geography:
(the most hated subject!)

hydrologic cycle
the continuous movement of water frm the air to the eqrth's surface and back frm the earth's surface to the air.

• water will drop down to the earth's surface as rain
• some of the water will then seep through the ground which are absorbed by plants, while the rest of the water flows as surface runoff ino rivers/lakes/seas
• the water will be evaporated into water vapour due to the Sun's heat
• plants will also transpire to procuse water vapour that is released into the air
• warm air cools as it rises, so the water vapour will condense to form water droplets. small water droplets will combine together to form bigger water droplets and when millions of water droplets gather together, clouds will be formed
• when the clouds are heavy enough, the water droplets will fall to earth as rain and this cycle continues...

upper course

• the river channel is shallow and narrow
• the gradient is steep as little amt of water flows in the river
• as there is a high energy level in the river, vertical erosion takes place, causing the channel to deepen. thus, a v-shaped valley is formed

middle course

• the river channel is wider
• the gradient is not as steep as the upper course
• more volume of water is flowing
• as there is a medium energy level in the river, vertical and lateral erosion take place, causing the river to deepen and widen. thus a u-shaped valley is formed

lower course

• the river channel is wider that the middle course
• the gradient is very gentle and there is a high amt of water flowing
• as the is a low energy level, lateral erosion takes palce, causing the river to widen. thus a broad, flat-floored valley is formed

factors affecting the speed of river

• GRADIENT OF CHANNEL--the steeper the channel, the higher the speed. the more gentle the channel, the lower the speed
• WETTED PERIMETER--the bigger the area of wetted perimeter, the higher the friction, thus speed is reduced. the smaller the area of wetted perimeter, the lesser the friction, thus speed is increased
• ROUGHNESS OF CHANNEL--the rougher the surface, the higher the friction, thus speed is reduced. the smoother the surface, the lesser the friction, this speed is increased

factors affecting the volume of river

• PERMEABILITY OF ROCKS--when there is a high permeability of rocks, there is high infiltration and less surface runoff, thus volume is reduced. when there is low permeability of rocks, there is low infiltration and high surface runoff, thus volume is increased.
• CLIMATE--places with high rainfall will have a larger volume of water. places with low rainfall will have a lower volume of water.
• PRESENCE OF VEGETATION--when vegetation is abundant, there is high interception and high infiltration, so there is low surface runoff and therefore less volume of water. when vegetation is sparse, there is low interception and low infiltration, so there is more surface runoff and therefore more volume of water.
• SIZE OF DRAINAGE BASIN--when there is a bigger area of drainage basin, it means that there is more land for the rain to fall on, and thus there is more volume fo water. when there is a smaller area of draingae basin, it means that there is less land for the rain to fall on, and thus there is less volume of water.

erosion

• VERTICAL EROSION:occurs when rocks & other materials are removed frm the river bed and banks, causing the channel to deepen.
• LATERAL EROSION:occurs when the rocks & other materials are worn away frm the river bed, causing the channel to widen.

4 types of erosion:

• HYDRAULIC ACTION: the process by which rocks and other materials are broken and dragged along the river bed and banks by the force of running water. when the water is fast-moving, the water will enter the cracks of rocks and exert a force that breaks and dislodges them
• CORRASION: the dragging of rocks and other materials on the river banks and bed. the grinding action of the rocks causes the river channel to deepen and widen. most effective during floods.
• ATTRATION: the process by which rocks collide against each other, causing the big rocks to become small rocks and smoothing the rocks' rough edges.
• SOLUTION: the process by which water reacts chemically with calcium bicarbonate in rocks and dissolve them

formation of waterfall

• EROSION OF ROCKS OF DIFFERENT RESISTANCE: the water flows on different resistance of rocks. the less resistant rocks are eroded more quickly than the more resistant rocks. overtime, the river plunges frm a great height with tremendous force and a waterfall is formed. when the less resistant rocks are eroded even more, a plungepool will be formed due to the swirling action of water from the waterfall.
• FAULTING: a river flows across a land before displacement. after displacement of rocks along a fault, a waterfall is formed and repeated pounding of the rocks will form a plungepool.

trasportation

• process by which materials are carried/transported downstream by the running water

4 types of transportation:

• TRACTION:process by which large materials(boulders/gravel/pebbles) are dragged along the rIver bed and banks
• SALTATION: process by which smaller materials(coarse sand) are lifted up and dropped again repeatedly
• SUSPENSION: process by which fine particles(clay/silt/sand) are carried along the river without touching the river bed
• SOLUTION: process by which dissolved materials are carried along the river

deposition

• occurs when the river does not have enough energy to either transport/erode the materials

factors:

• when there is a low precipitation
• when the speed of the river is low
• when there is an obstruction of aquatic plants/protuding bed rocks
• when there is a sudden increase in load or when incidents occur
• when the river flows in the shallower side of the channel, increasing friction and slows down the river

gorges

• when the river flows through a channel with resistant rocks along its sides, the river can only be eroded vertically. overtime, a narrow, steep-sided valley known as a gorge is formed

floodplains/levèes

• when there is heavy rain, the river overflows its banks. this causes both sides of the banks to flood. overtime, the water recedes and materials will be deposited on the bed and banks.
• coarse materials will be deposited nearer to the banks as they are heavy and thus levèes arre formed
• fine materials will be deposited further frm the banks as they are lighter and thus floodplains are formed

ok,done! this is cool lah:D i just noticed this. haha! so dumb. aniwaes, gg to gym later at 8 and i hav to do more literature study and recap all geog notes. urgh!