Flashcards in Exam 3 Deck (48)
What does the rock cycle explain ?
Explains interrelations among earth materials
What are the three main types of rocks ?
Igneous: can be changed into sed. rock or into meta. rock
Sedimentary: can be changed into meta. rock or onto igneous rock
Metamorphic: can change into igneous or sed. rock
What are the six pathways ?
Heat and pressure
Weathering, erosion, and deposition
Compaction and cementation
What is metamorphism ?
The process that changes sedimentary and igneous rocks into metamorphic rock
Alteration of the minerals and textures of a rock by changes in temperature and pressure, and/or by a gain or loss of chemical components
What is erosion ?
The processes that loosen sediment and move it from one place to another on earth’s surface
What is weathering ?
The breaking down of rocks, soil and mineral as well as artificial materials through contact with Earth's atmosphere, biota and waters
What are the two types of weathering ?
Physical weathering- no chemical changes
Chemical weathering- the process by which rocks are decomposed, dissolved, or loosened by chemical processes to form residual materials, chemical changes
How is sediment transported ?
The processes that carry sediment or other materials away from their point of origin
What is sediment deposition ?
The settling of materials out of a transporting medium like water or wind
Describe lithification and two related phenomena
The process by which sediment is converted into sedimentary rock including cementation and compaction
Define the term stream
A body of water flowing in a channel or watercourse
What is a flood ?
A rising and overflowing of a body of water especially onto normally dry land
A large amount of water covering an area of land that is usually dry
What are the most important factors that control the way a stream behaves ?
The cross sectional area of the channel
The average velocity of the water
What is stream gradient ?
Water on a slope (which all channels have) will be influenced by gravity
That’s the energy in the system.
Gravity pulls the water downstream
The vertical distance that a channel falls between two points along its course is the gradient
Elevation changes of the vertical distance
What is stream velocity ?
The speed at which water flows through a stream
The quantity (volume) of water passing by a given point in a certain amount of time
What is hydraulic action ?
The erosion that occurs when the motion of water against a rock surface produces mechanical weathering
How are larger particles (bed load) transported in a stream ?
Moves by rolling, sliding, and/or saltating (hopping). Generally, bed load downstream will be smaller and more rounded than bed load upstream
What is the term for transported particles that stay close to the bed, but aren’t in contact with it; they bounce or jump ?
How is most of a stream's load transported and what material is it made of ?
Stream load is composed of dissolved or solution load, suspended load, and bed load
The dissolved load comes primarily from groundwater seepage into the stream
Ions in solution also come from the solution of materials that line the channel
What happens to sediment when the stream velocity decreases ?
A river will deposit a part of its load of sediment when either its velocity or its discharge decreases
What marks the edges of floodplain ?
What three conditions change stream discharge ?
Transition from a drought to a wet period
Times of heavier rainfall or snow melt
Where tributaries add water to the stream
What factors influence stream velocity ?
By the slope of the surrounding terrain, the depth of the stream, the width of the stream, and the roughness of the substrate or stream bottom
If the surrounding terrain is steep, then rain water and snow melt will have less time to soak into the ground and runoff will be greater
What is channel roughness ?
A measure of the resistivity offered by the material constituting stream channel margins to the flow of waterx
Describe a meandering channel
Series of smooth bends
Where is sediment deposited ? Eroded ?
Can be found anywhere in a water system, from high mountain streams, to rivers, lakes, deltas and floodplains
Describe a braided channel (include comments on water velocity)
Resembles pattern of braided hair - water repeatedly divides and reunites
Describe a floodplain
The flat area along a stream channel