1Topics:Overview of Virginia GeologyPh i hi iPhysiographic provincesFormation and differentiation of the earthPhysiographic provinces and Virginia geologic overview• Google Earth overview of North America• USGS Tapestry of Time and terrain maps http://tapestry.usgs.gov/http://pubs.usgs.gov/imap/i2206/• N America physiographic province discussion/activity• GE overview of Appalachian and coastal landscapes• http://home.wlu.edu/~kuehns/Geo100/W10/VA-Physio-Geo.pdf• Local geologic maps (Rockbridge County and BV 100K maps)• http://web.wm.edu/geology/virginia/Æ maps & diagrams Æ Tectonic historyHow was the Earth formed?3NASA imageOr, more generally, how was our solar system formed?Figure 1-3 in Understanding Earth4Nebular hypothesis of solar system formation: The planets formed about 4.6 to 5 billion years ago from a large nebula (cloud of dust and gas) that began to condense. Figure 1-2 in Earth Science5Formation of our solar system Material continued to condense and form the planets.Figure 1-2 in Earth Science6Individual planets may have required a few million years to form or possibly as little as a few hundred years.Earth Science27Craters on the moonCollisions of meteorites with planets is a continuation of the process that formed the solar system.Image credit: Consolidated Lunar Atlas - NASA (LPI)http://www.lpi.usra.edu/research/cla/maps/thumbs.htmCraters on the Earth:Meteor Crater, Arizona~3/4 mile wide & ~50,000 years oldproduced by the Canyon Diablo meteoriteNational Museum of Natural History8NASA (JPL)The process continues today9Photo above taken from India http://www imo net/photo/Leo2001 htmlMeteors in the night sky2001 Leonids meteor showerhttp://www.imo.net/photo/Leo2001.htmlPhoto above taken from Australiahttp://www.space.com/scienceastronomy/astronomy/leonids_wow_011119.htmlLayers of the earthHow did it get this way?10One clue: meteorite compositionsChapter 19 Understanding Earth11Relative abundances of the top 8 elementsWhy is it like this?Figure 1-6 Understanding EarthDifferentiation of the earth into layers1. The initially homogeneous earth12homogeneous earth(Why do we think it was homogeneous?)Figure 1-6 in Understanding Earth3Differentiation of the earth into layersThe earth partially melts and then differentiates as heavier elements sink and lighter elements 13float.Heat sources:- accretion- radioactive decay- gravitational potentialenergyFigure 1-6 in Understanding
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