Lecture 02 - 19 Jan.doc

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Environmental Science
Environmental Science 1021F/G
Christie Stewart

Environmental Issues 19 January, 2011 ES1021G Lecture 2 Part One: The Physical World Reading: Freedman Chapter 3 ← • Origin and Structure of Earth • Earth’s Geologic Dynamics • Hydrosphere • Atmosphere • Climate and Weather Big Bang • 12-15 billion years ago • only two elements existed: hydrogen and helium Star Formation • hydrogen and helium aggregate • under gravitational forces, high temperature & pressure • nuclear fusion forms heavier elements Solar System • excess material from our sun aggregated to form planets • inner planets are heavier, denser and more solid • outer planets lighter and gaseous • organized by gravitation, rotation, and orbiting • formed at least 4.6 billion years ago • Earth is the 3 closest planet to the Sun The geological structure and dynamics of planet Earth • Earth is composed mainly of heavy elements (iron, nickel, magnesium, aluminum, silicon) • It is a dense, spherical, rocky planet, comprised of four layers: o An innermost, molten, metal-rich core (diameter 3500 km) o A less-dense mantle of semi-molten minerals (2800 km thick) o A light, solid, rocky lithosphere (80 km thick) o A rocky crust (10-15 km under the oceans; 20-60 km continental) 1 Composition of the Earth’s Crust Igneous rock: • basalt (dominate oceanic crust) • granite (dominate continental crust) Sedimentary rock: • e.g. limestone Metamorphic rock: • formed from igneous or sedimentary rock under heat and pressure during crustal movement • e.g. gneiss (formed from granite), marble (formed from limestone) th (end of lecture September 14 , 2011) 2 Geological structure and dynamics of planet Earth (continued) Crustal dynamics involve tectonic forces associated with granitic continental ‘rafts’ riding upon basaltic oceanic plates • The oceanic plates move slowly in response to convective forces associated with magma in the mantle • Mountains are built where continental plates collide • Volcanoes occur where magma erupts at the surface • Earthquakes occur mostly where plates slip across each other 3 Geological structure and dynamics of planet Earth (continued) Earth is also impacted by extraterrestrial bodies, including exceedingly rare large meteorites The importance of glaciation in modifying the landscapes of Canada The most recent glacial epoch began about 100-thousand years ago, and ended 10,000 years ago • Virtually all of Canada was covered by ice, up to several km thick • Present ecosystems have developed on this deglaciated terrain • We are presently in a relatively warm, interglacial period • Wisconsin glaciation 4 Effects of glaciation Common glacial features include: • Moraines - series of long, mounded hills consisting of mixed rocky debris known as till • Drumlins - teardrop-shaped hills composed of mixed rocky materials • Eskers - serpentine mounds of crudely sorted debris deposited by rivers running beneath a glacier • Erratics – scattered, rounded boulders on the landscape • Fiords - long, narrow, steep-sided, oceanic inlets that were carved by glacial flow Weathering & Erosion Slow forces that can influence landforms in large ways Weathering: physical and chemical processes through which rocks are broken down. Rocks are fractured, then dissolved • e.g. rain, wind, freeze-thaw cycles, plant roots Erosion: physical removal of rock and soil through flowing water, ice, wind, and gravity. • Removed material is deposited elsewhere, e.g. downstream. 5 The Hydrologic Cycle: compartments • Water is contained. or stored, in four types of compartments. • These compartments, and the fluxes among them, comprise the hydrologic cycle. • The major compartments of the hydrosphere are: o The oceans, containing >97% of the water on Earth o Surface waters, accounting for 2.3% of global water (most of which is in glaciers) o Groundwater, 0.32% (aquifers, soilwater) o The atmosphere, only 0.001% • These compartments, and the fluxes among them, comprise the hydrologic cycle The hydrologic cycle: fluxes • Water moves/cycles between compartments. These movements are termed ‘fluxes. • The major fluxes of the hydrologic cycle are: o Precipitation (rain, snow etc.) o Evaporation (from terrestrial and water surfaces) o Atmospheric Circulation o Surface Runoff (from surfaces to water bodies) o River Flow (to lakes and oceans) o Seepage /Infiltration(into ground) o Drainage (from soil into surface waters) o Uptake (into vegetation from soil) The hydrologic cycle: other terms We can also discuss fluxes between compartments in terms of filling, and draining. That is, gaining water and losing water. 0 Discharge: loss of water from a compartment 0 e.g. water flows out of river into lake 1 Recharge: gain of water to a compartment 0 e.g. aquifer refills as precipitation falls over it Water table is a misunderstood term that simply refers to the level of the water in soil, i.e. the top of the waterlogged zone. 6 The atmosphere and its circulation The atmosphere consists of four layers: • The troposphere, or surface atmosphere, extending up to 8-20 km above the surface • The stratosphere, to as high as 50 km • The mesosphere, to about 75 km • The thermosphere, to 450 km or higher The troposphere has great variations in the distribution of heat, so there are abundant convective currents (wind). • It is referred to as the ‘weather atmosphere’ The atmosphere is composed of the following gases: • Nitrogen (or dinitrogen, N 2, accounting for 78% of the mass • Oxygen (O ),221% of the mass • Argon (Ar), 0.9% • Carbon dioxide (CO ), 2.04% • various other trace gases, including ozone (O )3and sulphur dioxide (SO ) 2 7 The elements of climate and weather Climate refers to the prevailing conditions of temperature, precipitation, humidity, wind speed and direction, insolation, fog, and cloud cover for a place or region • Climatic conditions have a large influence on the kinds of vegetation that can grow, and also on economic activities Weather refers to shorter-term conditions, over hours or days, of these same environmental factors • Extremes of weather, such as hurricanes and tornadoes, can be environmental catastrophes • The sun is crucial because it is the major source of heat to Earth, and its spatial variations give rise to mass flows of air (wind) and water (oceanic 8 currents) • Factors affecting atmospheric reflectivity (e.g., clouds, fine particulates) and absorptivity (water vapour and other greenhouse gases) have a huge influence of Earth’s heat balance • Night & day, and season of the year have a huge effect on the input of solar radiation • Latitudinal position also affects incoming radiation – low latitudes are much warmer than high ones • Altitudinal position is also influential – low altitudes are warmer than high ones • Aspect and slope affect microclimate – south-facing aspects are warmer, and the closer the slope comes to the angle of incidence of sunlight, the warmer it is • Darker surfaces are warmer, including coniferous forest and asphaltic roads • Areas covered by snow and ice are highly reflective, and are colder than darker surfaces • The evaporation of water also produced a c
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