Chapter 2


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Chapter 2

  1. 1. Physical Geography A Living Planet The geography and structure of the earth are continually being changed by internal forces, like plate tectonics, and external forces, like the weather. NEXT
  2. 2. SECTION 1 The Earth Inside and Out SECTION 2 Bodies of Water and Landforms Physical Geography Looking at the Earth SECTION 3 SECTION 4 Internal Forces Shaping the Earth External Forces Shaping the Earth NEXT
  3. 3. Section 1 The Earth Inside and Out • The earth is the only habitable planet in the sun’s solar system. • The drifting of the continents shaped the world we live in today. NEXT
  4. 4. Earth Continental Puzzle • The seven continents on earth fit together like a jigsaw puzzle • Continents—landmasses above water on Earth • Francis Bacon (1620) first to suggest 7 continents were once one The Earth Inside and Out SECTION 1 NEXT
  5. 5. SECTION 1 The Earth’s Neighborhood • Earth is third planet in the solar system of the sun • Sun is medium-sized star at edge of the Milky Way galaxy • The solar system includes: - sun and nine known planets - comets—icy spheres orbiting the sun - asteroids—large chunks of rocky material orbiting the sun The Solar System NEXT
  6. 6. The Structure of the Earth Matters of Size • Circumference of the earth: about 24,900 miles • Diameter of the earth: about 7,900 miles SECTION 1 Inside the Earth • The core is the center of the earth; made up of iron, nickel • Outer core is liquid; inner core is solid • The mantle surrounds the core: - has several layers - contains most of Earth’s mass Continued . . . NEXT
  7. 7. SECTION 1 Inside the Earth • Magma—molten rock that forms in the mantle • Crust—thin layer of rock at Earth’s surface continued The Structure of the Earth On and Above the Earth • Atmosphere is the layer of gasses surrounding the earth: - contains oxygen - protects Earth from radiation, space debris - is the medium for weather and climate Continued . . . NEXT
  8. 8. SECTION 1 On and Above the Earth • Lithosphere—solid rock portion of Earth’s surface, forms ocean floor • Hydrosphere—water elements on Earth including atmospheric water • Biosphere—atmosphere, lithosphere, hydrosphere combined • Plants and animals live within biosphere continued The Structure of the Earth Continued . . . NEXT
  9. 9. SECTION 1 continued The Structure of the Earth Continental Drift • Continental Drift—1912 hypothesis of Alfred Wegener: • Earth once one supercontinent; Wegener calls it Pangaea, “all earth” • Pangaea splits into many plates that slowly drift apart NEXT
  10. 10. Section 2 Bodies of Water and Landforms • Water covers about three-fourths of the earth’s surface. • The earth’s surface displays a variety of landforms. NEXT
  11. 11. Bodies of Water Ocean Motion • The ocean circulates through currents, waves, tides • Currents act like rivers flowing through the ocean • Waves are swells or ridges produced by winds • Tides are the regular rising and falling of the ocean - created by gravitational pull of the moon or sun • Motion of ocean helps distribute heat on the planet - winds are heated and cooled by ocean water Bodies of Water and Landforms SECTION 2 Continued . . . NEXT
  12. 12. SECTION 2 Hydrologic Cycle • Hydrologic Cycle—cycle of water between atmosphere, oceans, earth Lakes, Rivers, and Streams • Lakes hold more than 95% of the earth’s fresh water • Freshwater lakes, like the Great Lakes, are result of glacial action • Saltwater lakes form when outlet to sea is cut off: - streams and rivers carry salts into lake - salts build up with nowhere to go Continued . . . continued Bodies of Water NEXT
  13. 13. SECTION 2 Lakes, Rivers, and Streams • Rivers and streams carry water to and from larger bodies of water • Tributaries are smaller rivers, streams that feed into larger ones • Drainage basin—area drained by river and its tributaries Ground Water • Ground water—water held in the pores of rock • Water table—level at which the rock is saturated continued Bodies of Water NEXT
  14. 14. Landforms Landforms • Landforms are naturally formed features on Earth’s surface SECTION 2 Oceanic Landforms • Continental shelf—sea floor from continent’s edge to deep ocean • Sea floor has ridges, valleys, canyons, plains, mountain ranges • Islands are formed by volcanoes, sand, or coral deposits NEXT
  15. 15. Section 3 Internal Forces Shaping the Earth • Internal forces reshape the earth’s surface. • Internal forces shaping the earth often radically alter the lives of people as well. NEXT
  16. 16. Landforms Continental Landforms • Relief—difference in landform elevation from lowest to highest point • Four categories of relief—mountains, hills, plains, plateaus • Topography—the configurations and distribution of landforms • Topographic map shows vertical dimensions, relationship of landforms Internal Forces Shaping the Earth SECTION 3 NEXT
  17. 17. SECTION 3 The Earth Moves • Tectonic plates are massive, moving pieces of Earth’s lithosphere • Plates ride above circulating, heated rock •  Geographers study plate movements to understand: - how the earth is reshaped - how earthquakes and volcanoes are formed Plate Tectonics Plate Movement •  Plates move in one of four ways: - by spreading, or moving apart - subduction, or diving under another plate - collision, or crashing together - sliding past each other in a shearing motion Continued . . . NEXT
