You are a field geologist, dropped off in a new area. You examine the rocks of this area and find rhyolite, welded tuff, and scattered pumice. All are very young. You begin mapping the area, and soon have a rough sense of the distribution of rock units, as shown here:

Note that the welded tuff varies systematically in its thickness, and that a lake is present near the center of your mapping area. How do you interpret this pattern?

Question

You are a field geologist, dropped off in a new area. You examine the rocks of this area and find rhyolite, welded tuff, and scattered pumice. All are very young. You begin mapping the area, and soon have a rough sense of the distribution of rock units, as shown here:
  
Note that the welded tuff varies systematically in its thickness, and that a lake is present near the center of your mapping area. How do you interpret this pattern?

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The Answer of You are a field geologist, dropped off in a new area. You examine the rocks of this area and find rhyolite, welded tuff, and scattered pumice. All are very young. You begin mapping the area, and soon have a rough sense of the distribution of rock units, as shown here:
  
Note that the welded tuff varies systematically in its thickness, and that a lake is present near the center of your mapping area. How do you interpret this pattern?

You Are a Field Geologist, Dropped Off in a New