GEOL 101 1nd Edition Lecture 24 Outline of Last Lecture I Types of Glaciers II Formations III Glacial Budget IV Glacial Erosion Outline of Current Lecture I Alpine Glaciers II Landforms III Continental Glaciers IV Ice Ages Current Lecture Features of Alpine Glaciers Cirque bowl shaped features in the higher altitudes this is where snow accumulates Crevasses fractures in the ice that form as it flows down the valley Moraine accumulation of rocks and sediment collectively called till that have been eroded and entrained in the glacier o Lateral forms along the sides of the glacier o Medial forms as lateral moraines from two glaciers meet to form one larger glacier o Terminal Moraine forms at the toe of the glacier where it dumps out all the rocks and sediment it was carrying Valleys U shaped valley glacially carved valleys o Recall that river valleys are typically V shaped These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute o The ice erodes and flattens the bottom of the valley and creates steep concave walls Hanging Valley U shaped glacial valleys that get cut off by a larger valley o Often times there will be waterfalls in the hanging valleys Landforms Cirques bowl shaped depressions zone of accumulation Tarn Cirque Lake Paternoster lakes series of tarns connected by mountain streams Horn Glacially carved mountain peak Ar te Glacially carved mountain ridge Fjords U shaped valleys that have been filled in with sea water Braided Streams Multi channeled outwash of glacier melt water Continental Glaciers Continental glaciers cover a much more expansive area than alpine glaciers Several glacial features that are associated with alpine glaciers are also common with continental glaciers o Moraines o Till Loess o Braided streams outwash plain Continental glaciers exhibit some features that alpine glaciers do not Landforms Drumlins Smooth elongated parallel wills Eskers Ridges deposited by streams flowing on top of or beneath glacier Kettles depressions formed when icebergs become partially buried in the glacial sediment Kettle lakes kettles filled with water o Typically only 30 feet deep Ice Ages Ice age Period of long term temperature reduction of the Earth s climate There have been several identified ice ages in geologic history o Stuartian Varangian ice age 950 600 Ma Snowball Earth Earth entirely covered in ice o Andean Saharan ice age 460 430 Ma o Karoo ice age 360 260 Ma o Holarctic Antarctic ice age 30 Ma to present Most specifically the Pliocene Epoch 3 Ma to 1 8 Ma the Pleistocene Epoch 1 8 Ma to 11 000 y and the Holocene Epoch 11 000 y to now This is the major ice age that we are still coming out of Stages of the Pleistocene Ice Age o Four recognizable stages of ice advance and retreat pulses Nebraskan 1 Kansan 2 Illinoian 3 Wisconsinan 4 Causes o Plate tectonics Changes in the arrangement of the continents result in changes in climate as well as changes in oceanic circulation More land mass in polar regions allows for the formation of glaciers and ice sheets Pangaea o Variations in the Earth s orbit Eccentricity variation in the shape of the earth s orbit around the sun Changes on order of 400 000 yrs Obliquity changes in the tilt of the earth s axis with respect to the orbital plane Changes on the order of 41 000 yrs Precession wobbling of the earth s axis with respect to stars Changes on the order of 26 000 yrs o Variations in the earth s atmosphere and thus the climate Reduction of greenhouse gases cool climate o Changes in the albedo how much solar radiation is absorbed or reflected Snow and ice reflect a lot of radiation which cools the climate which creates more ice and snow snowball Earth o Changes in ocean currents that bring warm water to cooler regions North Atlantic current moderates the temperature along the NW Europe Basic idea behind Day After Tomorrow More than ice Volcanic Ash tells us age of ice and about volcanism Organic material Paleoclimate paleobiotic information Dust pollun pales climate indicators Air Bubble paleo atmosphere
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