  18. 18. SECTION 3 Plate Movement • Movement of plates effects surface of the earth • Saudi Arabia–Egypt’s plates are spreading apart, widening Red Sea • India’s plate is crashing into Asian continent, building up Himalayas •  Three types of boundaries mark plate movement: - divergent boundary - convergent boundary - transform boundary continued Plate Tectonics Continued . . . NEXT
  19. 19. SECTION 3 Folds and Faults • Two plates meeting can cause folding, cracking of rock • Fault occurs when pressure causes rock to fracture, or crack • Fault line is place where plates move past each other continued Plate Tectonics NEXT
  20. 20. SECTION 3 The Earth Trembles • An earthquake occurs when plates grind or slip at a fault line • A seismograph detects earthquakes and measures the waves they create Earthquakes Earthquake Locations • Location in the earth where an earthquake begins is called the focus • Epicenter—the point directly above focus on the earth’s surface • Nearly 95% of earthquakes occur at tectonic plate boundaries Continued . . . NEXT
  21. 21. SECTION 3 Earthquake Damage •  Earthquakes release energy in the form of motion, causing: - landslides - land displacement - fires (broken gas lines) - collapsed buildings • Richter Scale—numeric scale showing relative strength of earthquake continued Earthquakes Tsunami • Tsunami, a giant ocean wave, begins at epicenter of an earthquake: - travels at up to 450 mph - waves of 50–100 ft. or higher NEXT
  22. 22. SECTION 3 The Explosive Earth • Volcano—underground materials pour from crack in the earth’s surface • Most volcanoes occur at tectonic plate boundaries Volcanoes Volcanic Action • Eruption—lava, gases, ash, dust, explode from vent in Earth’s crust • Lava—magma that has reached the earth’s surface; may create landform Continued . . . NEXT
  23. 23. SECTION 3 Ring of Fire • Ring of Fire—zone around rim of Pacific Ocean: - meeting point of eight tectonic plates - vast majority of the earth’s active volcanoes located here • “Hot spots” are where magma rises to surface from mantle • Hot springs, geysers indicate high temperatures in earth’s crust • Some volcanic action is useful: - volcanic ash produces fertile soil - hot springs are tapped for heat, energy continued Volcanoes NEXT
  24. 24. Section 4 External Forces Shaping the Earth • Wind, heat, cold, glaciers, rivers, and floods alter the surface of the earth. • The results of weathering and erosion change the way humans interact with the environment. NEXT
  25. 25. Weathering External Forces Shaping the Earth SECTION 4 Altering the Landscape • Weathering—processes that alter rock on or near the earth’s surface • Can change landscapes over time and create soil for plant life • Sediment—mud, sand, silt created by weathering processes Mechnical Weathering • Mechanical weathering—processes that break rock into smaller pieces • Does not change rock’s composition, only size • Examples: frost, plant roots, road construction, mining Continued . . . NEXT
  26. 26. SECTION 4 Chemical Weathering • Chemical weathering—interaction of elements creates new substance • Example: when iron rusts it reacts to oxygen in air and crumbles • Warm, moist climates produce more chemical weathering than cool, dry continued Weathering NEXT
  27. 27. SECTION 4 Weathered Material Moves • Erosion—when weathered material moves by winds, water, ice, gravity - movement grinds rock into smaller pieces, carries to new location • Example: water carries topsoil from hill to river, river narrows Erosion Water Erosion • Most streams erode vertically and horizontally - a valley cut by a stream gets deeper, wider; forms v-shaped valley - a river deposits sediment at ocean, creates delta—fan-like landform Continued . . . NEXT
  28. 28. SECTION 4 Wind Erosion • Wind transports sediment from one place to another • Loess—wind-blown silt and clay sediment; produces fertile soil continued Erosion Glacial Erosion • Glacier—large, long-lasting mass of ice; forms in mountainous areas • Glaciation—changing of landforms by slowly moving glaciers • Example: cutting u-shaped valleys in land • Moraine—hill or ridge formed by rocks deposited by glacier NEXT
  29. 29. SECTION 4 Soil Formation • Soil—loose mix of weathered rock, organic matter, air, water • Soil supports plant growth; fertility is dependent on three factors: - texture - amount of humus, which is organic material in soil - amount of air and water Building Soil Continued . . . NEXT
  30. 30. SECTION 4 Soil Factors • When geographers study soil, they look at five factors: - parent material—the chemical composition of the original rock - relief—the steeper the slope, the greater erosion; less soil made - organisms—plants, worms, ants, bacteria loosen soil; supply nutrients - climate—hot, cold, wet, dry climates produce different soils - time—about 2.5 cubic cm. of soil produced each century continued Building Soil NEXT
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