1 / 30

Destructional Processes

Destructional Processes. This thing, all things devours. Birds, beasts, trees, flowers. Gnaws iron, bites steel. Grinds hard stones to meal. Slays kings, ruins towns, and beats high mountains down. J. R. R. Tolkien: The Hobbit.

tyler
Download Presentation

Destructional Processes

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. Destructional Processes • This thing, all things devours. • Birds, beasts, trees, flowers. • Gnaws iron, bites steel. • Grinds hard stones to meal. • Slays kings, ruins towns, • and beats high mountains down. • J. R. R. Tolkien: The Hobbit Glacially-modified topography associated with the Prairie Coteau of SD, ND, MN.  During the Wisconsinan, the glacier divided into two southward-flowing lobes. Paraphrased from here. U-shaped Valley, Main Trunk, Hanging Valley Glacial Erosion

  2. Weathering Destructional Landforms are shaped by Weathering and Erosion Eastern New Mexico, northwestern Texas.  Included is the area of White Sands National Monument and Guadalupe Mountains National Park White Sands Guadalupe Mountains Carlsbad Caverns http://www.ndsu.nodak.edu/instruct/schwert/anaglyph/

  3. Weathering and Soils • Mechanical Weathering • Chemical Weathering • Soils Almon Harris Thompson Prof. A.H.Thompson, Dirty Devil River, 1872 Thompson Construction of Topographic Maps Flipbbok USGS geologists studying weathering in the Mancos Shale Powell and Thompson Exploration of the Colorado River

  4. 1. Mechanical weathering Frost Wedging

  5. Evidence of Frost Wedging in Wheeler Park, Nevada Source: Tom Bean/DRK Photo

  6. Salt Weathering

  7. Unloading = Exfoliation

  8. Thermal Expansion andContraction Source:Tom Bean

  9. Spalling • Frost • Fire

  10. Tree Roots Growing in Rock FracturesAnimal Burrows Source:Runk/Schoenberger/Grant Heilman

  11. Mechanical Weathering, Cubes/Surface Area

  12. 2. Chemical Weathering • Major processes of chemical weathering • Dissolution • Soluble ions contained in underground water • Oxidation • Chemical reaction where compound loses electrons • Important in breaking down mafic minerals • Rust colored weathering of Basalt • Hydrolysis H+or OH- ions • Reaction of any substance with water • Water’s ions replace different ions in mineral • Feldspars, most abundant crust minerals, become fine clay particles. Easily transported. Role of Water

  13. DissolutionWeathered and Unweathered Limestone Boulders CaCO3 +2HCl => H2CO3 + Ca++ + 2Cl- H2CO3 => H2O + CO2 Source:Ramesh Venkatakrishnan

  14. Hydrolysis – Feldspar to Clay Feldspars become Mechanical fracture due to chemical weathering

  15. Vegetation and Soil Development Need the extra humic acid to dissolve limestone

  16. Oxidation of Basalt Rust (Iron Oxide) forms

  17. Bowens Reaction Series and Weathering Mg2SiO4 + 4CO2 + 4H2O => 2Mg+ = 4HCO3- + H4SiO4 (aq) 2KAlSi3O8 + 2H2CO3 + 9H2O => Al2Si2O5(OH)4 + 4 H4SiO4 (aq) + 2K+ + 2HCO3 -

  18. 3. Soils An idealized soil profile

  19. Remember the different horizons O A E B C Organic Activity Exited Back Crushed Rock

  20. pedalfer pedocal laterite Evergreen forests Shortgrass tropics Note no E or C in some

  21. Rainfall seasonal "Laterite"

  22. Soil FormationFactors • Climate: • Temperature • chemical weathering faster hot climates • Rates of frost wedging increased by fluctuations of temperature around freezing • Thermal expansion & contraction extreme in hot cloudless areas • Rainfall • increases chemical weathering • Parent Rock characteristics • Limestone easily dissolved, Basalt easily oxidized, Granite easily hydrolyzed, Sandstone resistant to soil formation • Time • Slope • Organisms

  23. Equator Equator to Poles Climate Factors Arctic and tundra regions Temperature Annual precipitation Equatorial and tropical rain forests Low-latitude deserts and semi-deserts Temperate regions and mixed boreal forests Grasslands (steppes) Savannahs 30 degrees Latitude 40ºC Precipitation 1800 mm Temperature 30ºC Evaporation 20ºC 10ºC 600 mm Bedrock at or very near surface Soil Soil Deeply weathered bedrock (~40 - 50 meters deep) Bedrock Increasing depth of weathering Climate

  24. Factors related to bedrock composition "Parent Rock" Weathering-resistant sandstone yields little soil Soil Soil Soil Chemical weathering by hydrolysis Iron-rich basalt Chemical weathering by oxidation Feldspar-rich granite Chemical weathering by dissolution Limestone

  25. Parent Rock Resistant Sandstone in humid climates develops very poor soil on which the dominant natural vegetation is woodland as in this forest in PA From Drury, Ch. 4

  26. Parent Rock Soluble Limestone 1. Prolonged chemical weathering of carbonates in humid climates leaves a thin residual veneer of clay-rich soil, which is often quite fertile, as in Kentucky However, the extremely good internal drainage may preclude all but the largest surface streams.  The often low-lying surface is generally pock-marked by many depressions over sink holes. From Drury, Ch. 4

  27. Time Limestone 2. In recently glaciated areas, such as northern England, soil development has not been possible over limestones despite very humid conditions.  Vegetation only occupies those surfaces veneered with glacial till.

  28. Slope and Soil Thickness

  29. Slope Soil thickness depends on many factors, including parent rock weather-ability, and slope. • Massanutten Mt., Va., a syncline • Ridges sandstone • Valleys limestone and shale are less resistant • The north and south forks of the Shenandoah River flank Massanutten Mountain. Note the meanders on floodplains of thick, fertile soils http://www2.jpl.nasa.gov/srtm/virginia.html

More Related