Today: Chapter 12: Glaciers & glaciation What is a glacier? Glaciers are: Thick deposits of snow and ice Form on land Flow downhill by gravity Basic types: • Alpine, or mountain • Piedmont (small ice caps) • Continental ice caps Part of Earth’s hydrological cycle Fig 22.01 b Stephen Marshak Glaciers form where more snow accumulates in winter than melts in the summer Types of glaciers… Fig 22.04 a W W Norton The Greenland ice cap… Fig 22.05 a W W Norton Modified from Flint, 1971 The Antarctic ice cap… Fig 22.05 b Fig 22.04 c Stephen Marshak At any given time, snow and ice accumulation on the Earth varies with elevation and latitude Fig 22.06 As snow accumulates and is buried to greater and greater depths, it begins to change crystal form and density, progressing through a series of transitions that lead to an increase grain size and granularity Begin with a young river valley system… Fig 22.18 a W W Norton Global climate change leads to glaciation Fig 22.18 b W W Norton Erosional landforms left behind by glaciers… Fig 22.18 c W W Norton Glacially-eroded landforms U-shaped valleys… Fig 22.20 Stephen Marshak Fjords: Drowned glacial valleys that were formed in high latitude coastal areas following the sea level rise at the end of the last glaciation Glacially-eroded landforms Cirques… Bowl-shaped depressions carved by ice Cirque Glacially-eroded landforms Tarns… Lakes in bowlshaped basins, (cirques) along a glacial valley… Roche Moutonnees… Fig 22.17 b W W Norton Eroded hills of bedrock lying on the floor of a glacial valley Steep slope on downstream side Forming truncated spurs and handing valleys… Truncated spurs…Yosemite Valley Glacially-eroded landforms Hanging Valleys… Bridalveil Falls Yosemite, CA Glacially-eroded landforms Aretes: Sharp-edged ridges separating glacial valleys… What is this feature called? Glacially-eroded landforms Horns… Sharp-peaked mountains formed by cirque enlargement from opposing directions Matterhorn Glacial deposits…