Conversations with the Earth Tom Burbine tburbine@framingham

1. Conversations with the EarthTom Burbinetburbine@framingham.edu

2. Quiz • Monday for M,W, Th class • Tuesday for T, Th class • Covers material after last quiz • Chemistry • Global warming • Dinosaur extinction

3. Geologic time scale • System of measurement relating stratigraphy to time that is used to describe the timing and relationships between events that have occurred during the history of the Earth.

4. Stratigraphy • Stratigraphy – study of rock layers and layering

5. Original Horizontality • Layers of sediment are originally deposited as an even, horizontal layer • Layers inclined at angles were moved by disturbances after deposition

6. Superposition • Each layer was deposited on top of older preexisting layers below

7. Principle of Superposition http://earthsci.org/fossils/geotime/time/Super.gif

9. Exercise #3 • Question 1 • What is used to differentiate between different time periods?

10. Question 2 • How long ago did the dinosaurs become extinct?

11. Question 3 • How long were there dinosaurs living on the Earth?

15. Index fossils are fossils used to define and identify geologic periods • The shorter the lifespan of a species, the more precisely different sediments can be correlated

17. K-T layer • K-T layer is the boundary between the Cretaceous (K) and Tertiary (T) time periods • Clay layer that is found all over the globe Colorado

18. Wyoming

19. Italy

20. K-T Boundary • 65 million years ago • Boundary in the rock record separating the Cretaceous and Tertiary Periods • Corresponds to one of the greatest mass extinctions in history • ~1 cm global layer of clay separating the two periods • A reason for the extinction was proposed by Walter Alvarez and Luis Alvarez in 1980

22. Question 4 • Why is a high concentration of iridium evidence that an asteroid hit the Earth?

23. Iridium • Iridium (Ir) is a chemical element with atomic number 77 • Iridium is one of the least abundant elements (0.001 ppm) in the Earth's crust • Iridium is much more abundant in meteorites (0.5 ppm or higher)

24. What happened? • An asteroid roughly 10 km (6 miles) across hit Earth about 65 million years ago. • This impact made a huge explosion and a crater about 180 km (roughly 110 miles) across. • Debris from the explosion was thrown into the atmosphere, severely altering the climate, and leading to the extinction of roughly 60% of species that existed at that time, including the dinosaurs.

25. Environmental Damage • http://www4.tpgi.com.au/users/horsts/climate.htm

26. The worst hit organisms were those in the oceans. • On land, the Dinosauria of course went extinct, along with the Pterosauria. • Mammals and most non- dinosaurian reptiles seemed to be relatively unaffected. • The terrestrial plants suffered to a large extent, except for the ferns, which show an apparently dramatic increase in diversity at the K-T boundary, a phenomenon known as the fern spike.

27. Pterosaurs were flying reptiles

28. Dinosaurs lived during the Mesozoic Era, from late in the Triassic period (about 225 million years ago) until the end of the Cretaceous (about 65 million years ago).

29. Question 5 • What species today are direct descendants of the dinosaurs?

30. Archaeopteryx • Modern birds are considered to be the direct descendants of dinosaurs • Idea first formulated in 1860s-1870s

31. Rahonavis

32. http://www.hulu.com/watch/63729/nova-the-four-winged-dinosaurhttp://www.hulu.com/watch/63729/nova-the-four-winged-dinosaur

33. Any Questions?