EAR 105 1st Edition Lecture 11Outline of Last Lecture I. RiversII. Ground WaterIII. GlaciersOutline of Current Lecture IV. Intro to GlaciersV. Types of Glacial MovementCurrent LectureIV. Glaciers- Glaciers are a sensitive indicator of trends in global climate changeIn CNY there were once 2 miles of glaciers 15,000 years ago. Today, the remainders of these glaciers exists in the parallel configuration of the Finger Lakes. o The depth of these lakes provides one of our main water supplies in Central New York. The Great Lakes are even more important in this sense.- Less than 3% of Earth’s water is fresh—most of it is locked up in glacial iceo This is a problem because freshwater is already scarce, additionally inaccessible- Glacial ice sheets once covered the expanses of the world’s northern regions- Formation of glacial ice: Necessitates net gain of snow.o i.e. more snow needs to fall in the winter than melt in the summer, resulting in accumulation. o The accumulated snow undergoes compaction and recrystallization new substance called firno Recall: ice is a mineral! Glaciers are then an active part of the rock cycle- A glacier is a thick, long-lasting mass of ice that has or is flowing.- Types of glaciers: continental and alpine/valley/mountain glacierso Continental glaciers: ice sheetso There is no land at the North Pole—it’s actually just swathing sheets of ice!o Large scale that convers Greenland and Antarctica Greenland’s ice sheet is 1.7 square kilometers Antarctica’s Ice Sheet spans 14 million square kilometers I.e. Ice sheets are really massiveThese 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. Glacial melting on land is the main contributor to rises in sea levels (in comparison to ice shelves—which are basically glaciers in the ocean)V. Glacial movement- Zone of accumulation: more snow falls each winter than melts each summer- Zone of wastage: all the snow from the previous winter melts along with some glacial ice.o The glaciers move when the snow melts (in a severe oversimplification)- Plastic flow: bottom of the glacier flows under the surface—the top of the glacier is rigid like the earth’s crust, thus fractures to form the crevasses common to glacier heads.- Water is a lubricant: Thus when the bottom of the glacier is liquidified, the glacier will move more rapidly in what is called a surge.- Ice is 80-90% the density of water— about 20% of the glacier will protrude from the waterlineo Glaciers that are already submerged in water do not have a significant impact on sea level changes because they are already in the ocean- Glaciers erode by:o Plucking: lifting of rock blockso Abrasion: scraping over the top of the land Results in rock flour (pulverized rock) and striations (scratches in land surface)- Glaciers move along the preexisting topographical features of the land. - Among the various features sculpted by erosional glacial movement, some key landformsinclude:o Glacial troughs: aka U-shaped valleys—formed from the contours of previously carved V-shaped valleys, formed by riverso Hanging valleys: formed along the contours of tributarieso Arête: an erosional rock/ridge that occurs between two tributary valleyso Cirque: land features with very steep slopes. Basically forms a circle in the groundwhere the glacier moved through Ex. formation of Matterhorn—Cirques on all four sides sculpted out a high, angular peako Fiords: a flooded glacial valleyo- Glaciers deposit by:o Glacial drift: general term for glacial deposits laid down All sediment is of glacial origin; glaciers can carry whatever they want Till drift: material that is deposited directly by ice Stratified drift: sediment deposited by meltwatero Depositional Features include: Moraines: layers or ridges of till- An end moraine forms when the sediment carried by a glacier leaves a residual pile during its final stages of movement Outwash Plain: the frontal water carrying sediment in from the glacier results in an outwash plain- Increased rates of melting result in more melt water which is able to carry more sediment in its stream load braided rivers Kettle Lakes: If a glacier moves in surges, large chunks of ice can break off and be left behind. - This results in a perforation of the ground that fills with the eventual meltwater from the ice Eskers, Drumlins- Eskers: are economic resources because they are well sorted and provide good sources of sand and gravel- Drumlins: residual hills- Glacial activity is one of Earth’s many cycles- Effects of Ice Age glaciers:o Migration of animals and plantso Rebounding upward of the crusto Worldwide change in sea level Sea level is on the rise (by 3-400 ft.) with the increased melting of glaciers- Potential causes of Ice Ageso Milankovitch hypothesized that it was due to variations in Earth’s orbit If the Earth’s axis shifted further from the Sun in a particular region, the planet would be cooler in some spots i.e the northern