The Earth as a Planet. The Earth's Structure

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1 The Earth as a Planet Earth's age: formed 4.6 billion years old from particles orbiting the Sun To determine the age of the Earth, you cannot simply measure the age of the oldest rocks - most of them have long since eroded away. The Earth's Structure Core: nickel-iron metal, about 3500 km thick. Mantle: surrounds the core, most of the way out to the surface Crust: a thin outer layer of lower-density rock about 5 km thick under the oceans and about 30 km thick under the continents. Plate Tectonics Earthquakes Magnetic Field

2 The Earth's Atmosphere The Earth has a complex, efficient set of life-support systems. The familiar atmosphere we experience extends only about 12 kilometers above the surface. Above that is the stratosphere, 35 km thick, which includes the protective layer of ozone. Higher still are several more layers, each with their own composition and temperature. The atmosphere gradually turns into the vacuum of space at an altitude of about 500 km. It is estimated that one or two meteorites strike the Earth each day.

3 The Earth's Oceans Water covers 70% of the surface of the Earth. Less than one-third of the surface is dry land. Salty ocean waters make up 97 percent of all the waters on the Earth. We ourselves are made up mostly of water. We must drink it daily to survive. All the rivers, streams and lakes combined contain less than 1 percent of the world's non-oceanic waters. Fully 77 percent of the fresh waters of the world are locked up in ice.

4 Ice At the North Pole, sea ice, from which the salts have been frozen out, forms a dense pack on the Arctic Ocean. The ice sheet is 1,725,000 square kilometers in area and over 3,200 meters thick. At the South Pole, the immense ice sheet on the continent of Antarctica is 12 million square kilometers in area, 4,800 meters thick, and stores 24 million cubic kilometers of fresh water - 75% of the world's supply.

5 The Astronomical Connection In reality, water and oxygen are extremely rare in the Solar System. The Solar System is a forbidding place. We inhabit the single oasis in a vast solar system. The Earth has special attributes - water, free oxygen, life, and tectonic dynamism. We know that each of these attributes depends upon a planets size and geographical place in the Solar System. A few degrees of temperature fluxuation either up or down could irreversibly alter the delicate balance that maintains life.

6 Overview- Relationships among Population, Resource Use, and Technology Our Planet In Perspective: Population 5.5 billion people, living in 183 countries 1 billion in 33 "more developed countries" (MDC), mostly in the Northern Hemisphere, using 80 percent of the fossil fuels, metals, and other nonrenewable supplies we get from the Earth's crust. 4.5 billion live in 150 "less developed countries" (LDC),mostly on the continents of Africa, Asia, and Latin America in the Southern Hemisphere. The gap between the rich and poor peoples continues to widen. Our population is likely to grow to about 6.1 billion by the year 2000 and could reach 10.8 billion by the year 2045.

7 The Role of Women in the World Today women do almost all of the world's domestic work and child care, mostly without pay. They also do more than half the work associated with growing food, gathering fuelwood, and hauling water. Women provide more health care with little or no pay than all the world's organized health services combined. The worldwide economic value of women's domestic work is estimated at $4 trillion annually. THIS UNPAID WORK IS NOT INCLUDED IN THE GNP OF ANY COUNTRY, so the central role of women in the world economy is both unrecognized and unrewarded.

8 Impacts of Population - I Who Is Using What? The average U.S. citizen, when compared to the average citizen of India, uses: 50 times more steel 56 times more energy 170 times more synthetic rubber and newsprint 250 times more motor fuel 300 times more plastic The U.S. has 4.7% of the world's population uses 25% of all processed mineral resources. uses 33% of all paper products. produces 25% of pollution and trash. produces 18% of global emissions of greenhouse gases. produces 22% of ozone-destroying CFCs.

9 Impacts of Population - II India has 16% of the world's population (3.4 X more people than U.S.) uses 3% of all processed mineral resources. produces 3% of pollution and trash. produces 4% of global emissions of greenhouse gases. produces 0.7% of ozone-destroying CFCs. The impact of 258 million Americans = 12.9 billion Indians (more than twice the world's population)

10 People-overpopulation" in the poorer countries "Consumption-overpopulation" in the rich countries. Billions of tons of soil are being washed or blown away each year. Tropical forests are being chopped down at an alarming rate We ravage the ocean fisheries and pollute the seas and inland lakes, rivers, and deposits of groundwater. We are burning up the worlds supply of fossil fuels Nuclear power has been promoted by some as the answer to our energy needs. Experts urge that we begin a global effort to reduce waste of matter, energy, and biological resources and shift our use of nonrenewable fossil and nuclear fuels to renewable energy sources.

11 Today - WE ARE FACED WITH A CONFOUNDING SET OF PROBLEMS, OLD AND NEW 2 : Many Air Quality programs have helped clear the air in the vicinity of emission sources, however many pollutants escape and are carried much longer distances in the upper atmosphere than was previously thought. Indoor Air Pollution is a serious problem that most programs do not address. The Allocation of Fresh Water Supplies Groundwater is becoming increasingly contaminated Pesticide review and registration in the country is far behind where it should be. Since 1972, the EPA has been trying to investigate the 600 basic pesticide ingredients in use today. 2 The Conservation Foundation, State of the Environment, A View Toward The Nineties, The Conservation Foundation Press, Washington, D.C., 1987.

12 More - The Superfund Program, after eight years and $1.5 billion, to clean toxic waste dumps has yielded disappointing results. Wildlife Refuges and National Parks continue to be degraded. Soil Erosion continues at rates that are unacceptably high. Wetlands continue to be lost Degradation of the American Landscape is proceeding unchecked. The Nation's Budget Situation provides major sources of conflict. The Decision Making Processes by which polices are set leaves much to be desired. Integration and Cooperations between political boundaries or local, state and federal agencies is lacking.

13 Some of Today's Problems are less visible, less tangible, and thus more difficult to study and solve. The Sources of many environmental problems are becoming far more diffuse. Some of the Problems now facing the country are likely to cause environmental and economic damage on a global scale.

14 Population Exponential Growth The J - Curve it takes less than 5 days to replace a number of people equal to all Americans killed in all U.S. wars. in about 9 months, you replace all that were killed during the Black Plague in the 14th century (75 million) in 21 months you replace the equivalent of all soldiers who died in all wars fought on this planet during the last 200 years (165 million)

15 Where Does The Population Live? Gross National Product - the total market value of all goods and services produced per year. Excludes the work and value of women More Developed Countries - MDC (33) include the U.S., the Soviet Union, all European Countries, Japan, Australia, and New Zealand. Less Developed Countries - LDC (150) include Africa, Asia, and Latin America. over 92 percent of the world's annual population growth is taking place in the LDC's. during your lunch hour, about 2,000 people died of starvation, malnutrition, or diseases brought on by contaminated drinking water. Zero Population Growth a state in which the number of annual births equals the number of deaths per year.