Lecture 27 more glaciers

Today: Chapter 12: Glaciers & glaciation Today’s Lecture: Chapter 22: Glacial erosion Fig 22.01 b Glacial deposition Causes of glaciation Stephen Chapter 23 Marshak Aspects of global change Glacial deposits  Sediments of glacial origin are called “drift”  Deposits 10-100’s m thick  Consist of materials dropped when ice melts Deposited by Unstratifed drift: glaciers (Called Till or tillite) Stratified drift: melt water streams or lakes (Example: Glacial varves) Fig 22.21 c W W Norton Glacial deposits are called drift… Fig 22.22 a Stephen Marshak Unstratified glacial drift is called till… Glacial Erratic Fig 22.22 c Courtesy Duncan Heron Stratified glacial Lake deposits Loess… Fine grained glacial material (rock flour) redistributed by the wind How to find a meteorite… Fig 22.14 W W Norton Glacial deposits ● Moraines end moraine: ridge of till at end of stable glacier recessional moraine: a series of terminal moraines formed when a glacier recedes in steps ground moraine: blanket of till left when a glacier retreats rapidly lateral moraine: till deposited along the side of glacier medial moraine: formed where two or more glaciers merge Effects of Continental Glaciation Ice retreat/advances: Animal/plant distribution change, extinctions ensue with climate change Stream drainages altered “Pluvial” lakes Post-glacial uplift Sea level changes Effects of Glaciation Ice retreat/advances: some animal/plant migration forced some extinctions Stream flow changes Post-glacial uplift Sea level changes Pluvial lakes Global Sea Level Changes If all Earth’s ice melted: Sea level changes Causes of Glaciation ● Ancient Ice Ages Evidence from “tillites” billion years ago 600 million years ago 250 million years ago Lithified glacial till Prof Agassiz Fig 22.36 a Modified from Skinner and Porter, 1995 Fig 22.36 b Modified from Skinner and Porter, 1995 Fig 22.30 a1 W W Norton Fig 22.30 a2 W W Norton Fig 22.30 a3 W W Norton Causes of Ice Ages ● Earth orbit variations Shape of orbit (more elliptical) changes in tilt of rotation axis wobbling of axis Milankovitch Cycles ● Variations in the Earth’s orbit and distance from the Sun Shape of orbit (more elliptical) Changes in tilt of rotation axis Wobble of axis Fig 22.41 a W W Norton Fig 22.41 b W W Norton Fig 22.41 c W W Norton Fig 22.41 d W W Norton [...]... W W Norton Fig 22 .27 W W Norton GLACIERS Glacial deposits Stratified drift landforms ● outwash plains ● kettle lakes ● eskers Glacial deposits Till landforms ● Drumlins Smooth elongated parallel hills Fig 22.25 a W W Norton Glacial deposits Till landforms ● Drumlins Smooth elongated parallel hills GLACIERS Glacial deposits Till landforms ● Drumlins Smooth elongated parallel hills GLACIERS Glacial deposits...Glacial deposits ● Lateral moraines: formed along margins of glacier GLACIERS Glacial deposits ● Medial Moraines Medial moraines: Joining of two or more glaciers Fig 22.21 a W W Norton Glacial deposits Unstratified drift ● Moraines End moraine: ridge of till at end of stable glacier Recessional moraine: all other