GEOL 101 1nd Edition Lecture 24 Outline of Last Lecture I. Types of GlaciersII. FormationsIII. Glacial BudgetIV. Glacial ErosionOutline of Current Lecture I. Alpine GlaciersII. LandformsIII. Continental GlaciersIV. Ice AgesCurrent LectureFeatures 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 glaciero Lateral– forms along the sides of the glaciero Medial – forms as lateral moraines from two glaciers meet to form one larger glaciero 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 valleyso Recall that river valleys are typically V-shapedThese 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 valleyo 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- Arête – 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 Moraineso Till & Loesso 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 watero 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 iceo Andean-Saharan ice age – 460-430 Mao Karoo ice age – 360-260 Mao 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 Ageo 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 climateas 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 yrso Variations in the earth’s atmosphere (and thus the climate) Reduction of greenhouse gases cool climateo 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 Eartho 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