Lecture 2

Introduction to Physical Geology

Lecture Outline

I Geological ParadigmsII Origins

A) The Solar SystemB) The Earth

III Fundamental Concepts of Physical GeologyA) Geologic TimeB) The Earth's Structure

i. Earth's Layersii. Plate Tectonics

- From Continental Drift to Plate Tectonics- Lithospheric Plates- Plate Boundaries

C) The Rock CycleIV Planetary GeologyV Conclusions

Physical Geology

Geological Paradigms

paradigm, n: a collection of beliefs shared by scientists; a set of agreements about how problems are to be understood

James Ussher(1581-1656)

catastrophism

James Hutton(1726-1797)

uniformitarianismrock cycle

Charles Lyell(1797-1875)

geologic time

Alfred Wegener(1880-1930)

continental drift

Physical Geology

Origin of the Solar SystemThe Nebular Hypothesis

Palomar Observatory

Physical Geology

Origin of the Solar SystemThe Nebular Hypothesis

Physical Geology

p a i n ti n g b y W il li a m K . H a r t m a n n

Origin of the Solar SystemThe Nebular Hypothesis

clumps of dust grains (cm)

Planetesimals (km)

planetesimals (10-100 km)

protoplanet(100-1000km)

physicalcollision

gravity

Physical Geology

The Solar SystemWhat is a Planet?

Physical Geology

(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”.

Origin of the EarthGeological Differentiation

Earth melted by:gravitational energy left from formation of planetmeteor bombardmentradioactive decay

Gravity concentrated denser materials (Ni & Fe) in centerLess dense materials (silicates) forced to outer layersCrust became stable after 1 billion years

Compositional ZonesCrust

ContinentalOceanic

MantleCore

Outer (Liquid)Inner (Solid)

Physical Geology

Fundamental ConceptsEarth's Layers

Compositional ZonesCore

Solid inner coreLiquid outer coreRadius of ~3500 km16.2% of Earth's vol.31.5% of Earth's massGenerates Earth's magnetic field

MantleThickness ~2900 km82.3% of Earth's vol.67.8% of Earth's mass

CrustOceanic – 4-20km thickContinental – 30-70km thick

Mechanical Zones

CoreMesosphere

Lower mantleRigidVery HotCapable of gradual flow

Asthenosphere"weak" layerConvecting mantleSoft and readily flows

LithosphereCrust and Upper MantleRigidBrittle

Physical Geology

Fundamental ConceptsGeologic Time

DivisionsEon

EraPeriod

EpochAge

Phanerozoic Eon -"Eon of Evident Life"Paleozoic Era -"Era of Old Life"Mesozoic Era -"Era of Middle Life"Cenozoic Era -"Era of Modern Life"

Physical Geology

Fundamental ConceptsPlate Tectonics - The Evidence

Physical Geology

Fundamental ConceptsPlate Tectonics - The Ocean Floor

Mid-Ocean Ridge System

Physical Geology

Fundamental ConceptsPlate Tectonics - The Ocean Floor

Mid-Ocean Ridge System

underwater mountain range80,000 km long1500-2500 km wideup to 3000 m above sea floorrift valley, 1-2 km deep, runs along axis4000 km wide fracture systems

Physical Geology

Fundamental ConceptsPlate Tectonics - The Ocean Floor

crustal age

magnetic striping

Physical Geology

Fundamental ConceptsPlate Tectonics - The Ocean Floor

Physical Geology

Fundamental ConceptsPlate Tectonics - The Engine

Physical Geology

Fundamental ConceptsPlate Tectonics - Lithospheric Plates

Physical Geology

Fundamental ConceptsPlate Tectonics – Plate Boundaries

Physical Geology

Fundamental ConceptsThe Rock Cycle

Atmospheric ProcessesWeathering

Physical WeatheringChemical WeatheringBiological Weathering

Sediment TransportLithospheric Processes

BurialCompaction and CementationHeat and PressureStressPlate TectonicsExposure

Physical Geology

Planetary Geology

Venus Jupiter

Io

Europa

Mars

Magellan

Viking 1 Voyager 1

Galileo

Galileo

Physical Geology

Planetary GeologyMars

Physical GeologyPhysical Geology