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Chapter 2 The Earth Section I. Planet Earth What do you know about the Solar System? A. Our Solar System The sun is at the center of our Solar System Sun creates a strong pull of gravity Keeps objects such as Earth revolving around the Sun Our Solar System Revolution – in astronomy, the Earth’s yearly trip around the sun 365 ¼ days Why is the ( ¼ ) important to know?? Rotation axis – the Earths daily trip turning on its How long is a day? In history…. People believed that the solar system revolved around Earth Geocentrism Connected to religion But it was Galileo (16th century) that actually fought for the now accepted theory that we were the ones moving Heliocentrism What’s the idea behind the theories? Why would people think we were geocentric?? Which theory would you side with if you had to choose? What would happen without the sun? The “Classical” Planets: Neighbors in Space Before it was believed we had nine planets now we just classify eight Inner Planets (Terrestrial) Mercury Venus Earth (only one with sustainable life) Mars The “Classical” Planets: Neighbors in Space Outer Planets (Gas Giants) Jupiter Saturn Uranus Neptune All have moons except Mars & Venus There are also asteroids, comets and meteoroids Pluto……..planet?? Discovery Channel, August 24th, 2006 [Much-maligned Pluto doesn't make the grade under the new rules for a planet: "a celestial body that is in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a ... nearly round shape, and has cleared the neighborhood around its orbit.“] [Pluto is automatically disqualified because its oblong orbit overlaps with Neptune's.] B. Getting to know the Earth The earth is divided into categories Hydrosphere – part of Earth made up of oceans, lakes, rivers, and other bodies of water Lithosphere – part of Earth made up of continents and islands Atmosphere – a layer of gases that surrounds the Earth Biosphere – the part of the Earth that supports life Hydrosphere = WATER Earth is 70% water Lithosphere = Land Earth is 30% land Atmosphere = Air Above gases earth’s surface you have a layer of 78% nitrogen, 21% oxygen and the rest argon and other gases Our natural vegetation is essential to the recyclement of our oxygen Biosphere = life The part of earth that supports life Life outside of the biosphere only exist with mechanical life support system Space shuttle Air + Land + Water = Biosphere! Bio=life! Hence, Biology…. C. Landforms Natural features of the earth’s surface that vary in shape and elevation 4 major landformsMountains All contain rivers, lakes and Hills streams Plateaus Plains Also have valleys, canyons, and basins Underground Landforms Landforms underwater are as diverse as those found on dry land Range from flat plains to mountain ranges, cliffs, valleys and deep trenches Earth’s most visible landforms From space the most visible landforms are the 7 continents Australia Antarctica Europe Asia North America South America Africa **** Locate continents on your map **** Continental Shelf Part of a continent that extends underwater Long narrow underground canyon (Pacific Ocean) Section II. Forces of Change How does earth change? What processes are responsible for such changes? Forces of Change On the surface Wind, water, etc Originate from the interior Volcanic eruptions, earthquakes, etc Earth’s Structure The earth is composed of three layers Core Inner core is made up of iron and nickel under enormous pressure Outer layer is liquid made up of melted iron and nickel Mantle Thick layer of hot dense rock Mixture of elements that continually rises, cools, sinks, warms up and rises again Responsible of 80% of heat generated from earth’s interior Crust Broken up into more than a dozen great slabs of rock called plates that rest (float) on a partially melted layer in the upper mantle Carry the earth’s oceans and continents Continental Drift Theory Pangaea Theory that all the continents were once joined and slowly started to drift apart Plate theory “Continental Drift” Pangaea – a gigantic supercontinent that eventually broke apart (drifted) into smaller continents due to plate movement Crust=Plates Plate Tectonics Plates are continually moving At times they may crash, pull apart, grind or slide past each other Constantly changing the face of the planet They push up mountains, create volcanoes, and produce earthquakes Theory: heat rising from the core create slow-moving currents within the mantle which then shift the plates around Crust=Plates Internal forces of change 1. 2. 3. 4. 5. 6. 7. 