PowerPoint Presentation: LANDFORMS along RIVERS PowerPoint Presentation: Weathering is the weakening , breaking up, rotting and disintegration of rocks Weathering is followed by erosion which is a process of scraping, scratching, and grinding of the surface rock. All land forms are affected by the cycle of erosion Weathering and Erosion PowerPoint Presentation: Natural agents of weathering and erosion: Action of running water Action of moving ice Action of wind Action of waves These agents derive their energy indirectly from the sun and work together with the force of gravity PowerPoint Presentation: Aggradations or deposition The result of weathering ,erosion and transportation is known as denudation or degradation Aggradations or deposition means filling up of depression on the earth’s surface. Each agent has its erosive as well as depositional role in changing the landscape slowly, but surely. PowerPoint Presentation: Both surface water and ground water act as agents of erosion. Depending on the terrain it flows, it performs three functions- erosion, transportation and deposition. The course of a river may be divided into- lower, middle and upper course Running Water PowerPoint Presentation: Rivers A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including stream, creek, brook, rivulet, and tributary. PowerPoint Presentation: River course…...... PowerPoint Presentation: The river erodes a v-shaped valley, the path is fairly straight and it flows downhill steeply . Valleys Upper course of the river forms……… : Upper course of the river forms……… V-shaped valleys Rapids Waterfalls Gorges PowerPoint Presentation: Rapids are stretches of fast-flowing water tumbling over a rocky-shallow riverbed. Different resistance among rocks cause rapids. They are formed when the water goes from one hard rock that resists the water's erosion to a softer rock that is easily eroded. Rapids PowerPoint Presentation: Waterfalls are found in the upper course of a river. They usually occur where a band of hard rock lies next to soft rock. Waterfalls may often start as rapids. As the river passes over the hard rock, the soft rock below is eroded (worn away) more quickly than the hard rock leaving the hard rock elevated above the stream bed below. Waterfalls PowerPoint Presentation: In arid areas of little rainfall the, valley sides fail to be widened and the river cuts only in its floor. Gorges are also developed in highly porous and permeable rocks like limestone where the rain water seeps into the ground leaving little scope for the valley to widen at the top. Gorges PowerPoint Presentation: Difference – Rapids , Waterfall, Gorge PowerPoint Presentation: Middle Course of the river forms…… Meanders Ox bow lakes Flood plains River Cliff Slip off slope PowerPoint Presentation: Meander A meander is a bend in a river which will eventually erode to form an ox-bow lake which is a thing in a river! A meander is formed around a ox-bow lake. PowerPoint Presentation: The sediments removed from the outer bank are carried forward by the flow of the water to the inner bank and deposited. With successive deposition, the water at the inner bank gets shallower, resulting in a slip-off slope. Slip-off slope PowerPoint Presentation: River cliff A steep-sided river bank caused by the undercutting of the concave / outer bank over a period of time. The outer bank gets eroded by the force and velocity of the fast moving water, resulting in the formation of a river cliff. PowerPoint Presentation: The volume of water in a river is at its greatest in the lower course. This is due to the contribution of water from tributaries. The river channel is deep and wide and the land around the river is flat. Energy in the river is at its lowest and deposition occurs. . Lower course of the river forms…. Flood Plains Ox-bow Lakes Levees Delta Estuary Mouth PowerPoint Presentation: When a river breaks its banks and floods, it leaves behind layers of rock and mud. These gradually build up to create the floor of the flood plain. Floodplains generally contain unconsolidated sediments , such as accumulations of sand, gravel, loam, silt, and/or clay. Flood plains PowerPoint Presentation: A levee is a type of dam that runs along the banks of a river or canal. Levees reinforce the banks and help prevent flooding.. A natural levee is formed when sediment settles on the river bank, raising the level of the land around the river Levees PowerPoint Presentation: OXBOW LAKES An oxbow is a crescent-shaped lake lying alongside a winding river. The oxbow lake is created over time as erosion and deposits of soil change the river's course . PowerPoint Presentation: Meander scar Meander scar - feature left behind when the water in an ox-bow lake dries up or formed by the remnants of a meandering water channel. PowerPoint Presentation: River mouth A river mouth or stream mouth is a part of a stream where it flows into another stream, river , lake, reservoir, sea, or ocean. PowerPoint Presentation: River Delta Deltas are deposits of alluvial (soil or sediment) material at the mouth of streams or rivers. They are made up of both land sediments and biological remains which are deposited when the river enters the sea, lakes or lagoons. They are called deltas because their shape resembled that of the letter “Delta” Δ in the Greek alphabet. PowerPoint Presentation: An estuary is a body of water formed where freshwater from rivers and streams flows into the ocean, mixing with the sea water. Most modern-day estuaries were formed by the flooding of river-eroded or glacially scoured valleys when sea level began to rise about 10,000-12,000 years ago The Estuary PowerPoint Presentation: Have a Nice Day……..