ENVS 101 1st Edition Lecture 15Outline of Last Lecture I. Earth’s cover of Snow and Ice/The CryosphereII. Overview of Glaciers (Formation and Types)Outline of Current Lecture II. GlaciersIII. Glacial Erosion and DepostitionIV. Glaciations and Sea IceCurrent LectureThe movement of glacier ice occurs by Internal flow, as well as by Basal slidingMeltwater at the base actors as a lubricantThe uppermost ice in the central part of a glacier flows faster than the sides and the base, similar to a river- Flow velocities also vary from changes that can be measured by as little as millimeters orbig enough to be measured by meters per day.- With glacier movement, the top of the glaciers surface will have the highest velocity, andthe least amount of deformation. By contrast, approaching the base of a glacier, the velocity will be lower, and more deformation will occurThe terminus of a glacier responds to changes in mass balance. Even as a terminus is retreating, ice that is in the glacier will continue to flow downslope. Coastal glacier retreat is characterized by frontal calving, which occurs when the glacier has moved to a region where there is no longer land to support the structure of the glacier in its entirety, and thus sections of the glacier being to break off.As glaciers flow, they end up sculpting the land they move across:Glaciers carve U-shaped valleys (as opposed to river canyons that are typically V-shaped)- This unique shaping of the landscape occurs because glaciers will typically have a rather wide profile to them, and they are extremely large masses of ice that effectively widen the bottom of whatever land they end up moving through. While glaciers flow, they also create sharp ridges, called aretes, as well as peak formations, called horns, formations that are left between the valleys glaciers create as well.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.As glaciers flow, they will sculpt the land much like sleds, as they carry away sediment, and also much like plows do, scraping up any weathered rock in their path. Glaciers even act as files, rasping and scratching, polishing the firm rock that lies in its path. The glaciers rasping/scrapping along the firm rock effectively forms striations, stripe-like patternsThe glacial deposits are characterized by being neither stratified or layered.- A glacier can carry very large boulders as well as very fine sediment, but due to the viscosity of the glacier's material, there is no segregation of the sediment it carries.Till is unsorted, unstratified (not layered) glacial sediment. Glaciers do not sort out any of the dirt and rocks that they may be carrying along, so till is different types of sediment mixed together all in a jumble.Moraines are the deposits of till often forming ridges near the glacier terminusOther Glacial Landforms include the following:Fjords: which are glacial valleys that are now partially flooded by the oceanDrumlines: are mounds of till that are sculpted under the glacierEskers: ridges of sediment deposited by sub-glacial streamsKettles: are small lakes that form where one church of ice melts out, and leaves a depression within the till.- Periglacial (near glacial) features include permafrost, which occurs in areas that are generally high latitude, northern Europe, northern Asia, Canada, Alaska. Consists of a layer of ice that is underground, as well as ice above ground. When it melts, the ground collapses. Many people that live in Alaska will move about by small planes, it is hard to move about on land, because the land is constantly, freezing or melting, making it difficult to build roads because it is softer, unstable terrain.- Sea Ice forms by freezing of the ocean surface, not by precipitation, salt crystals are excluded. It doesn't change the sea level, but can affect the salinity of the ocean- Typically forms in the arctic ocean and along the continent of antarctica. It grows and shrinks throughout the year, reaching a minimum around the month of September each year, there is a large change in the volume of the sea ice around this time of year.Glaciations the earth fluctuates between periods of extended cooler and warmer temperaturesglaciations: glaciers expand, and new ones form. This occurs during an ice ageInterglacialsoccur when the ice sheets retreat and the sea levels rise (We are currently in an interglacial period)Many glaciations have occurred in the past 2.5 million yearsLast Glacial Maximum occurred about 21,000 years ago Continental ice sheets covered up large areas of North America, Europe, and AsiaSea level was about 120 meters lowerBering land bridge connected Asia and North America, and allowed people to cross over into new areas.Going into more recent climate change, the Little Ice age was a cool period that lasted from the 1600s well into 1800 ADAdditionally, Global Warming has been taking place from the 1900s and will continue into the 22nd century