Discovering the Core
We may know more about the Moon than Earth’s core, but is that surprising? We can see the Moon and have even visited the far side. It’s a lot harder to learn about the center of the Earth. We can’t go there and we can’t drill there. How can we learn about the core?
Amazing But True!
- Richard Oldham was the first person to notice the separate arrival times of P-waves, S-waves and surface waves on seismograms.
- From his mathematical analysis he determined that Earth had a core equal to less than 40% its radius.
- Inge Lehman was the first to discover the P wave shadow, indicating the presence of an inner core.
- Lehman later discovered a change in seismic wave velocity in the mantle, which was called the Lehman discontinuity.
With the link below, learn more about discovering the core. Then answer the following questions.
- 100 Greatest Discoveries: The Core of the Earth: http://science.discovery.com/tv-shows/greatest-discoveries/videos/100-greatest-discoveries-the-core-of-the-earth.htm
- Oldham noticed that seismic waves appeared to hit an obstacle, which was the core. What do the P-waves and S-waves do at the core?
- What did Lehman observe that indicated to her that there were two cores?
- What are the two main differences between the inner core and the outer core?
- Why is it important that the outer core is liquid?