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Transcript
Earth Formation of the Solar System The Nebular Hypothesis is the most widely accepted model of the formation of our solar system. Nebular Hypothesis About 4.6 bya a great cloud of gas and dust was rotating slowly in space. Forces of gravity caused the cloud to begin to shrink. As the size of the cloud shrank the rotation increased. 90% of the material rotating in the cloud began to gather around the center and this compression of material made the interior so hot that hydrogen fusion occurred. The fusion formed a star (our sun). The remaining 10% of material in the cloud formed a plate-like disk which surrounded the sun. The mass and material within the disks formed solid patches of ice and rock – eventually forming our planets, which orbit our sun. (solar system) Earth is the 3rd planet from the sun. Approximately 71% of Earth is covered with water and 29% is covered with dry land. Earth has 4 main layers: •Inner Core •Outer Core •Mantle •Crust The Lithosphere is the crust and upper portion of the mantle. (The more rigid material). Lithosphere = The Plates The Asthenosphere is the lower mantle (partially melted layer), and is responsible for the movement of the Earth’s crust (plates – also known as plate tectonics). Asthenosphere = What the plates move on Some of the heat that caused Earth’s layers came from meteor impacts over 4 billion year ago, from decay of radioactive isotopes (elements releasing heat as they disintegrate into more stable forms), and from weight of overlying materials that caused compression in Earth’s interior. Now Earth is slowly losing heat because: some rocks lose heat more quickly than others, the thickness of the crustal rock varies from place to place, and the percentage of radioactive materials in rocks varies. Earth’s Rotation Earth is tilted on its axis about 23.5º and moves in a counterclockwise direction. (This gives the appearance the sun rises in the east and sets in the west). Earth rotates (completes one turn on its axis) 360º about every 24 hours = our days and nights. In the Northern Hemisphere, Earth’s axis points towards Polaris (the North Star). Evidence and effects of Earth’s rotation are: Foucault’s pendelum and the Coriolis Effect. Evidence and effects of Earth’s rotation are: • Jean Foucault’s Pendelum – (moving about 11º in a clockwise direction each hour) • The Coriolis Effect - (winds appear to turn or be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere). Earth’s Revolution Earth rotates and revolves in a counterclockwise direction. Earth makes one revolution (one orbit) around the sun every 365.24 days = about 1 year. Evidence for Earth’s revolution was the appearance that stars were shifting positions in the sky. This appearance of stars shifting in the sky is called parallax. The Earth’s orbit is an ellipse, or elliptical, therefore, there are times when Earth is closer to the sun and times when its further from the sun. Periphelion is when Earth is closest to the sun. Aphelion is when Earth is furthest from the sun. Earth’s tilt causes the seasons on Earth. Seasons and variations in the length of days and nights are effects of the Earth’s revolution and tilt. The hemisphere tilted towards the sun receives more direct sunlight, so that hemisphere has warmer temperatures and longer days. (Therefore, the hemisphere tilted away from the sun receives indirect sunlight, so that hemisphere has cooler temperatures and shorter days). The Summer Solstice is June 21st and it is the 1st day of summer in the Northern Hemisphere (N.Hemi at its maximum tilt towards sun). Because we tilt 23.5º, the sun is straight overhead at locations along the 23.5º N latitude line (Tropic of Cancer). Areas above the 66.5º N latitude (Arctic Circle) experience 24 hours of daylight. This the Longest Day of the Year. The Winter Solstice is December 21st and it is the shortest day of the year in the Northern Hemisphere (N.Hemi at its maximum tilt away from the sun). This is the Shortest Day of the year. The Vernal Equinox is on March 21st The Autumnal Equinox is on September 22nd. Day and night are equal in length all over the world on these dates. Sunlight falls directly on the equator (so day and night are equal because neither hemisphere tilts toward the sun). What do winds and ocean currents and evidence for Earth’s rotation all have in common??? Coriolis Effect Link Apparent curving of moving objects (ie- Water) due to the Earth’s rotation Surface Current Link Controlled by three factors Global winds Coriolis Effect Continental Deflections Deep Thought Oceanography Questions from Ch. 22: 1.What elements make up a water molecule and how are they arranged? 2.How much of Earth’s surface to oceans cover? 3.Why does ice float on top of water? 4.Why do people float in the Dead Sea? 5.Is there salt in icebergs? 6.What happens to the salt when water freezes? Deep Thought Oceanography Questions from Ch. 22: 7. How does salt get into oceans? 8.Does seawater freeze at 32ºF (0ºC)? 9.Why are there different temperature zones in the oceans? 10.Name a few things that are found in deep ocean life? 11.Would ocean salinity be lower or greater in areas of heavy rainfall and areas where large amounts of fresh water enter the ocean? Ocean Floor http://www.earthscape.org/t2/meg01/meg01c.html#margin Oceanography Questions from Ch. 24: 1.Currents flowing away from the warm equator carry (A. warm B. cold) water, and currents flowing toward the equator come from the poles and carry (A. warm B. cold) water. 2.Gulf Stream carries warm water that originates and ends where? 3.What is the primary cause of surface currents? 4.Why is Labrador Current hazardous to ships going from Europe to North America? Oceanography Questions from Ch. 24: 1.What causes tides? 2.What is a high tide? 3.What is a low tide? 4.How are spring and neap tides different from high and low tides? 5.Why do tides occur 50 minutes later each day? 6.Draw the position of the sun, moon, and earth during a spring and neap tides.