An Overview of Our Planetary Environment

1. An Overview of Our Planetary Environment Chapter 1 The solar system formed over 4.5 billion years ago. The earth is unique among the planets in its chemical composition, abundant surface water, and oxygen-rich atmosphere The interaction between geologic environments and our 6 million human beings reshapes our planet

2. Earth in space and time • Big Bang, the origin of today’s universe • The Big Bang Theory is the dominant scientific theory about the origin of the universe. Although the Big Bang Theory is widely accepted, it probably will never be proved. • According to the big bang, the universe was created sometime between 10 billion and 20 billion years ago from a cosmic explosion that hurled matter and in all directions.

3. Earth in space and time • Stars formed from the debris of the Big Bang. Local high concentrations of mass were collected together by gravity and formed stars and planets. • The sun and its system of circling nine planets formed from a rotating cloud of gas and dust. • Most of the mass of the cloud coalesced to form the sun. Dust condensed from the gases remaining in the flattened cloud, and the dust clumped into planets.

4. Earth in space and time • The compositions of the planets formed depended largely on how near they were to the hot sun. • The nearest planets to the sun contained mainly metallic iron, a few very high temperature minerals, and little water or gas. Farther from the sun, the planets incorporated much larger amounts of low temperature minerals, liquid water, and condensed gases. • A series of planets with a variety of compositions was born.

5. Figure 1.1 The distance scale is logarithmic

6. The planetary densities are consistent with a higher metal and rock content in the four planets closest to the sun and a much larger proportion of ice and gas in the planets farther from the sun.

7. Earth in space and time • Third planet from the Sun • over 4 billion years old • Mean temperature 15 oC, not too hot or cold • Nine chemically distinct planets in our Solar System • Four rocky and metallic inner planets • Inner-most planets very hot (nearest the Sun) • Four gaseous outer planets • Outer planets very cold • Ninth planet, Pluto, may not be a planet • Universe is over 15-20 billion years old

8. Fig. 1.2 the planets of the solar system have different composition and physical properties

9. Solar System • About five billion years ago, out of a swirling mass of gas and dust, evolved a system of varied planets hurtling around a nuclear-powered star -- the system is our solar system. • Formed after the universe • Planets revolve around Sun • One complete trip for Earth equals one year • Earth at 23.5o tilt from the vertical • Hemispheres of the Earth do not receive equal solar energy year round • Because of the tilt • Produces seasons

10. Earth – continuous change • Early Earth – a barren world with a cratered surface • lacked oceans • Lacked atmosphere • Earth heated up and was molten • Earth was target of many impacts • Asteroids • Dust Particles • Meteors • Comets

11. Earth – continuous change • As cooling progressed, dense materials, such as metallic iron, would sink toward the middle of the earth while lighter, low-density minerals crystallized and floated out toward the surface. • Differentiation of this world developed compositional zones • Central core: dense and hot • Composed of nickel (Ni) and iron (Fe) • Mantle: thick zone that surrounds the core • Composed of ultramafic and mafic rocks and magma • Heat from core escapes by convective circulation • Crust: chemically different from core or mantle • Two types of crust: Oceanic (mafic) and Crustal (felsic) • Water and atmospheric gases interact only with outermost crust

12. Figure 1.3 A chemically differentiated earth

13. Table 1.02

14. Early Atmosphere • The heating and subsequent differentiation of the early earth led to the formation of the atmosphere and oceans. • Many minerals that contained water or gases in their crystals released them during the heating and melting, and as the earth’s surface cooled, the water could condense to form the oceans and gases form the atmosphere. • Chemically different than today • No modern pollution • Lacked free oxygen (O2) • Dominated by nitrogen (N) and carbon dioxide (CO2) • Minor amounts of other gases: • Methane (CH4) • Ammonia (NH3) • Sulfur gases • Barren of life

15. Figure 1.4 the geologic spiral

16. First Life • Early atmosphere required modification before life could evolve • Single-celled blue-green algae flourished first • Abundant oxygen was required for other life • Photosynthesis by algae produced oxygen • Sunlight energized a chemical reaction in algae • Food was produced from CO2 • Oxygen given off as a by-product • Oxygen accumulated in the atmosphere • Life for oxygen meant breathing organisms could evolve

17. Life Evolves on EarthUp to 500 million years ago • Early life forms – little evidence • no hard parts (no teeth, bones, shells, or claws) • Earliest rocks – limited life forms, single-celled organisms • 2 billion years ago some rocks show evidence of blue-green algae • Multicelled creatures appear 1 billion years ago • Oxygenated atmosphere developed • Marine animals with shells widespread by 600 million years ago

