Glaciers and Glaciation Today ice covers about 10% of land surface 12,000 years ago - Ice Age - ice covered > 30% large areas of earth's surface are affected by glaciers glacial erosion - deposition of glacial sediments Types of Glaciers Continental Ice Sheets - Greenland and Antarctica today large areas of North America, Europe, Asia during ice age Ice Shelves - floating ice attached to land - Antarctica Alpine (Valley) Glaciers - mountain glaciers Ice Caps - small ice sheets - Iceland Piedmont - lowlands at the base of mountains Formation of Glacial Ice glacial ice is formed by a process of recrystallization - (Figure 12.4) Snow Granular snow Firn Glacier ice Glaciers Move Glacial slip - wet-base glaciers - glaciers slide on water base of glaciers often at melting point Plastic Flow if ice > 50 m thick will behave plastically - will deform and flow under pressure Upper 50 meters - zone of fracture - crevasses (Figure 12.2 and 12.6) Rates of Glacial Movement - commonly 1-2 meters/day Glacial Surges - 50 meters/day Glacial Budget glaciers advance and retreat or remain stationary - depends on rates of: accumulation - zone of accumulation ablation - loss of ice due to melting/sublimation Budget = accumulation - ablation if accumulation > ablation - ice advances accumulation &lt; ablation - ice retreats accumulation = ablation - stationary Glacial Erosion Glaciers, and rocks carried by them, are major agents of physical erosion.
(ice; covers ago; about 10% of land surface) (Snow Granular snow Firn Glacier ice Glaciers; Move; Glacial slip - wet-base glaciers - glaciers slide on water base of glaciers) (glaciers; remain; ) (glacial erosion - deposition of glacial sediments Types of Glaciers Continental Ice Sheets - Greenland and Antarctica; flow; L:under pressure Upper 50 meters - zone of fracture - crevasses) (ablation - ice retreats; are; major agents of physical erosion) (Glaciers and Glaciation Today ice covers about 10% of land surface 12,000 years ago; are affected; by glaciers) (rocks; carried; by them) (if ice > 50 m thick; will behave; plastically) (ice age Ice Shelves - floating ice; attached; ) (large areas of North America, Europe, Asia during ice age Ice Shelves - floating ice; is formed; by a process of recrystallization - (Figure 12.4)
ice Snow Granular snow Firn Glacier ice Glaciers glaciers glacial erosion - deposition of glacial sediments Types of Glaciers Continental Ice Sheets - Greenland and Antarctica ablation - ice retreats Glaciers and Glaciation Today ice covers about 10% of land surface 12,000 years ago rocks if ice > 50 m thick ice age Ice Shelves - floating ice large areas of North America, Europe, Asia during ice age Ice Shelves - floating ice
covers ago Move remain flow are are affected carried will behave attached is formed
about 10% of land surface
Glacial slip - wet-base glaciers - glaciers slide on water base of glaciers
L:under pressure Upper 50 meters - zone of fracture - crevasses
major agents of physical erosion
by glaciers
by them
plastically
by a process of recrystallization - (Figure 12.4