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River Studies 3: The 3 courses of a river The 3 courses of a river. Rivers have 3 main course: Lesson aims: The upper Over thecourse next few lessons we will learn about the different The middle course courses of the river. The lower course Source of river Upper Course Middle Course Lower Course V-Shaped valley with steep sides Large load (eg big rocks) Fast flowing water Lots of vertical erosion The upper course of the river Task: Look at the picture that comes up and write down everything Lots of “energy” Interlocking in the water Spurs you can see in it. Think about the shape, the Shallow water speed and the load. A typical upper course valley with , steep valley sides and active slope processes Characteristics Upper Course Depth Width Shallow narrow Speed Fast Middle Course Lower Course Straightness winding Load What do you think the land here could be used for by people? large Type of load angular Features Land Use V-Shaped Valleys, Interlocking Spurs, Waterfalls Land Use in the Upper course Gorge-walking Hill sheep farming Hydro-electric power (HEP) reservoirs Rock Climbing (No crop farming as the land is too steep, not many roads and communication links) Formation of a V-Shaped Valley This is VERY IMPORTANT as it comes up all the time! When doing this you must: Draw at least 3 diagrams Label the diagrams Have some text explaining what is happening Terms you need to know Vertical erosion Hydraulic action Freeze thaw action (Weathering) Mass movement Freeze Thaw When water gets into cracks in rocks and then freezes. This causes it to expand and then break the rocks apart. Mass-movement. This is when gravity pulls material down slopes. It causes rocks to fall into the river. Task part 1 Diagrams You are going to be given a textbook answer to the formation of a V-shaped valley. You must come up with the 3 diagrams that will help you to explain what is going on. To do this collect a mini white board. 2 minutes to read through the text. 5 minutes to come up with 3 diagrams. Quick test The force of the water weakens and 1. HYDRAULIC breaks up the rocks.ACTION 2.inSOLUTION The water the river dissolves the minerals3. inATTRITION the rocks As the pebbles carried by the river crash into 4. they ABRASION each other, become smaller and rounder The material carried in the river wears away the river bed Suspension Traction Solution Saltation Diagrams 1 2 3 Task part 2 labels Now you have the diagrams and the text The next thing you need is detailed labels. Using the paper you have been given in two’s write on all of the labels you can think of. Labels for a V-shaped valley. Valley start of with slightly sloped sides. The fast flowing river begins to erode the valley Processes such as abrasion/corrasion take place Mass movement begins to weaken the material at the sides of the valley. Vertical erosion takes place eroding the valley downward. Weathering (freeze thaw) weakens the valley sides. Hydraulic action takes place wearing down the rock. Eventually the material is weakened so much it falls into the river The fast flowing river transports much of the material A V-shaped valley is left with steep sides You also have to write some text The example you have in your jotter is a good one but it could be simplified. Read over it and try and turn it into 4 sentences. Interlocking spurs are formed when the relief of the land changes and therefore the river changes direction Formation of interlocking spurs: Interlocking spurs are formed exactly the same as a V-shaped valley. (so you would start with the same diagrams andalso text.) This may occur if the river hits a large rock or area of hard rock it can’t erode. Next Feature. Waterfalls Waterfall 1) Water flows over hard rock and then onto soft rock 2) Over time the soft rock is eroded 3) A waterfall is created Watch waterfall video Formation of a waterfall Waterfall Retreats upstream Hard rock Soft rock Undercutting The overhang The erodesprocess the Eventually Vertical erosion startsrock again softer collapses Forms plunge pool forming an overhang Steep sides ( gorge ) Eroded rock Waterfall Formation Water flows over areas of hard rock and onto soft rock Eroding the soft rock more quickly. Over time the hard rock sticks out over the soft rock. River Landscapes Standard Grade •The soft rock underneath is eroded further by the force of the water (hydraulic erosion). •This area is called the plunge pool. River Landscapes Standard Grade •In time the hard rock above the plunge pool collapses falling into the plunge pool •The pieces of hard rock help to erode the plunge pool further (corrasion) and are themselves eroded by attrition. •The waterfall continues to move upstream over time forming a gorge. UPSTREAM . . WATERFALL RETREATS . . OVERHANG UNDERCUT SOFT ROCK PLUNGE POOL Waterfall video again Middle course of a river. Key features: Everything is medium: The width is medium The depth is medium The speed is medium What doisyou land The type