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Download 2.3 Land ppt - Maryville City Schools
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Transcript
2.3 The Land Pages 35‐41 Learning Target: PG7 – I can recognize specific processes that operate on the Earth’s surface. (i.e. erosion, volcanoes, earthquakes, wind and water currents, plate tectonics, and weathering) Landforms • Landforms are shapes on the planet’s surface • Because they play an important role in geography, many scienOsts study how they are made and how they affect human acOvity Earth’s Plates • Layers of the the Earth – Inner & outer core – inner is a solid ball of metals surrounded by outer core which is molten metal – Mantle – is a liquid layer – Crust – solid outer layer (conOnents are part of crust Plate Tectonics • Theory geographers use to explain how forces below have shaped our landforms • Suggests that Earth’s surface is divided into about a dozens slow moving plates • Some plates are large, some are small, some are under the oceans, some are under the conOnents ‐ but they cover the enOre Earth • Energy deep inside the Earth puts pressure on the crust, as pressure builds it causes the plates to shiW or move ConOnental DriW • The theory that the Earth used to be one big conOnent (Pangaea) but the plates under the conOnents have shiWed and moved the conOnent • Plates are sOll moving – over Ome, colliding, separaOng, and sliding plates have shaped Earth’s landforms Plates Collide (Converge) • The collision of different types plates creates different shapes on the Earth’s surface • 2 ocean plates collide – one pushes under the other and ocean trench (deep valley in the ocean floor) is created • Mariana Trench (near Japan) is the world’s deepest trench • When ocean plate & conOnental plate collide – ocean plate drops beneath the conOnental plate and crumples the land above forming mountain ranges • South American Andes Mountains is an example • 2 conOnental plates colliding also produces mountain ranges – land pushes up to great heights • Himalayas the world’s highest mountain range (29,000 W above sea level) Plates Separate (Diverge) • As plates move apart, gaps between the plates allow magma (liquid rock from Earth’s interior) to rise to the crust • Lava (magma that reaches the Earth’s surface) emerges from the gap • As lava cools it builds mid‐ocean ridges or under water mountains • Can grow high enough to reach the surface & create volcanic islands • Largest is the Mid‐AtlanOc Ridge Plates Slide • As plates pass by one another, they someOmes grind together • This grinding produces earthquakes (sudden, violent movements of the Earth’s crust) • Earthquakes take place along faults (breaks in the Earth’s crust where movement occurs) • San Andreas Fault located in California is where the Pacific plate and the North American plate meets Ring of Fire • Region that circles the Pacific Ocean plate • Know for fiery volcanoes & powerful earthquakes • Stretches from the Op of South America all the way up to Alaska, and from Japan down to the islands east of Australia Mount Saint Helens in Washington State • One of the best know volcanos in the Ring of Fire • Dormant since 1857 then erupted in May 1980 • Ash clouds 15W high for 9 hrs – ash blanketed towns 200 miles away ‐ ash reached eastern US in 3 day – enter jet stream circled Earth in 2 wks • Heat melted snow and created deadly mudflows Weathering • The process by which rock is broken down into smaller pieces • Several factors cause rock to break down: – DayOme heaOng & nighhme cooling – desert areas – Freezing water in cracks of rocks – ice expands and breaks them apart • Small pieces of rock is known as sediment • Sediment is moved from place to place by wind, ice, and water Erosion • Is the movement of sediment from one locaOon to another • It can wear away or build up landforms • Causes of erosion are wind, ice, and water Wind • LiWs sediment into the air and carries it across great distances • Blowing sand can wear down rock – acts like sandpaper to polish away rock Trey’s Glaciers • Large slow‐moving sheets of ice • Flow slowly downhill like rivers of ice eroding the land by carving large U‐shaped valleys & sharp mountain peaks • Crushes rock in sediment Rebecca – New Zealand Water • Most common cause of erosion • Ocean waves wear away shoreline creaOng jagged coastlines • Over many years rivers cut through rock forming canyons Rebecca • Water can also build landforms • Rivers carry sediment • Flooding rivers create floodplains by deposiOng sediment along the banks • Rivers carry sediment to the sea creaOng delta where the river and sea meet Mississippi River before aWer flood 1997 Landforms Influence Life • Landforms influence where people sejle • SomeOmes people sejle near certain landforms – flood plains & deltas have ferOle soil – rivers make transportaOon of good easier • SomeOmes landforms discourage sejlement – rugged tall mountains like the Himalayas, or deserts with lijle water • Landforms affect culture • Rich mineral deposits in Colorado led to mining industry (jobs) • Landforms affect things like language – large mountain ranges on the island of New Guinea keep people isolated & there are more than 700 languages on the island Changing landforms • People someOmes change landforms to suit their needs • Building of the Panama Canal made travel from the AtlanOc to the Pacific easier • Cut terraces into step hillsides to grow crops • Build dams to divert water to nearby farms or create electricity Show What You Know • 1. What is the difference between weathering and erosion? Weathering is the breaking down of rock into sediment and erosion is the movement of sediment. • 2. The earliest urban civilizaOon was built between the Tigris and Euphrates rivers in the Middle East. How did the locaOon help the civilizaOon thrive? People had plenty of water to drink and grow crops. And used the rivers for trade & transportation. • 3. What are some landforms in our area and how do they influence our lives? Mountain influence weather, transportation, and jobs. Rivers rivers provide electrical power.
