Lecture 6 - 1/27/2011 Announcements Earth’s Environmental...

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Unformatted text preview: 1/27/2011 Announcements Earth’s Environmental Systems II– Scales, Systems, II– Cycles Cycles ENV200H1S – January 27, 2011 Tutorial #1 - finishing up today Note RL 14081 (T0701C – [email protected]) is on the T14th Floor of Robarts Library, bring your Tcard to get entry Will be posting Tutorial #2 worksheet early next week Did you forget your recorder in class on Tues? Guest announcement by Prof Tony Davis to discuss summer field course in Ecuador/Galapagoes Ecuador/Galapagoes 1 2 The Long Now Foundation Outline www.longnow.org/about/about.htm Earth’s Environmental Systems Scales of time Earth Sciences Systems Thermodynamics 3 The clock of the long now www.longnow.org/about/about.htm The Long Now Foundation hopes to provide counterpoint to today's "faster/cheaper" mind set and promote "slower/better" thinking. hope to creatively foster responsibility in the framework of the next 10,000 years. 4 Trying to understand “deep time” I want to build a clock: that ticks once a year that has a century hand that advances once every hundred years, with a cuckoo that comes out on the millennium. When I tell my friends about the millennium clock, either they get it or they don't. (Danny Hillis) "The Millennium Clock" from Wired Magazine (1995) 5 www.longnow.org/about/ 6 1 1/27/2011 If we really could condense 4.5 billion years into a single year: 1 Jan 00:00:00 - the Earth is a molten mass It takes a month for the Earth to cool sufficiently for rocks to form. It takes another month for the oceans to accumulate, to set up the hydrologic cycle and for interactions between what was an acidic atmosphere and a basic lithosphere to neutralize the environment. 7 •1 Aug move into the Cambrian • Slide through the age of fishes, land plants (carboniferous), age of amphibians, insects, reptiles and birds. til bi • How late in the year do the dinosaurs go extinct? 9 1 Mar - appearance of primitive, single celled lifeforms (but the Earth is still anaerobic, there is no oxygen in the atmosphere). From Mar to May primitive plants create sufficient oxygen in the atmosphere atmosphere to allow formation of the ozone ozone layer – creation of a two layered atmosphere (troposphere and stratosphere) which cuts off input of ionizing radiation 1 June (50% of the Earth’s lifetime has passed) when we enter the Precambrian (pre(pre-life) era. 8 19 December!! 97% of the Earth’s history is past when the dinosaurs go. Yet the extinction of the dinosaurs is about as far back as most of us can even imagine (65 million + years ago). Humans appear on 31 Dec at 8:00 p.m. Common Era (which began 2010+ years ago) begins 11:46:00 (14 minutes to midnight) 10 •Earth is organized into crust, mantle and core. •Crust & upper mantle = lithosphere Industrial Revolution 11:59:58 (1.2 seconds to midnight) How can Earth’s systems possibly adapt to the mass perturbations that humans have caused in such a “short” time? How can we even comprehend how the Earth will respond? 11 11 12 2 1/27/2011 245 M 286 M Permian Triassic 208 M •Thin crust of rock floating atop a malleable mantle surrounding a molten core made mostly of iron Earth’s internal heat drives convection currents that push the mantle’s soft rocks upwards as it warms and downwards as it cools 144 M Jurassic Cretaceous Present 13 14 Plate Tectonics As mantle moves, it drags large plates of crust Earth’s surface consists of about 15 tectonic plates, most including combination combination of continent and ocean Move roughly 2-15cm per year 2Large scale, gradual upward and downward movement of the lithosphere, including sudden horizontal displacements, occurs along fault lines Red dots represent global distribution of volcanoes 15 16 Why & How are the plates moving? Systems 17 Planet’s environment consists of complex network of interlinked systems, e.g. ecological webs, interaction of living species with surrounding landscapes, ith biogeochemical biogeochemical cycles Network of relationships among parts that interact and influence one another Feedback loops 18 3 1/27/2011 Positive Feedback Positive and Negative Feedback Loops (leading (leading to divergent behaviour) behaviour) Fig. 4-9A Feedback Loop circular process Positive Feedback Loop change becomes more pronounced Negative Feedback Loop change is reduced or inhibited explosion No intermediate situation start blocking 19 20 Positive feedback just means the system is changing In everyday language we may use “positive” feedback to describe something “good” that has happened, i.e. something i.e. “positive.” There is no “good” or “bad” when we are speaking of positive feedback in systems. There is just change! Examples of + feedback Exponential growth in human population Disease epidemics out of control expansion Cancer } Bankruptcy Economic depressions Erosion } inescapable spiraling down 21 22 Negative Feedback Examples of - feedback: (change is reduced leading to stability) Fig 4-9B 23 Thermostats Cruise control Our body’s temperature (at least until we suffer suffer heat stroke or hypothermia) 24 24 4 1/27/2011 Energy Most systems in nature involve negative feedback loops since enhances stability in the long run, and only systems that are stable will persist Positive feedback loops can alter s stems systems substantially substantially Rare in nature But common in systems altered by human impacts Capacity or ability to do work Flows through ecosystems Why do organisms need energy? Thermodynamics d Rules by which energy is transformed from one state to another. 25 26 First Law of Thermodynamics Second Law of Thermodynamics Conservation of Energy (p.131-132) (p.131- Energy cannot be created or destroyed Energy can be changed from one form to another 27 When energy is changed from one form to another, some is degraded into heat Heat is a less usable form of energy Increases entropy (disorder) in the universe Everything in the universe tends to fall apart, slow down, disperse: becoming more disorganized, unless we continually supply energy (e.g. gas for the car, cleaning up your room) 28 5 ...
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This note was uploaded on 08/10/2011 for the course ENV 200 taught by Professor Karening during the Spring '11 term at University of Toronto.

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