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Transcript
Chapter 2. Earth: unique in the solar system –Water exists in all three phases Solid, Liquid, and Gas 70 % covered with liquid water = Global Ocean * Atmosphere contains oxygen * Earth can support life Basic Earth Characteristics • Third rd (3 ) planet from the sun • A solid or terrestrial planet • Approximately 4.6 billion years old • Shape = oblate spheroid Layers of the Earth • CRUST – thin, rocky – outermost zone – Oceanic crust • Thinner, denser, younger – Continental crust • Thicker, less dense, older • MANTLE – – – – middle zone largely plastic (rock in motion) Thickest layer very dense • CORE – Earth’s center sphere; – Made of nickel and iron Layers of the Earth • “MOHO” • Mohorovicic discontinuity – The boundary between the crust and the mantle * Seismic (earthquake) waves change speed at this imaginary line. MOHO Layers of the Earth • Lithosphere – Crust and Upper part of mantle – Solid (brittle, rigid) • Asthenosphere – Upper mantle – Solid (Less rigid “plastic”) • Mesophere – Lower mantle – Solid (rigid) • Outer core – Upper core – liquid • Inner core – Inner core is solid/rigid (due to high pressure) • Center of gravity Structural or Earth as a Magnet • Magnetic North • Produced by the movement of hot, liquid iron in the outer core. • Not the same as: True or Geographic North (North Pole) • The moon and sun may also have a magnetic field. Magnetic North • Geographic north /True north. The earth rotates around the imaginary axis here. • Geomagnetic north is located by a deposit of lodestone (a magnetic rock) in northern Canada. The position of this has changed many times over the years. It is about 250 miles from True North. A compass points toward this. Magnetosphere – the magnetic field that surrounds the Earth from pole to pole. • When the solar wind (a stream of radiation coming from the sun) hits the earth, the magnetic field reacts with it. It protects us! Solar Wind influences Magnetosphere Earth’s Gravity • Isaac Newton – 1st to describe the effects of gravity. • The force of attraction between any two objects depends on the masses of the objects and the distance between them. WEIGHT AND MASS • Earth has a gravitational force that pulls objects toward the center (core) of the Earth. Weight is a measure of the strength of this pull. • Unit of weight is a Newton (N) WEIGHT AND LOCATION • Weight varies according to location on Earth. Because Earth is an oblate spheroid, you would weigh about 0.3% less at the equator as you would at the poles. • Mass does not change with location, but weight does. Internal Sources of Energy • Internal heat in the core due to “primitive heat”, radioactive decay and gravitational contraction. External Energy Sources • The sun is the most important external energy source. • Solar radiation warms Earth’s atmosphere and surface. • The heating causes the movement of air masses which generates winds and ocean currents. HOT AIR RISES CONVECTION CELL COLD AIR SINKS