From Brian Gilligan

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From Brian Gilligan
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Methods of Thermal Energy Transfer
3. RADIATION Heated objects radiate energy as
well.
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Methods of Thermal Energy Transfer
Convection is the most important mechanism for
geologic processes.
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Rock Types and the Rock Cycle
ROCK - a naturally occurring aggregate of
minerals formed within the Earth.
Basaltic Dike Acadia Natl Park, Maine
Delicate Arch, Arches Natl Park, UT
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Rock Types and the Rock Cycle
A MINERAL is a naturally occurring, inorganic
solid, consisting of either a single element or
compound, with a definite chemical composition
(or varies within fixed limits), and a
systematic internal arrangement of atoms.
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Pyrite FeS2
Diamond C
Beryl Be3Al2(Si6O18)
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Rock Types and the Rock Cycle
Three types of rocks. These are present in the
crust and at the Earths surface. Each have
fundamentally different origin. IGNEOUS SEDIMENT
ARY METAMORPHIC
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Igneous Rocks
- Cooled and solidified from MOLTEN material. -
Formed either at or beneath the Earths
surface. - MELTING of pre-existing rocks required.
Granite
Basaltic Lava
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Sedimentary Rocks
- Pre-existing rocks are weathered and broken
down into fragments that accumulate and are
then compacted or cemented together. - Also
forms from chemical precipitates or organisms.
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Metamorphic Rocks
- Form when pre-existing Earth materials are
subjected to heat, pressure and/or chemical
reactions and change the mineralogy,
chemical composition and/or structure of the
material.
Gneiss
Slate
Coal
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Any rock type can become any other rock type
given time and processes acting on them. These
changes are reflected in the ROCK CYCLE.
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Time and Geology
For most geologic processes a great deal a time
is needed. Earth is 4.6 billion years old. Time
is available for these processes to operate very
slowly. Geologists measure time in two
ways 1. RELATIVE AGE DATING 2. ABSOLUTE AGE
DATING
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Time and Geology
Relative Age Dating - Determined by spatial
relationships between adjacent rock bodies and
one another. - Provides relative age, no numbers
involved. - Makes use of Principle of
Superposition Principle of Cross-Cutting
Relationships Principle of Inclusions Principle
of Original Horizontality
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Time and Geology
Relative Age Dating
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Time and Geology
Absolute Age Dating - Determine actual age of
the rock or structure. - Provides absolute age,
actual numbers of years are involved and
applied. - Places rocks and events in Geologic
Time Scale. - Makes use of Radiometric
techniques Tree-Ring Dating (Dendrochronology) F
ission Track Dating Lichenometry
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Time and Geology
Absolute Age Dating GEOLOGIC TIME SCALE -
Subdivided into Era, Periods and Epochs - Based
on fossil evidence, initially. - Actual years
added using techniques mentioned earlier.
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The Theory of Plate Tectonics
Underlying unifying principle of geology. Evolved
in the late 1960s, early 1970s. Realization that
certain parts of the Earth were more affected by
earthquakes and volcanoes. Also noted that large
mountainous regions occur on margins of
continents. Changes in sea level were related to
these events. Was not a random occurrence.
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Distribution of major volcanoes and earthquakes
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The Theory of Plate Tectonics
Many hypotheses presented to answer these
questions. None answered all the questions at
all localities. Led to hypothesis of PLATE
TECTONICS. Became widely accepted in a few short
decades.
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The Theory of Plate Tectonics
Steps in Development
1. Benjamin Franklin (late 1700s) Recognized
that crust of Earth was a shell. Surface could
be broken and parts moved about.
2. Alfred Wegener (1912) German
meteorologist-geophysicist Proposed theory of
Continental Drift. Proposed continents float on
a denser underlying interior of the
Earth. CONTINENTS periodically break up and
DRIFT apart.
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The Theory of Plate Tectonics
Wegener believed all continents were joined
together. Supercontinent of Pangaea existed about
200 myBP. Pangaea covered 40 of the Earths
surface.