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Transcript
Land Form Patterns Introductory Lesson Topography is a general term referring to the surface features of the earth like, hills, mountains, valleys, plains, plateaus and other relief features. Your book defines it as " the natural and human features of the earth's surface". The map to the right shows the topographical features of South America. Hills are typically defined as areas of upward relief less than 300 600M. Mountains are defined as areas of upward relief greater than 300600M. It is important to note that books differ on the actual relief required for a hill to be a mountain but the difference is one of the degree of elevation. See if you can find a contradiction in your own book!! Plains are areas of flat land with very little relief. They are found at low elevations often along coasts and in the center of continents. Plateaus are areas of flat land with little relief. They occur at high elevations and are associated with mountains. Like hills and mountains plains and plateaus differ based on elevation. Assigned Readings "Structures on Earth's Surface" pp 6-7 in your text book. Assigned Activities Open, print and complete "Active Learning Lesson #1". Test Yourself 1. Observing the elevation profile below which province would be least likely to have extensive plains. 2. Imagine you flew from the west coast of South America to the east coast and you flew right along the equator. What land forms would you fly over? 3. ___?___ is a general term referring to the lye of the land. 4. Hills are typically defined as areas of upward relief less than ___?___m. 5. Mountains are defined as areas of upward relief greater than ___?___m. 6. Plains are areas of flat land with very little relief. They are found at ___?___ elevations often along coasts and in the center of continents. 7. Plateaus are areas of flat land with little relief. They occur at ___?___ elevations and are associated with mountains. Test Yourself Answers 1. Observing the elevation profile below which province would be least likely to have extensive plains. With its abundance of mountains British Columbia seems like the least likely place to have plains which occur at low latitudes. Having said that, this profile is one cross section of British Columbia and there may be other latitudes where there are plains especially along the coast. 2. Imagine you flew from the west coast of South America to the east coast and you flew right along the equator. What land forms would you fly over? You would fly over Plateaus, Mountains and then Plains. 3. Topography: is a general term referring to the lye of the land. 4. Hills are typically defined as areas of upward relief less than 300600m. 5. Mountains are defined as areas of upward relief greater than 300600m. 6. Plains are areas of flat land with very little relief. They are found at lower elevations often along coasts and in the center of continents. 7. Plateaus are areas of flat land with little relief. They occur at higher elevations and are associated with mountains. Land Form Patterns Have a look at the map below to see where the world's major mountain ranges lie. Is there a pattern to these mountain ranges? You may be able to see other patterns. Later in this section we will explain the reason for these patterns. Can you identify the "Rockies in North America", the "Andes in South America", and the "Himalayas in Asia" on the map? Most mountains and high elevations are located on coasts of continents. Large mountain ranges occur along the west coast of North and South America. This is quite evident in the relief image. What is not evident is that major mountain ranges coincide with "tectonic plate boundaries". You may or may not be familiar with tectonic plates. That concept will be covered Later in this section. In any event by clicking on the map below you can see that the plate boundaries coincide with the major world mountain ranges. Test Yourself 1. Which topographical feature do you find along the west coast of North and South America? 2. When a continent contains a mountain range, on which part of the continent is it usually found? 3. The boundaries between tectonic plates often coincide with which type of topographical feature? Earth's Interior The earth's interior is neither all solid nor is it all molten. There are layers with a different density, thickness and composition. Furthermore the earth's crust is not one continuous layer. It is broken into many sections known as plates. Some plates are quite small while others are quite large. They all float and move on top of the molten asthenosphere. When they push together and when they pull apart they create "tectonic forces". It is interesting to note; without this liquid layer called the asthenosphere we would not experience earthquakes or volcanoes. Inner Core: The deepest part of the earth (1512 miles deep) is a solid that contains both iron and nickel. It is because of this that the centre of the earth is a magnet, a compass. It generates a magnetic field that protects the earth from flying out of orbit. Outer Core: Outside of the inner core lays the outer core (1419 miles deep). This is much like the inner core with the exception that it is a liquid that contains sulphur and oxygen (which lowers the melting point). Mantle: Occupying 1789 miles of the earth is the magma (iron and magnesium) that makes up the mantle. It is mostly solid except the outer 200-300 Km which is extremely hot and goopy; very plasticlike. This outermost liquid layer of the mantle is referred to as the asthenosphere. Mohorovicic Discontinuity: Boundary between the mantle (asthenosphere) and the Lithosphere. Lithosphere (crust): This is the top layer of the earth, which is basically hardened mantle (magma). It contains two segments, the oceanic and continental crusts. Note: this is the same crust, it just depends how thick it is to determine if it is part of the Oceanic or Continental Crust. For instance, if you drained all of the water from earth, then there would be one, giant Continental Crust. Likewise, if you flooded everything, you'd have one, giant Oceanic Crust. Assigned Readings "The Structure of Earth" p. 4-6 Assigned Activities Complete question #3 both part "a" and "b". Share your answer with the class. Plate Tectonics Explaining Compressional and Tensional tectonic Forces: Tectonic plates move or float on top of the asthenosphere (orange in the figure). However they do not float freely. The plates are forced in specific directions by the flow of magma beneath. Just like a