Surficial Processes: Glacial and Eolian (Desert)

1. Surficial Processes: Glacial and Eolian (Desert)

2. Environmental Implications of Glacial and Eolian Processes • Glacial • Active processes generally less important than resulting materials and landforms • Main exception: Permafrost • Explain? • Eolian: Wind/Deserts • Active process and resulting materials are important • Explain?

3. Environmental Implications of Glacial and Desert Systems: Examples • Processes: Important for land use • Landforms: Physical characteristics important for human use (e.g., stability) • Represent response (feedback) mechanisms to climatic changes • Evidence/(Indicators of environmental change) for past and future changes in the global environment e.g., climate • Coupled with other processes (e.g., plate tectonic, volcanism, atmospheric) affects other systems and processes (e.g., biogeochemical, surficial, etc.)

4. Surficial Processes and Landforms Associated with Ice and Wind • Landforms & environmentally sensitive areas • Coastal, desert, arctic, subarctic • Effects of ice and wind on rocks and landforms • Environmental problems associated with wind and ice

5. Ice: Glaciation • Glaciers: (Land-bound) masses of moving ice • Cover about 10% of earth • Accounts for <2% of earth’s water (w/ other forms of ice) • Types • Continental: Cover large areas of land • Alpine: Confined to mountain valleys • Both types are associated with distinctive erosional and depositional processes and resulting landform features • Permafrost

6. Continental Glaciation Landforms • Erosional • Expansive areas of exposed, eroded, flattened, polished bedrock • Kettles/pothole lakes • Depositional Expansive areas/fronts of deposition • Morain: highly variable, loose, jumbles of eroded material (typically unstable?) • Drumlins • Eratics • Loess (windblown, very fine glacial silt)

8. Drumlin

10. Extent of glacial ice sheet in North America

13. Alpine Glacial Landforms • Erosional • U-Shaped valleys • Fjiords • Horns, cirques, aretes • Depositional • Various types of till/morain

20. Permafrost • Permafrost: Permanently frozen ground • Underlies ~20% of world’s land area • Types: • Continuous: Predominantly frozen all the time • Discontinuous: Areas of thawed ground in areas of predominantly frozen ground • Potential for perturbation from human activities • Examples?

22. Environmental Significance • Building/engineering challenges associated with • Glacial deposits & landforms • Permafrost • Environmental implications of man-made perturbations in permafrost areas • Distribution & physical characteristics of areas affected by glaciation • Till/Morain vs. bedrock • Groundwater implications • Episodic effects • Hubbard Glacier example

23. Arid Environments

24. Wind • Simultaneous erosion and deposition • Dunes • Mass transport/deposition of sand close to the ground • Dune type dependent on wind characteristics • Physical Characteristics: Loose, porous, variable • Negative implications for flora/agriculture?? • Loess • Fine-grained material carried up to thousands of meters in altitude • Associated with expansive “Dust storms” (100’s km in diam.) • Found in specific geographic locations • Highly susceptible to erosion • Variable stability (e.g., for foundations, etc.) • Can be good for agriculture

26. Dune characteristics vary with conditions: • Recognition/appreciation is important • Memorization of the types & details isn’t (for this class)

28. Environmental Implications of Eolean Deposits & Processes • Loess = hazardous foundations • Problems of migrating sand, silt (e.g., expensive construction & maintenance for highways, buildings, hydraulic structures • Implications for geography, climate in geologic past • Implications of desertification, global warming or cooling on the environment (later)

29. Section Summary • Recent (geologically) continental glaciation produced a variety of earth materials • Widespread • have implications for planning, design, building • Permafrost • environmentally sensitive • Requires specialized engineering to prevent adverse effects • Windblown sand, silt, dust • Widespread • Concentrated in specific areas (coasts, interior, rivers) • Loess potential foundation problems/agricultural benefits • Sand Dunes (Migrating & Stabilized) • Implications for construction & maintenance of highways, buildings, hydraulic structures

30. Other Things to Remember • Erosional AND depositional implications of glacial and eolian processes • Some of the more important examples • Landforms • Physical properties of e.g., till, loess • Where do these types of materials occur (geographic distribution) • Recognition (general) of landforms/materials • Environmental implication for: • The past • The present • The future