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Tuesday, January 17 Unscramble the following words for your science starter today: Can you unscramble all the words below? Hint: They all start with the letter D. E D C M O P S E O R 1. I’m called nature’s recycler. ATDA 2. I can help you make a decision. SIDSLOEV 3. This happens in a solution. GAMRIDA 4. You might label me. EDCBEISL 5. How loud can you be? The answers are … DECOMPOSER 1. I’m called nature’s recycler. DATA 2. I can help you make a decision. DISSOLVE 3. This happens in a solution. DIAGRAM 4. You might label me. DECIBELS 5. How loud can you be? Introduction to Planet Earth Let’s dig a hole to China! Earth Stats • The Earth's mass is about 5.98 x 1024 kg. • Earth is the densest planet in our Solar System (mass/volume). • Earth is made of several layers with different compositions and physical properties, like temperature, density, and the ability to flow. The Composition of the Earth The Composition of the Earth Crust •Thinnest layer (5-100 km) •Two types of crust •Continental •Like granite •Average 30 km •Oceanic •Like basalt (Basalt is denser than granite!) •Average 5-8 km The Composition of the Earth Mantle •Extremely Thick! (2,900 km) •It is too far down to drill •How do we know what it is made of? •Scientists infer based on: •Pushed up rock •Ocean floor/molten rock •What is it like? •Like the mineral olivine •Large amounts of iron and magnesium www.soc.soton.ac.uk The Composition of the Earth N Core •Pretty darn big. (6,856 km) •(Slightly bigger than Mars!) •33% mass of the Earth •Scientists think…. •Made mostly of iron •Some nickel, sulfur, oxygen •What is the evidence? •The particular way seismic waves travel •Earth’s Magnetic field S The Structure of the Earth Lithosphere Solid Asthenosphere Viscous Liquid Outer Core Liquid Mesosphere Solid Inner Core Solid Lithosphere = ‘rock sphere’ Crust and upper rigid part of Mantle Asthenosphere = ‘weak sphere’ Lower part of Mantle How HOT is it? Convection • Convection (heat) currents – carry heat from the hot inner mantle to the cooler outer mantle. • The mantle gets warmer with depth • top of the mantle is ~ 1,600° F (870° C) • bottom of the mantle is ~4,000-6,700° F (2,200-3,700° C) • The mantle contains most of the mass of the Earth Let’s Make Models of the Earth! • • • • • Inner Core (yellow) diameter 2 cm (4) Outer core (orange) diameter 6 cm (4) Mesosphere (red) diameter 11cm (4) Asthenosphere (brown) diameter 12cm (2) Lithosphere (sand) – -after assembly roll edges of asthenosphere in glue and then sand (1.5mM thick) How do scientists know what makes up the earth’s interior if we can’t actually dig a hole through the earth to see it directly? 1.Direct evidence from rock samples. and 2.Indirect evidence from seismic waves when we have an earthquake. (The speed of seismic waves and the path they take through the earth reveal the structure of the planet.) Why does the earth have high temperatures in the center? Where does the heat come from? The high temps. inside the earth are the result of heat left over from the formation of the planet. Also, radioactive substances inside the earth release energy. What kind of rock makes up the oceanic crust? Basalt A dark rock with a smooth texture. What kind of rock forms the continents? Granite A rock that is light in color and has a coarse texture. 3 Types of Heat Transfer 1. Radiation--through space, no direct contact. Ex: Sunlight to earth, campfire 2. Conduction--between materials that are touching. Spoon gets hot as it sits in a pot of hot soup. 3. Convection--movement of fluids and currents in the fluids. Ex: boiling water Convection Caused by: • temperature differences • density differences • gravity Occur in the outer core (magnetism)and mantle (plate tectonics) Alfred Wegener 1915 German man who proposed the Continental Drift Theory. Pangaea--super continent “all lands” Evidence: 1. land features 2. fossils 3. climate change Sea-floor Spreading The sea floor spreads apart along both sides of a mid-ocean ridge (forms a crack in the ocean floor) as new crust is added. As a result, the ocean floors move like conveyor belts, carrying the continents along with them. Molten material fills in the crack as it rises to the surface. As it cools, it forms a strip of rock in the center of the ridge. Evidence of Sea-floor Spreading Read pages 24 F-29 F Rocks shaped like squeezed toothpaste Magnetic Stripes Drilling Samples Subduction at Trenches • Where the oceanic crust bends downward and sinks back into the mantle • Pacific Ocean is shrinking!! • Subduction is occurring faster than new crust is being produced. Plate Tectonics The lithosphere is broken into separate sections called PLATES that move because of convection currents in the mantle. This is the sea-floor spreading and continental drift theories wrapped into one. Plate Boundaries--Faults Divergent--where two plates move apart, at mid-ocean ridges where sea-floor spreading occurs. Convergent--where two plates come together and collide. The density determines which sinks. Creates Mountain ranges. Transform--slipping past each other. Earthquakes occur here.