1. What Do We Know About the Inside of Our Earth?

2. Core No direct samples Probably heavy stuff Inner core –Solid –Density of pure iron or nickel/iron –~ 12-13 g/cm 3 –~ size of moon Outer core –Molten (does not transmit S- waves) – Includes ~ half of diameter of Earth –~ 10-12 g/cm 3 –Core-mantle boundary (Gutenberg Discontinuity) is largest density contrast in Earth

3. Mantle Density – between crust and core 3.3 - 5.5 g/cm 3 Probably material such as peridotite (lots of heavy olivine - Fe, Mg) Samples from kimberlites, xenoliths in volcanic eruptions, basalt composition; lab experiments MOHO - Mohorovicic Discontinuity Core mantle boundary - change in mineralogy

4. Crust Our deepest hole: 12 KM ….. we have a long way to go! Two types of crust: –Continental 30% of crust Granites and Diorites - rich in silicates and feldspars (lighter materials) 40 Km thick Oldest is 3.8 billion years (90% solar system age; missing ~700 m.y.) –Oceanic crust Basalt - Mg, Fe (heavier materials) 5-10 Km thick 200 Ma oldest; 100 Ma average

5. Kola Superdeep Borehole

6. Well to Hell? Kola Peninsula, Russia Studied: –deep structure of the shield; –seismic discontinuities; –crustal thermal regime; –physical and chemical composition; –transition from upper to lower crust; –lithospheric geophysics; –technologies for deep geophysical study Reached 12.261 km in 1989 Year off to celebrate 2.7 Ga rocks at bottom Too hot to drill deeper http://acoustpol.narod.ru/intas/out/images/image_37/Viev-SD3-researcers_web.jpg