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The
Exciting Rock Display |
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The three categories of
rock are: Igneous, Metamorphic, and Sedimentary. Igneous Rocks (pictured to
the right) are “. . . formed from the cooling of molten material in the earth.”
Granites and Basalts are examples of the many different types of Igneous
Rocks. Generally there are no fossils found in igneous rocks, because these
rocks were once molten (liquid, melted rock) and the extreme heat incinerates
or melts anything it contacts. Igneous
rocks are frequently dated using radiometric dating techniques to try and
determine the age of the rock and how long ago the liquid rock
solidified. These radiometric dating
methods often suggested enormously old ages.
However, there are no igneous rocks in the Sideling hill area. |
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Metamorphic Rocks
(pictured to the left) are “. . . formed by intense pressure, heat or
chemical change to pre-existing rock.” These rocks are generally very pretty.
Marble, slate and quartzite are examples of rocks that have undergone a
metamorphosis and become metamorphic rock.
Due to the intense heat and pressure that a rock needs to be subjected
to in order to initiate metamorphosis, there are never any fossils in a truly
metamorphic rock. |
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The third type of rock,
called Sedimentary (pictured on the right) is formed “. . . when particles
carried by wind or water settle and are compacted or cemented together.” Limestone, shale, siltstone, sandstone and conglomerates
are a few of the many different types of sedimentary rock that together cover
over 4/5’s of the earth’s surface. Fossils are always found in sedimentary
rock. Interestingly enough, sedimentary rock cannot be dated by traditional
radiometric dating methods since this would yield as many different dates as
there are sources of sediment. All 600 feet of exposed layers that make up
Sideling Hill are entirely made up of sedimentary rock. |
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