Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Themes in World Regional Geography Geo100 - Fall 2003 Julie Hwang Lecture #3 Outlines • Environmental Geography – – – – – Landform Climates Vegetation Water resources Food resources How is Earth’s surface shaped? • Jigsaw puzzle fit of South America to Africa • Mid-Atlantic Ridge • Himalaya Mountains Continental Drift • The continents are in constant movement resting upon the plates • Some 250 million years ago, continents were connected into one single landmass called Pangaea • Pangaea was later separated into continents in the present day Laurasia Pangaea Gondwanaland 225 million years ago 180 million years ago The present day 65 million years ago Continental Drift • So what drives continental drift? – Exchange of heat energy from the inner Earth • Described by Plate Tectonics theory Earth’s interior • Core • Mantle • Crust Plate Tectonics (solid) Plates (molten) Plates drift upon the asthenosphere Plate Tectonics Plates Convection cell Plates move relative to one another driven by convection cell Plate Tectonics • Convergent plate boundary Subduction zone Volcanoes Plate Tectonics – landforms shaped by convergent plate boundary Plate Tectonics • Divergent plate boundary Rift Valley Mid-Ocean Ridge Plate Tectonics – landforms shaped by divergent plate boundary Olduvai Gorge (Tanzania) Global tectonic plates Global earthquakes & volcanoes Plate Tectonics • Earth is made up of a large number of geological plates that move slowly across its surface • Explains the inner workings of our planet and many landforms in a global scale • Gives clues about the world distribution of earthquakes and volcanoes What determines climates? 1. Solar Energy Greenhouse effect 2. Latitude 3. Arrangement of oceans and continents • Land areas heat and cool faster than do bodies of water – Continentality – Maritime climates 4. Pressure & Wind patterns 40° N 20° N Equator 20° S 40° S World Climates Global Pressure Systems World Precipitation Climographs • Horizontal line show average high and low temperature in degree Fahrenheit. • Vertical bars show precipitation in inches. • For an entire year Köppen climate classification systems • • • • • A - Moist Tropical Climates B - Dry Climates C - Humid Middle Latitude Climates D - Continental Climates E - Cold Climates Climate Type (cont.) • Tropical (A) – Tropical rain forest (Af, Am) – Tropical savanna (Aw) • Dry (B) – Steppe (BS) – Desert (BW) • Temperate – Mild and rainy winter (C) – Mediterranean (Cs) – Humid subtropical (Ca) – Marine west coast (Cb) Climate Type • Temperate – Cold and snowy winter (D) – Humid continental, warm summer (Da) – Humid continental, cool summer (Db) – Subarctic (Dc) • Polar (E) – Tundra (ET) – Icecap (EF) • Highland (H) World Climate Regions Global Warming Increasing earth surface temperature Causes of Global Warming • Emission of anthropogenic (human-caused) greenhouse gases – – – – Carbon dioxide (CO2) Chlorofluorocarbons (CFCs) Methane (CH4) Nitrous oxide (N2O) Effects of Global Warming • Climate changes – – – – Increase in global temperature Rise of sea levels Intensity and frequency of cyclones Drought and flood • Shift in major agricultural areas • Depletion in the earth’s ozone layer (CFCs) International debate on limiting greenhouse gases • Rio de Janiero Earth summit (’92) – The first legal instrument addressing global warming was formulated • Kyoto protocol (’97) – 38 industrialized countries agree to reduce the emissions of major greenhouse gases below 1990 levels Conflict with economic growth • Fear that controls will constrain business, slow the economy, and increase the cost of living • U.S. more reluctant to comply than other nations World Vegetation Vegetation • Product of climate, geology, and hydrology • Influence on climate, geology, and hydrology • Human modification (eg. domestication, agriculture) • Threatened by global economy Biome (Bioregion) • Grouping of the world’s flora and fauna into a large ecological province or region • Closely connected with climate regions, but the linkage has got less clear since industrialization (eg. irrigation, domestication) • Globalization is having an impact on world bioregions Vegetation Type Tropical Dry, Temperate Tropical forest Savannas Deserts Grasslands: Mediterranean, Temperate Temperate Temperate Forests: Deciduous, Coniferous Polar, Highland Tundra Icecap Vegetation Type (cont.) • Tropical forests and Savannas – Mostly found in equatorial climate zones – Covers around 7% of the world’s land area • Deserts and Grasslands – large areas of arid and semi-arid climate that lie poleward of the tropics – Comprise one-third of the Earth’s land surface – Prairie: North American grassland – Steppe: shorter, less dense grassland found in Russia and Southwest Asia Vegetation Type • Temperate forests – Large tracts of forests found in middle and high latitudes – Two major tree types dominate: Coniferous and deciduous – In many regions, these forests have been cleared for agricultural purposes World bioregions Deforestation in the Tropics • Cutting-off of tropical forests in Africa, Latin America, and Southeast Asia • Caused by – International wood sales – Cattle grazing (demand for beef) – Settlement purposes Desertification in the Grasslands • A spread of desert-like conditions in Africa, Australia, and South Asia • Caused by – – – – Poor cropping practices Overgrazing The buildup of salt in soils from irrigation Climatic fluctuations Water Resources Water stress • Calculated from the amount of fresh water available per person • describes and predicts where water resource problems will be the greatest • Africa stands out as a region of high water stress Water stress in Africa and SW Asia Flooding • Cause the most deaths of all natural disasters (accounts for 50% of natural disaster-related deaths) • Caused by – Population growth (forced people to settle in low-laying delta lands subject to flooding) – Deforestation Food Resources Industrial agriculture and traditional agriculture • Industrial agriculture: practiced on about 25% of the world’s croplands – High use of fossil fuels for mechanization, fertilizer, and pesticide • Traditional agriculture: practiced by about 50% of the Earth’s population – Labor intensive; requires less mechanization, less fertilizer, fewer pesticides; generates lower yields The Green Revolution • The increases in global food production since 1950 • resulted from – Change from traditional mixed crops to monocrops of genetically altered, high-yield rice, wheat, and corn seeds – Intensive applications of water, fertilizers, and pesticides – Intensification via the reduction in fallow periods The Green Revolution • Associated problems are – Heavy use of fossil fuels makes Green Revolution agriculture more vulnerable to oil price fluctuations – Environmental damage – Social costs Food resources - problem • Local and regional problems are usually responsible for food unavailability • Political problems are usually more responsible for food shortages as compared to natural events • Globalization is causing a worldwide change in food preferences • Africa and South Asia are regions of greatest concern Web resources • To download the demographic data for each country http://esa.un.org/unpp/ • To create population pyramids for each county http://www.census.gov/ipc/www/idbpyr.html • To know more about plate tectonics theory http://pubs.usgs.gov/publications/text/understanding.html • To know more about world climates http://www.uwsp.edu/geo/faculty/ritter/geog101/lectures/climates_toc. html • To know more about global warming http://yosemite.epa.gov/oar/globalwarming.nsf/content/index.html • To know more about world biome http://www.blueplanetbiomes.org