ESC 102 Evolution of Earth and Life Historical Geology Spring 2011

1. ESC 102 Evolution of Earth and Life Historical Geology Spring 2011

2. Earth Systemscan you identify them? • When we view the Earth from space what Earth systems are observable? • What is most obvious? • Are these systems independent or do they interact with one another?

3. Systems = Spheres of the Earth • Lithosphere: Earth’s solid rocky mass • Hydrosphere: All of earth’s water • Atmosphere: The thin gaseous layer above Earth’s surface • Biosphere: All of earth’s life forms

4. Three Themes tell the story of the evolving Earth • The Theory of Plate Tectonics Solid Earth is composed of plates that move over Earth’s surface. • The Theory of Organic Evolution Earth’s biota – all living things – has evolved or changed through history. • The Geologic Time Scale Geologic processes take place within extensive geologic time -~ 4.6 billion years of Earth’s history.

5. Something Happened….. James Hutton observed tilted sedimentary layers overlain by near-horizontal layers.He realized that whatever processes created this rock outcrop must have taken millions of years.In 1785, published his Theory of the Earth and is considered founder of modern geology.

6. Charles Lyell wrote “Principles of Geology in 1830. He furthered the work of James Hutton: concept ofUniformitarianism Rock layers reveal sequences of events based on processes that occur today.

7. Historical Geologyapplies geologic principles to help predict and explain Earth’s materials • William Smith was an English surveyor who realized that rock types and fossils occur in repeated patterns. He was able to predict rock sequences that would be encountered in constructing canals • Smith mapped the geology of much of England. (1815)

8. Smith’s map took many years to complete and helped establish the geologic time scale. ?

9. Hypothesis or Theory? • The scientific method brings an orderly and logical approach to decoding geologic evidence. • A hypothesis is a tentative explanation for observations • Scientists make predictions using hypotheses – then they are tested • After repeated testing, a theory may be proposed • Some phenomena cannot be tested or explained

10. A theory is formed • A theory is more than an “educated guess” • A theory explains natural phenomena and may relate several observations • A theory is well-tested and well-supportedby objective evidence • Examples include: Plate Tectonics Theory Theory of Organic Evolution

11. Where do scientists look for evidence for the following? • The origin and age of the universe • The origin and age of the solar system • The origin and age of the Earth and Moon • The origin of life on Earth • Evidence of plate movement on Earth • Explanation for large scale extinctions on Earth

12. How old is the universe? • When? Scientists believe the universe was formed about 15 billion years ago • How? The Big Bang is a model for the “beginning” of the universe • “Show me”! What is the evidence?

13. Evidence of the Big Bang • Pervasive background radiation of 2.7o C above absolute zero is observed in space(-273o C or -460o F) “Afterglow” of the Big Bang discovered in 1965 As predicted, it was cosmic microwave radiation from .space

14. Evidence of the Big Bang • Galaxies moving away – expanding universe(proposed by Hubble) Imagine the surfaceof a balloon as itis inflated. Locations on the surface move away from one another.ther.

15. Evidence of the Big Bang Determine the Age of the Universe Determine rate of expansion“Back-model” to a time when the galaxies would be together in the same space

16. Research • A 7 year satellite observation project mapped the cosmic microwaves in space • Revealed the nature of many components that had been predicted in various models. • The WMAP project since 2002 has enabled scientists to refine the age of the universe to 13.7 billion years and the “shape” of its surfaces.

17. Big Bang model • Initial state: NO time, NO matter, NO space • Universe was pure ENERGY • During the FIRST second of time: --very dense matter came into existence --The four basic forces separated: gravityelectromagnetic force strong nuclear and weak nuclear forces Enormous expansion occurred

18. Big Bang Model • 300,000 years later: • Atoms of hydrogen and helium formed • Light (photons) burst forth for the first time • Next 200 million years: • Continued expansion • Stars and galaxies began to form • Elements heavier than hydrogen and helium began to form within stars by nuclear fusiion

19. 9 billion years later….. The formation of the solar system

20. Origin of Our Solar System Solar nebula theory • cloud of gases and dustformed a rotating disk • condensed and collapsed due to gravity • forming solar nebula • with an embryonic Sun • surrounded by a rotating cloud

21. 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

23. The planets formed with distinctorbits around the sun.Some planets have satellites which orbit individual planets.

24. Solar Nebula Theory Is there Evidence? The Hubble Telescope image shows a solar nebula as a protoplanetary disk or “proplyd” located in Orion Nebula with dozens of others. The proto star is the bright glow; dark area is a dense molecular cloud.