boat caught in a current plates move with the flow of magma. The magma forms convectional currents. The magma closer to the core heats and then rises towards the surface as its density decreases. Once the rising magma reaches the lithosphere it moves in opposite directions. Compressional Forces occur where two tectonic plates come together. They compress against each other. Subduction Zones sometimes occur where compressional forces result from two plates colliding. Tensional Forces occur where two tectonic plates are pushed apart. The tension is created as the plates move away from each other. Ridge Zones sometimes occur where two plates move apart. The magma rises between the plates and forms a ridge. Reading a Tectonic Plates Map The map below is similar to the one on p. 12 of your text. Notice that subduction zones occur where the tectonic plates are moving towards each other while Ridge zones occur where the plates are moving apart. Notice that the Americas (North American Plate and South American Plate) are moving away from Europe and Africa (Eurasian Plate and African Plate. The Developer Alfred Wegener was one of the first to propose the theory of continental drift. While pondering the similarities between the coastlines of South America and Africa, Wegener came up with an idea: What if the continents were once all connected and just drifted over the years? It is this German man to whom we credit with the proposal of the theory of Continental Drift. The Evidence Ferns and Reptiles in many different continents Glaciers that were then tropical forests Same types of rocks on continents close to each other (yet separated by an ocean) The coastlines of Africa and South America The Flaw in Wegener's Theory However, there was one major flaw in Wegener's theory of continental plates. He thought that each of the continents were a separate plate--they were just drifting on a never-changing ocean. The Canadian Correction J. Tuzo Wilson was the 1960’s Canadian scientist who resurrected Wegner’s theory after years of disbelief by the science community. Today, we know that that's false, thanks to the discovery of crustal plates. The plates of the earth are not composed of just land; they're composed of ocean, too. In some cases, the plates are just land, in others they're just ocean, and, in still other cases, they consist of land and ocean. They each have different boundaries and move in all different directions. Continental Drift It refers to the movement of the more than 20 plates (9 major) due to convergent, divergent, and transform boundaries. The continents drift at a rate of 2 inches a year, or, as fast as a fingernail grows. It is believed to have started 200 million years ago. The original single continent was named Pangaea and the original ocean that surrounded the land was called Panthalasa. Figure1.8 on p. 10 of your book shows the process of the continents moving apart. View the animation above to see an approximation of how continental drift might have occurred Assigned Readings page 10-12 of your book Test yourself 1. In the figure above which letter is located at a ridge zone. 2. In the figure above which letter is located at a subduction zone. 3. In the figure above which letter is located where some of the earth's crust is melting back into magma? 4. In the figure above which letter is located at a point where a volcano might occur? 5. In the figure above what color is the asthenosphere. 6. In the figure above which letter is located at a point where compressional forces might occur? 7. In the figure above which letter is located at a point where tensional forces might occur? 8. In the figure above which letter is located at a point where new crust is forming? 9. When you read about Wegener and the theory of continental drift you saw the terms converging plates. Do you think the border between converging plates coincides with any term we have used this lesson? 10.When you read about Wegener and the theory of continental drift you saw the terms diverging plates. Do you think the border between diverging plates coincides with any term we have used this lesson? Plate Tectonics Lab Major Mountain ranges tend to coincide with subduction zones at the boundaries between two converging plates. The tremendous compressional forces literally fold the thin crust in to mountains. Remember this occurs over millions of years. Volcanoes can occur at subduction zones or at ridge zones. At subduction zones the compressional forces sometimes leave a crack in the crust that allows the magma to reach the surface. At ridge zones the plates are moving apart which allows magma to reach the surface from the asthenosphere. Because of the excessive number of active volcanoes on the coast around the pacific ocean it is known as the Pacific Ring of Fire. Earthquakes often occur at transform zones where the plates are moving beside each other instead of toward or away from each other. Look Closely at figure 1.10 on page 12 and you can see transform zones where the plates are moving side by side. Notice that subduction zones occur where the tectonic plates are moving towards each other while Ridge zones occur where the plates are moving apart and transform zones occur where plates are moving side by side. Notice that the Americas (North American Plate and South American Plate) are moving away from Europe and Africa (Eurasian Plate and African Plate. Assigned Activities Get an atlas and some coloured pencil leads. Click on "Tectonic Plates Lab" open it, print it and complete it. Folded Mountains Most Major Mountain ranges were formed by folding. The collision of continental plates causes the thin crust (lithosphere) to bend. For example the Appalachian mountains and the atlas mountains were formed by folding when North America and Africa collided 400 million years ago. All rock that is put under extreme pressure for long periods of time (thousands or millions of years) will fold like clay. Folding is a process in which the Earth's plates are pushed together in a roller coaster like series of high points and low points. Folding bends many layers of rocks without breaking them. The peaks are known as anticlines while the valleys are known as synclines. Test yourself 1. 2. 3. 4. 5. 