Geology 102 - Outline for Lecture 1
EARTH AS A SYSTEM. CYCLES :- ROCK, PLATE TECTONIC, HYDROLOGICAL
TIME, THE GEOLOGICAL CALENDAR, FUNDAMENTAL LAWS
OVERVIEW OF CLASS
syllabus
OVERVIEW OF OUR PLANET
UNIQUE
PLACE IN SOLAR SYSTEM
"goldilocks effect"
EARTH STSTEM HISTORY - how is the Earth a system?
ROCK CYCLE
(p. 5-10. Not this detailed yet)
Igneous Rocks
Sedimentary Rocks
Metamorphic Rocks
ROCK CYCLE with PLATE TECTONICS
(p 14-17. Not this detailed yet)
Divergent / constructive plate margins
Convergent / destructive plate margins
Transform plate margins
HYDROLOGICAL CYCLE
Water
( p.18-20)
WATER CYCLE
Water moves above, over and into the Earth
Gravity holds it in the atmosphere.
driven by solar energy.
Significance of H2O
- only planet with abundant H2O
- essential for life “as-we-know-it”
- holds heat
- density at 4OC
- surface factors – attraction – or a gas
Reservoirs - %
- oceans
- lakes
- rivers
- atmosphere
- glaciers
- groundwater
TIME, THE GEOLOGICAL CALENDAR
Eons
HADEAN -
ARCHEAN-
PROTEROZOIC-
PHANEROZOIC-
Reasons for names
Life started much earlier than Phanerozoic - we know this as:-
Eons are divided into ERAS
The Phanerozoic is divided into
Paleozoic
Mesozoic
Cenozoic
Eras are divided into PERIODS
Cambrian
Ordovician
Silurian
Devonian
Mississippian
Pennsylvanian
Permian
Triassic
Jurassic
Cretaceous
** Carboniferous
Tertiary - 3
Quaternary - 4
NEOGENE
PALEOGENE
Periods are divided into EPOCHS
Definition of Epoch -
Pleistocene
Recent
Earth is believed to be 4600 million years old - why?
no rocks of this actual age on the Earth
BUT assume all the rocks in the solar system were formed at the same time.
Oldest moon rocks were dated at 4.53 million years.
BUT no plate tectonics on the moon.
Meteorites are all about 4600 million years.
FUNDAMENTAL LAWS
Principle of superposition
Principle of Original Horizontality
Principle of Lateral Continuity
(These are attributed to STENO, Steno's three Principles)
Principle of cross-cutting relationships
Principle of Inclusions
Principle of Fossil succession
Principle of Unconformities
Angular Unconformity
Disconformity
Nonconformity
HISTORICAL GEOLOGY
The history - geologically - of the area of the world we now call
the USA
changed in 1) longitude and latitude
2) shape / outline
Scientific method
observe processes and events
record observations and results
form a hypothesis
test and retest
WE WILL - apply this to old rocks that we find on the Earth’s surface.
But as we are considering the past we have to make a few major surmises
CATASTROPHISM VERSUS GRADUALISM
1) CATASTROPHES
Past belief - long periods of stability with dramatic, short lived drastic changes
mountains, valleys fossils the result of such catastrophic forces.
e.g. the Great Flood
2) GRADUALISM
JAMES HUTTON (1726-1797) recognized the slow processes
creep, river erosion, waves
suggested these may have had a dramatic effect over long periods of time
"we find no vestige of a beginning, and no prospect of an end"
GREATLY RESISTED
- church teachings - accepted literally-
- Earth a few thousand years old.
- This new idea (gradualism) would make the Earth much older.
Processes we see operating today must have been operating in the past
In geology we call now this the
PRINCIPLE OF UNIFORMITARIANISM OR ACTUALISM
DEFN -
Why do we need to assume this...
This theory was finally accepted after much debate in about 1830's
The birth of modern geology
Millions of years of the same processes made todays landscape
BUT we know that rates do vary.
some events are catastrophic
some events are gradual
SEDIMENTARY ROCKS
Sedimentary rocks are the major key to the past
5% of the total volume of the top 10 miles BUT 75% of the outcrop
RECORD IS NOT COMPLETE IN ANY ONE LOCATION