* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Plate Tectonics - Department of Physics and Astronomy
Survey
Document related concepts
Physical oceanography wikipedia , lookup
Geomorphology wikipedia , lookup
Schiehallion experiment wikipedia , lookup
Spherical Earth wikipedia , lookup
Post-glacial rebound wikipedia , lookup
Geochemistry wikipedia , lookup
Oceanic trench wikipedia , lookup
Magnetotellurics wikipedia , lookup
Geomagnetic reversal wikipedia , lookup
History of Earth wikipedia , lookup
History of geomagnetism wikipedia , lookup
Age of the Earth wikipedia , lookup
History of geology wikipedia , lookup
Large igneous province wikipedia , lookup
Transcript
Plate Tectonics 5 November 2015 Chapter 17 Great Idea: The entire Earth is still changing, due to the slow convection of soft, hot rocks deep within the planet. 1 Chapter Outline • The Dynamic Earth • Plate Tectonics: A Unifying View of Earth • Another Look at Volcanoes and Earthquakes 2 The Dynamic Earth 3 The Dynamic Earth • Small-scale changes – Construction site • Erosion by rain • Large-scale changes – Volcanoes – Earthquakes – Erosion 4 The Case of the Disappearing Mountains • Erosion – Few hundred million years – Mountains continually forming • Earth’s surface is not static 5 Volcanoes and EarthquakesEvidence of Earth’s Inner Forces • Volcano – Magma breaks through surface • Earthquake – Rocks breaks along fault – Energy transmitted as wave – Richter scale 6 The Movement of the Continents • F. Bacon – Continents like a puzzle • Wegener – Continental Drift • Continents in motion • Current Evidence – Ocean Floors – Magnetic Reversals – Rock Ages 7 Ocean Floors • Mapping – Ocean floor dynamic • Canyons, mountains • Mid-Atlantic Ridge – Earthquakes, volcanoes, lava flows 8 Magnetic Reversals • Earth’s magnetic field – Changes periodically • Magnetite – Crystals in lava align to magnetic field • Paleomagnetism • Seafloor Spreading – New rock comes to surface 9 Magnetic Reversals 10 Rock Ages • Radioactive Isotopes – Rocks near Mid-Atlantic Ridge younger – Rocks farther away older 11 New Support for the Theory • Measuring motion of continents • Radio Astronomy – Measured arrival of radio waves – Repeated over several years • North America and Europe – Separating at 5 cm per year 12 Plate Tectonics: A Unifying View of Earth 13 Plate Tectonics • Plate Tectonics – Large-scale surface features – Related phenomena • Tectonic plates – Rigid, moving sheet of rock – Crust and upper mantle – Continental • 100 km thick • Lower density (granite) – Oceanic • 8-10 km thick • Dense rock (basalt) • Earth’s surface – ¼ continent, ¾ water 14 Earth’s Plates 15 The Convecting Mantle • Mantle convection – Motion driven by Earth’s interior heat energy • Sources of energy – Gravitational potential energy – Decay of radioactive elements • Movement – Heat moves to cooler regions – Convection cells in mantle – Very slow • 200 million years for one cycle 16 Plate Boundaries • Three Main Boundary Types – Divergent – Convergent – Transform 17 Divergent Boundaries • Characteristics – Volcanoes • Chain of mountains – Earthquakes • Seafloor spreading – Plates pushed apart – Old spreading centers • Located in middle of ocean – New spreading centers • May begin anywhere 18 Convergent Plate Boundaries • Types – Oceanic-oceanic • Subduction zone – Deep oceanic trench – Island arc – Continental-continental • High, jagged mountain chain – Continental-oceanic • Subduction zone – Deep oceanic trench – Coastal mountain range 19 Transform Plate Boundary • Two plates move past each other – NOT smooth – Earthquakes as a result of movement 20 The Geological History of North America • Northeastern Canada and Greenland – Several billion years old • Western US – Terranes • Added to continent over time • Appalachian Mountains – Formed 450-300 million years ago – Continental-continental convergence zone • Rocky Mountains – 60 million years ago – Warping, folding and fracturing of continent • The Colorado Plateau – Gentle uplift • The Sierra Nevada – Molten rock pushed up sediments 21 Another Look at Volcanoes and Earthquakes • Plates and Volcanism – Divergent Plate Boundaries – Convergent Plate Boundaries • Subduction zones – Hotspots • Source stationary, plates move • Chain of volcanoes • Earthquakes – At plate boundaries or elsewhere 22 Seismology: Exploring Earth’s Interior with Earthquakes • Seismology – Study of sound vibrations within earth – Used to determine earth’s inner structure • Seismic waves – Compressional or longitudinal • P-waves (pressure waves) – Transverse or shear waves • S-waves 23 Seismology: Exploring Earth’s Interior with Earthquakes 24 • Plate tectonics is involved in the formation of the three major categories of rocks – Igneous Rock • cooled from molten material – Sedimentary Rock • Layered eroded material formed by the action of wind, water, or ice – Metamorphic Rock • Rock that has been altered in the solid state by extreme heat and pressure 25