1 / 44

Landscapes: Why, How & Their Dynamics

Landscapes: Why, How & Their Dynamics. Dr. F. Kenton “Ken” Musgrave West Virginia University Pandromeda Inc. Earth’s Climate History. [roll the plantary zoom video]. My Favorite Fractal: What is This?. How Big Is It?. Fractal Dimension. Fractional Brownian Motion (fBm).

Download Presentation

Landscapes: Why, How & Their Dynamics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Landscapes:Why, How & Their Dynamics Dr. F. Kenton “Ken” Musgrave West Virginia University Pandromeda Inc.

  2. Earth’s Climate History

  3. [roll the plantary zoom video]

  4. My Favorite Fractal:What is This?

  5. How Big Is It?

  6. Fractal Dimension

  7. Fractional Brownian Motion (fBm)

  8. Ubiquity of 1/f (or “Scaling”) Noises

  9. Multifractals: a Second Approximation

  10. Why Terrain on Earth? From the Top

  11. Pair Instability Collapse Supernovae Why Terrain on Earth? · 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

  12. Pair Instability Supernovae

  13. 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?

  14. 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

  15. Exponential Decay of Heat Over Time

  16. 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

  17. 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.

  18. 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.

  19. 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

  20. 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

  21. Dynamic Fluvial Erosion Models

  22. 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!

More Related