GEO 102 1st Edition Lecture 9 Outline of Last Lecture I. What the Earth is made ofOutline of Current Lecture II. Original ThoughtsIII. Dynamic Earth TodayIV. Evidence of Tectonics and what drives itV. convectionCurrent LectureOriginal Thoughts► Earth was flat, stationary, and young► All else orbited the Earth► It had always been this way► It would more or less stay this wayQuakes, tsunamis, volcanoes, location of mountains, continents, & oceans were all considered unrelatedAll of these thoughts were overturnedThe Earth is not Static► Continents move► Mountains form and erode awayThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-Mountains typically form on the active margins of the plates► Oceans open and close, rise and fall► New Earth is formed while old is recycled► It changes the deeper you goAtmosphere – Oceans – Continents are all dynamically linked Dynamic Earth Today► The Atlantic is growing► The Appalachians are shrinking (eroding)► The Andes, Himalayas, Cascades, and others are growing higher► LA is not going to slide into the sea…it will slide north to Canada!► South Louisiana is sinkingEvidence for Tectonics is Overwhelming► Magnetic reversals in sea floor rocks► Paleomagnetism► Common fossils and rocks on different continents► Distribution of earthquakes► Distribution of volcanoes► Distribution of mountains► “Hot Spots”► Direct measurements of movement todayWhat is going on…► New sea floor rocks are being made all the time in long ridge volcano systems► Continental and oceanic rocks are different (as we will learn)► As plates contact, ocean slide beneath continents, melt, creating volcanoes and mountain ranges.► When continents strike continents both crush and form larger mountains.-oceanic rocks are similar, dense, and heavy-continental rocks are heavy-plate either move towards each other, away from each other, or move past one another.What Drives it?► Not perfectly understood► Convection of heat within the Earth► Crust forms at ridges (~5cm year average)► Plates are “pulled” once subducted► The upper mantle and crust form a rigid lithosphere► It overlies a less rigid layer called the asthenosphere ► The upper mantle and crust form a rigid lithosphere► It overlies a less rigid layer called the asthenosphere -Lithosphere: where we live (the crust)-Asthenosphere: under the lithosphere, under the mantle. Plasticky area.The movement is related to to…► Divergent boundaries (rifts)► Convergent boundaries (subduction)► Transform boundaries
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