Global Biogeochemical Cycles10.docx

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Department
Earth & Environmental Sciences
Course
EESC 1158
Professor
Donald James
Semester
Fall

Description
January 312/2013 Class Geologic Time Scale - When did the Earth turn solid? Absolute Age of the Earth = amount of time since the earth solidified - How did it become a molten sphere?  Originally was formed from solid particles of rock that were orbiting solar system (vincitnity of earth’s orbit) and because of gravity…chunks of rock material formed a solid body - 2 reasons why it melted Meteorite Impact Radioactivity (elements inside the Earth) – when they decay it creates heat that gets turned into electrical energy *Principle of Uniformitarianism – th Missed Feb 5 Class Method of Determining Earth’s Age… Principle of “Parsminoy” or Principle of Simplicity One should always choose the simplest explanation of a phenomenon, the one that requires the fewest leaps of logic. Occam’s Razor One should not increase beyond what is necessary, the number of entities required to explain anything A logical principle attributed to the mediaeval philosopher William of Occam One should not make more assumptions than the minimum needed Often called the principle of Parsimony Underlies all scientific modeling and theory building Admonishes us to choose from a set of otherwise equivalent models of a given phenomenon the simplest one Age of the Earth III Earth’s earliest rocks have been recycled, and we need to look beyond Earth to find evidence of when it solidified Examples of Very old rocks on Earth: South Africa – 3.4 billion year old granites Greenland – 3.7 billion granites Oldest Terrestrial rocks – 3.8 billion (Deep in the interiors of continents) Meteorites Remains of rocky and metallic material that fall to the Earth from inter-planetary space Thought to be representative samples of material that formed the early solar system Believed to have solidified at about the same time as the Earth Ex. Meteor Crater, Arizona – created approximately 50,000 years ago Major Impact Structures 200 million year old eroded impact structure in Quebec Radiometric Dating of Meteorites Found to be about 4.4 to 4.6 billion years old Thought to be samples of material that formed the early solar system…The Earth is now believed to be about 4.4 to 4.6 billion years old Lunar Rocks On moon Remnants of the early formation of the solar system Oldest lunar rocks have been found to be 4.4 to 4.5 billion years old (Radiometric dating) The Moon: Maria, Craters, Highlands Oldest lunar rocks are found in The Highlands Origin of the Solar System Nebular Hypothesis: The planets formed at essentially the same time and from the same primordial material as the sun Formed from the accretion of tiny particles that condensed out of a primordial solar nebula Proposed by Immanual Kant (German philosopher) in 1755; also proposed by French mathmetician Pierre Simon LaPlace in 1796 Between 5.0 – 4.6 billion years ago…. The Solar Nebula condensed into a number of discrete clusters of mass that eventually formed into the planets Molten Earth Early Earth: Homogenous Mixture Differentiation: Iron sinks to center, lighter material floats up to form crust Present: Dense iron core, crust of light rok, mantle in between Missed week of Feb 5/7 North Korea Nuclear Test Hong Kong (CNN) – NK said it conducted new powerful underground nuclear test Using more sophisticated technology Jolting already fragile security situation in North East Asia Drawing condemnation from around the globe *First nuclear test carried out under their leader KIM JONG UN – sticking to father’s policy of building up isolated state’s military deterrent to keep its foes at bay, shrugging of resulting international condemnation/sanctions October 9 . 2006 = Detonated a nuclear device Underground Nuclear Blasts P waves dominate Compressional waves Similar to sound waves Natural Earthquakes S waves dominate Transverse waves Similar to shaking one end of rope Frequencies of 6-8 hertz – Nuclear Explosions consistently have LARGER ratios of primary-to-secondary wave amplitude than earthquakes Why is underground testing controversial? NK is only country to do atomic explosions on planet since 98’ (Pyongyang 2006/09) 1996 Treaty = signed by 183 nations – aims to ban ALL nuclear testing on the planet, whether in atmosphere or underground Only NK, India, Pakistan have broken moratorium on nuclear testing Testing in atmosphere/underwater was banned by 1963 Partial Test Ban Treaty – after public concerns over radioactive fallout US, Soviet Union, Britain signed the treaty – France/China did not France’s last test = 1974, China’s 1980 Seismology and Nuclear Test Ban Treaties One of the *major areas of scientific and technological research and development during 60’s… Development of Nuclear Weapons Fearful of Russians to develop nuclear weapons that would give them advantage over the USA Seismological community given generous amounts of research funding to work on the problem of monitoring nuclear tests from a distance How to distinguish between earthquakes and explosions based on seismograms? Major research efforts during “Cold War’ = solving the problem of monitoring nuclear tests from a distance Evolution Lecture Evolution: “descent with modification” Decent = The transmission of characteristics by inheritance Modification = changing Characteristics of individuals change from one generation to the next Modification of characteristics is due to genetic inheritance “Family Tree” or “Phylogeny” Change, but NOT Evolution… Ex. Beetles in a drought All have same chances of survival and reproduction, but because of food restrictions, beetles in the population are smaller than the preceding generation of beetles Most of beetles in the population (90%) have the genes for bright green coloration, and few (10%) have a gene than makes them more brown Generations later…Beetles are now more common to be brown Gene: A unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring A region of DNA with a particular phenotypic effect May mean a stretch of DNA that includes a transcribed and regulatory region Phenotype: Observable physical or biochemical characteristics of an organism, determined by both genetic makeup and environmental influences Evolution: Change in gene frequency over time Beetle example difference = because of environmental influence, NOT because of a change in gene frequency The changing color is evolution – hav
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