6. What type of tectonic force is required to create folded mountains? What name is given to the peaks created in folded mountains? What term is given to the valleys created in folded mountains? Are many of the worlds mountains formed by folding? How long does it take for folded mountains to form? At which type of tectonic zone would you find folded mountains? (ridge, transform or subduction) Tectonic Faults Fault lines are great cracks in the crust. Mountains Formed by Normal Faults Normal Faults are caused by tensional forces. When the land moves apart at a fault line one plate drops down lower that the other. Mountains Formed by Reverse Faults Reverse faults are caused by compressional forces where plates move together at the fault. The land that rises above can form a mountain. Fault Block Mountains Fault Block Mountains sometimes form when many layers of the Earth's crust are moved vertically upward between two parallel fault lines. Vertical force is caused by the earth's internal pressure. The mountains that are formed in this way are called fault-block mountains. The Sierra Nevada mountains in California and Nevada, and the Grand Teton range of Wyoming are examples of fault-block mountains. Overthrust Faults Overthrust Faults are caused by compressional forces where plates move together at the fault. They are a class of reverse faults that have had folding occur before the faultformed. Assigned Readings "Mountains Formed by Volcanoes" on page 14 of your text. Volcanic Mountains Volcano is an opening in the earth's crust through which magma, gasses, and ash erupt. The shape of the volcano depends on the thickness of lava. Most volcanoes occur on plate boundaries. Three Types of Volcanoes Ash and Cinder cones are the simplest type of volcano. They are built from particles and blobs of congealed lava ejected from a single vent. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as cinders around the vent to form a circular or oval cone. Most cinder cones have a bowl-shaped crater at the summit and rarely rise more than a thousand feet or so above their surroundings. Cinder cones are numerous in western North America as well as throughout other volcanic terrains of the world. They are very explosive because the lava is very thick and slow flowing. It blocks the vent causing pressure to build up to high levels before it finally blows. Shield volcanoes built almost entirely of fluid lava flows. Flow after flow pours out in all directions from a central summit vent, or group of vents, building a broad, gently sloping cone of flat, domical shape, with a profile much like that of a warrior's shield. They are built up slowly by the accretion of thousands of highly fluid lava flows called basalt lava that spread widely over great distances, and then cool as thin, gently dipping sheets. These are the least explosive because the lava is so thin and fluid that it does not block the vent and prevents pressure build up. Composite volcanoes have a conduit system through which magma, from a reservoir deep in the earth's crust, rises to the surface. The volcano is built up by the accumulation of material erupted through the conduit and increases in size as lava, cinders, ash, etc., are added to its slopes. The lava varies causing it to be explosive one time while the next time it can be gentle flowing. Assigned Readings "Mountains formed by volcanoes" on page 14 of your book. Assigned Activities Complete Questions #14 and 15 on p.16 of your text. Share your answers with the class. Test yourself 1. Which type of volcano is most explosive? 2. Which type of volcano is least explosive? 3. Which type of volcano is explosive at times and slow flowing lava at times? 4. Which type of volcano has the thickest lava? 5. Which type of volcano has the thinnest, most liquid lava? 6. Which type of volcano often has side vents? 7. Which type of volcano has the gentlest slope? 8. Which type of volcano is steepest? Ash & Cinder 9. What term is given to the opening of a volcano? 10.Liquid, fluid, melted rock below the earth's surface is known as: 11.Liquid, fluid, melted rock that reaches the earth's surface is known as: Answers 1. Which type of volcano is most explosive? Ash & Cinder 2. Which type of volcano is least explosive? Shield 3. Which type of volcano is explosive at times and slow flowing lava at times? Composite 4. Which type of volcano has the thickest lava? Ash & Cinder 5. Which type of volcano has the thinnest, most liquid lava? Shield 6. Which type of volcano often has side vents? Composite 7. Which type of volcano has the gentlest slope? Shield 8. Which type of volcano is steepest? Ash & Cinder 9. What term is given to the opening of a volcano? Crater 10.Liquid, fluid, melted rock below the earth's surface is known as: Magma 11.Liquid, fluid, melted rock that reaches the earth's surface is known as: Lava Assigned Activities Click on "Mountains Lab" open it and complete the lab. Weathering Physical Weathering Weathering vs. Erosion Weathering is the breakdown of rock and minerals. Erosion is a two-part process that starts with (1) breakdown of land (weathering) and also includes the movement (transportation) of these weathered materials and is followed by (2) Deposition of the eroded material occurs when it is dropped in a new location. Denudation is a term that refers to the wearing down or smoothing off of land features. The processes of weathering and erosion are denudational. They are also gradational because they grade the earth’s surface. Physical Weathering vs. Chemical Weathering Physical weathering is the breakdown of rock and minerals by mechanical stress whereas chemical weathering breaks down rock with chemical reactions often including water. Types of Physical Weathering Frost fracture: the expansion of freezing water that causes rocks to crack. Heat expansion: rocks can expand and subsequently fracture. Plant growth: expansion due to root growth as shown in the picture below. Burrowing animals: tunnelling animals can increase the size of existing cracks Exfoliation: as internal pressure is released from certain rocks, it can cause layers to split and fall off. Environment's Affect on Physical Weathering Fast temperature changes like occur in the desert increases the amount of physical weathering due to heat expansion. Conversely, regions like the tropics where there is little temperature change the amount of physical wreathing due to heat expansion is minimal. Abundant precipitation combined with alternating freezing/thawing temperatures increases the amount of frost fracture. Conversely, the absence of those climatic conditions reduces the amount of frost fracture. Running water increases physical erosion as friction occurs between water and rock. Ocean waves cause hydraulic pressure and abrasion on the shore leading to physical weathering. Assigned Readings "Weathering" on page 23-24 of your text. Test yourself 1. The term that refers to the break down of rocks and minerals. 