Geologic
Principles:
An
introduction
How do scientists apply
principles to place the
different rock units in the
correct chronological order?
Andy
Goldsworthy
●
represents time in
ephemeral
sculptures
composed of natural
materials such as
snow, mud, leaves,
and branches
Human concept of
time
vs
Deep time
Human concept of time
Deep time
Relative Time
● placing events in the order in which
they occurred
● describing the order or sequence of
geologic events.
● Grand Canyon in Arizona
Exploration of the Colorado River of the West
the rocks in the canyon walls to be the result
of long-lived geological processes that he
believed had been operating “through ages
too long for man to compute.”
John Wesley Powell
Tom Vail
● the canyon’s rock
layers were deposited
following Noah’s flood
● the canyon was
formed in a few days
by a rapidly eroding
river that quickly
carved through the
relatively soft deposits
left behind as
floodwaters receded.
Who is right
Steno’s Geologic
Principles
Nicholas Steno
Steno’s Geologic Principles
Principle of Original Horizontality
Principle of Superposition
Hutton’s Geologic
Principles
●
●
●
●
Father of Modern Geology
Invented the modern concept
of geologic time
The landscape of farmlands
remained unchanged with
the passage of time
“Uniformitarianism”
James Hutton
Hutton’s Geologic
Principles
●
all land should be
worn flat unless
some process acts to
renew the landscape
by forming new
mountains,
Hutton’s Geologic
Principles
● lower layers of rock formed first
(superposition) as flat layers (original
horizontality)
● Unconformities are evidence of breaks in
the geologic record representing a gap in
time
Hutton’s Geologic
Principles
● “Principle of cross-cutting relationships”.
● older rocks may be cut by younger rocks or
other geologic features
Hutton’s Geologic
Principles
● “Principle of inclusions”.
● to identify older pieces of
rock surrounded by younger
igneous rocks
Read and answer the
following:
1.
How did Steno used the teeth of sharks that led to his
geologic principle?
2.
What principle states that younger rocks cut older
rocks?
Homework
1.
How are the different geologic principles applied to
examine the geology of the Grand Canyon?
THANK
YOU!