Transcript Geology of the Hawaiian Islands

Dynamic Earth
Class 7
January 31, 2006
Homework #2 is due
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
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
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.
Homework #2

How old is the oldest oceanic crust?
➛ 200 million years old
Today:
Video:
Journey to the Ocean Floor
Thursday
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Please read Chapter 3 in the text