2. The term that refers to the breakdown, transportation and deposition of rock and mineral. 3. Weathering that relies on mechanical processes/forces to break down rock and mineral. 4. Weathering that relies on chemical processes to break down rock and mineral. 5. Physical weathering that that causes rocks to break off due to internal pressure. 6. Physical weathering that that causes rocks to break due to freezing water expanding in rock cracks. 7. Physical weathering that that causes rocks to break due to fast changes in temperature Answers 1. The term that refers to the break down of rocks and minerals. EROSION 2. The term that refers to the breakdown, transportation and deposition of rock and mineral. WEATHERING 3. Weathering that relies on mechanical processes/forces to break down rock and mineral. PHYSICAL WEATHERING 4. Weathering that relies on chemical processes to break down rock and mineral. CHEMICAL WEATHERING 5. Physical weathering that that causes rocks to break off due to internal pressure. EXFOLIATION 6. Physical weathering that that causes rocks to break due to freezing water expanding in rock cracks. FROST FRACTURE 7. Physical weathering that that causes rocks to break due to fast changes in temperature. HEAT EXPANSION Chemical Weathering Types of Chemical Weathering Chemical weathering is the breakdown of rocks and minerals by chemical reactions and usually involves the action of rainwater. There are three different types of chemical weathering described below. The formation of solutions as rainwater absorbs CO2 , SO2, and other chemicals from the atmosphere along with organic acids from the soil which then reacts with rock and minerals causing some to dissolve and move away. Hydrolysis, like the first process, involves the minerals in solution. In this case, carbonic acid reacts with silicates in some rocks leaving a soft clay from which potassium, sodium and magnesium are subsequently leached. Oxidation is the reaction of metallic minerals to oxygen (mainly in water). This results in the formation of oxides, which tend to be softer than the original mineral. For example, rust on iron. How Environmental Conditions Affect Chemical Weathering Heavy rain, running water and abundance of water increases the amount of dissolving that occurs. Conversely less abundance of water leads to less dissolving. High temperatures will increase the rate of chemical reactions. It is a fact of chemistry that heat increases the speed of many reactions like oxidation. Ocean water contains salt which can increase the rate of many reactions like oxidation. Assigned Readings "Chemical Weathering" on page 24-25 in your text book. Assigned Activities Click on "Weathering active learning lesson" , open it, print it and complete it. Test yourself 1. Which type of chemical weathering involves organic acids dissolving minerals allowing them to move away from the parent rock? 2. Which type of chemical weathering involves organic acids dissolving silicate causing the formation of soft clay which can easily be leached away? 3. Which type of chemical weathering involves the formation of oxides, often in the presence of water, which tend to be softer than the original mineral? 4. What affect would high ambient temperature have on the rate of chemical weathering? 5. What affect would an extreme lack of water, like desert conditions, have on the rate of chemical weathering? 6. What affect would heavy wind have on the rate of chemical reactions? 7. How does the presence of ocean water affect the rate of chemical weathering? Answers 1. Which type of chemical weathering involves organic acids dissolving minerals allowing them to move away from the parent rock? FORMATION OF SOLUTIONS 2. Which type of chemical weathering involves organic acids dissolving silicate causing the formation of soft clay which can easily be leached away? HYDROLYSIS 3. Which type of chemical weathering involves the formation of oxides, often in the presence of water, which tend to be softer than the original mineral? OXIDATION 4. What affect would high ambient temperature have on the rate of chemical weathering? INCREASE CHEMICAL WEATHERING 5. What affect would an extreme lack of water, like desert conditions, have on the rate of chemical weathering? DECREASE CHEMICAL WEATHERING 6. What affect would heavy wind have on the rate of chemical reactions? NO AFFECT UNLESS IT HAS AN AFFECT ON TEMPERATURE OR PRECIPITATION 7. How does the presence of ocean water affect the rate of chemical weathering? INCREASE CHEMICAL WEATHERING Erosion and Running Water River Life Cycle Drainage Basins Drainage Basin is the area of land drained by a river and its tributaries. The Amazon Basin, is the planet's largest body of fresh water with 1100 tributaries 17 of which are more than 1000 miles long. Many of the tributaries begin in Colombia and Peru. The Nile river, in Africa is the longest river in the world Rivers change over time and seem to go through three stages: 1. Youth 2. Maturity 3. Old Age Youth (figure 2.7 p.28) o Are usually found in highland or mountain regions. o They tend to have a steep slope (high gradient) o Usually have a small volume of water They have a rapid flow of water There is usually very rapid erosion especially vertically A narrow “V” shaped valley is characteristic Water falls and rapids are common Maturity (figure 2.7 p.28) o Most high relief is eroded o Gentler slope o Many well developed tributaries o Broad flat river valley o Well developed flood plain o More lateral erosion than vertical o Meandering results Late Maturity (figure 2.7 p.28) o Remember the stages are not distinct. o These changes occur over long periods of time. Old Age (figure 2.7 p.28) o Almost no slope o Very little relief o Elaborate meandering o Oxbow lakes develop o Often swampy areas around river o Very muddy due to slow speed o Most susceptible to flooding because of large flood plain. o o o o Evaluating Evidence to Determine the Age of Rivers There are six common pieces of evidence you can look for to determine the stage of a river. 1. 2. 3. 4. 5. 6. Slope of the river (steeper = younger) Relief of the banks (steeper = younger) Width of the valley (wider = older) Meandering (more = older) Size of flood plain (wider = older) Rapids or water falls (more = younger) Two Directions of River Erosion 1. Vertical erosion makes rivers deeper as is the case in young rivers 2. Lateral erosion makes rivers wider leading to the meandering of mature rivers. Assigned Readings "Rivers as Agents of Erosion" on pages 25-28 of your text book. Assigned Activities Click on "River active learning lesson" open it, and complete it. Test yourself 1. What term is given to the land area that is drained by a river and its tributaries? 