The Study of Earth’s
History
Chapter 8 Sec 1
What you will learn
– Earth processes today are similar to those
that occurred in the past and slow geologic
processes have large cumulative effects
over long periods of time.
– The history of life on Earth has been
disrupted by major catastrophic events, such
as major volcanic eruptions or the impacts of
asteroids.
Geology
• Geo- means Earth
• -ology means study of
• -ist means someone who studies
• Geology – the study of Earth
• Geologist – scientist who studies the Earth
What scientist and philosophers
used to think…
• Up until the end of the 1700’s people
believed that the Earth was only 2000
years old.
• They believed that the landforms
(mountains, rivers, oceans, valleys, etc)
formed suddenly.
Catastrophism:
 This is the idea that geologic change only
happens suddenly.
 Example: asteroid hitting the Earth
Uniformitarianism
• Idea that geologic processes occurring
now are the same as those in the past.
James Hutton came up with this idea.
• It is a gradual, slow process.
• Example: the gradual erosion that formed
the Grand Canyon.
Modern Geology
• Today scientists believe that NEITHER
uniformitarianism nor catastrophism can
explain ALL geologic changes.
Modern Geology cont.
• Today it is believed that most geologic
change is slow and uniform, but
catastrophes or sudden changes have
also formed our Earth.
• So…. Modern Geology combines both
principles of uniformitarianism and
catastrophism.
Paleontology
• It is the study of the life forms that lived on
Earth and how they lived.
• A paleontologist studies all fossils (not
only dinosaurs) to see how the
environment has changed.
Rock Cycle
• Forming of new rocks from other types of
rocks
• Igneous rocks form from
the cooling of magma.
• Sedimentary rock forms from fragments
of other types of rocks. THIS IS WHERE
FOSSILS ARE FOUND!
• Metamorphic rock forms when
sedimentary or igneous rock are heated
and squeezed (extreme heat and
pressure)
What you have learned
• Catastrophism is the idea that the Earth
changed suddenly.
• Uniformitarianism is the idea that the Earth
changes slowly or gradually.
• The rock cycle describes how one form of
rock turns into a different form of rock.
What to do now….
Write a 6 sentence summary about
what you learned.
1.
2.
3.
4.
5.
6.
Introduction sentence (what is the big picture?)
Detail
Detail
Detail
Detail
Why is what you learned important for you
science education?