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Uniformitarianism
James Hutton – 1700’s
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The scientific community up to Hutton’s, time
believed in a strict biblical interpretation that the
Earth was created around 4000 B. C., all fossils
were “mineral freaks”, and effects of the flood
were seen everywhere.
Uniformitarianism’s main idea was that of
gradual forces gave rise to all order we see
today.
Mountains uplifted by gradually occurring natural
forces, leading to the term gradualism.
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Uniformitarianists were opposed to the short history
of the earth and the idea of divine intervention in
geologic interpretation. To list a few things they
believed in, they defended that:
Landscape passes through a continuous cycle of
uplift, erosion, and uplift. Hinting that there is no
evidence of a beginning or prospect of an end.
 Geologic time is very immense.
 “The present is the key to the past” (the most
noteworthy contribution in geologic thought today).
 Landforms are produced by slow and uniform actions
of sub-aerial processes such as running water.
Main Ideas of Uniformitarianism
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In short:
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Uniformitarianism is the belief that the
physical processes occurring today are the
same as in the past, and will continue into
the future
Geology
James Hutton is often
cited as the “father of
Geology”
 The study of planet earth
including its composition
and structure
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Constructive Forces –
 Forces that shape the earth by mountain building
and creation of other land areas ( islands )
Geologic Forces
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Destructive Forces
 Forces that slowly wear away mountains and other
land features
Early in Earth history
the incessant
bombardments
melted the Earth and
the dense iron sunk to
the center to form the
core.
Initially the core was
all liquid, but over
time the Earth has
cooled and a solid
core has formed.
http://ngm.nationalgeographic.com/2
006/12/early-earth/video-interactive
The lightest rocks,
and the most
volatile (bubbly,
gassy material)
including silica rich
minerals and
rocks such as
granite, as well as
water and gas rose
to form the
atmosphere,
oceans, and
continental crust.
The denser rocks
formed the mantle
in the middle.
Cross
Section
of Earth
Crust
Mantle
Core
lithosphere
asthenosphere
mesosphere
inner core
outer core
Depth of Crust in Km
ISOSTASY
The lighter continental
crust towers well
above sea level
because it “floats” on
the denser mantle,
much like an iceberg
with deep roots
below sea level.
Layers are divided based on the materials
that make each layer
 Temperature and pressure increase with
depth
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Layers of Earth
https://www.youtube.com/watch?v=
o3n69P6Xelc
Rocky outer layer of earth
 Composed mostly of silicates and oxygen
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◦ Often contain metals of Fe, Al, Ca
Continental Crust – composed of less dense
rocks such as granite, 8 – 75 Km thick
Oceanic Crust – composed of more dense rocks
like basalt, @ 7 Km thick
Crust
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1. Lithosphere
◦ Upper layer of mantle
◦ 100 Km thick
◦ Mostly solid rock
2. Asthenosphere
3. Mesosphere
Mantle
- stronger, stiffer rock
- high pressures
- softer weaker rock
- flows slowly
- will some day solidify
In this view of a flattened-out mantle from the northwest, the blue
blobs show where colder, denser material is sinking into the mantle.
Mostly a large
sphere of metal
- Iron and nickel
Two Layers:
Outer Core
Inner Core
The Core
http://www.bing.com/videos/search?
q=the+core&FORM=VIRE5#view=det
ail&mid=2CAD03F51D2B7A60276D2
CAD03F51D2B7A60276D
Outer Core
2,260 Km thick
 Composed of liquid metal
 Creates the earth’s magnetic field
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It appears that the process of creating
planets, by gravity drawing particles
together, results in a lot of friction and
collisions, which creates heat in the core.
That heat dissipates out into space as
infrared radiation. A crust then forms and
holds the heat in. Heat moves slowly through
the crust, but not fast enough to heat the air
much. It's mostly the sun that heats the
atmosphere. However, the earth's core does
add significant heat to bodies of water
including oceans and lakes.
1,220 Km thick
 Solid due to
extreme pressure
 3.6 million times
the pressure at
earth surface
 5,500 oC ( almost
equal to surface
of sun )
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Inner Core
Gary Glatzmaier of Los Alamos and
UC Santa Cruz used a supercomputer
to model flow patterns in Earth's
liquid core, source of the geodynamo.
Complex fields in the core contribute
to the dipole field at the surface.
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http://volcano.oregonstate.edu/vwdocs/v
wlessons/lessons/Earths_layers/Earths_la
yers1.html
Review
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Alfred Wegener - 1915
Plate Tectonics
Wegeners ideas ignored until 1960’s
 Discovered “bands” of rock on ocean floor
with alternating magnetic polarities
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Continental Drift Evidence
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The lithosphere is composed of 7 large
pieces that move 1 – 16 cm per year
Plate Tectonics
Plate
Boundaries
Types of Plate Boundaries
Plate Boundaries
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http://www.bing.com/videos/search?q=co
nvergent+plate+boundaries&view=detail&
mid=1B91BC27FBBEF0EF676B1B91BC27F
BBEF0EF676B&first=0&FORM=NVPFVR&a
dlt=strict
Convergent Plate Boundaries
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http://www.bing.com/videos/search?q=tr
ansform+plate+boundaries&view=detail&
mid=8D784168FE4D53BEAC528D784168
FE4D53BEAC52&first=0&FORM=NVPFVR&
adlt=strict
Transform Plate Boundaries
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http://www.bing.com/videos/search?q=se
a+floor+spreading+video&mid=9D3454F
38B0C152F89209D3454F38B0C152F8920
&view=detail&FORM=VIRE5&adlt=strict
Sea Floor Spreading
Himilayans are still growing
Read Section 21.1
 Write a description of a “Journey to the
Center of the Earth”
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