Transcript Chapter 2
Earth as a system Chinese (780B.C.)– earthquakes Greeks (200B.C.) – minerals Mayans (1100B.C.) - astronomy Geology Oceanography Meteorology Astronomy Environmental Science • • • • Formed about 5 billion years ago. 71% of earth is covered in ocean. Not a perfect sphere because of rotation. From space height and depth of mountains and space do not appear significant. Seismic activity both manmade and natural give clues to the composition of earth’s interior. Three distinct layers Crust Mantle Core Crust – thin – accounts for 1% of the earth’s mass. – Moho (Mohorovicic) the boundary between crust and mantle layer just inside of crust. – 2 types of crust • Continental – 15-80km in thickness – 2.7g/cm3 density • Oceanic – 5 to 10km in thickness. – 3.0 g/cm3 density Denser material than the crust. Thickness 2900km. 2/3 of the earth’s mass. Center of the earth. Composed primarily of iron and nickel. The iron core is about 7000km in diameter. The outer portion being liquid and the inner portion being solid. • 1. Composed of 5 structural zones. Lithosphere upper most part of the mantle and crust. – Solid and rigid. – 15 to 300km thick. – 2. Asthenosphere middle portion of mantle. – Solid but plastic like (plasticity). – 200 – 250 km in thickness. – 3. 4. 5. Mesosphere – Layer below Asthenosphere more rigid is structure. Outer Core – 2900km depth start the outer core believed to be liquid. Inner Core – 5,150km depth starts the inner core believed to be solid. The earth generates a magnetic field thought to be caused by the rotation of the outer liquid iron nickel core. This field is known as the magnetosphere and it shields the earth from cosmic radiation (solar wind). Atmosphere – 78% nitrogen and 21% oxygen. Upper atmosphere provides UV protection. Hydrosphere – 71% of earth’s surface. 97% of water is salt water. The 3% that is fresh is found in lakes , streams, aquifers and ice. Geosphere – Rock, soil, continents and oceanic floor and the molten portion of the earth. Biosphere – The volume 8km above the earth’s surface to 8km below the earth’s surface and organic material. Gaia hypothesis – all organic and inorganic things work together as a system. Two components of any system are matter and energy. Closed System – energy can enter or exit but matter does not enter or leave. Open System – energy and matter can leave or enter the system. All life at one time was believed to be dependent on energy from the sun. In the 1970’s it was found that food webs could also be dependent on chemicals ejected through deep volcanic vents found in the ocean floor. Internal energy comes from radioactive decay and gravitational contraction. External energy comes from the sun. Nitrogen cycle – used in the formation of proteins. 78% of air is Nitrogen gas. Bacteria fix Nitrogen (make it into a useable form) for plants and then animals. NH3 , NO3, NO2 Carbon forms the backbone for many organic molecules. Carbohydrates are a primary energy source for many organisms. Carbon dioxide can be fixed by plants into a useable form. Phosphorous does NOT cycle well. Phosphorous is trapped in rocks and as weathering takes places phosphorous is released. It is absorbed by plants and then consumed by animals. Phosphorous is used in the formation of nucleic acids. Evaporation Transpiration Condensation Precipitation Roles Consumers Producers Decomposers Carrying Capacity Foods and Webs Succession Primary Secondary Trophic Levels 4 to 5 levels tops More levels at equator than at poles. Energy Loss Repair Regulation Response Loss of habitat Water pollution Greenhouse effect Ozone Depletion Overpopulation …