1 / 17

A Short Look at Earth History

A Short Look at Earth History . Formation of Sun. Formation of Universe: 13.7 billion years Formation of Galaxy: 11 billion Years Formation of Solar System: 4.6 billion years Sun is probably a third generation star Probably takes 10-100 million years for planets to form .

edison
Download Presentation

A Short Look at Earth History

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. A Short Look at Earth History

  2. Formation of Sun • Formation of Universe: 13.7 billion years • Formation of Galaxy: 11 billion Years • Formation of Solar System: 4.6 billion years • Sun is probably a third generation star • Probably takes 10-100 million years for planets to form

  3. Formation of Planets • Planets made of same material as Sun, minus elements that remain mostly in gases • Inner Rocky Planets: iron and magnesium silicates • Outer gas giants and moons: water ice • If a protoplanet gets big enough, it can hold everything (Jupiter, Saturn) • Very far from sun: methane, ammonia, nitrogen ice

  4. Our Solar System May Not Be Typical • Over 400 extrasolar planets known • Barely can detect Jupiter-size planets, don't yet have technology to see small planets • Many have very eccentric orbits • Some have gas giants very close in to sun ("hot Jupiters")

  5. Formation of Earth • Planets formed by accretion of smaller objects = impact • Very tiny objects hold together by atomic forces • Objects kilometers across hold together by gravity • How do objects the size of a refrigerator hold together? • As planets get bigger, gravity gets stronger, impacts get more violent • Big impacts throw out ejecta, trap heat • Magma ocean • Formation of core early in earth history as iron sinks

  6. Formation of Moon • It's very hard to account for the Moon: • Very big compared to its parent planet • Orbits nearly in plane of earth's orbit, not over equator. • Co-creation with Earth? • Fission? • Capture?

  7. Collision • A collision takes no finesse at all • Can explain why moon orbits in earth's orbital plane • Can explain why moon's composition differs from earth • Models of solar system evolution suggest that last stage is mega-collisions • Impact would have melted most of earth and moon • Earth would have been incandescent for about 10,000 years.

  8. Unstable Early Earth • May have been several moon-forming events • 1000-km impactors can melt crust • 100-km impactors create temporary atmosphere of vaporized rock, vaporize oceans • Life not possible until large impacts cease • To have life on Earth, we need Jupiter? • Sweeps up debris and reduces impacts • Stabilizes orbits of other planets • To have life on Earth, we need Moon? • Stabilizes changes in earth's axis tilt

  9. Conditions on Early Earth • Oldest existing earth materials: 4.1 billion years old • Oldest rocks: 3.9 billion years old • Oxygen-poor atmosphere (present oxygen is created by life) • Faint Early Sun: perhaps 30 per cent less bright • Evidence for liquid water from very early on • Atmosphere and sun must have evolved in tandem • Carbonate-Silicate Cycle: life not essential but liquid water is.

  10. Life • What Is It? • "Life is what dies when you stomp on it“ --Dave Barry • A self-replicating chemical system • Feedback (Homeostasis)

  11. How Did Life Originate? • Certainly not as complex as anything now alive • Lots of candidates for first self-replicators • Role of minerals as catalysts and templates? • Simplest organisms are extremophiles • At least since 3 billion years, probably much earlier

  12. Tolerance Ranges

  13. Major Events in the History of Life • Oxygen levels in atmosphere • Plants release waste oxygen • Eventually organisms developed a way to utilize oxygen (6CO2 + 6H2O = C6H12O6 + 6O2) • Sex: Who Needs It? • We are a team: Mitochondria • Snowball Earth: what survived and how? • Cambrian "Explosion"

  14. Mass Extinctions

  15. Causes ? • Climate Change • Disease • Mountain-building • Sea Level Change • Competing Organisms • Over-specialization • Volcanism • Meteor Impact

  16. Plate Tectonics • Very early earth may have had thin, unstable crust • Large areas of continental crust existed by 2.5 billion years • Plate tectonics since at least two billion years • Wilson Cycle and Supercontinents • Supercontinents • Dispersal • Reassembly • Rodinia 800 million years • Pangaea 250 million years

  17. Humans • Lumpers vs. Splitters • Australopithecus > 2 m.y. • Homo erectus 1-2 m.y. • Homo ergaster 1-2 m.y. • Homo habilis < 1 m.y. • Homo neanderthalensis 500,000-30,000 yr. • Homo sapiens<100,000 years

More Related