2. What river is depicted in the map to the right? 3. The red river meanders along with a slow flow rate. It floods frequently. What stage do you think it is in? 4. River "X" is a very fast flowing river with lots of rapids. It is a favourite site for X-Games enthusiasts who like to "run the rapids" in kayaks. What stage is this river in? 5. When a river digs deep down into the river-bed what type of erosion is occurring? 6. When a slow moving meandering river gouges out the sides of the river at the turns which type of river erosion is occurring? 7. Which stage of river has the steepest sides? 8. Which stage of river has the most meandering? 9. Which stage of river has the fastest flowing water? 10.Which stage of river has oxbow lakes associated with it? 11.Which stage of river has a broad flat flood plain? 12.Which stage of river is usually associated with mountains? 13.Which stage of river has a V-shaped valley? 14.Which type of erosion is very common in youthful rivers? 15.Which type of erosion is very common in old rivers? Test yourself 1. What term is given to the land area that is drained by a river and its tributaries? DRAINAGE BASIN 2. What river is depicted in the map to the right? NILE 3. The red river meanders along with a slow flow rate. It floods frequently. What stage do you think it is in? OLD AGE 4. River "X" is a very fast flowing river with lots of rapids. It is a favourite site for X-Games enthusiasts who like to "run the rapids" in kayaks. What stage is this river in? YOUTHFUL 5. When a river digs deep down into the river-bed what type of erosion is occurring? VERTICAL 6. When a slow moving meandering river gouges out the sides of the river at the turns which type of river erosion is occurring? HORIZONTAL 7. Which stage of river has the steepest sides? YOUTHFUL 8. Which stage of river has the most meandering? OLD AGE 9. Which 10.Which 11.Which 12.Which 13.Which 14.Which 15.Which stage of river has the fastest flowing water? YOUTHFUL stage of river has oxbow lakes associated with it? OLD AGE stage of river has a broad flat flood plain? OLD AGE stage of river is usually associated with mountains? YOUTHFUL stage of river has a V-shaped valley? YOUTHFUL type of erosion is very common in youthful rivers? VERTICAL type of erosion is very common in old rivers? HORIZONTAL River Deltas Delta is a low lying area at mouth of river formed by deposition of silt deposition occurs because river slows as it enters ocean or lake. There are three types, arcuate, digitate and estuarine. Arcuate Delta: Digitate Delta: From Latin for finger Delta with long fingers of sediment reaching into the sea Named from Latin word for curved in the shape of a bow. Fan shaped The Nile Delta depicted on p. 32 of your text is a good example To the right is a satellite photo of the Nile Delta, notice the fan shape on the right-hand side of the mount of the river. The Mississippi Delta is a good example depicted on p. 32. To the right is a satellite photo of the Mississippi Delta, notice that it runs out into the Gulf of Mexico like a finger - unlike the Nile Delta above. Estuarine Delta: Formed when river runs into a bay or estuary Tidal mud flats form which can be seen at low tide Sediment deposited from river outflow and from Tidal inflow The Seine River Delta depicted in figure 2.12 on p. 32 of your book is a good example. To the right is a satellite photo of the Amazon Delta, notice the tidal flats or islands that cover and uncover with the tide. This picture below shows a small estuarine delta in Notre Dame Bay. Assigned Readings "Erosion and Deposition Process" on page 30-32 of your text. Test yourself 1. The term given to the low lying land at the mouth of a river. Silt is deposited there. 2. The term given to a fan shaped delta. 3. The name give to a finger shaped delta 4. The name given to a delta that forms in a bay or estuary. 5. Why does so much deposition occur at the delta of a river? Answers 1. The term given to the low lying land at the mouth of a river. Silt is deposited there. DELTA 2. The term given to a fan shaped delta. ARCUATE 3. The name give to a finger shaped delta DIGITATE 4. The name given to a delta that forms in a bay or estuary. ESTUARINE 5. Why does so much deposition occur at the delta of a river? THE FLOW RATE SLOWS BECAUSE THE WATER ENTERS A LAKE OR OCEAN> THE SLOWER MOVING WATER DROPS THE SILT Red River Case The lion's share of this lesson is actually doing the case study as is outlined in "activities". However you should take some time to consider the following questions. They are not intended to have you to write an answer, rather they are intended to make you ponder "social issues". This is a social studies course and during its course of study you will be challenged to think about social issues. Many of the case studies you will do in this course will help you prepare for the case study questions on the public exam. However they have a much greater significance than that short term objective. In ten years time when you are raising your family and working in the peak of your productivity, you may forget the book definition of hydrolysis or of arcuate delta, but you will have to take stances on social and environmental issues. It might be at voting time and an environmental issue is on the table. You might be part of a company trying to solve problems in regions affected by volcanoes or floods. The issues that arise in case studies are real life issues that you will be dealing with in your life ahead of you. You may not deal with a flood as we will look at there but you have to deal with a freezing rain storm or a forest fire. Take some time to ponder the questions below. Do we need to change they way we treat the environment? Should we change the way we have always done things to reduce the harm to the environment. Do governments have the right to tell people they can not live in flood prone areas. When solving problems or addressing issues are many heads (partnerships) better than one. Who should have to pay for clean-up after a disaster? When solving complicated problems like protecting Winnipeg from a looming flood is only one best way? Assigned Readings "CASE STUDY the Red Rive Flood" on pages 29-30 of your text book. Assigned Activities Complete question #7 in its entirety. Part a and part d have two questions within them. Make sure you answer