1.3 River Landscapes Flashcards
Define Ribbon Lake
Large, narrow lake, occupying a v-shaped valley
Define V-Shaped Valley
A valley formed where a glacier used to be
Define Meltwater
River which form when glaciers melt
Define Moraine
A mass of rocks/ sediment carried and deposited by a glacier
Define Hydraulic Action
Water is forced into cracks in the rock and air is forced out explosively, breaking off pieces of the banks
Define Abrasion
This is when pebbles grind along a rock platform, much like sandpaper. Over time the rock becomes smooth.
Define Attrition
This is when rocks that the sea is carrying knock against each other. They break apart to become smaller and more rounded.
Define Corrosion
When acid rain causes chemical weathering
Define Chemical Weathering
Acids in seawater slowly dissolve rocks
Define Biological Weathering
Roots of growing plants and burrowing animals or nesting birds can cause rocks to weather
Define Mechanical Weathering
Caused by repeated freezing and thawing of water in a crack or hole in the rock.
What is deposition?
When sediment, usually carried by waves is laid down or deposited
When does deposition occur?
When their is not enough energy to carry sediment any further
Define Source
The beginning of the river
Define Confluence
Where 2 rivers meet
Define Watershed
An area of highland between two drainage basins
Define Mouth
Where a river flows into a lake or the sea
Define Tributary
A small river/ stream that flows into a larger river
Drainage Basin
The area drained by a river and its tributaries
How does the channels shape change through the course of a river?
The channel becomes larger the further down the river it is.
How does the gradient change through a river course?
Decreases. The gradient starts very steep but the steepness evens out as it reaches the lower course.
How does the discharge change through a river course?
It increases as it goes down the river.
How does the velocity change through a river course?
It increases due to less friction.
How does the sediment size change through a river course?
The sediments erode one another getting smaller through the river course.
Describe how a plunge-pool forms
When hard rockets on top of soft rock, the waves erode at the soft rock creating an undercut. Hydraulic action and abrasion then deepen this into a plunge-pool.
What is likely to occur if you have an overhang?
The overhang is likely to collapse