25. This NASA image clearly shows that this star has 4 distinct rings. These rings will eventually coalesce into solid bodies called planets.

26. Terrestrial Planets Mercury Venus Earth Mars Small in size Composed of rock Metallic cores Asteroid Belt Jovian Planets Jupiter Saturn Uranus Neptune Large in size. Composed of hydrogen, helium, ammonia, methane Small rocky cores Kuiper Belt Pluto: no longer has planet status The Planets

28. Earth’s Very Early History • Started out cool about 4.6 billion years ago probably with uniform composition/density • Temperature increased. Heat sources were: • meteorite impacts • gravitational compression • radioactive decay • Heated up enough to melt iron and nickel within the newly formed Earth

29. The earth and moon were heavily bombarded in Earth’s early history.

30. Earth’s Differentiation • Differentiation = segregated into layers of differing composition and density • Early Earth was probably uniform • After heating, molten iron and nickel sank to form the core • Lighter minerals flowed up to form mantle and crust

31. Forming the Moon • Impact by Mars-sized planetesimal with early Earth 4.6 to 4.4 billion years ago Ejected a large quantity of hot material that cooled and coalesced to form the moon

32. Impact hypothesis for moon

33. Most of the lunar material came from the mantle of the colliding planetesimal The material cooled and crystallized into lunar layers Moon is smaller than Earth and cooled quickly.Light colored surface areas are lunar Highlands – heavily cratered. evidence of massive meteorite Bombardment Mare: areas of lava flows more likely due to impact than tectonics

34. Earth—Dynamic Planet • Earth was also subjected • to the same meteorite barrage • that pock-marked the Moon • Why isn’t Earth’s surface also densely cratered?

35. Major elements on Earth Top 4 most abundant elements:OxygenSiliconaluminum

36. Earth’s Interior Layers • Lithosphere • solid upper mantle and crust -- broken into platesthat move over the • asthenosphere • Asthenosphere • part of upper mantle • behaves plastically and slowly flows

37. Plate Tectonics Theory • Lithosphere is broken into individual pieces called plates • Plates move over the asthenosphere • as a result of underlying convection cells

38. Plate Tectonic Theory • Movement at plate boundaries • plates diverge • plates converge • plates slide sideways past each other • At plate boundaries • Volcanic activity occurs • Earthquakes occur

39. Modern Plate MapActive tectonic boundaries are in red

40. Plate Tectonic Theory After decades of puzzling evidence, the theory was developed in the1960s • Provides a framework for • interpreting many aspects of Earth on a global scale • and relating many seemingly unrelated phenomena • Key to interpreting Earth historyThe “unifying theory of geology”

41. Plate Tectonics and Earth Systems Mechanism: Plate tectonics is driven by convection in the mantle and in turn drives mountain building and associated igneous and metamorphic activity • Global effects of plate movement:Arrangement of continents affects • solar heating and cooling, • winds and weather systems • Rapid plate spreading and hot-spot activity • may release volcanic carbon dioxide • and affect global climate

42. History of Earth • The history of the early earth through the present is revealed mainly in the rock and fossil records. • By applying principles of formation and determining environments from life forms, early interpretations about Earth’s land masses and oceans have been made

43. Theory of Organic Evolution • Provides a framework for understanding the history of life • Darwin’s • On the Origin of Species by Means of Natural Selection, published in 1859, • revolutionized biology • Provided the mechanism of natural selection

44. Central Thesis of Evolution • All present-day organisms • are related and descended from organisms that lived during the past • Natural selection is the mechanism • that accounts for evolution • Natural selection results in the survival • to reproductive age of those organisms • best adapted to their environment

45. History of Life • The fossil record provides perhaps • the most compelling evidence • in favor of evolution • Fossils are the remains or traces • of once-living organisms • Fossils demonstrate that Earth • has a history of life

46. Geologic Time • From the human perspective time units are in seconds, hours, days, years • Ancient human history hundreds or even thousands of years • Geologic history millions, hundreds of millions, billions of years

47. Geologic Time Scale Resulted from the work of many 19th century geologists who • pieced together information • from numerous rock exposures, • constructed a sequential chronology • based on changes in Earth’s biota through time • The time scale was subsequently dated in years • using radiometric dating techniques

48. Uniformitarianism: The Present is the key to the past • Uniformitarianism is a cornerstone of geology • is based on the premise that present-day processes • have operated throughout geologic time • The physical and chemical laws of nature • have remained the same through time