8. Colliding Subduction Accretion Spreading Folds Faults Earthquakes Volcanic Eruptions 1. Colliding Giant continental plate collide Creates mountains Himalayas 2. Subduction A heavier sea plate dives beneath the lighter continental plate Plunging into the earth’s interior, the sea plate becomes molten material Then as magma it bursts through the crust to form volcanic mountains Andes 3. Accretion Pieces of earth’s crust come together slowly as the sea plate slides under the continental plate Creates underwater mountains with steep sides and sharp peaks Creates new land often island chain at the boundary 4. Spreading Sea plates pull apart Deep cracks (rift) allow magma from within the earth to well up between the plates Magma hardens to build undersea volcanic mountains or ridges Spreading keeps Europe and N. Ame apart 5. Folds (bends) Moving plates squeeze the earth’s surface until it buckles or creates folds in layers of rock 6. Faults Plates grind or slide past each other creating cracks in earth’s crust When land can no longer be folded the earth’s crust cracks and breaks into huge blocks Small tremors occur San Andres Fault in CA 7. Earthquakes Sudden, violent movements of plates along a fault line Dramatically change the surface of the land and the floor of the ocean Happen when different plates meet each other. Tension builds up as the plates stick. The strain becomes so intense that the rocks suddenly snap and shift. This releases stored up energy along the fault. Eventually the ground trembles as sends shock waves which are felt Ring of Fire Earthquake and volcano zone surrounding the Pacific Ocean Boundary where the plates that cradle the Pacific meet the plates that hold the continents surrounding the ocean 8. Volcanoes Volcanoes are mountains formed by lava or magma that breaks through the earth’s crust Often rise along plate boundaries where one plate plunges beneath another In such a process the rocky plate melts as it dives downward into the hot mantle. Pressure builds, a funnel is created and hot magma rushes to the surface. The lava will eventually create a volcano Volcanoes As a moving plate passes over these hot spots, molten rock flowing out of the earth’s surface may create volcanic island chains Hawaiian Islands Molten rock may also heat underground water causing hot springs or geysers Yellowstone External Forces of Change Wind and water change the earth’s surface (two processes) Weathering – process that breaks down rocks on the earth’s surface into smaller pieces Erosion – wearing away of the earth’s surface by wind, glaciers, and moving water 1. Weathering 2. Wind Erosion 3. Glacial Erosion 4. Water Erosion Weathering Either physical weathering or chemical weathering Physical – when large masses of rock are physically broken down into smaller pieces Water seeps into the cracks in a rock and freezes, then expands and causes the rock to split Chemical – changes in the chemical makeup of rocks (transforming their minerals or combining them) Water mixed with carbon dioxide from the air easily dissolves certain rocks such as limestone Wind Erosion Movement of dust, sand, and soil from one place to another Can be devastating or beneficial Dust Bowl China Yellow River basin is thickly covered with loess (fertile yellow-gray soil deposited by wind) Glacial Erosion Glaciers – large bodies of ice that slowly move across the earth’s surface Glacial movements change the landscape by destroying forests, carving our valleys, etc However, when glaciers melt and recede they leave behind large pules of rocks and debris (moraines) Moraines can form long ridges of land or create glacial lakes Water Erosion Most significant cause of erosion Fast moving water – rain, rivers, streams, and oceans – cuts into the land wearing away the soil and rock The resulting sediment (small particles of soil, sand and gravel) act like sandpaper and cut away at land Grand Canyon Section 3 – Earth’s water Hydrosphere!! Almost all of the hydrosphere is salt water found in the oceans, seas and seawater lakes The remainder is freshwater found in lakes, rivers, and springs Water Cycle Regular Evaporation – sun, changing liquid into vapor or gas Condensation – excess water vapor changes into liquid form 1. 2. 1. 3. movement of water through Forms clouds Precipitation – rain, snow, or sleet that sinks into the grounds and soon is evaporated again Bodies of Salt Water (97%) Oceans 1. 2. 3. 4. 5. Pacific Atlantic Artic Southern Indian Seas, Gulfs, and Bays Desalination – conversion saltwater into freshwater Freshwater (3%) Lakes, Streams, and Rivers Groundwater – freshwater that lies beneath the earth’s surface Comes from rain and melted snow that filter through the soil and from water that seeps into the ground from lakes and rivers Can use wells to tap into freshwater Aquifer – underground porous rock layer saturated with water in the form of streams