both. Erosion and Glaciers Continental Glaciers Continental Glaciers vs. Alpine glaciers Continental glaciers cover parts of continental land masses like Greenland; Alpine glaciers are found high in mountain valleys, above the snowline. Differences: o Location; Alpine glaciers are only found on mountain tops whereas continental glaciers are only found at the earth's poles regardless of elevation. o Size; Alpine glaciers are smaller compared to Continental glaciers. Similarities: o Both move and cause erosion o Both change the landscape o Both developed in constantly cold temperatures below freezing. o Figure 2.13 on page 34 of your text shows a continental glacier and the the land forms it creates through weathering and deposition. Features of Continental Glaciation Outwash plain: like a river Delta; meltwater flowing from a glacier deposits silt like river deltas; silt is deposited in layers; small particles are carried further away; larger particles drop closer to the glacier. Terminal Moraine: heap or ridge of bulldozed gravel that marks the end of the forward motion of a glacier; as a glacier retreats it deposits debris/gravel. Erratics: large boulders that were transported long distances and dropped; they now sit in a region and look very much out-of-place. Drumlins: egg shaped hill; formed under glaciers; sloped or pointy end points in direction of ice flow; formation o ice melts under glacier o deposits of gravel are made o glacier moves forward o deposits are bull-dozed along and catch up in rough areas forming piles or drumlins. Eskers: long deposits of eroded glacial material; formed by sub-glacial streams that deposit material like all rivers; sometimes known as Highways of the North because they are good for traveling on with ATV's. Evidence for Direction of Glacier Movement The gently-sloped end of drumlins point in the direction of glacier movement. The terminal moraine marks the furthest extent of the glacier. The layers of silt in an outwash plain can indicate direction of glacier movement. fine particles would be at the leading edge while larger particles would have been closer to the glacier. Assigned Readings "Glaciers as Agents of Erosion" on pages 32-34 of your text book. Assigned Activities Complete Question # 12 on page 33 of your text book. Test yourself 1. Where are continental glaciers found? 2. Where are alpine glaciers found? 3. Many land forms are created by continental glaciers. Which one is very similar to a river delta? 4. Many land forms are created by continental glaciers. Which one is created by a river running under the glacier? 5. Many land forms are created by continental glaciers. Which one is a large boulder that looks out of place in its surroundings? 6. Many land forms are created by continental glaciers. Which one marks the furthest extent of the glaciers movement? 7. Many land forms are created by continental glaciers. Which one is an egg-shaped hill? 8. Which end of a drumlin indicates the direction of glacier motion? Answers 1. Where are continental glaciers found? THE POLES OF EARTH 2. Where are alpine glaciers found? HIGH IN MOUNTAIN VALLEYS 3. Many land forms are created by continental glaciers. Which one is very similar to a river delta? OUTWASH PLAIN 4. Many land forms are created by continental glaciers. Which one is created by a river running under the glacier? ESKERS 5. Many land forms are created by continental glaciers. Which one is a large boulder that looks out of place in its surroundings? ERRATICS 6. Many land forms are created by continental glaciers. Which one marks the furthest extent of the glaciers movement? TERMINAL MORAINE 7. Many land forms are created by continental glaciers. Which one is an egg-shaped hill? DRUMLIN 8. Which end of a drumlin indicates the direction of glacier motion? POINTY Alpine Glaciers Alpine glaciers are like very slow moving rivers of ice flowing down high mountain valleys. Like continental glaciers, alpine glaciers create land forms by weathering and deposition. They typically erode the mountain beneath them into a u-shaped valley with steep sides. Some alpine or valley glaciers are 1000m thick and up to 160 km long, though most are only a few km in length. Features of Alpine Glaciation Cirque a circular hollow cut into bedrock during glaciation; side and back walls are steep but front wall opens downward. Cirque Formation alpine glacier freezes onto mountain valley and as is proceeds it plucks/gouges rock from the mountain top leaving the cirque shape. Arête steep knife edged ridge between two cirques in a mountainous region. Hanging Valley a high level tributary valley from which the ground falls sharply to the level of the lower, main valley. The depth of the lower valley is due to more severe glaciation. Lateral Moraines land-form deposited at the side of a glacier. Terminal Moraines deposits that mark the farthest extent of the alpine glacier the same as with continental glaciers. Fjords alpine Glaciers erode troughs and valleys in the mountain; glacier valley reaches the coast; glacier melts and sea water floods the valley; fjords are very common in Norway and a quick search on web can find you some amazing pictures. Assigned Readings "Alpine Glaciation" on pages 34-36 of your text book. Assigned Activities Do Question # 14 on page 36. Test yourself 1. What alpine glaciation feature consists of a circular hollow cut into the bedrock. 2. What alpine glaciation feature consists of a knife-like edge between adjacent cirques? 3. What alpine glaciation feature consists of a valley that abruptly ends as the main valley is at a much lower level? 4. What alpine glaciation feature consists of deposits along the side of the glacier. 