1. Introduction to Physical Geology
Lecture 2
Introduction to Physical Geology

2. Lecture Outline I Geological Paradigms II Origins
Physical Geology
Lecture Outline
I Geological Paradigms
II Origins
A) The Solar System
B) The Earth
III Fundamental Concepts of Physical Geology
A) Geologic Time
B) The Earth's Structure
i. Earth's Layers
ii. Plate Tectonics
- From Continental Drift to Plate Tectonics
- Lithospheric Plates
- Plate Boundaries
C) The Rock Cycle
IV Planetary Geology
V Conclusions

3. Geological Paradigms Physical Geology
paradigm, n: a collection of beliefs shared by scientists; a set of agreements about how problems are to be understood
James Ussher
( )
catastrophism
James Hutton
( )
uniformitarianism
rock cycle
Charles Lyell
( )
geologic time
Alfred Wegener
( )
continental drift

4. Origin of the Solar System The Nebular Hypothesis
Physical Geology
Origin of the Solar System The Nebular Hypothesis
Palomar Observatory

5. Origin of the Solar System The Nebular Hypothesis
Physical Geology
Origin of the Solar System The Nebular Hypothesis

6. Origin of the Solar System The Nebular Hypothesis
Physical Geology
Origin of the Solar System The Nebular Hypothesis
physical
collision
gravity
clumps of dust grains
(cm)
Planetesimals
(km)
planetesimals
( km)
protoplanet
( km)

7. The Solar System What is a Planet?
Physical Geology
The Solar System What is a Planet?
(1) A “planet”1 is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.
(2) A “dwarf planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape2 , (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.
(3) All other objects3 except satellites orbiting the Sun shall be referred to collectively as “Small Solar-System Bodies”.

8. Origin of the Earth Geological Differentiation
Physical Geology
Origin of the Earth Geological Differentiation
Earth melted by:
gravitational energy left from formation of planet
meteor bombardment
radioactive decay
Gravity concentrated denser materials (Ni & Fe) in center
Less dense materials (silicates) forced to outer layers
Crust became stable after 1 billion years
Compositional Zones
Crust
Continental
Oceanic
Mantle
Core
Outer (Liquid)
Inner (Solid)

9. Fundamental Concepts Earth's Layers
Physical Geology
Fundamental Concepts Earth's Layers
Compositional Zones
Core
Solid inner core
Liquid outer core
Radius of ~3500 km
16.2% of Earth's vol.
31.5% of Earth's mass
Generates Earth's magnetic field
Mantle
Thickness ~2900 km
82.3% of Earth's vol.
67.8% of Earth's mass
Crust
Oceanic – 4-20km thick
Continental – 30-70km thick
Mechanical Zones
Core
Mesosphere
Lower mantle
Rigid
Very Hot
Capable of gradual flow
Asthenosphere
"weak" layer
Convecting mantle
Soft and readily flows
Lithosphere
Crust and Upper Mantle
Brittle

10. Fundamental Concepts Geologic Time
Physical Geology
Fundamental Concepts Geologic Time
Phanerozoic Eon -"Eon of Evident Life"
Paleozoic Era "Era of Old Life"
Mesozoic Era "Era of Middle Life"
Cenozoic Era "Era of Modern Life"
Divisions
Eon
Era
Period
Epoch
Age

11. Fundamental Concepts Plate Tectonics - The Evidence
Physical Geology
Fundamental Concepts Plate Tectonics - The Evidence

12. Fundamental Concepts Plate Tectonics - The Ocean Floor
Physical Geology
Fundamental Concepts Plate Tectonics - The Ocean Floor
Mid-Ocean Ridge System

13. Fundamental Concepts Plate Tectonics - The Ocean Floor
Physical Geology
Fundamental Concepts Plate Tectonics - The Ocean Floor
Mid-Ocean Ridge System
underwater mountain range
80,000 km long
km wide
up to 3000 m above sea floor
rift valley, 1-2 km deep, runs along axis
4000 km wide fracture systems

14. Fundamental Concepts Plate Tectonics - The Ocean Floor
Physical Geology
Fundamental Concepts Plate Tectonics - The Ocean Floor
magnetic striping
crustal age

15. Fundamental Concepts Plate Tectonics - The Ocean Floor
Physical Geology
Fundamental Concepts Plate Tectonics - The Ocean Floor

16. Fundamental Concepts Plate Tectonics - The Engine
Physical Geology
Fundamental Concepts Plate Tectonics - The Engine

17. Fundamental Concepts Plate Tectonics - Lithospheric Plates
Physical Geology
Fundamental Concepts Plate Tectonics - Lithospheric Plates

18. Fundamental Concepts Plate Tectonics – Plate Boundaries
Physical Geology
Fundamental Concepts Plate Tectonics – Plate Boundaries

19. Fundamental Concepts The Rock Cycle
Physical Geology
Fundamental Concepts The Rock Cycle
Atmospheric Processes
Weathering
Physical Weathering
Chemical Weathering
Biological Weathering
Sediment Transport
Lithospheric Processes
Burial
Compaction and Cementation
Heat and Pressure
Stress
Plate Tectonics
Exposure

20. Planetary Geology Physical Geology Venus Europa Jupiter Mars Io
Magellan
Galileo
Mars Io
Galileo
Viking 1
Voyager 1

21. Planetary Geology Mars
Physical Geology
Physical Geology
Planetary Geology Mars