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Lecture 4

Lecture 4 (2010 fall semester)


Department
Environmental Science
Course Code
EESC04H3
Professor
Cynthia Bongard
Lecture
4

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Lecture 4
Changing Geography and the Influence of Climate
Continental drift:
Main driving force of environmental change
Earthquake activity defines the margins of plates
Low density materials on top of the plates are continents
Changes from the Paleozoic time can be reconstructed
Plate Tectonics
A mosaic of huge plates (10s of kms thick; 1000s of kms wide)
Plates interact with neighbours, results in crustal stresses reflected by earthquake
activity at margins
Zones of spreading: represented by mid-ocean ridges; reflect tensional stress; expose
lower density plates (continent)
Zone of subduction: the denser plate goes down and forms ocean trench
Orogeny: forces and events leading to severe structural deformation of Earths crust
due to engagement of plate tectonics
Simplified Earth Layers
Crust => upper mantle => mantle => outer core => inner core
Asthenosphere => conveyor belt: a highly viscous mechanically weak ductilely-
deforming regions of upper mantle of Earth; lies below lithosphere
Paleographic Reconstructions
1. Identify areas that acted as separate continents
2.Positions these paleocontients in their correct orientations
3.Compile data indicative of geographical and climatological features
4. Interpret the distributions of environmental conditions on each paleocontinent
(gathering andsynthesizing data from different fields of study -> interdisciplinary)
www.notesolution.com

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Paleogeography: Interdisciplinary interpretation
1). paleomagnetism 2). lithological and fauna evidence 3).present distribution of climatic
features
Paleomagnetism:
cornerstone of continental positioning
establishes latitude and N/S orientations
iron bits align while molten due to polar magnetic forces, then rock solidifies and
becomes indicator of continental positioning, frozen in time
Lithological and faunal evident:
Cambrian rocks found in Maritime Canada unique in North America, but similar to
Western Europe; supports the theory for modern North America
Environmental conditions throughout history are interpreted from the processes
known to have formed particular types of rock: distinguishes highlands, floodplain
and etc
oLimestone: conditions warm, shallow and marine
oDetrital sediments: coal => only laid down in regions of humid, semi-tropical
swamps
Fossils give clues to where sediments laid down (marine freshwater terrestrial)
Present Distribution of Climatic Features
Modern day climate models can be an indicator of past climate conditions via
reconstructions
Plate Tectonics and Paleozoic
Pre-Cambrian Era (Prior to 550 MYA):
1 BYA, supercontinent Rodinia
Trace fossils indicated metazoan (multi-cellular) life did exist => radiometric dating
of fossils
Pre-Cambrian to Post-Cambrian:
www.notesolution.com
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