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1 Chapter 7 Key Terms Topography Landform Elevation Fold Mountain Erosional Mountain Moraines Isostasy Relief Actual Height Depositional Mountain Plateaus Sediment 2 Chapter 7 MOUNTAINS AND HILLS 3 What is a mountain? Why does Mt. Everest seem to be getting taller? Movement of the India plate into the Eurasian plate causes an increase of almost 2.4” per year If that is correct and constant, how much may Mt. Everest have risen from when it was first measured (1856) until now? 31.8 feet How old are the Himalayas if Mt. Everest is 29,035 ft. tall? 145,175 years 4 Topography “Topo” – shape Study of surface shape and features of the Earth (variations in elevations) 5 Topography Oceanic crust is fairly thin and dense Basins – low level areas on earth’s surface (oceans & seas) Continental crust has lighter, less-dense rocks 6 Isostasy “Iso” – equal ; “stasis” – to stand still The balance of the weights of rocks, water and ice with the upward force of the mantle Determines the topography 7 Landforms Structures on the earth’s surface Mountains, hills, lakes, beaches, deserts… Orogeny “Oro” – mountains ; “Gene” – beginning (the way to make) Study of mountain formation Definition: Mountain – natural elevation of the earth’s surface rising more or less abruptly to a summit Also applies to a hill 8 Landforms Heights are usually given in meters or feet above sea level Elevation Actual height – height above lowest elevation of surrounding terrain/base Relief – difference in height between highest and lowest elevations of the terrain Tallest mountain in the world? By elevation: Mt. Everest (29,034 ft) By actual height: Mauna Kea (33,000 ft) 9 10 Groups of Mountains Mountain Range A series of mountain peaks in the same geographical area Mountain System Group of mountain ranges connected over a large area Longest mountain system Mid-Atlantic long) Ridge (over 10,000 miles 11 Mountains Geologists classify mountains based on how they think mountains formed Landforms Tectonic Nontectonic 12 Tectonic Mountains Mostly found near convergent tectonic plate boundaries However, they can also be found at divergent zones Mid-Atlantic Ridge These landforms are classified by the forces that cause them Convergent Divergent Uplift Subsidence 13 Landforms Nontectonic Tectonic Convergent Divergent Uplift Subsidence 14 Convergent Landforms Sediment Deposits Layers of eroded earth materials that eventually harden are called strata Fold Mountains Formed 3 from folded rock strata basic types of folds 15 Fold Mountains Anticlines – an arch of rock layers 16 Fold Mountains Synclines – a trough of rock strata (downward fold) Both anticlines and synclines are formed by compression forces 17 Fold Mountains Anticlines – an arch of rock layers Synclines – a trough of rock strata (downward fold) Monoclines – an area of smoothly folded strata above a fault that forms a single “step” Complex tectonic mountains Most mountains will have multiple of these fold throughout them 18 Divergent Landforms Rift valleys Series faults of steep-walled valleys lined with high cliffs rising from Grabens Low Most areas where rocks cracked and dropped downward rift valleys are underwater 19 20 Uplift Landforms Plateaus Broad region of relatively undisturbed sediment that has been lifted Usually Made level or gently tilted of sediment or lava Domes Landform bowl Usually with sedimentary strata that looks like an upside-down forms when magma pushes small area upward 21 22 Subsidence Landforms Basins Bowl shaped structure formed when a deep magma chamber emptied causing the rock strata above to sag 23 Tectonic Landforms Landforms Fold Mountains Anticline Syncline Monocline Rift Valleys Grabens Uplift Plateaus Domes Nontectonic Tectonic Subsidence Basins Convergent Divergent Uplift Subsidence 24 Non-Tectonic Landforms Erosional Forms when land is taken/eroded away by some force Depositional Formed Forms by process called sedimentation/deposition when sediment is “deposited” in certain places 25 Erosional Landforms Mesas and Buttes Flat-topped Talus hills that have steep cliff-like sides are piles of broken rock at the base of these formations 26 Erosional Landforms Pinnacles Tall spires of rock that are remnants of a plateau 27 Depositional Landforms Wind formed Sand dunes – hills of sand that vary in size Glacier formed Glacial till – pieces of bedrock broken out and crushed by a glacier Moraines – long, low ridges of glacial till formed at the front and sides of a glacier Drumlins – low hills formed as glaciers dragged over piles of till 28 29 Volcanoes Volcanoes also play a part in deposition Considered both tectonic and depositional landforms