Surficial Processes: Glacial and Eolian (Desert)

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?

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.)

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

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

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)

Drumlin

Extent of glacial ice sheet in North America

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

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?

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

Arid Environments

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

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

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)

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

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