1. Introduction to Physical Science Monday, Wednesday, Thursday Tom Burbine tomburbine@astro.umass.edu

3. Earth How do we determine the composition of the Earth’s interior?

4. Planetary densities mass

5. ρ = Mass/Volume ρ Earth = 5.515 g/cm 3 Density (g/cm 3 ) Metallic iron7.87 Basalt3.3 Water1.0 Cold ices and hydrogen0.07-0.09

6. Density (g/cm 3 ) Iron7.87 Basalt3.3 Water1.0 Cold ices0.07-0.09 Density What do these densities tell us?

7. http://college.cengage.com/geology/resources/protected/physicallab/thelab/interior/index.htm

8. Earth’s Interior

10. Earth’s crust 46.6% O 27.7% Si 8.1% Al 5.0% Fe 3.6% Ca 2.8% Na 2.6% K 2.1% Mg

11. Earth is made of minerals

12. How do we know what’s in the interior of the Earth?

13. Seismic Waves – vibrations created by earthquakes

14. Seismic Waves P waves – primary waves – (pushing) – travel faster – can travel through anything S waves – secondary – (side to side) – travel slower – only through solids

15. http://alomax.free.fr/alss/examples/hodo/hodo_ex ample.htmlhttp://alomax.free.fr/alss/examples/hodo/hodo_ex ample.html

16. Surface Waves Travel on the surface of the Earth Love Wave – side by side http://www.geo.mtu.edu/UPSeis/images/Love_ani mation.gifhttp://www.geo.mtu.edu/UPSeis/images/Love_ani mation.gif Rayleigh Wave – rolling movement http://www.geo.mtu.edu/UPSeis/images/Rayleigh _animation.gifhttp://www.geo.mtu.edu/UPSeis/images/Rayleigh _animation.gif Most of the shaking felt from an earthquake is due to the Rayleigh waves

18. P (primary) waves S (secondary) waves Surface waves: Rayleigh and Love waves

24. Richter Scale Measures the magnitude of an earthquake Single number to quantify the amount of seismic energy released by an earthquake. Amplitude of largest displacement Under 6.0 - At most slight damage to well-designed buildings. Can cause major damage to poorly constructed buildings. 6.1-6.9 - Can be destructive in areas up to about 100 kilometers across where people live. 7.0-7.9 - Major earthquake. Can cause serious damage over larger areas. 8 or greater - Great earthquake. Can cause serious damage in areas several hundred kilometers across.

28. How do we get information? The precise speed and direction of the waves depends on the composition, density, pressure, temperature, and phase (solid or liquid)

29. Which of these bodies have they used seismic waves to study?

30. How can you study the interior of a planet?

31. Density Density = mass/volume If the density is higher than the surface rock, there must be denser material in the interior

32. Gravity If you can measure gravity (force) with a spacecraft as it rotates around a body, you can determine how mass is distributed on the body

33. Magnetic Field Tells if a planet has a molten metal interior

34. http://www.gcsescience.com/pme1.htm

35. Earth’s magnetic field is believed to be caused by the convection of molten iron, within the outer liquid core along with the rotation of the planet http://geomag.usgs.gov/images/faq/Q6.jpg Electrons flow

36. http://www.scifun.ed.ac.uk/card/images/left/earth-magfield.jpg

37. Magnetic pole moves http://science.nasa.gov/headlines/y2003/29dec_magneticfield.htm

39. North Magnetic Pole However, the "north pole" of a magnet is defined as the one attracted to the Earth's North Magnetic Pole By this definition, the Earth's North Magnetic Pole is physically a magnetic south pole

40. Glatzmeier and Roberts simulations :

41. Geomagnetic Reversals Based upon the study of lava flows of basalt throughout the world, it has been proposed that the Earth's magnetic field reverses at intervals, ranging from tens of thousands to many millions of years

42. What may happen during the reversal? There may be a slight rise in the per capita cancer rate due to a weaker magnetic field. We may also be able to see the northern lights at lower latitudes If you own a compass, it will have difficulty finding north until the magnetosphere settles.

43. Any Questions?