18. Life Evolves on EarthLast 500 million years • Vertebrates appear about 500 million years ago • Land plants appear about 400 million years ago • Insects develop about 300 million years ago • Dinosaurs appear about 200 million years ago • Birds appear about 150 million years ago • Mammals and birds well established by 100 millions years ago • Primitive human beings appear by 3 to 4 millions years ago • Modern humans (Homo sapiens) appear during last 500,000 years

19. Geology as a Science • Geology at first was an observational science • People would see a geologic curiosity and describe it • Later, people would attempt to explain it • Modern geology combines observation and laboratory activities (measurements and calculations) to explain natural phenomena • Geology has grown rapidly into an analytical science • Experiments must consider changes in temperature, pressure, stress, chemical parameters, and time • Not just a descriptive science, but a more quantitative and more interdisciplinary science through time • Starting materials that form rocks and minerals often are completely changed during the course of time • Time – seconds, minutes and hours are units of time that are replaced by time intervals of thousands, millions, or billions, of years

20. Scientific MethodA means to discover basic scientific principles • Starting Point – a set of observations and/or a body of data from measurements of phenomena and/or experiments • Hypothesis is formed to explain the observations or data • Conceptual framework or model is developed • Multiple explanations or equations developed • Must be testable and test must be reproducible • Proof of a hypothesis is sought as well as evidence to disprove it • Test the hypothesis repeatedly and systematically • Make set of predictions and perform series of experiments • Theory formed as accepted explanation for an observation or set of data • Hypothesis becomes a theory only after extensive testing of the hypothesis

21. Theory versus Hypothesis • Theory – accepted explanation • Must be a well tested model • Is subject of considerable investigation and data collection that is required to evaluate it • A hypothesis is elevated to a theory only after extensive debate and experimentation

22. Geology and the Scientific MethodGeology has problems that other sciences do not! • Problems with size • A volcano is big • A river is not easily contained within a laboratory • Plate Tectonics involves the whole Earth • Problems with time • Geologic processes take millions of years to complete • Geologists are limited by human time (years to decades) • Problems with resolution of data • New technology and procedures often impact, or challenge, old theories • We can see more details now than a century ago

23. Why Environmental Geology? • Environmental geology explores the many and varied interactions between humans and geologic environments • Earth is a dangerous place! • Earthquakes and Volcanoes • Floods, Mass wasting, and Soil erosion • Global Warming • Quest for more energy • Pollution and Storage of toxic waste • Find and manage fresh water • Find new resources (they are limited) • Remediate sites of mineral extraction

24. Figure 1.5

25. Figure 1.6

26. Figure 1.7

27. Figure 1.8

28. Figure 1.9

29. Population Growth • Population has experiencedexponential growth: • Possibly 9 billion people by 2050 • Slow population growth up until mid-19th century • Doubling times have become shorter • Life expectancy has increased • Birth rates have greatly exceeded mortality rates • People are more mobile and can live anywhere • New perils will confront us because of our increasing population • AIDS epidemic • Impacts dictated by economic, social, or religious values • Limited exploitation of new sources of natural resources • Growing demand by third world countries wanting to become first world countries

30. Figure 1.12

32. Figure 1.13

33. Impacts of the Human Population • Rapid growth of humans results in problems obtaining an adequate food supply • Expect problems with maintaining adequate: • Water supplies for irrigation, drinking, and industry • Farmland to produce crops to feed a hungry earth • Food production is an energy-intensive business • Supply of energy and minerals for our material based lifestyle • Pollution of air, land, and water pursuing • Our ever expanding, high energy, and resource consuming life styles • Genetic engineering contributes to food production

34. Figure 1.14 Population distribution by region in 2002 with projection to the year 2050

35. Figure 1.17 Global population density; the darker the shading, the higher the population density.

36. Impacts of the Human PopulationHow do we resolve the issues? What consequences will we face because of our growth of the human population? • Energy and natural resources are finite supplies on earth • Where do we find more? • Water supplies have been exhausted in many places • Where do we find more? • Croplands are replaced by homes and cities • Where do we find more? • Waste, the products of our life style, must be put somewhere • Where do we put it and at what cost? • Carrying Capacity, its ability to sustain its population at a basic, healthy, moderately comfortable standard of living • Have we exceeded it? • Global Warming, the activity of billions of people is impacting the climate of earth • Can we reverse it?