Rivers Flashcards
River
A large natural stream of fresh water flowing in a channel to the sea, a lake, or another river.
Upper Course of a River
Near to the source in a mountainous area and cuts downwards as it erodes the landscape.
Features of Upper Course of a River
Narrow V-Shaped Valley
Interlocking Spurs
Riverbed
Waterfalls
River Processes
Erosion - the wearing away of the land and the stones carried in the river.
Transportation - the movement of rocks, sand, and silt by the river.
Deposition - the dumping of rocks, sand and silt wherever the river slows down.
Erosion
The wearing away of the land and the stones carried in the river.
Four Types of Erosion
Solution - river water dissolves minerals like salt and carries them away.
Hydraulic Action - where the river forces air and water into cracks in the rocks eventually snapping bits off.
Abrasion - Small bits of rocks in the water rub along the river banks/bed and wear it away like sandpaper.
Attrition - rocks in the water smash into each other, wearing each other down and rounding them off and form pebbles.
Transportation
The movement of rocks, sand, and silt by the river.
Four Types of Transportation
Traction - the geologic process by which a current transports larger, heavier, rocks by rolling or sliding them along the bottom of the river bed.
Saltation - small stones which the water cannot lift, bounce off each other and are carried forward for short distances by the water above the river bed.
Suspension - if particles are small enough the river can lift them and carry them long distances.
Solution - when the river dissolves minerals from the rocks they are carried in the water itself.
Deposition
The dumping of rocks, sand and silt wherever the river slows down.
When a river slows down and the inside bends or when it meets deeper water - such as a lake - it loses energy and cannot carry so much. This causes it to drop some of its load.
V-Shaped Valley Formation
Rivers begin high up in the mountains so they flow quickly downhill eroding the
landscape vertically.
The river cuts a deep notch down into the landscape using hydraulic action, when the sheer force of the water gets into small cracks and breaks down the sides of the river valley.Corrosion (abrasion)also occurs which is when the river bed and banks are eroded by the load hitting against them. Another type of erosion that happens iscorrosion (solution), when the river water dissolves minerals from the rocks and washes them away.
As the river erodes downwards the sides of the valley are exposed tofreeze-thaw
weatheringwhich loosens the rocks (some of which will fall into the river) and
steepens the valley sides.
The rocks which have fallen into the river assist the process of corrasion and this
leads to further erosion.
The river transports the rocks downstream and the channel becomes wider and
deeper creating aV-shaped valleybetweeninterlocking spurs.
Interlocking (Overlapping) Spurs
One of any number of projecting ridges that extend alternately from the opposite sides of the wall of a young, V-shaped valley down which a river with a winding course flows.
