Dynamic Earth

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Dynamic Earth

• Class 7
• January 31, 2006

Homework 2 is due
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Homework 2

• 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
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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

? a. You would expect to find volcanic and
high-grade metamorphic rocks
? b. The crustal thickness would be around 35 km
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Homework 2

• 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.
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Homework 2

• How old is the oldest oceanic crust?

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TodayVideoJourney to the Ocean Floor
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Thursday

• Please read Chapter 3 in the text