GEOL 101 1nd Edition Lecture 23 Outline of Last Lecture I. GeysersII. PorosityIII. PollutionOutline of Current Lecture I. Types of GlaciersII. FormationsIII. Glacial BudgetIV. Glacial ErosionCurrent 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) glacierso Exist in mountainous areaso Very numerous, found all over the worldo Snow accumulates at high altitudeso Flows as a stream of ice down the valley- Continental Ice sheetso Exist on a larger scale than valley glacierso 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 centersThese 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 lowlandsFormation- 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 sleet2. 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 firn4. Once the thickness of the ice and snow exceeds 50 meters, firn fuses into a solid mass ofinterlocking 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 wintero 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 glaciero 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 budgeto If more ice accumulates then is lost, then the glacier will ADVANCEo If more ice ablates than is accumulated, then the glacier will RETREATGlacial 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
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