Chapter 18 Amazing Ice: Glaciers and Ice Ages
Chapter 18 Amazing Ice: Glaciers and Ice Ages Geology 101
Popular in Geology
verified elite notetaker
Popular in Geology
This 12 page Class Notes was uploaded by Alanna Wight on Wednesday December 2, 2015. The Class Notes belongs to Geology 101 at Washington State University taught by Wilkie in Fall 2015. Since its upload, it has received 81 views. For similar materials see Geology in Geology at Washington State University.
Reviews for Chapter 18 Amazing Ice: Glaciers and Ice Ages
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 12/02/15
Lecture Notes Chapter 18 Amazing Ice Glaciers and Ice Ages Key Points for today How do glaciers form and how do they move How do alpine glaciers modify the landscape Be able to recognize erosional and depositional features from photo How do continental glaciers modify the landscape Be able to recognize erosional and depositional features from photos Glaciers are moving bodies of ice Form from the accumulation and compaction of snow Form under low temperatures high latitudes high altitudes in wet regions Move under the in uence of gravity Ice Ages are periods during which the earth s climate is signi cantly cooler than usual Ice Ages are composed of glacial periods interglacial periods Types of Glaciers AlpineValley Glaciers Confined to mountain valleys Continental Ice sheet Unconfined blankets topography large Modern EX Antarctica Greenland Requisites for a glacier 1 You need cold 2 You need snow more snow than melts The glacier is always in motion even if it is not physically getting larger Accumulation Zone where snowfall exceeds melting Ablation Zone where melting exceeds snowfall If accumulation exceeds ablation then the glacier front advances If accumulation equals ablation then the glacier front remains the same If accumulation is less than ablation then the glacier front recedes Ablation can be 1 Melting 2 Calving ice breaks off 3 Sublimation ice evaporates 4 Wind Erosion As glaciers move over the land surface they act as a transport agent moving eroding material from one location to another deposition Rivers form quotVshapedquot valleys meandering streams with oodplains might not How do glaciers erode and shape the landscape Glacial ice is not clean it contains rocks fragments Flowing ice pulls up rocks and the grinding action abrades a path as it moves Erosional features of Alpine Glaciers you will need to be able to identify erosional and depositional features for the exam Glacial striations parallel scratches show the direction of movement Glaciers carve out quotushapedquot vallevs Cirgue steepwalled bowlshaped Hanging valley tributary valley that has been isolated by downcutting of the glacier in the main valley Arete jagged ridges along the divide produced by erosion of cirque or tributary glaciers Horn pyramidal peak surrounded by three or more cirques Fjord a glacial valley ooded by seawater ushaped Surface features of glaciers Crevasses deep fissure or crack in a glacier They are caused by brittle behavior of ice at the surface as the deeper ice moves plastically over an uneven surface Glacial deposits When ice melts unsorted sediment called till is deposited m a random mixture of rock debris in a fine grained matrix The different moraines are just an accumulation of till found at different parts of the glacier Depositional Alpine Features Lateral moraine rock debris till which collects between the glacier and mountain Medial moraine rock debris till which is trapped where two glaciers join End moraine an accumulation of unconsolidated material deposited at the end of a glacier Terminal moraine marks the furthest advance of a glacier Recessional moraines are end moraines caused as a glacier retreats Ground Moraine unconsolidated material deposited directly beneath the base of a glacier Outwash Plain Debris deposited in front of glaciers by glacial streams often sorted Continental Glaciation Key Points for today How do continental glaciers modify the landscape Be able to recognize erosional and depositional features from photos How were the Channel Scablands formed What factors contribute to the onset of glaciation Global warming what is it and how it might affect you Continental Ice Sheet Features Typically topography resulting from continental ice sheet glaciation is mostly related to deposition tum l M Ha Funpawn a my Chiba 39 m u 1 M om quot 0 39 R on tarnu r 39 m mann 39 01quot I g 09 Sn an 7nd o H 830 I CAIviquot Surface features often affect the glacial features Holes in glaciers that water ows through connect surface streams to subsurface streams Sediment deposition forms kames Kame Caused by sediment deposition from water owing through a circular opening on the glacier Generally coneshaped hill of sand and gravel SubGlacial Streams drain from the surface of the glacier and ow along its base Streams can be lOkm in length or more and deposited sediments can form eskers The water can also cause glacial surges Esker Longsinuous ridge formed by sediment deposition in sub glacial streams Drumlin an asymmetric elongate hill parallel to the ice ow direction made of glacially deposited sediments Kettle lake formed from buried ice block in outwash Erratic a glacially deposited rock different from the bedrock on which it rests Large boulders left by glaciers in areas Where they obviously don t belong Moraines Ground End Recessional and Terminal Moraines are the same as those found in Alpine Glaciation each is composed of poorly sorted glacial sediments called till Poorly Sorted Glacial Sediments Outwash plain stream deposited sediments at the front of the glacier Characterized by braided streams Palouse Loess Wind blown silt Video The Great Floods Cataclysms of the Ice Age At least one question from this video will be on the nal After Viewing this Video you should be able to answer the following questions 1Exp1ain brie y how the Channeled Scablands formed Be sure to include the type of glaciation involved Channeled Scablands are formed by ooding megaripp1es type of glaciation involved continental glaciation 2 What key piece of geologic evidence indicated the magnitude of water involved Hint It is a sedimentary structure Giant ripple marks created by