of load smallthink and medium rounded . (nobe bigthis rocks) userocks could time? Land is quite flat. Although you may get slight hills at edges. It has meanders (bends in the river) Land use Settlement - towns built on flat land near river bridging point. Routes along the valley often meet at bridges. Farming - on flat valley floor where soils and weather are better. Tourism - farmers provide simple accommodation (B&B, caravan, camping) to supplement their income. Middle course location provides tourists with access to both uplands and lowlands. Fishing - good source of income for landowners, especially in salmon rivers. Formation of a meander. Important points. Erosion occurs on the OUTSIDE of bends. Deposition occurs on the INSIDE of bends. Lesson starter: Take the title Formation of a meander. Take half a page in your jotter and draw a river along it. Then swap it with the person next to you and they have to draw on the areas of erosion and deposition. Formation of a meander. It’s the same as all other features: Diagrams Labels Text I am going to give you the text. Your task it to draw the diagrams. Collect a whiteboard and pen. For each of the statements you see you must draw one picture. Diagram sheet 1) As a river moves down stream is does not flow straight, it curves slightly. This is because it will follow the easiest route and due to it flowing faster in some paces than others. 2) The river flows faster on the outside of these curves and slower on the inside. 2) Due to this we get erosion on the outside of the curves and deposition on the inside of them. 3) Over time this erosion and deposition causes the river to bend. Diagram sheet 4) The erosion continues and the curve becomes bigger. The ares of erosion and deposition become bigger too. 5) Eventually large meanders are left in the river. They continue to grow as the erosion and deposition get greater. River bend Fastest current slowest current Bank will collapse Small river cliff Outer bank Is undercut Deepest part of the river Slip off slope ( river beach ) Deposition of Sand and shingle Quick quiz: part 1 Erosion Or Transportation Get a whiteboard and pen. On one side write erosion. On the other side write transportation. Corrasion Corrasion – rivers use the stones and pebbles they carry (its load) to smash against the sides and bottomof the river. Hydraulic action Hydraulic Action - the sheer force of the water causes the outer banks of the river to break up and collapse. It is most effective in times of flood. Traction Traction – the largest boulders roll along the river bed at times of flood when the energy level in the river is high. Attrition Attrition - the stones and pebbles the river carries (its load) rub against each other. Over time the size of this load becomes smaller and more rounded. Saltation Saltation – larger particles bounce along the river bed. These particles can cause other larger particles to become dislodged Quick quiz part 2 You are going to see a statement. You must draw a picture that goes along with it. V-shaped valley 1. The valley starts of with gently sloping sides. 2. Fast flowing water begins to erode the valley vertically. 3. Processes such as abrasion take place as the rocks in the river are transported. V-shaped valley 1. Hydraulic action makes the valley deeper. 2. Mass movement and freeze thaw action make the sides of the valley weak. 3. Vertical erosion takes place. Waterfall 1. Water flows over hard rock then onto soft rock. The soft rock is eroded more quickly. 2. Overtime an overhand and plunge pool are formed. Waterfall 1. The rocks in the plunge pool as well as vertical erosion cause the soft rock to erode backwards. 2. The overhang becomes too heavy and eventually falls. Homework: Tuesday 27/03/2012 Explain the formation of a v-shaped valley and a waterfall. You may use diagrams to in your answer. 8 KU Lesson starter. With the person beside you each take a number 1 or 2. Number 2: What are the Number 1: 2: Explain how a characteristics of the rivers You will take turns the v-shaped meander Waterfall valley isexplaining formed. is formed. featuresmiddle of a river course? of river course to ach other. The lower course of a river You are going to see a picture of the lower course of a river. Using this and your new knowledge of rivers you must write down what you think the characteristics of the river will be. Include: Its width Depth Speed Load (amount and type) The land around it. Features Land use • • • • • • • Width Depth Speed Load (amount and type) The land around it. Features Land use Lower Course of the river features: Its width: Very wide Depth Very deep Speed Slow Load (amount and type) Large load (lots of it), but small rocks, sands ad silt. The land around it. Large flat flood plain Features Ox-bow lake. Delta Mouth of river. Land use Large settlements. Transport routes. Industry. Ports for trade. • Mystery feature: • How were these features formed on the landscape? The formation of an Ox-bow lake. Occasions