Origin of the Universe

1. Origin of the Universe

2. Origin of Universe • Big Bang model (Hubble, 1929) - The universe began with an explosive expansion of matter, which later became what we know as stars, planets, moons, etc. This event is thought to have occurred 10 - 15 billion yrs ago. • Nebular Hypothesis (Kant, Laplace 1796) - Earth and the other bodies of our solar system (Sun, moons, etc.) formed from a “vast cloud of dust and gases” called a nebula.

3. Big bang theory • There was a big bang some 15 billion years ago, when the size of the universe was zero and the temperature was infinite. The universe then started expanding at near light speed. • At about 10,000 years after the Big Bang, the temperature had fallen to such an extent that the energy density of the Universe began to be dominated by massive particles, rather than the light and other radiation which had predominated earlier. This explains the formation of galaxies and other large-scale structures observed in universe today.

4. Nebular Hypothesis • According to this hypothesis, the nebular cloud consisted of H and He, and a small percentage of the heavier elements we find in the solar system • Within the rotating disk, the rocky material and gases began to nucleate and accrete into protoplanets

5. Formation of Earth’s Interior • As Earth was formed, it was extremely hot from the bombardment of space debris, radioactive decay, and high internal pressures. • These processes caused Earth’s interior to melt, and then to differentiate into regions of chemical and physical differences as it cooled.

6. Continental drift Alfred Wegener • Theory that continents and plates move on the surface of the Earth proposed by Alfred Wegener in 1915.

7. Maps by Wegener (1915), showing continental drift

8. Theory of continental drift

9. Evidence for continental drift • Matching coastlines • Matching mountains • Matching rock types and rock ages • Matching glacier deposits • Matching fossils

10. Evidence for continental drift Matching coastlines

11. Evidence for continental drift Matching mountain ranges

12. Evidence for continental drift Matching rock types and ages of rocks

13. Evidence for continental drift Matching glacier deposits 300 million years ago

14. Evidence for continental drift Fossils of of Mesosaurus (aquatic reptile) found on both sides of Atlantic

15. Theory of Plate tectonics • The theory of Plate tectonics was proposed in 1960s based on the theory of continental drift. • This is the Unifying theory that explains the formation and deformation of the Earth’s surface. • According to this theory, continents are carried along on huge slabs (plates) on the Earth’s outermost layer (Lithosphere). • Earth’s outermost layer is divided into 12 major Tectonic Plates (~80 km deep). These plates move relative to each other a few centimeters per year.

16. Earth’s magnetic field Basic Data used in formulating plate tectonics: Magnetic stripes on the sea-floor. Magnetic field of Earth reverses on semi-regular basis. Minerals act like compass needles and point towards magnetic north. “Hot” rocks record the direction of the magnetic field as they cool.

17. Tectonic plates of Earth

18. Types of plate boundaries • Divergent plate boundaries: where plates move apart • Convergent Plate boundaries: where plates come together • Transform plate boundaries: where plates slide past each other

19. Types of plate boundaries Divergent (Tension) Convergent (Compression) Transform (shearing)

20. Types of plate boundaries

21. What drives plate movement? • Ultimately: heat transported from core and mantle to surface • Heat transported by convection • Core is ~5,000°C and surface is ~0°C • Where mantle rises: rifting • Where mantle dives: subduction zones

22. What are Seismic Waves? Presentation based upon information retrieved from: http://www.geo.mtu.edu/UPSeis/waves.html Movie clips from United Streaming

23. Seismic Wave • Seismic waves are the waves of energy caused by the sudden breaking of rock within the earth or an explosion. They are the energy that travels through the earth and is recorded on seismographs. • There are several different kinds of seismic waves, and they all move in different ways. The two main types of waves are body waves and surface waves.

24. Earth Stats • The Earth's mass is about 5.98 x 1024 kg. • Earth is the densest planet in our Solar System (mass/volume). • Earth is made of several layers with different compositions and physical properties, like temperature, density, and the ability to flow.

25. The Composition of the Earth

26. The Composition of the Earth • Crust • Thinnest layer (5-100 km) • Two types of crust • Continental • Like granite • Average 30 km • Oceanic • Like basalt • (Basalt is denser than granite!) • Average 5-8 km

27. The Composition of the Earth • Mantle • Extremely Thick! (2,900 km) • It is too far down to drill • How do we know what it is made of? • Scientists infer based on: • Pushed up rock • Ocean floor/molten rock • What is it like? • Like the mineral olivine • Large amounts of iron and magnesium www.soc.soton.ac.uk

28. N S The Composition of the Earth • Core • Pretty darn big. (6,856 km) • (Slightly bigger than Mars!) • 33% mass of the Earth • Scientists think…. • Made mostly of iron • Some nickel, sulfur, oxygen • What is the evidence? • The particular way seismic waves travel • Earth’s Magnetic field

29. Lithosphere Solid Asthenosphere Viscous Liquid The Structure of the Earth Outer Core Liquid Mesosphere Solid Inner Core Solid

30. Lithosphere = ‘rock sphere’ Crust and upper rigid part of Mantle Asthenosphere = ‘weak sphere’ Lower part of Mantle

31. How HOT is it? Surface of Sun! 5,500°C Sun Core 15,000,000°C

33. Mystery Box • Do we know for sure