Geological processes are naturally occurring events that directly or indirectly impact
the geology of the Earth. Examples of geological processes include events such as
plate tectonics, weathering, earthquakes, volcanic eruptions, mountain formation,
deposition, erosion, droughts, flooding, and landslides. Geological processes affect
every human on the Earth all of the time, but are most noticeable when they cause
loss of life or property. These threatening processes are called natural disasters.
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1.ROCK
Sedimentary rock, also called stratified rock, is
formed over time by wind, rain and glacial
formation. These rocks may be formed by erosion,
compression or dissolution. Sedimentary rock may
range from green to gray, or red to brown,
depending on iron content and is usually softer
than igneous rock.
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3. Stratigraphy
The branch of geology concerned with the order
and relative position of strata and their
relationship to the geological time scale.
The analysis of the order and position or layers
of archaeological remains.
The structure of a particular set of strata.
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Geologist often need to know the age of
material that they find. Absolute and relative
dating methods have been used to establish
tentative chronologies for rock art. They use
absolute dating methods, sometimes called
numerical dating, to give rocks an actual
date, or data range, in number of years. This
is different from relative dating, which only
puts geological events in time order.
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The AGE of
stratified rocks
intrigues almost
everyone. Almost
everyone wants to
know how old a
stratified rock is,
but they want to
know how that
age was
determined.
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Absolutedating methods that rely on specialized laboratory
analysis such as dendrochronology, radiocarbon, and
luminescence measurements are available to historical
archeologist. This method measures the age of an event
or object in years. To determine the absolute ages of
fossils and rocks. Scientist analyze the isotopes of
radioactive elements.
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The three different methods to determine the age
of stratified rocks.
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Relative dating- estimate whether an object is younger or older
than other things found at the side. Relative dating does
not over specific dates, it simply allows to determine if
one artifact, fossils, or stratigraphic layers is older than
another.
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• Most isotopes are stable, meaning that they stay in
their original form.
• Other isotopes are unstable.
scientist call unstable isotopes radioactive.
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Radioactive decay
• Radioactive isotopes tend to break down into stable
isotopes of the same or other elements
Unstable isotope
6 protons
8 neutrons
Radioactive Decay
When some unstable isotopes
decay, a neutron is converted
into a proton. In the process, an
electron is released.
Stable isotopes
7 protons,
7 neutron
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Dating rocks- howdoes it work?
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• In radioactive decay, an unstable
radioactive isotope of one element
breaks down into a stable isotope.
the stable isotope may be of
the same element or of a different
element.
• Parent isotope
the unstable radioactive isotope.
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• Daughter isotope
the stable isotope
produced by the
radioactive decay of the
parent isotope
• The rate of radioactive
decay is constant, so
scientist can compare
the amount of parent
material with the
amount of daughter
material to date rock
• The more daughter
material there is the
older the rock is
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Radiometric dating
• determining the absolute age of
sample, based on the ratio of parent
material to daughter material.
• If you know the rate of decay for a
radioactive element of rock
• You can figure out the absolute age of
the rock
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• Half life
• The time needed for half of a sample
of a radioactive substance to undergo
radioactive decay
• After every half-life, the amount of
parent material decrease by one-half.
Types of radiometric dating-scientist
use different radiometric-dating
methods based on the estimated
age of an object.
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There are four types of radiometric-dating techniques.
1.Potassium-Argon method
2.Uranium-lead method
3.Rubidium-strontium method
4.Carbon-14 method
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Howold is that rock?
The age of a rock in years is called its absolute
age. Geologist find absolute ages by measuring the
amount of certain radioactive elements in the rock.
When rocks are formed, small amount of
radioactive elements usually get included.
As time passes, the “parent” radioactive elements
change at a regular rate into non-radioactive
“daughter” elements. Thus, the older a rock is, the
larger the number of daughter elements and the
smaller the number of parent elements are found in
the rock.
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