Transcript Physical Geology

Formation of Earth
Birth of the Solar System
Nebular Theory
– Nebula compresses
– Rotation flattens nebula
– Collapse into center formed
solar nebula and finally, the sun
– Condensation formed planets,
planetesimal, moons and
asteroids during planetary
accretion around 4.6 billion
years ago
– (Meteorites are iron-rich or
rocky fragments left over from
planetary accretion)
See Fig. 1.9
(a), (b) and (c)
http://www.psi.edu/projects/planets/planets.html
Orion Nebula
www.hubblesite.org
www.geol.umd.edu/~kaufman/
ppt/chapter4/sld002.htm
www.psi.edu/projects/
planets/planets.html
See Fig. 1.9
Formation of the Planets
• Nuclear fusion began
Terrestrial Planets
within the mass at the
center of the solar system
forming the sun
• The inner planets were
hotter and gas was driven
away leaving the
terrestrial (rocky) planets
• The outer planets were
cooler and more massive
?
so they collected and
Gas Giants
retained the gasses hence
the “Gas Giants”
www.amnh.org/rose/backgrounds.html
Differentiation of the Planets
• The relatively uniform
iron-rich proto planets
began to separate into
zones of different
composition: 4.5bya
• Heat from meteor
impact, pressure and
radioactive elements
cause iron (and nickel)
to melt and sink to the
center of the terrestrial
planets
See Fig 1.10
Further Differentiation
of Earth
• Lighter elements such as
Oxygen, Silicon, and
Aluminum rose to form
a thin, rigid crust
• The crust, which was
originally thin and
basaltic (iron rich
silicate), further
differentiated to form
continental crust which
is thicker, iron poor, silica
rich and lighter
Mid-Ocean
Ridge
(New Crust)
Deepest
Mine
Deepest
Well
Continental
Crust
(Silicic)
Oceanic
Crust
(Basalt)
See Fig. 1.11
Composition of Earth and Crust
Element
(Atomic #)
Chemical
Symbol
Before and After Differentiation
% of
% of
Change in
whole
Crust
Crust Due to
Earth
(by Weight)
Differentiation
Oxygen (8)
O
30
46.6
Increase
Silicon (14)
Si
15
27.7
Increase 
Aluminum (13)
Al
<1
8.1
Increase 
Iron (26)
Fe
35
5.0
Decrease 
Calcium (20)
Ca
<1
3.6
Increase 
Sodium (11)
Na
<1
2.8
Increase 
Potassium (19)
K
<1
2.6
Increase 
Magnesium (12)
Mg
10
2.1
Decrease 
~8
1.5
All Others
Crust and Mantle
Lithosphere and Asthenosphere
• The uppermost mantle and
crust are rigid solid rock
(Lithosphere)
• The rest of the mantle is soft
but solid (Asthenosphere)
• The Continental Crust
“floats” on the uppermost
mantle
• The denser, thinner
Oceanic Crust comprises
the ocean basins
Figure 1.11, Detail of crust and Mantle
A Large Variety of Rocks
(and Sediment)
Products of an Active Planet
Earth’s structure leads to
intense geologic activity
– Inner core: Solid iron
– Outer core: Liquid iron,
convecting (magnetic field)
– Mantle (Asthenosphere) :
plastic solid, iron-magnesium
silicate, convecting
– Crust (Lithosphere): Rigid, thin
• O, Si, Al, Fe, Ca, Na, K, Mg…
47%, 28, 8,
5,
4,
3,
3, 2
Crust:
Rigid,
Thin
Mantle:
Plastic,
Convecting
Lithospheric Plates
See Kehew, Figure 1.19
• The Lithosphere is broken into “plates” (7 maj., 6 or 7 min.)
• Plates that “ride around” on the flowing Asthenosphere
• Carrying the continents and causing continental drift
Lithospheric Plates
Fig. 1.13 and 2.14
Three Types
of Plate
Boundaries
• Divergent
• Convergent
• Transform
See Fig. 1.14 and 1.13
Things to Know About
Plate Tectonics
• Composition and properties of Zones
– Iron core (solid & liquid, convecting, magnetic field)
– Mantle: Plastic solid, convecting, ultramafic (Si, O, Fe,Mg)
• Composition and Properties of the Crust
– Oceanic Crust: Basalt, Thin (5-10km) (O, Si, Fe, Mg, Ca)
– Continental Crust: Granitic, Thick (10-50km) (O, Si, Al,
Na, K)
Things to Know About
Plate Tectonics
• Features and Geologic Phenomena
– Convergent: trenches, mountain
chains, granitic magma, granitic rocks,
composite volcanoes,
– Divergent: Mid ocean ridges, rift
valleys, shallow earthquakes, basaltic
magma and lava, basalt, lava floods
(volcanoes rare)
Things to Know About
Plate Tectonics
• Features and Geologic Phenomena
– Transform: Offset ocean ridges or
mountain chains, shallow earthquakes,
no magma or lava
– Hotspots: Shallow earthquakes,
basaltic magma and lava, basalt, lava
floods, sometimes shield volcanoes
The 3 rock types form at
convergent plate boundaries
• Igneous Rocks: When rocks
melt, Magma is formed, rises,
cools and crystallizes.
• Sedimentary Rocks: All rocks
weather and erode to form
sediments (e.g., gravel, sand,
silt, and clay). When these
sediments accumulate they are
compressed and cemented
(lithified)
• Metamorphic Rocks: When
rocks are compressed and
heated but not melted their
minerals re-equilibrate
(metamorphose) to minerals
stable at higher temperatures and
pressures
The
Rock Cycle
Geological Materials
Transformation Processes
• Geologic materials
(blocks)
• Are transformed
and transported
• By geologic
processes
(arrows)
• To form other
geologic materials
• Driven by internal
and external
processes
Fig. 3.1
See Fig. 1.15
Igneous and Sedimentary Rocks
at Divergent Boundaries and
Passive Margins
• Igneous Rocks (basalt)
are formed at divergent
plate boundaries and
Mantle Hot Spots. New
basaltic, oceanic crust is
generated at divergent
plate boundaries.
• Sedimentary Rocks are
formed along active and
passive continental
margins from sediments
shed from continents
• Sedimentary Rocks are formed on continents where a basin forms
and sediments accumulate to great thicknesses. E.g., adjacent to
mountain ranges and within rift valleys.
Learning Plate Tectonic Geography
Brushing up on basic geography will help you learn Plate Tectonics
Once you know your basic geography and ocean basin features
(Mid Ocean Ridges, -Oceanic Trenches) you can
- Learn the 7 major plates
- Learn the types of plate boundaries
- Learn why those features are where they are