Transcript Venice-2015
Landscapes: Why, How & Their Dynamics Dr. F. Kenton “Ken” Musgrave West Virginia University Pandromeda Inc. F. Kenton “Ken” Musgrave VICCS Spring School 2015 Earth’s Climate History F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 [roll the plantary zoom video] F. Kenton Musgrave VICCS Spring School 2015 My Favorite Fractal: What is This? F. Kenton Musgrave VICCS Spring School 2015 How Big Is It? F. Kenton Musgrave VICCS Spring School 2015 Fractal Dimension F. Kenton Musgrave VICCS Spring School 2015 Fractional Brownian Motion (fBm) F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 Ubiquity of 1/f (or “Scaling”) Noises F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 Multifractals: a Second Approximation F. Kenton Musgrave VICCS Spring School 2015 Why Terrain on Earth? From the Top F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 Pair Instability Collapse Supernovae Nucleosynthesis: fusion of lighter elements Fusing elements heavier than iron is endothermic Products must be distributed into interstellar space Binding energy The energy required to escape a gravity well Equivalent to energy to reach escape velocity What can accomplish this for heavy stars? Ordinary core-collapse supernova: recent era, leaving remnant Earliest epoch of star formation: PICS (pair inst. coll. su.) Runaway nuclear reactions detonate & disrupt entire star F. Kenton “Ken” Musgrave VICCS Spring School 2015 Pair Instability Supernovae F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 More Recent Supernovae Much smaller than PICS Progenitor star maybe several solar masses Provide shorter-lived radionuclides in local dust clouds Shock interstellar clouds triggering gravitational collapse Thus causing formation of new stars & planets Leave a remnant Neutron star or black hole Quantity of ejecta much smaller than PICS Same kind of runaway nucleosynthesis Radioactive ejecta cause terrain on Earth And Earth’s magnetic field? F. Kenton Musgrave VICCS Spring School 2015 Earth’s Internal Energy Budget Internal energy: core heat ~50% binding energy: heat from gravitational collapse ~50% radioactive decay of supernova ejecta Binding energy Finite supply Decays exponentially with time: cooling Radioactivity Primarily thorium & uranium isotopes Radionuclides with long half-lives Also decays exponentially, but more slowly F. Kenton Musgrave VICCS Spring School 2015 Exponential Decay of Heat Over Time F. Kenton Musgrave VICCS Spring School 2015 Plate Tectonics Convection in Earth’s mantle Unique to Earth Mercury, Venus & Mars have none Related to Earth’s magnetic field? Plates are quite mobile over geologic time Bash together, form supercontinents: Pangea, Gondwanaland Form mountains: orogenesis Plate dynamics Continental cratons Continental margins F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 Mountain Building: What Goes Up Must Come Down Uplift Causes orogenesis Limited by plasticity of Earth’s crust Mt Everest is as tall as a mountain can get on Earth Olympus Mons on Mars is much taller Erosive transport Fills in depressions: lakes become meadows Generates arable “bottom land” (sediment is fertile) Generates continental shelves Generates temporary features: river deltas, barrier islands, etc. F. Kenton Musgrave VICCS Spring School 2015 Modes of Erosion Fluvial: water Drainage networks Most dynamic of modes Glacial: ice Slow Powerful: moves mountains Coastal: storm surf Coastal erosion Mobile barrier islands Diffusive: various Thermal & chemical weathering Aeolian: mobile sand dunes & sandblasting of rock Rain splash, animal trampling, dry creep, etc. F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 Erosion Erosion is what shapes terrain Bedrock is fractal; erosion works on this fractal substrate Creates context-sensitive fractals: river networks Diffusive erosion Dry creep, rain splash, animal activity, etc. Temporal low-pass filter: easy to implement, very efficient Fluvial erosion: running water Rivers and glaciers are principal (inland) geomorphic agents Very important—but complex and slow to compute F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 Erosion Thousand-year floods: extreme events Major fluvial geomorphic events Appear (to me) to be what really makes changes Like redirecting the Po or Mississippi rivers Ice ages: extreme—also the norm Geomorphic events of greatest magnitude Prealpine Lakes (here), Lake Baikal (Siberia), Great Lakes (USA) Depression & rebound of crust F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 Dynamic Fluvial Erosion Models F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 Simulating Nonlinear Phenomena Fluvial erosion models (FEMs) vs. GCMs FEMs illustrate complexity and difficulty Solving nonlinear PDEs Formulating ad hoc “laws” of Nature Exploring high-dimensional parameter spaces Earth’s overall energy budget Internal energy: a tiny fraction Insolation: all the rest Albedo of planet Earth: reflected portion of insolation Sun’s power spectrum Modulated by clouds Requires good cloud models—entirely missing in GCMs Aerosols, convection, phase transitions, turbulence—too hard! F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015 F. Kenton Musgrave VICCS Spring School 2015