Unit 1 Landforms and Water Forms

Transcription

1 Unit 1 Landforms and Water Forms Earth is divided into specific structural zones; 1. Inner core 2700 km in diameter - Solid - Made mostly of iron, with a little nickel - Temperature of degrees Celsius 2. Outer core km thick - molten (fluid) - made mostly of iron and nickel - temperature of 4000 degrees Celsius 3. Mantle km thick -divided into lower and upper layers - moderate density largely solid except for the upper km of upper layer called the asthenosphere - made mostly of magnesium and iron silicates 4. Mohorovicic Discontinuity - Boundary between mantle lithosphere, at which earthquake waves abruptly change speeds. 5. Lithosphere km - lowest density; solid and rigid - made up of the lightest elements and compounds ( mostly magnesium, aluminum, and iron silicate such as qranite) - can be divided into two layers, one under ocean basins (sima) and one making up the continents (sial) 1.1 And 1.2 Explain how compressional forces are caused. Explain how tensional forces are caused. Questions #9 a, b, c page 11 - The earth is made up of plates - large pieces of crust that move about. This movement is called Plate Tectonics. - Basically, 2 patterns of plate movement 1. Compressional forces - two plates move towards each other and squeeze together which causes rock forces to bend, warp or be

2 pushed upwards. Example, Andes mountains are a result of compressional forces. 2. Tensional forces plates break apart and move away from or past each other which may form trenches as one plate drops down. Example, the Merianas trench is a result of tensional forces. 1.3 Relate selected plate movement to compressional or tensional forces. RWS 1.6 (handout) Question #10 page Explain how compressional forces create fold mountains. When two plates move toward each other they create a compressional force. As a result, folding occurs. Folding is the process whereby layers of rock bend, buckle, and are pushed upward. The resulting mountains are called fold mountains. 1.5 Differentiate between the terms anticline and syncline. Anticline simple fold mountains contain upwardly and downwardly pushed layers resembling waves. The peak of the wavelike structure created as a result of the creation of fold mountains is called anticline. Syncline simple fold mountain contain upwardly and downwardly pushed layers resembling waves. The trough of the wavelike structures created as result of the creation of the fold mountains. 1.6 Explain how tensional forces create a normal fault. Normal fault when a plate on one side drops down lower than the place on the other side. Tensional forces exist when two plates break apart or move away/past each other possibly causing one plate to drop down. If one plate on one side drops down lower than the plate on the other side, a normal fault will result. 1.7 Explain how compressional forces create reverse and overthrust faults. Reverse If simple rock layers around a fault push against each other, one block can be pushed up over the other creating a reverse fault. Overthrust If a plate that has undergone folding has its folded layers pushed up and thrust over layers on the faults other side, overthrust faults occurs.

3 1.8 Explain what causes a volcano to erupt. The main trigger for volcanic eruption is heat. Plate boundaries, where oceanic and continental crusts meet, are intensely hot because of friction, pressure and decay of radioactive materials. Frequently, this intense heat melts rock beneath the crust producing magma. If the molten rock fragment called ash or cinder, and blobs of molten rock with trapped volcanic gas inside can be ejected to the surface in the form of an eruption. Depending on the chemical composition of the lava and the amount of trapped gas, volcanic eruptions can be violent and explosive or quiet and calm. 1.9 Describe the characteristics of an ash-and-cinder, a shield cone, and a composite cone. Cone- buildup of volcanic material. Ash-and-cinder- A volcanic peak with a roughly circular base tapering to a point, formed by layers of ash and lava thrown out during volcanic eruptions. Ash-andcinder cones are associated with thick lava and much ash. Ash- small molten rock fragments. Shield cone- A volcano formed of successive eruptions of free-flowing, relatively thin lava which spreads over a large area, creating a broad, gently sloping dome tens of kilometers across and around 1 km high. Composite cone- A volcanic peak with a roughly circular base tapering to a point, formed from lava flows and layers of ash. In a composite cone, smaller cones form through vents that flanks (sides) of the volcano. Page 16 figure 1.14 A) Ash-and-cinder cone B) Composite cone C) Shield cone 1.10 Conclude how the location of active volcanos is related to places where plates meet. Plate boundaries are where continental and oceanic crust meet. These areas are intensely hot due to friction, pressure and decay of radioactive materials. Since the main trigger for volcanic activity is heat, plate boundaries are thus areas of active volcanoes.

