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Exit
Pioneer Cemetery down the north steps and weave your way to the
courtyard at the east end of Gerlinger Hall. The round stones
set in the pavement are actually river cobbles from a variety
of volcanic rocks. How do you think rough volcanic rock turns
into the smooth rounded stones you see here?
Erosion
Geologists
call the process that shapes these round cobbles erosion. Erosion
consists of a group of natural processes, such as weathering,
corrosion, and abrasion by which a geologic material is worn away.
When rocks are transported by water in streams, rivers, and oceans,
they are wearing against each other. Large pieces of rock may
be rolled along the riverbed and bounced off other rocks, which
helps break them into smaller ones*. The water and wind of our
planet affects the ways rocks are moved, shaped, and located.
Have you been to the ocean and seen smooth rocks like these lying
in the sand? Small rocks may weather away into the soil. Wind
may help to wear down the surface of rocks or transport thousands
of tons of soil many miles at a time. This process can smooth
the surfaces of jagged rocks like the ones in this courtyard into
what builders call stream-rounded cobbles.
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