5. What alpine glaciation feature is formed when a valley glacier reaches the ocean and eventually melts back. 6. What alpine glaciation feature is this. 7. What alpine glaciation feature is this. 8. What alpine glaciation feature is this. Answers 1. What alpine glaciation feature consists of a circular hollow cut into the bedrock. CIRQUE 2. What alpine glaciation feature consists of a knife-like edge between adjacent cirques? ARETE 3. What alpine glaciation feature consists of a valley that abruptly ends as the main valley is at a much lower level? HANGING VALLEY 4. What alpine glaciation feature consists of deposits along the side of the glacier. LATERAL MORAINE 5. What alpine glaciation feature is formed when a valley glacier reaches the ocean and eventually melts back. FJIORD 6. What alpine glaciation feature is this. CIRQUE 7. What alpine glaciation feature is this. ARETE 8. What alpine glaciation feature is this. HANGING VALLEY Erosion and Ocean Waves/Currents Erosion of Submerging Coastlines Terms Related to Water/ Wave Erosion Three Weathering Terms Hydraulic pressure: The pounding force of water/waves Corrosion: Minerals such as calcium carbonate and limestone dissolve in the water Abrasion: rock and sand particles suspended in the water bump, grind, scrape and gouge surfaces the water hits. Longshore drift terms Headlands: the protrusions of land that extend the farthest out into wave action. Longshore drift: refers to the fact that dominant waves have enough energy to carry silt/sand from headlands along the shore where it is later deposited. Wave Refraction: waves bending around headlands as they hit the shallow water by shore Spit: A ridge of sand running away from the coast, usually with a curved seaward end. Spit grows in the prevailing direction of longshore drift. Ends are curved by the action of waves in different directions. Bay Bar: A ridge of mud sand or silt extending across a bay. Formed when spits stretch across the mouth of the bay. Bay Beach: An accumulation of sediment deposited by waves and longshore drift along the shore of a bay. Straightening of an Irregular Submerging Coastline Irregular submerging coastlines have headlands that protrude out from the shore line. The erosion of the headland can deposit silt in the bay which forms a bay beach as it tends to reduce the irregularity of the coastline. The headland is reduced due to erosion and the bay is being filled by deposition. Longshore drift results in some sand being deposited parallel to the shore but connected to the headland. These silt deposits are known as spits. Longshore drift and deposition can continue to the point that the spit closes off the mouth of the bay. This extensive deposit is known as a bay bar. As you can see it tremendously reduces the irregularity in the coastline. Continued erosion and deposition can straighten a coastline over a long period of time. Assigned Readings "Wave Movement and Direction" on pages 41-42; "Effects of Wave erosion and Deposition" on pages 42-44. Assigned Activities Click on "Wave Erosion", open it, print it and complete it. Test yourself 1. Water weather process where the pounding force of water/waves causes physical weathering. 2. Water weather process where minerals such as calcium carbonate and limestone dissolve in the water 3. Water weather process where rock and sand particles suspended in the water bump, grind, scrape and gouge surfaces the water hits. 4. The protrusions of land that extend the farthest out into wave action of the sea. 5. Refers to the fact that dominant waves have enough energy to carry silt/sand from headlands along the shore where it is later deposited. 6. Waves bending around headlands as they hit the shallow water by shore 7. A ridge of sand running away from the coast, usually with a curved seaward end. 8. A ridge of mud sand or silt extending across a bay. Formed when spits stretch across the mouth of the bay. 9. An accumulation of sediment deposited by waves and longshore drift along the shore of a bay. 10.What is this structure? 11.What is this structure? 12.What structure is this? Answers 1. Water weather process where the pounding force of water/waves causes physical weathering. HYDRAULIC 2. Water weather process where minerals such as calcium carbonate and limestone dissolve in the water. DISSOLVING 3. Water weather process where rock and sand particles suspended in the water bump, grind, scrape and gouge surfaces the water hits. ABRASSION 4. The protrusions of land that extend the farthest out into wave action of the sea. HEADLAND 5. Refers to the fact that dominant waves have enough energy to carry silt/sand from headlands along the shore where it is later deposited. LONGSHORE DRIFT 6. Waves bending around headlands as they hit the shallow water by shore. REFRACTION 7. A ridge of sand running away from the coast, usually with a curved seaward end. SPIT 8. A ridge of mud sand or silt extending across a bay. Formed when spits stretch across the mouth of the bay. BAY BAR 9. An accumulation of sediment deposited by waves and longshore drift along the shore of a bay. BAY BEACH 10.What is this structure? SPIT 11.What is this structure? HEADLAND 12.What structure is this? BAY BAR Curonian Spit Case Study Assigned Readings "CASE STUDY the Curonian Spit" on pages 45-46. Assigned Activities Complete Question #17 on page 46. Erosion of Emerging Coastlines The Evolution of Sea Stacks Sea stacks are common in eastern Canada. Many have plant growth on top. Sea stacks are columns of land standing in the ocean just off shore. They are created over a long period of time after a series of other land structures have eroded away. First sea caves are formed in a headland. Continued erosion turns sea caves in to the second land feature, searches. sea arches are an interesting sight too and have drawn many tourists to the northern Peninsula of Newfoundland. Erosion and eventual collapse of the arch top leaves a sea stack standing in the ocean. Figure 3.11 on pages 49-49 shows this evolution from three different points of reference. You must look at this figure it will help cement the concepts in your mind. Sea Cave Formation: "a" in figure 3.11 on page 48 waves strike the headland first; waves refract around the headland and put hydraulic pressure on both sides of the headland; erosion of the weak portions create caves and blow holes in the sides of the headland. Sea Arch Formation : "b" in figure 3.11 on page 48 eventually sea caves, on alternate sides of the headland get deeper until they connect inside the headland forming a complete passage way or tunnel or “arch” through the head land. Sea Stack Formation: "c" in figure 3.11 on page 48 continuous erosion, of sea arches, causes the collapse of the ground over the arch; this leaves a pillar or column or “STACK” of land standing alone where the headland was. Straightening of Emerging Coastlines emerging coastlines straighten in much the same fashion as submerging coastlines; erosion of headlands creates sea caves, sea arches and sea stacks instead of bay beaches, spits and bay bars; however the result is similar in that headlands are reduced in size which straightens the coastline. Compare the headland length in figure 3.11 before and after erosion. Assigned Readings page 46 Test yourself 1. What name is given to columns of land standing in the ocean just off shore. 2. Erosion of the weak portions in the sides of a headland create which type of shore line feature? 