Lecture 8 - Rocks Beneath our Feet

Lecture 8 - Rocks Beneath our Feet - Announcements Office...

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Unformatted text preview: Announcements! Office hours Mon, Wed, Fri, 11:30-12:30 GSB 219 Fieldtrip leaves at 1 pm on the 30th, 9am on the 1st buses will be in front of Hamilton Hall wear suitable clothing/footwear be prepared to take notes pizza and pop afterwards BSB 340 Quiz #1 Friday Sept 30, 9.30 am to Tues Oct 4, 8.30 am Why do we need to know about plate tectonics living here in Hamilton? Figure 2.1 Envir Sc 1G03 Earth & Environmental Science The Rocks Beneath our Feet Geology of the Hamilton region OUTLINE Geology of Ontario 4 layers Layer I Basement: the Canadian Shield Layer II Paleozoic cover Layer III Glacial deposits Layer IV The Built landscape Geology of Ontario: 4 layers IV: Current Landscape past 300 yrs III: II: I: Glacial Deposits Paleozoic Cover Basement: The Canadian Shield (before we have life forms) Ontario - 3.1 billion yr old rocks GEOLOGIC TIME: earliest formation Fig. 19.26 Big gaps in record! Layer I: Basement Canadian Shield rocks (Granites and gneisses - formed by even pressure underground) How did the Canadian Shield form? Geology varies acrossdifferences) shield (significant Made of Pieces of small continents joined together by Tectonic processes Now called geological provinces which are tied together by Suture zones (orogenic belts) Fig. 20.4 Orogenic belts have been eroded - folded and deformed rocks of the shield remain e.g. gneisses NORTH AMERICAN CRATER Fig. 20.10 Canadian Shield formed by 1 billion years ago Why do we need to know about plate tectonics living here in Hamilton? Figure 2.1 Is Hamilton at risk from an earthquake? Lies close to old suture zone in Shield called the CMBBZ - weakness in crust - potential site for earthquake activity N.American plate moving westward @ 2.7cm/yr - Stresses can get through weakness in crust = form earthquake Box 2.7 Over 50% chance of M M=7 Why is this important? VACUUM BUILDING 1 PRESSURE RELIEF DUCT 8 REACTORS PICKERING NUCLEAR GENERATING STATION !!! Layer II: Paleozoic sedimentary rocks Layer II: Paleozoic sedimentary rocks Shield Shield covered by younger sedimentary rocks in southern ontario Deposited - deposited 600-350 mya (slightly tilted towards the West) Paleozoic cover SHIELD PALEOZOIC COVER Paleozoic rocks are exposed along Niagara Escarpment nice distinct horizontal layering Paleozoic rocks Limestones, dolostones, sandstones, and shales (shallow sea formation) 400-500 million years old relatively flat-lying sedimentary rocks, slight dip to southwest How did these rocks form? Warm tropical oceans Limestones and dolostones water form in shallow, clearinput) (no sediment LIMESTONE'S FORM TO DOLOSTONES THROUGH DIAGENESIS Paleozoic rocks contain fossils CRINOID Why do we not find dinosaurs in Ontario? - no preservation because of high mountains - fossils have been eroded away - No rocks preserved from the time between 350 and 2 million years ago What happens approximately 2 million years ago? Climate cools, ice sheets grow Layer III glacial deposits (buried under southern ontario) About 20,000 years ago - The last ice sheets came across North America - Laurentide Ice Sheet (Southern Ontario covered in ice --> 2 km thick) As ice retreated - 12,000 years ago, lakes were formed - Ice blocked the St. Lawrence -- large, deep lakes formed (McMaster campus) - Lake Iroquois -- deep lake near Lake Ontario (45 m deeper then Lake Ontario) Lake Iroquois Ice blocked Lake Iroquois (approx 12,000 yrs) Areas around Lake Ontario flooded (Toronto and Hamilton) - Eroded steep shore bluff, beach deposits formed (Ford Plant near Toronto) Layer IIIsediments also control the flow of groundwater Important for water supply, contamination Layer IV: the built landscape 1918 HAMILTON FILL 1984 Urban areas are constructed on "fill" material (possibly contaminated) Toronto Harbourfront: 1923 GETTING RID OF GARBAGE: making new land! DDT sprayed onto garbage used as landfill material What is this? Municipal and industrial landfill sites often located in old quarries, pits CLOSED LANDFILL SITES 39 in Hamilton e.g. Upper Ottawa Street landfill - Leachate leaks into underlying b edrock, contaminates Redhill Creek How does urbanization affect surface water flow? 1955 1975 - Less infiltration of rainwater --> More storm runoff - increasing flooding Stream and creek modification Flood and erosion control flood hydrograph Things you have to do! ...
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This note was uploaded on 11/28/2011 for the course ENV SCI 1G03 taught by Professor Padden during the Fall '11 term at McMaster University.

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