1. Unit 7 - Ice Is Nice Glacier=pile of ice and snow that flows; Forms if snow exceeds melt enough to make a pile; Takes water (as ice) and sediment from accumulation zone (snow exceeds melt) to ablation zone (melt exceeds snow) or to calve icebergs; Flows in downhill direction of the upper surface (where ice meets air), even if that means the bottom flows uphill; Think of pancake batter flowing on a waffle iron. Ice Is Nice: Yosemite, Glacier, Rocky Mountain, Bear Meadows, and NE Greenland

2. Unit 7 - Ice Is Nice Slip Sliding Away: Glacier moves by deformation within ice, and if bed warmed to freezing point, by sliding over substrate or deforming sediment there; Most deformation deep, but top fastest because rides along on deeper layers; Ice deforms because almost hot enough to melt; Glaciers erode by plucking rocks loose, sand- papering bed, and by subglacial streams; Thawed-bed glaciers, especially those with surface meltwater reaching the bed, change landscape more rapidly than streams, etc.

3. Unit 7 - Ice Is Nice Ages of Ice: Recent (about 20,000-year-old), unique glacier tracks across broad areas now far from ice suggest past ice age(s); Ice-age hypothesis predicts land rising where ice was, sinking around, and that is indeed observed; Ice-age hypothesis predicts sea level was lower when ice big, and indeed observe dead shallow- water corals of that age in growth position deep, flooded river valleys, etc.

4. Unit 7 - Ice Is Nice Ice-Age Records: Isotopically lighter water evaporates more easily; Bigger ice-->isotopically heavier ocean and shells; Shell-isotopic history from ocean-mud cores shows biggest ice every 100,000 years, smaller wiggles about 41,000 and 19,000 years apart; Predicted by Milankovitch before observed-- these are wiggle-spacings in Earth’s orbit; Ice grows globally when little northern sunshine; Orbitally changing sun controls northern ice, which affects CO 2, which controls southern ice.

5. Unit 7 - Ice Is Nice Bear Meadows: Ice sheets today about 10% of land area; at height of ice age covered about 30% of modern land; central PA just beyond edge of Canadian ice; Rocky Mountain, coastal NE Greenland National Parks have permafrost--soil at some depth frozen year-round; Permafrost freeze-thaw and enhanced creep (summer melt can’t drain down, so soil soggy and creep easy) make distinctive features; Those features exist but are not forming in central PA; So, we were really cold in the ice age.

6. Unit 7 - Ice Is Nice Glacier Tracks: Abrasion (sandpapering) under ice makes striae (scratches) and polishes rock; Smooths upglacier, plucks downglacier sides of bumps; Glaciers make valleys with “U”-shaped cross- sections, often with side-valley floors hanging above main-valley floor; streams make “V” shape without hanging valleys; Glaciers gnaw bowls called cirques into mountains; Glaciers deposit all-different-size-pieces till and washed-by-meltwater outwash, often in outlining ridges called moraines.