GEOL 101 1nd Edition Lecture 23 Outline of Last Lecture I Geysers II Porosity III Pollution Outline of Current Lecture I Types of Glaciers II Formations III Glacial Budget IV Glacial Erosion Current Lecture Glaciers a thick mass of ice that originates on land from the accumulation compaction and recrystallization of snow capable of flawing under its own weight Glaciers are part of two cycles The hydrologic cycle The rock cycle glaciers are a major erosion agent in cold regions Types Valley alpine glaciers o Exist in mountainous areas o Very numerous found all over the world o Snow accumulates at high altitudes o Flows as a stream of ice down the valley Continental Ice sheets o Exist on a larger scale than valley glaciers o Two major ice sheets on Earth are over Greenland and Antarctica though more ice sheets have existed in the past o Ice flows out in all directions from one or more snow accumulation centers 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 Ice caps glaciers that cover uplands and plateaus Exit Glaciers valley glaciers or ice caps that flow into the ocean Piedmont Glaciers form as one or more alpine glaciers exit the mountain valleys and widen out into the broad lowlands Formation Glaciers form in areas where more snow falls in winter than melts during the summer Steps in the formation of glacial ice 1 Starts as snow or sleet 2 Air infiltrates snow evaporating the edges causing the snowflakes to become smaller thicker and more spherical Granular snow 3 More snow accumulates forcing the air out Snow is recrystallized into a much denser mass of small grains called firn 4 Once the thickness of the ice and snow exceeds 50 meters firn fuses into a solid mass of interlocking ice crystals glacier ice Glacial Movement Velocities vary from glacier to glacier Some glaciers move on the order of a couple meters per day Some glaciers move slowly enough for soil horizons and even vegetation to develop on top of glaciers Periods of extremely rapid movement are known as Surges Glacial Budgets Zone of Accumulation Area where snow accumulates and turns into ice Firnline above this line the snow will survive until the next winter o The firnline may change from year to year depending on the amount of snow and the amount of ablation Ablation amount of ice and snow lost from a glacier o Can occur by Melting Calving large pieces of ice break off the front of the glacier This process creates icebergs in exit glaciers The balance between the amount of ice generated in the zone of accumulation and the amount of ice lost by ablation is referred to as the glacial budget o If more ice accumulates then is lost then the glacier will ADVANCE o If more ice ablates than is accumulated then the glacier will RETREAT Glacial Erosion Glacial ice is able to erode and transport massive amounts of sediment This may be done by Plucking lifting of rocks off of the valley floor and transporting them along with the ice Abrasions rocks that are within the ice will scrape along the ground smoothing the surface below The abraded rocks often have striations grooves etched into the rocks formed when other rocks scraped past Glacial erosion may produce Loess pulverized glacial flour that may be picked up and transported by the wind and deposited in massive bluffs
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