3. When sea caves erode through a headland what shoreline feature is created? 4. What wave phenomenon causes headlands to be eroded from both sides? 5. Which type of water/wave erosion is mostly responsible for the erosion that leads to the development of sea stacks. 6. After sea stack formation are headlands longer or shorter? Answers 1. What name is given to columns of land standing in the ocean just off shore. SEA STACK 2. Erosion of the weak portions in the sides of a headland create which type of shore line feature? SEA CAVE 3. When sea caves erode through a headland what shoreline feature is created? SEA ARCHES 4. What wave phenomenon causes headlands to be eroded from both sides? WAVE REFRACTION 5. Which type of water/wave erosion is mostly responsible for the erosion that leads to the development of sea stacks. HYDRAULIC AND ABRASION 6. After sea stack formation are headlands longer or shorter? SHORTER Landforms Affect Human Activity Storm Surges in Bangladesh Human adaptation to land forms and water forms Humans have adapted to most conditions on earth. Look at the front cover of your book and you can see how people of the orient have adapted to farming on steep hillsides. Look at many small fishing villages in Newfoundland and you will see how people adapted to build houses up cliffs that overhang the ocean. The stilt houses of Bangladesh show how humans have adapted to living in delta regions. A drive through most communities in Newfoundland will see you crossing a number of bridges. Without the technology of bridge building access to many places would be restricted to boat traffic. The Tunnel that was recently completed under the English channel is a good example of overcoming restrictions to access. The Canadian railway finally overcame the restriction caused by the rocky mountains. Proposing Solutions to Problems Some of the following suggestions will help in many case studies. Many times you will be asked to put yourself in the position of government or other influential groups. You will be asked what you would propose as solutions to problems like the flooding in Bangladesh. Researching to determine, what is the root of the problem is a good idea. Funding a research facility to develop solutions to the problem. Develop a government department to be responsible for the issue. Study other world locations that have solved similar problems. It is not necessary to reinvent the wheel. It is always important to keep financial restrictions in mind, many countries like Bangladesh have limited resources. Searching for funding from world bank and international aid might be a good idea. Assigned Readings "Storm surges in Bangladesh" on p. 50-51 in your text book Assigned Activities Can you think of a land or water form that humans have adapted to or overcome in your community or region? If so share it with the class. Can you think of a land form or water form that has restricted human access in your community or region? If so share it with the class. Click on Hazard analysis model open it and print it to use as you complete question #22a p. 51. If you were a member of Government in Bangladesh what solutions would you propose to prevent further storm surge tragedies. Economic Proposal You will be expected to write an economic proposal for a given land form or water form. You could be asked to write a proposal for a river with many large water falls or with small rapids; you could be asked to write a proposal for a mountain near the coast. The point here is that you bring your knowledge of geography to the answer. You must propose what economic value there is in the area. Consider the following when you do a proposal. 1. The economic activity must fit the terrain. For example a hydroelectric generating station on a slow meandering old river might not be a good idea whereas boat tours might be. 2. How would the environment be impacted? Obviously you would need an environmental impact study and a means of reducing the impact on nature. 3. Is the area accessible to people or machinery? You must be able to access it to make money. 4. How might building and erosion forces impact your proposal in the short term and long term? 5. What types of potential problems accompany the land or water form. For example flooding accompanies old meandering rivers. Assigned activities Using the search engine of your choice find a picture of any land form or water form and write an economic proposal for use of it. Be sure to include at least the 5 points mentioned in the lesson. Type the proposal in word and include the photo of the land or water form. Erosion and Wind Wind Erosion Deflation: Process where soil particles are removed leaving the land slightly lowered or hollowed. See figure 3.2 on page 39. Abrasion: Wind-borne particles blown against any surface acts as a sand blaster Loess Originally referred to loose, fine grained soil in the Rhine river valley. Now it refers to any unconsolidated, unstriated soil composed of fine/clay sized soil particles. It is Very fertile agricultural soil. It Can blow long distances and collect in specific regions. Hamadas: rocky deserts. Rocky portion of desert where wind removes all sand and small particles. Jagged rocks and flat pans of bedrock are common. See Figure 3.3 on page 40. o Hamadas formation: o Wind blows away all loose soil and particles o Landscape appears jagged and bare with exposed bedrock o Any loose soil is compacted coarse stone Erg: Sandy deserts. Sandy portion of desert where wind blown sand is deposited. Sand dunes, ridges and mounds are common Barchan: Crescent shaped sand dunes. The horns or arms extend in the direction of the wind. See Figure 3.4 on page 41. o Assigned Readings "Wind Erosion" pages 38-39 in your text book; "Wind Deposition" pages 39-40 in your text book. Test yourself 1. Process where soil particles are removed leaving the land slightly lowered or hollowed? 2. Unconsolidated, unstriated soil composed of fine/clay sized soil particles. It can blow in the wind for long distances? 3. Wind-borne particles blown against any surface acts as a sand blaster 4. Rocky deserts? 5. Sandy deserts. Sandy desert? 6. Crescent shaped sand dunes? Answers 1. Process where soil particles are removed leaving the land slightly lowered or hollowed. DEFLATION 2. Unconsolidated, unstriated soil composed of fine/clay sized soil particles. It can blow in the wind for long distances. LOESS 3. Wind-borne particles blown against any surface acts as a sand blaster. ABRASION 4. Rocky deserts. HAMADAS 5. Sandy deserts. ERG 6. Crescent shaped sand dunes. BARCHANS