river test 1 Flashcards
what is traction
Boulders roll along the river bed because there isn’t a enough energy
what is surface run off
Water travels quickly on top of the soil back to the river
Rain, hail sleet snow fog
precipitation
Water helps to create a sliding plane so the soil moves downhill as a single slab
landslide
The global hydrological cycle
s a closed system because it has no extrenal inputs
The drainage basin hydrological
is an open system because it has external inputs.
Dranagine basin
total area of land drainage by a river and its tributaries
Floodplain
type of deposition the low lying wide floor
what is vertical erosion powerpoint
- downwards erosion in upper course of a stream
- load consist of large boulders peoples and sand
- mostly rolled along stream bed
- potholing is common
- so stream bed eroded most
what is lateral erosion powerpoint
- is sideways erosion in middle/lower course of a river
- river meanders and helicoidal flow common
- causes undercutting of river banks and slumping
- so sides of channel eroded more than bed
what does the watershed mark
dividing line between neighbouring drainage basin
how does channel density effect run off
high channel network density rapid run off
how does land use effect run off
cleared and paved surfaces = rapid un off
what is a hydrograph
a graph showing a rivers rate of discharge over time past a septic point
how is a v shaped valley formed
river has been cut down by vertical erosion and mass movement of material down the valley sides
how is interlocking spur formed
formed as river swings from side to side. the river cuts down between the spur rather than eroding them away
what happens when a waterfall retreats upstream
gorge
How are meanders formed
erosion and deposition
- lateral erison us more significant here because river is close to sea
- on the outside gf the bend ;lateral erosion forms a river cliff. on the inside of the bend the water flow is slower and deposition forms a slip off slope.
how are oxbow lakes fromed
the neck of the land within menders narrow iover time on the outside bend. deposition will occur to cut off the orginal meander, leavubgf a oxbow lake
chemical weathering
decomposition of rocks such as limestone dissolve slowly due to slightly acid rainfall
biological weathering
Burrowing - tree roots grow down into the rock and exert a physical force pushing apart the rock. Exploits any weakness in the rock
physical weathering
freeze thaw
Water enters cracks in the rock.
When temperatures drop, the water freezes and expands causing the crack to widen.
The ice melts and water makes its way deeper into the cracks.
The process repeats itself until the rock splits entirely.
what is a source
a rivers origin
what is confluence
where 2 rivers join
what is the mouth
where river flows into the sea
where does a waterfall occur on a drangainge basin
source and tributary
where does a oxbow lake occur in drainage basin
confluence and tributary
what is a tributary
a river or stream flowing into a larger river or lake
how is a waterfall formed
Waterfalls occur where a band of hard rock overlies a softer rock (1). This softer rock is eroded more quickly than the harder rock (1) and, over time, this creates an overhang of hard rock (1). This overhang is unsupported so it collapses (1).
