Fluvial Landforms Flashcards
All 10 cards in this deck
How do interlocking spurs form?
In the upper course the river has little energy for lateral erosion, so it winds around areas of more resistant rock, leaving ridges of higher land that interlock like teeth.
What are the steps in the formation of a waterfall?
e.g. a river flowing over a band of hard rock onto softer rock- The softer rock downstream is eroded faster by hydraulic action and abrasion, leaving a step of hard rock.
- Water falls over the step, eroding a plunge pool below and undercutting the hard rock to leave an overhang.
- The unsupported overhang collapses and the waterfall retreats upstream.
How is a gorge formed?
By a waterfall retreating upstream over many years, leaving a narrow, steep-sided valley behind it.
Where do erosion and deposition happen on a meander?
Erosion on the outside bend, where flow is fastest and deepest, forming a river cliff; deposition on the inside bend, where flow is slow, forming a slip-off slope.
What are the steps in the formation of an ox-bow lake?
e.g. a large meander on a flood plain- Erosion on the outside bends narrows the neck of the meander.
- During a flood the river breaks through the neck and takes the shorter, straighter route.
- Deposition seals off the old bend, leaving an ox-bow lake.
True or false? Levées are only ever built by people.
False. Natural levées are raised banks formed when a river floods and deposits its coarsest load first, nearest the channel.
How is a flood plain formed?
Repeated flooding deposits layers of fine silt (alluvium) across the valley floor, and migrating meanders widen it by lateral erosion.
Why does deposition take place in a river's estuary?
The incoming tide slows the river's flow, so fine silt and mud are deposited, building mudflats and salt marsh exposed at low tide.
What evidence on an OS map shows that a river is in its lower course?
Widely spaced contours (flat flood plain), a wide meandering channel, ox-bow lakes, embankments, and land close to sea level.
Name two landforms of erosion found in the upper course of the River Tees.
High Force waterfall and the gorge downstream of it (also interlocking spurs and a V-shaped valley).