Mountain building
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  • 1. Mountain Building - Orogenesis
  • 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. 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. Isostasy & Mountain Roots Fig. 6.31
  • 5. Mountain-Types • Fault-Block Mountains – Formed from tensional stress – Normal Faulting – Example: Basin and Range Provinces SW USA
  • 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. Mountain-Types • Folded Mountains – – – – Formed from compressional stress Reverse Faulting and Folding – highly deformed rocks Will have highly metamorphosed rocks Example: Appalachians, Himalayas
  • 8. Mountain-Types • Volcanic Mountains – Formed volcanic activity – Associated with plate boundaries or hot spots – Example: Cascade Mts. Or mountains within Japan
  • 9. Mountain Building (Orogenesis) Zones Convergence Zones Continental Collision Continental Rifting
  • 10. Convergence Zones • Oceanic-Continental – – – – – Folded Mt. Belts Thrust Faults Volcanic Chains Accreted Terranes Example: Andes Mountains, Cascades
  • 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. Convergence Zones • Oceanic-Oceanic – Volcanic Chains – Examples: Japan, Philippines
  • 13. Collision Zones • Folded Mt. Belts • Thrust Faults • Remnants of Volcanic Chains • Examples: Alps, Himalayas
  • 14. Continental Rifting • Fault-block mountains
  • 15. Mountain Building – Multiple Events Example: Appalachian Mountains
  • 16. Mountain Building, Rock Cycle and Plate Tectonics
  • 17. Why does the Earth have mountains of various height? • Erosion attacks mountains – remember Earth wants to be flat • Orogenic collapse.
  • 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. camera axis 1-vertical photographs 2-horizontal or terrestrial photographs 3-oblique photographs
  • 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. theodolites from camera station on the ground. 2-these are used for survey of structures and mounments of architectural or archaeological value.
  • 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. 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. 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. 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. 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. 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. -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. -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. 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. 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. -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.