4-8-2013Topic 10 Glaciers**Sharp ridge is an example of arete.Deposition Features:- Moraine and Till- moraine is the feature and it is made up of till- Outwash Plains- down below at the end of the glacier formed by outwash- Drumlins (continental glaciations only)- typical elongate hills formed under aglacier, dominantly made up of till, the point in the direction that the glacier/ice is moving.- Eskers- long sinuous ridge that forms as a channel deposit.- Kame- sediment deposited on ice is left behind.- Kettle lakes- melted ice block.Pleistocene- About 2 million years ago, Pleistocene there is a glaciation every 20 thousand years. THE LAURENTIDE ICE CAP COVERED SYRACUSE AND MUCH OF NEW YORK AND OTHER NORTHERN STATES. Ice is up to 3 km thick. There were a number of glaciations which means that the ice advances and retreats over and overand leaves miranes. (the wisconsinan was the last major advance)o There were four major advances in the Pleistocene (warmer periods between –Canada), -100 meters of sea-levelo Moraines all over NYo Drumlins all over NY state**Pleistocene= about 2 million years agoGlaciation Causes- The fall and then the rise of sea level (up to 300 feet difference)- Crustal depression and then isostatic rebound- Submerged end moraines (e.g. Long Island, Martha’s Vineyard)- Submerged river valleys’ (estuaries) (e.g. Chesapeake Bay)Ice Age Effects in the U.S- Formation of the Great Lakes- Changes in the river drainages- Isostatic Rebound- Glacial lake Agassiz 12,000 to ca. 7500 years- Glacial Lake Missoula- ice dam across Clark River o Dam would fail (40x)= Huge mega Giant Floods =Channeled scablands in Eastern Washington- Pluvial Lakeso Landlocked basin, endorheicc basin, fills with rainwater during times of glaciation when precipitation is higher it dries out, evaporatesGlacial Features near Syracuse- A finger Lake- Finger Lakes carved in pre-existing River Valley’s- We sit on a drumlin- There is lake sediment in downtown SyracuseCauses of Continental Glaciation- “Why has the world become cold and then warmer?”- Over the last 1 billion years, Earth has experienced several glacial episodes (non-periodic, widely spaced in time)- Caused primarily by movement of tectonic plates- Supercontinents formed over the polar regions allow for the build up of ice sheets- The location of the continents which is controlled by plate tectonics- Permian Glaciationo Formed on continents when they were at a more southerly location- Today we are in a warm period- The last glacial stage ended only about 12,000 years ago, there are about three cycles interactionsWhat is causing glacial/interglacial cycles?- In a way it is like the reason why we have seasons (change in insulation: solar radiation reaching a certain area).- There are three orbital parameters, which is the Milankoitch Cycles= variations in Earth’s orbit are largely responsible for flip-flops between glacial and interglacial stages. (Three are circling, tilt, and wobble of the tilt on the axis).o Circling= eccentricity (shape of the orbit: varies from being elliptical to almost circular) Varies from near circle to ellipse with a period of 100.000 years. It is not significant directly, but modulates the amplitude of the precision cycle.o Tilt= obliquity (tilt of the axis of rotation) 22.1-24.5 degrees, the tilt asa cycle of about 41,000 year cycle. The current tilt is 23.5. If there was no tilt there would be any seasons. 90 degrees is the largest possible tilt. Greater tilt- more intense seasons. It is more evident at higher-mid latitudes.o Wobble of the tilt= precession, positions of solstices and equinoxes in the eccentric orbit slowly change; this dominates at low and middle latitudes.*sea level used to be 300 feet lower, and it is