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Review slides. Topographic Maps. Streams and maps. Prime Meridian. The prime meridian is 0 degrees longitude.
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Prime Meridian The prime meridian is 0 degrees longitude. From Pole to Pole, the Prime Meridian covers a distance of 20,000 km. In the Northern Hemisphere it passes through UK, France and Spain in Europe and Algeria, Mali, Burkina Faso, Togo and Ghana in Africa. The land mass crossed by the Meridian in the Southern Hemisphere is Antarctica. http://www.portcities.org.uk/london/upload/img_400/Greenwich_meridian_20040512123830.gif
What do you see happening here? Evolution of a Meandering Stream http://www.wwnorton.com/college/geo/egeo/flash/14_1.swf Where is sediment deposited and why? Stream erosion and deposition
Sedimentation http://www.classzone.com/books/earth_science/terc/content/visualizations/es0604/es0604page01.cfm?chapter_no=visualization Transport of sediment in stream http://www.classzone.com/books/earth_science/terc/content/visualizations/es1303/es1303page01.cfm?chapter_no=visualization
How can you tell the difference between a young river and an old river? • You can judge the age of a river by the erosion it has made in the geography of the land, such as the Colorado river has cut canyons into the earth. New rivers are more turbulant because they haven’t had the time to smoothen the rocks and terrain it flows over.
Age of a River • Youthful river • a river with a steep gradient that has very few tributaries and flows quickly. Its channels erode deeper rather than wider. • Mature river • a river with a gradient that is less steep than those of youthful rivers and flows more slowly. A mature river is fed by many tributaries and has more discharge than a youthful river. Its channels erode wider rather than deeper. • Old river • a river with a low gradient and low erosive energy. Old rivers are characterized by flood plains.
Erosion vs weathering • Erosion is the removal of sediment, soil or rocks in the natural environment. Due to transport by wind, water, or ice; by down-slope creep of soil and other material under the force of gravity or by living organisms, such as burrowing animals • Weathering is the process of chemical or physical breakdown of the minerals in the rocks
Streams and Hydrology Now Check your understanding...Try out this Hydrological Cycle / Drainage Basins Walk the Plank Gameand check your understanding of Drainage Basin Features by matching up these key terms and definitions within the 30 second time limit!
Stars • What are stars made of? • Mostly Hydrogen (H) and Helium (He), with bits of heavier stuff like oxygen, carbon, iron, etc. • This is a similar composition to that of the universe as a whole.
Star Life Cycles • Video • http://www.metacafe.com/watch/752173/life_cycle_of_star/ • Site • http://www.seasky.org/celestial-objects/stars.html
Focus on Main Sequence of Hertzsprung-Russell cycle Main Sequence is where stars spend the majority of their lives. What trends do you notice about the Main Sequence stars?
Effect of Size on Stars More massive stars exert stronger gravitational pulls on the materials that comprise them. This results in greater pressure at the core and thus higher temperatures. This leads to a bluish tint. Fusion reactions occur faster at higher temperatures, so these stars burn out more rapidly, in as little as thousands of years.
Small Stars • Less massive stars are dim and red. • They have low core temperatures and undergo fusion very slowly. • So slowly, in fact, that even though they are starting out with much less mass than the most massive stars, they can stay in the Main Sequence for billions of years. • Our sun, which is pretty medium, is expected to last for about 10 billion years (only 5 billion more to go!)
Interactive HR answer the questions here: http://aspire.cosmic-ray.org/labs/star_life/support/HR_static_real.html
E • BCD • A • E • A • B • E • B • E • C • A • A • RED GIANT • VARIABLE
Planet formation • The Sun formed from a nebula (interstellar cloud of dust, hydrogen gas, helium gas and plasma • The inner planets are mostly rock and metal • The outer planets are mostly ice and gas
Solar System • The solar system was born about 4.5 billion years ago, when something disturbed and compressed a vast cloud of cold gas and dust -- the raw material of stars and planets. The disturbance may have been a collision with another cloud, or a shock wave from an exploding star. • Whatever the cause, the cloud fragmented into smaller, denser pockets of matter, which collapsed inward under the pull of gravity. In perhaps 100,000 years, one of the pockets, called a nebula, condensed into a volume about the size of the present-day solar system. In the dense center of the nebula, a star formed -- our Sun. • The newborn Sun was still surrounded by its nebula, which was spread into a thin disk because the nebula was spinning slowly.
Solar System • Atoms and molecules within the nebula combined to form larger particles. The Sun determined what kinds of particles could exist. Close to the Sun, solar heat vaporized ices and prevented lightweight elements, like hydrogen and helium, from condensing. • Inner PlanetsThis zone was dominated by rock and metal, which clumped together into ever-larger bodies, called planetesimals, eventually forming the rocky inner planets: MVEM
Outer PlanetsIn the solar system's outer region, though, it was chilly enough for ices to remain intact. They, too, merged into planetesimals, which in turn came together to form the cores of the giant planets: JSUN-- P
Solar System • Plenty of hydrogen and helium remained in this region far from the Sun. As the giant planets grew, their gravity swept up much of these leftovers, so they grew larger still. Jupiter and Saturn contain the largest percentages of hydrogen and helium, while Uranus and Neptune contain larger fractions of water, ammonia, methane, and carbon monoxide. • Most of the moons probably formed at the same time as their parent planets. Earth's Moon probably formed a bit later, when a body several times as massive as Mars slammed into our planet. The collision blasted a geyser of hot gas and molten rock into orbit around Earth; the material quickly cooled and coalesced to form the Moon.
Steps to the formation of stars and planets: • Clouds of gas form within galaxies. • Formation of structure within the gas clouds, due to "turbulence" and activity of new stars. • Random turbulent processes lead to regions dense enough to collapse under their own weight, in spite of a hostile environment. • As blob collapses, a disk forms, with growing "protostar" at the center. • At the same time, bipolar outflows from forming star/disk system begin. • Material is processed, moving in from the blob to the disk. What is not lost in the outflow builds up on the protostar. • When the protostar begins to undergo fusion, it becomes a real star. • Once the outflow ceases and the "accretion" phase that lead to the buildup of the star ends, a disk of "leftover" material is left around the star. • At or near the end of the star-formation process, the remaining material in the "circumstellar disk" (a.k.a. "protoplanetary disk") forms a variety of planets. • Eventually, all that is left behind is a new star, perhaps some planets, and a disk of left-over ground-up solids, visible as a "Debris Disk" around stars other than the Sun, and known as the "Zodaical Dust Disk" around the Sun.
