1. Dynamic Earth Class 7 January 31, 2006 Homework #2 is due

2. Homework #2 Are the interiors of continents usually younger or older than the margins? Why? Are the interiors of continents usually younger or older than the margins? Why? ➛ Older! ➛ The interiors of the continents are usually older than the margins because continents are formed by a series of orogenic episodes that enlarge the continental area by building new mountain ranges at its margins

3. Homework #2 Two continents collide, thickening the crust from 35 km to 70 km to form a high, Tibet-like plateau. After hundreds of millions of years, the plateau is eroded down to sea level. (a) What kinds of rocks might be exposed at the surface by this erosion? (b) Estimate the crustal thickness after the erosion occurred Two continents collide, thickening the crust from 35 km to 70 km to form a high, Tibet-like plateau. After hundreds of millions of years, the plateau is eroded down to sea level. (a) What kinds of rocks might be exposed at the surface by this erosion? (b) Estimate the crustal thickness after the erosion occurred ➛ a. You would expect to find volcanic and high-grade metamorphic rocks ➛ b. The crustal thickness would be around 35 km

4. Homework #2 What evidence would you look for to see if plate tectonics is occurring on other terrestrial planets? What evidence would you look for to see if plate tectonics is occurring on other terrestrial planets? ➛ magnetic anomalies, mountain chains, ridges, faults, volcanoes, etc.

5. Homework #2 How old is the oldest oceanic crust? How old is the oldest oceanic crust? ➛ 200 million years old

6. Today: Video: Journey to the Ocean Floor

7. Thursday Please read Chapter 3 in the text Please read Chapter 3 in the text