4 1.11 Describe global patterns in the location of landforms. Alfred Wegener initially suggested in 1924 that the earth was once a single land mass called Pangea. Over time, Pangea split into multiple land masses. These masses began spreading apart. In the 1960 s, J.Tuzo Wilson observed that earthquake and volcanic activity often occurred in mid ocean regions where ridges existed. These ridges split apart the rocky crust, or plates, of the ocean floor pushing continents further apart in a process called sea-floor spreading. Plates on each side of the mid-atlantic ridge are continuing to move both the north and south American plates further away from the African and Eurasian plates. However, the south American plate and the Nazca plate are pushing towards each other forming a subduction zone. Finally, the Southeast India Rise, the Pacific-Antarctic Ridge and the East Pacific Rise are pushing plates north causing the Australian Plate and the Pacific Plate to also move north Understand the impact of specific landforms by completing case study on page and completing the question on page 19 of text Distinguish between the terms physical weathering and chemical weathering. Physical Weathering The disintegration or splitting up of rock by the Physical environment without chemical changes occurring. Chemical Weathering Processes that involve the action of chemical elements or compounds that change the rock s chemical composition Describe the mechanical process by which physical weathering occurs. 1. In climate regions where temperatures fluctuate above and below the freezing point, frost fracture occurs. 2. In regions where temperatures fluctuate greatly between day and night or season to season. The temperature change itself can result in weathering. The sudden heating causes the rocks to expand while sudden cooling causes the rocks to contract. This is temperature induced weathering.

5 3. Some types of rock weather by breaking along curved surfaces, causing the rock to break apart in rounded sheets like layers of onions. This type of weathering is called exfoliation. 4. Plant growth and burrowing animals can also cause physical weathering by expanding existing cracks and fractures in rock Describe the main interactions that result in chemical weathering. Chemical weathering involves the breakdown of rock minerals by chemical reaction and is usually related to rainwater. Rain passes through the atmosphere and soils, absorbing chemicals along the way. When rain reaches rock, the rock minerals combine with chemicals in the rain and either swells or are loosened from the rock structure Infer the relationship between environmental conditions and the rate of physical and chemical weathering. Changes in temperature create physical weathering such as rock fracture and temperature-induced weathering. The greater the change in temperature and the more often they occur, the greater the rate of physical weathering. Areas where heavy raining occurs may result in solution, hydrolysis and oxidation happening at a faster rate that dryer areas; further, increased pollution and acid rain will also increase the speed of chemical weathering Describe the three stages in the life cycle of a river. When areas receive excess waterfall, it can no longer soak into the ground. The water begins to flow on the surface of the land instead. This excess develops into small streams that merge into larger streams, finally creating major rivers and river streams. Youthful rivers: - found in highland and mountainous areas - Steep slopes, relatively small volume of water and rapid flow - Soil particles roll along the ground, wearing downhill slopes as the water flows down. - Tends to have a narrow, relatively v-shaped valleys due to rapid erosion from fast flowing water. - Rapids and waterfalls are associated with youthful rivers.

6 Mature: - gentler slope and flatter land surface. - many have well developed branches called tributaries because the drainage patterns have had time to develop. -now characterized by a broad, flat river valley with a well-developed floodplain - the river channel will relatively broad as the river is now lower in elevation and works on eroding the sides of the channel. - Minerals are deposited along broad curves and now follows a gently meandering course over the flood plain. -River has reached equilibrium where erosion and deposition is nearly in balance -the river is moving a maximum amount of water in an efficient manner. Old age rivers: - Extremely flat, almost no slop, very little momentum or speed. - Very elaborate and intricately meandering courses. - Often swampy areas appear around old rivers because of lack of slope which leads to poor drainage. -Often very muddy as a result of low velocity. - Most prone to flooding. -formation on oxbow lakes 1.18 State two ways in which water erosion occurs. 1. Vertical erosion: The erosion causes the river bed on the floor to wear down and as a result the river valley will become deeper. The three agents of vertical erosions: a. Hydraulic Pressure: The weight of the water and the constant pounding of the water over the rock surfaces cause the rock to erode. b. Solution/corrosion: Plants give off carbon resulting in the formation of carbonic acid which dissolves minerals in the rock structure, making it weaker and vulnerable to erosion. c. Abrasion: If the river current is strong enough it will carry particles of rock with it. These rock particles of varying sizes will gouge, scratch, rub and grind against the sides and floor of the river, eroding it away. 2. Lateral Erosion (sides): This type of erosion occurs when the river side or slope becomes eroded. This, along with vertical erosion, happens in mountainous areas to create river valleys. Lateral erosion also occurs during the mature stage of a river, especially on the outside of a meander.

