Name:
Earth’s Story Ch. 6 Section 1
Uniformitarianism vs. Catastrophism
Human’s have wondered about Earth’s history for thousands of years. Was the Earth created in a series of
catastrophic events like earthquakes, volcanoes, floods, etc? Or, was the Earth created in a series of very slow
forming processes over the course of millions of years? The two differing viewpoints are described below.
Catastrophism – The belief that the past history of the earth and of living things has been interrupted or greatly
influenced by natural catastrophes occurring on a worldwide or very extensive scale.
Uniformitarianism – The belief or principle that the past history of the earth and its inhabitants is best
interpreted in terms of what is known about the present. Uniformitarianism explains the past by appealing to
known laws and principles acting in a gradual, uniform way through past ages.
Definition
Evidence/Support
Conclusion
Principle
that
says all geologic
change occurs
suddenly.
Biblical floods,
asteroid strikes,
and
other
catastrophes do
shape Earth.
“Present is the
key to the past”
The
same
geologic
processes
that
occur today have
been at work
throughout
Earth’s history.
Weathering,
Most of Earth’s
erosion,
and shaping occurs by
plate tectonics uniformitarianism.
are slow, gradual
processes
that
have
been
occurring
forever.
Catastrophism
Uniformitarianism
Yes, catastrophes
do shape Earth,
but most shaping
is a result of
uniformitarianism.
1. Why do Earth scientists need the principle of uniformitarianism to make predictions?
“The present is the key to the past” If these things are happening and have happened in the past, then they will
most likely happen in the future.
2. What is the difference between uniformitarianism and catastrophism? Uniformitarianism happens slowly,
Catastrophism happens suddenly
3. How has the role of catastrophism in Earth science changed? Scientist no longer believe that all change was
caused by catastrophes.
Ch. 6 Section 2
Which Came First? (CSI Rock Detectives)
Imagine you are a detective working a burglary. The first thing you do is try to discover
evidence. You goal is to figure out the sequence of events that took place before you
arrived at the crime scene. Geologists have a similar goal when investigating the Earth.
They try to determine the sequence of events that led to how the Earth looks/works today.
Instead of using finger prints and witnesses, geologists rely on rocks and fossils.
Fill in the chart below using your book and discussions from class.
Definition
Significance to scientists
Relative Dating
Making an observation to
determine if an object is
older or younger than other
objects.
Superposition
Principle that states that If the rock layers are undisturbed
younger rocks lie above superposition will always be
older rocks in undisturbed true.
layers.
Geologic column
Disturbances in
rock layers
Uncomformities
Is an ideal sequence of
rock layers that contains all
known fossils and rock
formations
on
Earth
arranged from oldest to
youngest.
Forces that disrupt the
layering of rock.
Earthquakes,
volcanoes,
faulting, uplifting, folding
Scientists can easily determine
which rock layers are older or
younger compared to other rock
layers.
When scientists study an
unknown rock sequence they can
compare the unknown sequence
to the geologic column.
Geologists use the relationship
between rock layers and
disturbances to assign them
relative ages. They know that
disturbance are always
younger than the rock layers
because the layers had to be
there before the disturbances
could cut through them.
Represents a gap or Scientists can determine if the
missing
layer.
Also missing rock layer was ever
represents missing “time”
formed
or
if
something
happened to remove or destroy
the missing rock layer
Picture/Examples