.
What is base level?
The level below which a stream cannot erode.
What are the 2 types of base levels?
Ultimate base level (sea level) and temporary or local base level (lakes, resistant rock layers and main streams).
How does a V-shaped valley forms?
When the stream’s gradient is steep and the channel is well above base level, downcutting is the dominant activity.
How does a broad valley forms?
When a stream is close to its base level, the downward erosion is less dominant. At this point the channel takes on a meandering pattern and presents continuous lateral erosion creating a broad, flat valley covered with alluvium.
What is a floodplain?
The flat, low lying portion of a stream valley that is subject to periodic inundation.
What is an incised meander?
A meandering channel that flows in a steep, narrow valley. Incised meanders form either when an area is uplifted or when base level drops.
What are stream terraces?
A flat, benchlike structure produced by a stream, which was left elevated as the stream cut downward.
What is a bar?
The common term for sand and gravel deposits in a stream channel.
What is a delta?
An accumulation of sediment formed where a stream enters a lake or an ocean.
What is a distributary?
A section of a stream that leaves the main flow.
What is a natural levee?
An elevated landform that parallels some streams and acts to confine their waters, except during flood stage.
What is back swamp?
A poorly drained area on a floodplain that results when natural levees are present.
What is yazoo tributary?
A tributary that flows parallel to the main stream because a natural levee is present.
What is alluvial fan?
A fan-shaped deposit of sediment formed when a stream’s slope is abruptly reduced.
What is a flood?
The overflow of a stream channel that occurs when discharge exceeds the channel’s capacity. Floods are the most common destructive type of geologic hazard.
How are floods controlled?
By building artificial levees, flood-control dams, channelization and a nonstructural approach.
What is a nonstructural approach?
By identifying high-risk areas, appropriate zoning regulations can be implemented to minimize development and promote more appropriate land use.
What is groundwater?
Water is the zone of saturation.
Which is the largest reservoir of freshwater readily available to humans?
Groundwater.
What is the zone of saturation?
The zone where all open spaces in sediment and rock are completely filled with water.
What is water table?
The upper level of the saturated zone of groundwater.
The is the unsaturated zone?
The area above the water table where openings in soil, sediment, and rock are not saturated, but filled mainly with air.
What 2 factors influence the rate of groundwater movement and the amount that can be stored?
Porosity and permeability.
What is porosity?
The volume of open spaces in rock or soil.
What is permeability?
A measure of a material’s ability to transmit water.
What are aquitards?
Impermeable beds that hinder or prevent groundwater movement.
What are aquifers?
Rock or soil through which groundwater moves easily.
What is a well?
An opening bored into the zone of saturation.
What is drawdown?
The difference in height between the bottom of a cone of depression and the original height of the water table.
What is the cone of depression?
A cone-shaped depression in the water table immediately surrounding a well.
What is artesian system?
A system in which groundwater under pressure rises above the level of the aquifer.
What is confined aquifer?
An aquifer that has impermeable layers (aquitards) both above and below.
What are springs?
A flow of groundwater that emerges naturally at the ground surface.
What is perched water table?
A localized zone of saturation above the main water table created by an impermeable layer (aquiclude).
What is a hot spring?
A spring in which the water is 6-9 Celsius warmer than the mean annual air temperature of its locality.
What is a geyser?
A fountain of hot water that is periodically ejected.