7 1.19 Examine evidence to determine the life cycle stage of a river. Completed in outcome Explain how deltas are formed. As a river approaches a larger, still body of water (pond, lake, ocean) it is carrying eroded materials such as dissolved minerals or fine suspended particles held up by the energy of the water flow. Other particles may also be rolling or bouncing down the river. Downstream it flows, slowing down as the slope decreases, until it encounters the still waters of an ocean, lake, sea, or bay. The river unloads its largest amounts first, closest to shore, forming a thick layer of sediment. The river drops smaller particles out in deeper water, forming a thinner layer. The river continues to flow over these deposits and repeats the process further and further out from shore Contrast the terms Arcuate delta, Digitate delta, and estuarine delta. Arcuate Delta- Fan shaped delta named from the Latin word curved in shaped of a bow Digitate Delta- a delta with long fingers of sediment extending into the sea. Estuarine Delta- A delta formed in that area of a river mouth which is affected by sea tides Define the terms outwash plain, terminal moraine, erratic, drumlin, and esker. Outwash Plain: A plain formed by sediments washed out by glacial melt water and deposited beyond the ice sheet or glacier supplying water and the debris. Such deposits are usually sorted with the coarest sediment being deposited nearer to the ice front and finer material being laid down further away. Terminal moraine: A landform deposited by a glacier or ice sheet which marks the end of a glacier. Erratic: A large boulder of rock differing in character (composition, structure, texture, and hardness) from the pre-existing rock on which it rests. The boulder has been moved on the surface of a glacier. Drumlin: A long hummock or hill, egg-shaped and deposited and shaped under an ice sheet or very broad glacier while the ice was still moving. The end facing

8 the ice is blunt while the other end is shallow and its point is in the direction of the ice flow. Esker: Long, winding ridge of stratified sand and gravel, examples of which occur in glaciated and formerly glaciated regions of Europe and North America. Eskers are frequently several miles in length and have a peculiar uniform shape Examine evidence for the direction of movement of a continental glacier. The direction of a continental glacier can be identify by a drumlin- the point is in the direction of the ice flow. Erractic and also indicate the direction of a glacier, for example, if a particular type of rock is only found on the west coast of Canada and that particular rock is found on the east coast well chances are that continental glacier move that particular rock to that location. Resulting in movement from the west coast to east coast Define the terms cirque, arête, hanging valleys, lateral moraine, and terminal moraine. Circque: Bowl shaped or horseshoe shaped depression carved out in the mountain by the glacier. Arete: the ridge formed when two cirques come back to back. Hanging valleys: Is the secondary valley which is located above the main valley of the mountain. It is separated by a steep cliff or slope form the main valley. (Note: Don t confuse hanging valley with a cirque) Lateral Moraine: ridge f glacier debris pushed along the side of the glacier as it advances down the mountain valley. Terminal moraine: moraine means ridge of the glacier debris. Ridge of glacier debris at the leading edge(front) of a glacier and it marks the furthest advance of the glacier. This ridge is created in front of the glacier because the glacier acts like a bulldozer Define the term fiord. Fiord A long, narrow arm of the sea which is the result of the drowning of a glaciated valley.

9 1.26 Define the term spit. Spit- a ridge of sand running away from the coastline, usually with a curved seaward end. Spits grow in the prevailing direction of longshore drift. Their ends are curved by the action of the waves coming from different directions Define the terms sea cave, sea arch, and stack. Sea Cave A large, naturally hollow in a headland caused by wave erosion. Sea Arch Two caves on either side of a headland are cut until they meet. Arches are relatively temporary, as roof fall isolates the seaward end when they become a stack. Sea stack an isolated islet (tiny island) or pillar of rock standing up from the sea bed close to the shore Explain how sea caves, sea arch, and stacks are formed. Sea caves are formed when the host rock is first contain a zone of relative weakness. The driving force in sea cave development is wave action. Erosion is ongoing anywhere that 1.29 Analyze the process that result in the straightening out of an irregular coastline. How do waves cause erosion? Lakes and oceans get their energy to erode from wind. When wind drags on the water surface, it transfers its energy through the water as friction. The result of this energy transfer is a wave. When waves strike coastal lands, erosion takes place. Aspects of wave movement affect coastal erosion? a) In open water, waves develop in long ridge, or fronts, roughly perpendicular to the direction of the wind. As the waves approach shore, they bend to line up parallel to the shoreline. This bending is called wave refraction and it occurs because water becomes shallow near the shoreline and the energy contained in the wave decreases. Wave refraction results in the energy of the wave being concentrated on the portions of land called headlands that jut out farthest into the water. b) Waves can transport eroded sand and gravel along the shoreline in a process called longshore drift. It develops because the largest, or dominant, waves in front strike the shoreline at an angle, moving loose sediment in the direction of the dominant waves.

10 How coastlines form? 1. Some are formed after a period of glaciation, when the land rebounded after the mass of an ice sheet was removed from it. 2. Sea levels may fall and the coastline may emerge as dry land 3. Sea levels may rise or plate movements may cause the shoreline to sink causing sea water to permanently flood valleys and low-laying land creating a new shoreline further inland. Two categories of coastlines: A) Submergent coastline: also called embayed coastline, drowned or submerged coastline or Ria coast. This coastline results from rising sea levels. B) Emergent coastline: also called cliff-and-terrance coastline. This coastline results when water deepens rapidly from shore and land rises steeply upward Examine how human activity adapts to landforms and water forms Examine how humans respond to hazards posed by selected landforms and water forms Develop a proposal for the economic use of selected land forms or water forms Justify a preference for the aesthetic appeal if selected landforms and water forms Propose a solution to a threat posed by selected landforms and water forms.