the drainage 3 Be able to put the following events that formed eastern Washington into relative order ooding from Lake Missoula eruption of the Columbia River Basalts formation of the Palouse Loess Oldest Eruption of the Columbia River basalts Formation of the Palouse Loess Flooding from Lake Missoula 4Why do you think Harlen Bretz stood alone by his hypothesis for so long Not enough evidence no aerial photos yet was very rude and made many enemies Glaciation and Global Warming How are these related Because glaciers are shrinking What is weather The day to day changes in our atmospheric conditions What is climate Long term average of all weather conditions Continental Glaciation The last ice age Have areas of erosion and deposition In the US we mainly see depositional features Max ice thickness 34 km During the last ice age the sea level drops Pulls water from ocean and locks it up as ice in glaciers The land surface expanded 18000 years ago during the last ice age because sea level dropped 85 meters Climate Change and Ice Ages LongTerm Causes Cause of Ice Age Large landmasses at or near poles Land surfaces of relatively high elevation Nearby oceans to provide moisture as snow Plate tectonics ShortTerm Fluctuations Glacial and Interglacial Periods Within ice ages 1 Eccentricity of orbit earth s path around the sun changes from a circular to elliptical orbit 100000 yr cycle 2Tilt of earth axis and rotation varies from 215 to 245 degrees 41000 yr cycle 3 Precession Earth s axis wobbles like a top 23000 yr cycle quotMilankovitch Cyclesquot moderate term uctuations in glaciation every 100000 years shorter ones every 20000 years Climate Change and Ice Ages Other global effects include the circulation of water in the oceans Information about glacial periods can be derived from fossils in sediment from the ocean oor Isotopic Record of Ice Volume The global ice volume increases during glaciations Ice on the continents is enriched in 160 Water in the oceans is depleted in 160 Calcareous ooze from the ocean oor contains a record of these isotopic variations So What does this show There has been many periods of glaciation in Earth39s past The Earth s Glacial History Precambrian 22 billion years ago Evidence layer of tillite Permian 245286 million years ago Striations on bedrock tillites found on Australia South America India and Africa Evidence of Pangaea Quaternary l 6 million years ago cooling began about 50 million years ago North American Ice Sheet stripped soil sediment and bedrock Glacial maximum 20000 years ago Pleistocene Ice Sheet began retreating about 12000 years ago interglacial period Additional Effects of Glaciation Changes in Sea Level Sea level m during glacial periods Sea level risi during interglacial periods Changes in Landscape The Great Lakes were formed during the last glacial period The Channeled Scablands What is the greenhouse affect What gass help increase this affect C02 methane Does this have an affect on Earth s temperature How much 33 degrees C Is humanity contributing to the warming of the Earth In other words are we causing global warming Probably the basic de nition of global warming is that earth39s temperature is rising It does not differentiate between natural and manincluded affects Is the climate change that is recorded really signi cant This is a highly debated topic V000 o 1 upquot awupopn 1 nquotl t n4 p 4 Ilihmqpot39 2l39wwl Mpan w av 01 v K s ow 98 no 039 Mwu a was huu1 or WV kw Anvgtl puiwcm nw m I 1 up Mpmrmoavobmp 397 runuu oAMr II39OIWquotD NIV mwn39 quot 203AD 39IMUW quot m db I M39VM39WH r39 I WVv39v AWNM A n In 4 u uv Annma o II4quot 39 1000 Wlulutu vbvvl pawu Iquot 394 Mw rvdl ALI 3903 10 0 10 10 10 10 30quot 90 039 0 on 0 a o M CO to alan 10 moles O 3 P 0 so so do 20 o Agomlllonsotyearn ago The last time there has been this high of concentration of C02 in the atmosphere was about 4050 million years ago In the geologic past there have been times that greatly exceeded this concentration but it is the rate that the C02 is increasing which is troubling What about Global warming What would be the theoretical effect on North America if all the glaciers on Earth were to melt Sea level would rise about 250 ft All land lower than this would be submerged including most of the cities along the coasts Florida would be underwater Many cities along the Mississippi River including Memphis TN would also be submerged Key Point How might a change in our climate affect mankind The Little Ice Age is a historical perspective of such a large change Video The Little Ice Age The Big Chill There will be a discussion following the video After viewing this video you should be able to answer the following questions 1 Why is it important to study the Little Ice Age Volatile climate shift reshaped the world and changed the course of history 2 When was the Little Ice Age between 1300 and 1870 3 The Little Ice Age averaged about 4 F cooler than today Climate scientists estimate that it took only a decade for the global temperature to drop 4 Scientists do not agree on a single cause for the Little Ice Age or Why it stopped List the 3 probable factors which are identi ed in the video Less radiation from the sun Earth is sensitive to changes Oceanic conveyor belt transport heat Surface water gets warm ow north then loose heat into the atmosphere Cold water deep in the ocean heat sucked out of the water Arctic ice melt medieval warm period 5 What are some of the catastrophes man experienced as a result of the Little Ice Age large Infant mortality change in weather was catastrophic little or nothing to eat crop failure famine diseases Could these catastrophes happen to today s society very unlikely as the earth39s temperature is rising 6 What cause is attributed to the year Without a summer summer of 1816 Huge volcanic eruption 100 times the amount of ash compared to Mt Saint Helens Sulfur gasses going into the atmosphere from volcanism cooling the earth39s temperature Snow and no sun 7 What are some of the potential consequences to a modern society if the climate dips back into an ice age Today39s rapid warming created by man Greenhouse effect Hurricanes and oods form melting polar ice
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'