GEOLOGY OF OLYMPIC NATIONAL PARK:
PART I OLYMPIC GEOLOGY
Forces in the Earth: Plate Tectonics

Fig. 23. Highly disrupted
thick sandstone beds in slate on the west side of Mount Olympus
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Geologists
have long sought an explanation for how sedimentary rocks derived from
flat-lying sediments in the sea could be so folded and compressed and
how they have been raised above the sea. It is now obvious that different
crustal blocks have moved toward each other, crushing and compressing
strata caught between them; it is not so obvious why these blocks moved.
In recent years, scientists using sophisticated electronic devices have
learned much about the physical properties of the earth, such as its magnetic,
gravitational, and heat-flow properties. Much of this information has
been gathered from the oceans. Sediments and rocks from the ocean floor
can now be sampled by drilling, and the exact ages of many rocks can be
determined by measuring their radioactive
elements. These new data from the ocean floor and the details of rock
structure on the land have been unified in the theory of plate tectonics.
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