1 / 40

GLACIERS AND GLACIATION

GLACIERS AND GLACIATION. GLACIER. A body of ice Formed on land Recrystallization of snow=> Firn => Ice Evidence of movement Alpine (valley) glaciation Continental glaciation. Ice Ages. Northern Europe & North America heavily glaciated Pleistocene 1.8 million years BP to 10,000 ybp

tarala
Télécharger la présentation

GLACIERS AND GLACIATION

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. GLACIERSAND GLACIATION

  2. GLACIER • A body of ice • Formed on land • Recrystallization of snow=> Firn => Ice • Evidence of movement • Alpine (valley) glaciation • Continental glaciation

  3. Ice Ages • Northern Europe & North America heavily glaciated • Pleistocene 1.8 million years BP to 10,000 ybp • 4 episodes • Peak of glaciation (Wisconsin) 18,000 years ago

  4. Glaciers-Where they are • Develop where all of annual snow doesn’t melt away in warm seasons: • Accumulation rate rate exceeds ablation (melting) rate • Polar regions • Heavy winter snowfall • High elevations • 85% in Antarctica • 10% in Greenland

  5. Types of Glaciers • Valley or Alpine glacier • Ice sheet • Continental Glaciers

  6. GLACIERS • Wastage of glaciers (“shrinkage”) • Melting • more melting at lower elevations • Evaporation • Calving into Icebergs • where a glacier flows onto a sea

  7. Movement of Glaciers • Valley Glaciers • Gravity driving force • Sliding along its base -basal sliding • Internal flowage- plastic flow • Rigid zone • Crevasses may form here • Ice sheets • Move downward & outward from central high

  8. Glacial Erosion • Under glacier • Abrasion & plucking • Bedrock polished & striated • Rock flour washes out of glacier • Polishing and rounding • “Sheep Rocks” • Striations- scratches & grooves on rock • Above glacier • Frost wedging takes place • Erosion by glaciers steepens slopes

  9. Erosional Landscapes Associated with Alpine Glaciation • Glacial valleys • U-shaped valleys • Hanging valleys • Rock -basin lakes (tarns) • Rounded knobs- rouche moutonnees

  10. Erosional Landscapes Associated with Alpine Glaciation • Cirque- at head of valley glacier • Rock steps • Rock basin lakes • Horn • Arete- sharp ridge

  11. Erosional Landscapes Associated with Continental Glaciation • Grooved and striated bedrock • Grooves may be channels • Rounded hills & mountains

  12. Glacial Deposition • Till • Unsorted debris (Boulders to Clay) • Erratic- Large Boulders moved from far away • Moraine- body of till • Lateral Moraine • Medial Moraine- where tributaries join • End moraine- • Terminal • Recessional • Drumlin

  13. Glacial Deposition • Outwash • Stream-deposited sediment • sorted • Braided streams typical • Esker • Kettle

  14. Effects of Past Glaciation • Glacial ages • Direct effects in North America • Scoured much of Canada • Cut Great Lakes • Deposited till & flattened Midwest • Extensive alpine glaciation in mountains

More Related