Text Historical Geology Evolution of Earth and Life Through Time 4th edition by Wicander and Monroe Chapter 1 The Dynamic and Evolving Earth The Movie of Earth s History What kind of movie would we see if it were possible to travel back in time and film Earth s History from its beginning 4 6 billion years ago It would certainly be a story of epic proportions with great special effect and a cast of trillions twists and turns in its plot with an unknown ending Although we cannot travel back in time the Earth s History is still preserved in the geologic record Subplot Landscape History In this movie we would see a planet undergoing remarkable change as continents moved about ocean basins opened mountain ranges grew along continental margins and where continents collided form and grow change circulation patterns cause massive ice sheets to form and grow and then melt away The oceans and atmosphere would Extensive swamps or vast interior deserts would sweep across the landscape Subplot Life s History We would also witness the first living cells evolving from a primordial organic soup between 4 6 and 3 6 billion years ago Cell nuclei would evolve then multicelled soft bodied animals followed by animals with skeletons and then backbones The barren landscape would come to life as plants and animals moved from their watery home insects amphibians reptiles birds and mammals would eventually evolve Earth is a Dynamic and Evolving Planet Changes in its surface Changes in life At the End of the Movie The movie s final image is of Earth a shimmering blue green oasis in the black void of space and a voice says To be continued The Movie s Theme Every good movie has a theme and The History of Earth is no exception Three interrelated themes run throughout it The first is that Earth s outermost part is composed of a series of moving plates Plate tectonics whose interactions have affected its physical and biological history The second is that Earth s biota has evolved or changed throughout its history organic evolution Earth is a System of Interconnected Subsystems Atmosphere air and gases Hydrosphere water and oceans Biosphere plants and animals Lithosphere Earth s rocky surface Interior mantle and core Interactions in Earth s Subsystems m At re e h p s o Bio e r e sp h Gases from respiration Transport of seeds and spores Interactions in Earth s Subsystems m At h p s o Wind erosion transport of water vapor for precipitation ere Li sp o th re e h Mountains divert air movements Interactions in Earth s Subsystems Source of sediment Hyd and dissolved rosp here material Lith o sp h ere Water and glacial erosion solution of minerals This class is about historical geology What is Geology From the Greek geo Earth logos reason Geology is the study of Earth Physical geology studies Earth materials such as minerals and rocks as well as the processes operating within and on Earth s surface Historical Geology In historical geology we study changes in our dynamic planet how and why past events happened implication for today s global ecosystems Principles of historical geology not only aid in interpreting Earth s history but also have practical applications William Smith an English surveyor engineer used study of rock sequences to help predict the difficulty of excavation in constructing canals Scientific Method The scientific method an orderly and logical approach Gather and analyze facts or data A hypothesis is a tentative explanation to explain observed phenomena Scientists make predictions using hypotheses then they test the predictions After repeated tests if one hypothesis continues to explain the phenomena scientists propose it as a theory Formulation of Theories Theory colloquial usage speculation or conjecture scientific usage coherent explanation for one or several related natural phenomena supported by a large body of objective evidence Origin of the Universe The Big Bang occurred 15 billion years ago and is a model for the beginning of the universe Evidence for the Big Bang Universe is expanding How do we determine the age measure the rate of expansion backtrack to a time when the galaxies were all together at a single point Pervasive background radiation of 2 7 above absolute zero is the afterglow of the Big Bang Big Bang Model Initial state No time matter or space existed There is no before the Big Bang Universe consisted of pure energy During 1st second Very dense matter came into existence The four basic forces separated gravity electromagnetic force 2 nuclear forces Enormous expansion occurred Big Bang Model cont 300 000 years later atoms of hydrogen and helium formed light photons burst forth for the first time During the next 200 million years Continued expansion and cooling Stars and galaxies began to form Elements heavier than hydrogen and helium began to form within stars by nuclear fusion Features of Our Solar System In a spiral arm of the Milky Way Galaxy Sun 9 planets 101 known moons satellites a tremendous number of asteroids most orbit the Sun between the orbits of Mars and Jupiter millions of comets and meteorites interplanetary dust and gases Relative Sizes of the Sun and Planets Solar System Configuration Origin of Our Solar System Solar nebula theory cloud of gases and dust formed a rotating disk condensed and collapsed due to gravity forming solar nebula with an embryonic Sun surrounded by a rotating cloud Embryonic Sun and Rotating Cloud Planetesimals have formed in the inner solar system and large eddies of gas and dust remain far from the protosun The Planets Terrestrial Planets Mercury Venus Earth Mars small composed of rock with metal cores Jovian Planets Jupiter Saturn Uranus Neptune large composed of hydrogen helium ammonia methane relatively small rocky cores Earth s Very Early History Started out cool about 4 6 billion years ago probably with uniform composition density Mostly silicate compounds iron and magnesium oxides Temperature increased Heat sources meteorite impacts gravitational compression radioactive decay Heated up enough to melt iron and nickel Earth s Differentiation Differentiation segregated into layers of differing composition and density Early Earth was probably uniform Molten iron and nickel sank to form the core Lighter silicates flowed up to form mantle and crust Forming the Earth Moon System Impact by Mars sized or larger planetesimal with young Earth 4 6 to 4 4 billion years ago ejected large quantity of hot material and formed the Moon Forming the