Mountain building


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Mountain building

  1. 1. Mountain Building - Orogenesis
  2. 2. Archimedes’ principle – The mass of the water displaced by the block of material equals the mass of the whole block – Thus for a material with a lower density than water, the proportion of material above the water surface is constant – For example wood (density 0.8 gm/cm) will have 20% of its mass above water (density of 1.0 gm/cm). Thus for a 1 m block 0.2 m will be above water and 0.8 m below, but for a 2 m block .4 m will be above water and 1.6 m below Fig. 6.28
  3. 3. Isostasy & Mountain Roots – Continental Crust has “roots” – As a result of isostacy, the thicker the surface exposure of rock, the thicker the crustal “roots” – As continental crust is compressed it shortens and thickens – Avg. continental crust is 35-40 km thick, under deformed crust avg. is 50-70 km, with the majority of the difference in the “roots” Fig. 6.29
  4. 4. Isostasy & Mountain Roots Fig. 6.31
  5. 5. Mountain-Types • Fault-Block Mountains – Formed from tensional stress – Normal Faulting – Example: Basin and Range Provinces SW USA
  6. 6. Mountain-Types • Upwarped Mountains – Formed from compressional stress – Broad arching of the crust or great vertical displacement along faults – Example: Black Hills SD
  7. 7. Mountain-Types • Folded Mountains – – – – Formed from compressional stress Reverse Faulting and Folding – highly deformed rocks Will have highly metamorphosed rocks Example: Appalachians, Himalayas
  8. 8. Mountain-Types • Volcanic Mountains – Formed volcanic activity – Associated with plate boundaries or hot spots – Example: Cascade Mts. Or mountains within Japan
  9. 9. Mountain Building (Orogenesis) Zones Convergence Zones Continental Collision Continental Rifting
  10. 10. Convergence Zones • Oceanic-Continental – – – – – Folded Mt. Belts Thrust Faults Volcanic Chains Accreted Terranes Example: Andes Mountains, Cascades
  11. 11. Accreted Terranes • As exotic blocks collide with continents they become sutured to the continent. • The blocks are referred to accreted terranes • Accreted Terranes are island arcs, portions of ocean floor, fragments of continental crust
  12. 12. Convergence Zones • Oceanic-Oceanic – Volcanic Chains – Examples: Japan, Philippines
  13. 13. Collision Zones • Folded Mt. Belts • Thrust Faults • Remnants of Volcanic Chains • Examples: Alps, Himalayas
  14. 14. Continental Rifting • Fault-block mountains
  15. 15. Mountain Building – Multiple Events Example: Appalachian Mountains
  16. 16. Mountain Building, Rock Cycle and Plate Tectonics
  17. 17. Why does the Earth have mountains of various height? • Erosion attacks mountains – remember Earth wants to be flat • Orogenic collapse.
  18. 18. classified on the basis of1-direction of the camera axis 2-combination of more than one photograph 3-according to angle of coverage 4-on the basis of colour
  19. 19. camera axis 1-vertical photographs 2-horizontal or terrestrial photographs 3-oblique photographs
  20. 20. 1-the lens axis is perpendicular to the surface of the earth. 2-it covers a relatively small area. 3-the shape of the ground area covered on a single vertical photo closely approximates a square or rectangle. 4-being a view from above, it gives an unfamiliar view of the ground 5-distance and direction may
  21. 21. theodolites from camera station on the ground. 2-these are used for survey of structures and mounments of architectural or archaeological value.
  22. 22. the optical axis of the aerial camera tilted fro, the vertical 2-these photographs cover large areas of ground. 3-but the clarity of details diminishes towards the far end of the phothgraph.
  23. 23. trapezoid, althouth the photo is square or rectangular. 3-the objects have a more familiar view, comparable to viewing from the top of a a high hill or tall building. 4-no scale is applicable to the entire photograph, and distance cannot be measured. Parallel lines on the ground are
  24. 24. all usable) 2-the ground area covered is a trapezoid, but the photographis square or rectangular. 3-the view varies from the very familear to unfamiliar, depending on the height at which the photograph is taken. 4-distances and directions are not measured on this photograph for the same reasons that they are not
  25. 25. camera exposed simultaneously at successive exposure station, with their axis tilted at a fixed inclination from vertical in opposite directions in the direction of flight line so that the forward exposure of the first station forms a stereopair with the backward exposure of the next station.
  26. 26. which the central photograph is vertical and the side ones are oblique. 2-this photography can be used for rapid production of reconnaissance maps on small scales.
  27. 27. through the front nodal point of the lens. 1-standard or normal angle photography- the angle of coverage is of the order of 60 2-wide angle photography-the angle of coverage is of order of 90/ 3-super wide angle-the angle of coverage is of order of 120.
  28. 28. -these photographs present the objects as they appear in their natural colour. -for good colour cintrast, scale larger than 1:25000 is normally used. -it has better in terpretation capabilities. -it is better ofr photogrammeric studies.
  29. 29. -infrared raiaions which are invisible to human eye have wavelengths ranging from 0.7 um to about 1.6um. -infrared photography can be black and white or in colouir depending on the type of film used.
  30. 30. of red. -the differentiation between types of healthy and unhealthy vegetation is brought out in distinctive colours. -infrared colour with the combination of panchromatic capabilities.
  31. 31. photography appears in lighter tones on ir black and white photographs. -water appears dark in ir black and white because water has high absorption characteristics in infrared. Yellow filter is used to reduce haze.
  32. 32. -the film used in iR black and white negatives. -dispositive are made from the negatives and the four images are combined in registration in an additive colour viewer to produce a true colour or a false colour viewer to produce a true colour or a false colour image on a screen which can subsequently be photographed.