Review terms Test 1 Scientific method o The means win which we figure shit out Make an observation Form a hypothesis Test said hypothesis Compare results to hypothesis Uniformitarianism o the assumption that the same natural laws and processes that operate in the universe now have always operated in the universe in the past and apply everywhere in the universe James Hutton Catastrophism o Founder of uniformitarianism o the theory that the Earth has been affected in the past by sudden short lived violent events possibly worldwide in scope Georges Cuvier o Cuvier s work is considered the foundation of vertebrate paleontology and he expanded Linnaean taxonomy by grouping classes into phyla and incorporating both fossils and living species into the classification o Cuvier also is well known for establishing extinction as a fact Neptunism o a superseded scientific theory of geology proposed by Abraham Gottlob Werner in the late 18th century that proposed rocks formed from the crystallisation of minerals in the early Earth s oceans It was named after Neptune the ancient Roman god of the sea Abraham Werner o Founder of neptunism o Father of german geology Age of the Earth o 4 54 billion years Iridium o There are iridium abundances in clay residues from pelagic limestones o Alvarez measured Ir o Expected slight enrichment due to hiatus time gap o Found huge Ir increase o Ir anomaly o Hiatus cannot explain Ir o Postulated impact of 6 10 km asteroid o Dust blocks out sun disrupts food chain o Barringer Meteor crater Arizona 1 km diameter Impact 50 ka Shocked quartz quartz o a form of quartz that has a microscopic structure that is different from normal o Under intense pressure but limited temperature the crystalline structure of quartz will be deformed along planes inside the crystal These planes which show up as lines under a microscope are called planar deformation features PDFs or shock lamellae o Eugene Shoemaker showed that shocked quartz is also found inside craters created by meteor impact such as the Barringer Crater and Chicxulub crater o The presence of shocked quartz proves that these craters were formed by an impact not volanoes Big Bang outwards Doppler effect o The theory of how the universe began from a single point and exploded o The effect of how we perceive sound as it moves towards and away from us o the change in frequency of a wave or other periodic event for an observer o as it moves towards you the frequency seems higher and as it moves away the moving relative to its source frequency seems lower Red Shift Blue Shift Galaxy o As light moves away from you it appears more red o Everything in the universe appears to be red shifting o As light moves towards you it appears blue o a massive gravitationally bound system consisting of stars stellar remnants an interstellar medium of gas and dust and dark matter Solar Nebula hypothesis o The way the sun and our solar system were formed o Begins with a molecular cloud Contains moderate amount of atoms compared to our atmosphere About 80 H and 20 He o Gravity begins to pull the atoms together o This produces more energy in the form of heat as the atoms impact o There is eventually enough heat and energy to cause fusion o The energy from this fusion creates stars o As stuff begins to spin towards the center the rate of spinning increases o This spinning eventually creates centripetal force and particles begin to stick together to form planetesimals o Planetesimals grow by continuous collisions Gradually an irregularly shaped proto Earth develops The interior heats up and becomes soft o Gravity reshapes the proto Earth into a sphere The interior of the Earth separates into a core and mantle Molecular cloud o a type of interstellar cloud whose density and size permit the formation of molecules most commonly molecular hydrogen H2 Most common elements in the whole earth Most common elements in the crust o Fe 35 o O 30 o Si 15 o Mg 13 o Ni 2 o O 46 o Si 28 o Al 8 o Fe 6 o Mg 4 Moon formation o About 4 5 billion years ago a Mars sized body impacted the Earth o The giant impact propelled a shower of debris into space o Earth re formed as a largely molten body o The Moon aggregated from the debris o The impact sped up Earth s rotation and tilted Earth s orbital plane 23 Crust o Top layer of the earth o The crust is the most heterogeneous layer in the Earth o Continental crust O Si Al Ca K Na 30 70km thick o Oceanic crust O Si Al Fe Mg Ca 5 8km thick Mohorovi i discontinuity moho o The boundary between the crust and the mantle which is mostly chemical o The crust and mantle have different compositions o It was discovered in 1910 by the Croatian seismologist Andrija Mohorovi i Mantle o The layer beneath the crust o The mantle extends from the bottom of the crust to a depth of 2900 km o The core mantle boundary is sharp Gutenberg discontinuity o The change in density across the core mantle boundary is greater than that at the Earth s surface o The rocky mantle is composed mostly of O Mg Fe and Si o It is subdivided into Upper mantle base of crust to 400 km Transition zone 400 670 km depth Lower mantle 670 2900 km depth Outer core Inner core Lithosphere o The molten iron outer layer of the core 2900 5150km o The outer core is liquid and it flows kilometers per year o The outer core is the most homogeneous part of the Earth o This portion is as hot as the surface of the sun o The solid iron inner portion of the core 5150 6370km o This portion is solid rock which is slowly freezing o Both cores are made up mainly of iron and nickel o This ranges from 10 200km deep o The lithosphere is the strong uppermost layer of the Earth o There is not a strict boundary between the lithosphere and the asthenosphere as there is between the crust and mantle o It consists of both crust and uppermost mantle o It behaves rigidly like a solid over very long time periods Aestenosphere o The asthenosphere is found 100 300 km below the surface o It is the weakest part of the mantle o It behaves like a solid over short time scales but behaves like a fluid over o The asthenosphere decouples the lithosphere tectonic plates from the rest of millions of years the mantle Mesosphere o The mesosphere ranges from 660 2900km deep o This consists of the majority of the mantle Lehman s Discontinuity o The boundary between the liquid outer core and the solid inner core o occurs at a depth of about 5150 km Magnetic field o It was first thought that the Earth s magnetic field