Conversations with the Earth Tom Burbine tburbineframingham edu
Conversations with the Earth Tom Burbine tburbine@framingham. edu
Quiz • Monday for M, W, Th class • Tuesday for T, Th class • • Covers material after last quiz Chemistry Global warming Dinosaur extinction
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.
Stratigraphy • Stratigraphy – study of rock layers and layering
Original Horizontality • Layers of sediment are originally deposited as an even, horizontal layer • Layers inclined at angles were moved by disturbances after deposition
Superposition • Each layer was deposited on top of older preexisting layers below
Principle of Superposition http: //earthsci. org/fossils/geotime/Super. gif
Exercise #3 • Question 1 • What is used to differentiate between different time periods?
• Question 2 • How long ago did the dinosaurs become extinct?
• Question 3 • How long were there dinosaurs living on the Earth?
• 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
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
Wyoming
Italy
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
• Question 4 • Why is a high concentration of iridium evidence that an asteroid hit the Earth?
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)
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.
Environmental Damage • http: //www 4. tpgi. com. au/users/horsts/climate. htm
• 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.
• Pterosaurs were flying reptiles
• 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).
• Question 5 • What species today are direct descendants of the dinosaurs?
Archaeopteryx • Modern birds are considered be the direct descendants dinosaurs • Idea first formulated in 1860 s-1870 s to of
Rahonavis
• http: //www. hulu. com/watch/63729/nova-the-fourwinged-dinosaur
Any Questions?
- Slides: 33