Rivers Flashcards
(35 cards)
Three types of rocks
Igneous
Sedimentary
Metamorphic
Method of formation for igneous
When rocks become hot and turn into liquid which is molten rock. When they cool down they turn into igneous rock.
Examples in the UK of igneous rock
Granite
Gabbro
Basalt
Method of formation for sedimentary rocks
Rocks are chipped away from side of mountains which get carried in rivers down to the sea. In the sea they fall to the sea floor. Layers build on the sea floor. They get squashed together with weight.
Examples in the UK of sedimentary rocks
Limestone
Sandstone
Chalk
Conglomerate
Method of format for metamorphic rock
When rocks are subjected to high hear, high pressure
Examples in the UK of metamorphic rocks
Gneiss
Slate
Marble
What is mechanical weathering (physical)
Specifically freeze-thaw weathering, occurs when water enters cracks in rock, freezes and expands, causing the rock to break apart over repeated cycles
What is chemical weathering
Breaks down rocks through chemical reactions, often involving water, acids, or gases, changing the rock’s mineral composition
Carbonation in chemical weathering
When acidic rain water decomposes alkaline rocks such as limestone
Oxidation in chemical weathering
The breakdown of rocks by oxygen and water
Biological weathering
When plant seeds grow in a crack in the rock their roots put pressure on the sides of the crack.
As the roots grow the rock is forced apart until it breaks.
Can also be caused by burrowing animals
Sliding - mass movement
where a section of land falls down a slope and dislodges other material on its way down
Slumping - mass movement
Slumping is a type of mass movement where saturated soil or rock slides down a curved surface, often after heavy rain, causing the land to slump in a rotational manner.
Erosion - abrasion
This is the scraping away of the bed and banks by material transported by the river
Erosion - hydraulic action
as waves of river currents crash against rock surfaces, they trap and compress air in cracks and crevices. This pressure weakens the rock structure. When the water retreats, the pressure is suddenly released, causing small pieces of rock to break off. Over time, this repeated process widens cracks and contributes to the breakdown of cliffs and riverbanks.
Erosion - corrosion (solution)
Chemicals in the river dissolve minerals in the rocks in the bed and banks, carrying them away in solution.
Transport - traction
Large boulders and pebbles are rolled along the river bed.
Transport - saltation
Small stones, pebble and slit bounces along the river bed.
Transport - suspension
Fine material such as clay and sediment is carried by the river
Transport - solution
Dissolved minerals and carried by the river
Deposition
The dropping of the bed load due to a decrease in the river velocity (speed) and/or weight of the load.
Width and depth of river - the upper course
Narrow and shallow
Width and depth of river - middle course
Fairly wide and fairly deep
