1 / 45

Landforms Geography

Landforms Geography. Glaciers. Development of a Glacier. Glacier – slowly moving mass of dense ice formed by gradual thickening, compaction, and refreezing of snow & water over time After summer melt, some snow left over

macy
Download Presentation

Landforms Geography

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. Landforms Geography Glaciers

  2. Development of a Glacier • Glacier – slowly moving mass of dense ice formed by gradual thickening, compaction, and refreezing of snow & water over time • After summer melt, some snow left over • With weight and partial melting, snow turns to Firn, crunchy transition from snow to ice • Further compaction, ice crystals align, become dense glacial ice which flows slowly downslope • At least 40-m thick to become glacier

  3. Glacial Mass Budget • Glacial input : Snow • Glacial output : ice, meltwater or water vapor • Zone of Accumulation – top of glacier where temps are cooler - input > output • Zone of Ablation – lower part of glacier where temps are higher – output > input • Equilibrium line – point on glacier where input = output

  4. Glacial Formation

  5. Glacial Mass Budget

  6. Glacial Mass Budget

  7. Glacial Movement • Glaciers move through internal deformation • Interior of glacier like malleable plastic

  8. Glacial Movement

  9. Glacier Types • Mountain Glaciers • Ice Cap – Continuous sheet of ice covering entire landscape • Ice Field – Buries all but tallest mountains – can be very thick • Alpine Glacier – Flows down valleys away from high country • Cirque - Bowl-shaped depression on mountain flank due to glacial erosion – snow source

  10. Alaskan Glaciers Hubbard Glacier

  11. Continental Glaciers • Huge ice masses covering a large part of a continent or large island – also called ice sheets • More than 3000 m deep in places • Covers most of Antarctica and Greenland • Weight of ice presses lithosphere down into asthenosphere, called isostatic depression

  12. Continental Glaciers

  13. Glacial Landforms • Rock & debris picked up by glaciers, transported in direction of movement & deposited • Glacial erosion: • Glacial Abrasion – scratch and gouge bedrock • Glacial Striations – caused by glacial abrasion • Glacial Grooves – deep striations • Glacial Plucking – boulders ripped from ground by glacier – deposited by retreating glacier, called Glacial Erratics

  14. Glacial Erosional Landforms • Roche Moutonnée – rounded hill, gradual on side toward direction from which glacier comes Glacial Erratic Glacial Striations

  15. Alpine Erosional Landforms • Glacial Erosion: • Cirque – bowl-like feature on mountain flanks • Tarn – small lake in bottom of cirque • Arête – narrow, steep ridges between cirques • Horn – mountain with 3 or more arêtes at summit • Glacial Trough – u-shape valley eroded by glacier • Hanging Valley – side trough above main trough – possible waterfall

  16. Alpine Erosional Landforms Cirque Horn “Matterhorn” Glacial Trough

  17. Glacial Depositional Landforms (Till) • Glacial Till – sediment directly deposited by glacier – many particle sizes • Moraine – winding ridge formed by till at the front or side of glacier – Moraine types: • Lateral – along former edges of glacier • Terminal – along front of former glacier • Recessional – formed as glacier recedes • Medial – between 2 glaciers • Ground – irregular deposition as glacier recedes

  18. Glacial Depositional Landforms (Till)

  19. Glacial Depositional Landforms (outwash) • Glacial Outwash – sediments deposited by water out & under a glacier as it melts – forms Outwash Plain, flat feature in front of former glacier • Kame – large mound deposited near glacier front • Esker – winding ridge from water flowing in tunnel through ice under glacier • Kettle Lake – big ice block fallen off glacier front is buried by outwash, melts later forming lake

  20. Glacial Depositional Landforms

  21. Glacial Depositional Landforms

  22. Physical Geography Arid Landscapes and Eolian Processes

  23. Arid Landscapes & Eolian Processes • Arid Landscapes • Eolian Erosion & Transportation • Eolian Deposition & Landforms • Human Interactions with Eolian Processes

  24. Arid Landscapes • 3 factors influence arid climates: • Subtropical high pressure • Rainshadow • Distance from large bodies of water

  25. Desert Geomorphology • Water important to landforms in arid regions – little vegetation to slow intermittent erosion • Arroyo – steep-sided gully cut into alluvium • In undisturbed, horiz. rock layers more resistant sandstone or limestone forms flat caprock above easily eroded shale • Result is landforms flat on top w/steep sides: • Plateau -Canyon -Butte -Mesa • Pinnacle -Playa

  26. Arroyo

  27. Desert Landforms Note: Tops of most landforms once part of same surface, since partially eroded away

  28. Playa

  29. Eolian Erosion and Transport • Wind-based processes important in deserts b/c: • Strong winds common in desert • Large supply of sand & silt to be blown • Vegetation minimal – wind free to erode

  30. Fluid Behavior of Wind • Wind acts like a fluid, like water, but less dense • Faster wind can move larger particles Threshold Velocity for wind to carry different sized particles

  31. Particle Transport • Silts and Clays carried in suspension • Sand bounces along – saltation, or • Sand rolls slowly along – creep

  32. Eolian Erosional Landforms • 2 types of wind erosion: • Deflation – wind blows loose soil away: • leaves coarser pebbles & cobbles, called Desert Pavement • when deflation causes basin to form, called Deflation Hollow

  33. Eolian Erosional Landforms • Abrasion – wind blows sand along a surface to polish & abrade it • Ventifacts – rocks shaped by abrasion: pitted, grooved, polished • Yardangs – elongated, wind-sculpted ridges caused by abrasion

  34. Eolian Erosional Landforms Deflation/Desert Pavement

  35. Eolian Erosional Landforms Abrasion Ventifacts Yardangs

  36. Loess • Fine-grained, wind-blown silt – high in calcium – usually from alluvial deposits or glacial till • Can be transported farther than sand

  37. Loess Deposits Arid Landscapes and Eolian Processes Loess Deposits around the World

  38. Loess Terraces

  39. Human Impact/Desertification • Desertification – transforming a vegetated landscape to one that is barren & susceptible to wind erosion • Population pressure has forced more people to clear marginal, semi-arid-to-arid land for agriculture & firewood • In wind, cleared land loses topsoil and nutrients • Vegetation unlikely to reestablish

  40. Regions Prone to Desertification

  41. Desertification in African Sahel • Semi-arid region in transition region from Sahara Desert in north to rainforest in south • Traditionally nomadic herders & small, sedentary farmers – north-south migrations to follow rain • Into 20th century, European borders & resource exploitation made people more sedentary – over-cultivation of soil, overgrazing, and tree removal • Add in extended drought since late 1960s, & you have desertification

  42. The Sahel

  43. Desertification in Great Plains • Great Plains lie east of Rocky Mts in semi-arid climate with short grass as dominant natural vegetation Dust Bowl Region

  44. Desertification in Great Plains • Early 1900s Americans moved to region to farm, plowing and clearing native grasses – unusually wet period • 1930s – terrible drought hits – topsoil blows into dust storms – called “Dust Bowl” • Many migrated to California & elsewhere • Those who stayed have employed irrigation & soil conservation, including windbreaks, and conservation tillage

More Related