Historical Geology - GLY 2 - Spring 2004
Exam 2 Review and Brief Notes

Evolution

what caused the fossil succession?

Linneaus (1758) biological classification system (Kingdom, Phylum, Class, Order Family, Genus, Species)

Smith and Cuvier (~1800): recognized unique fossil in successive strata

Cuvier proved extinctions had occurred (archaic elephants = wooly mammoths)

Cuvier (and Dobrigny)
posed Catastrophism and Special Creation as an explanation for fossil succession

others (below) posed evolution as explanation for fossil succession

Buffon: species, environment, inheritance

Erasmus Darwin: adaptation by method of eating; noted important relationship between environment and heredity (inherited characteristics)

Lamarck: mechanism for evolution - inheritance of acquired characteristics

Charles Darwin: (and Alfred Russel Wallace)

voyage of the Beagle, Galapagos finches, etc.

inspiration from Malthus: life in nature is a constant struggle for food

evidence for evolution

fossil succession, homology, vestigial structures, embryonic history, biogeography

mechanism for evolution: Natural Selection

Natural Variability + Selective Pressure -> Natural Selection 

Global Chemical Cycles

The carbon cycle

photosynthesis <-> respiration - carbon dioxide (CO2) and oxygen (O2)

burial of organic matter

carbon storage in sed. rocks on the continents (e.g., coal, black shale) and seafloor (limestone)

the role of CO2 in weathering of rocks (carbonic acid, hydrolysis of silicates)

outgassing from arc volcanoes of CO2 released by metamorphism of subducted carbonate rocks

outgassing from midocean ridges of CO2 stored in the mantle

CO2 and climate

the greenhouse effect - CO2, water vapor and others as a greenhouse gases

effects of temperature, rainfall, vegetation, weathering, seafloor spreading, mountain building

rate effects (e.g., changing rate of outgassing or mountain building)

negative feedbacks in the carbon cycle that buffer (moderate) the climate - how they work

Review of Geologic Structures

structures formed by compression (squeezing)
thrust faults (low angle, hanging wall moves up)
reverse faults (hi angle, hanging wall moves up)
folds

structures formed by extension (stretching)
normal faults (hi angle, hanging wall moves down)

structures formed by shearing
strike slip faults (vertical fault, all motion is horizontal)

Review of Geologic Structures and Plate Tectonics

lithosphere (crust and uppermost mantle)
asthenosphere

plate boundaries
divergent:
midocean ridge (plates spread apart, new crust forms)
continental rift
convergent:
ocean-ocean subduction zones (trenches, volcanic island arcs)
ocean-contintinent subduction zones (trenches, volcanic arcs)
continent-continent collisions - orogenic (mountain) belts
transform:
oceanic transforms (ridge offsets)
continental transforms (strike-slip faults, e.g., San Andreas)

Origin of the Universe Solar System and Earth

observation: the redshift = "the universe is expanding"

microwave background radiation as evidence that universe formed in great explosion

all matter and energy formed at a dimensionless point between 13-14 billion years ago

the matter formed by the Big Bang was almost entirely hydrogen (H) with a little helium (He)

dying stars (supernovas) produced all the rest of the elements (see below)

The life of a star (like our sun):

nebula (cloud of H) contracts under its own gravity

contraction amplifies any initial rotation or tumbling; the nebula rotates faster as it contracts

contraction causes increasing temperature and pressure; it heats up

when hot and compressed enough, hydrogen nuclei fuse to form helium,

great quantities of energy are released by this thermonuclear reaction - a star is born!

the star no longer contracts because outward pressure from the released energy counters gravity

the star may shine for billions of years by fusing hydrogen

when too much He and too little H, the fusion process slows and the star begins to contract again

1. small stars will fade out

2. big stars become red giants, fusing He, producing larger elements up to the mass of iron

3. really big stars: supernova explosions fuse the largest elements and disperse them into space

[4. really really big stars become black holes]

our sun is at least a second generation sun since it (and our solar system) contain elements beyond Hydrogen and Helium

The solar nebula: formation of the sun, planets, and Earth

protosun and protoplanets formed in a contracting nebula (see above)

Terrestrial planets (Mercury, Venus, Earth & Moon, Mars) formed near the protosun
metallic (iron) cores and rocky silicate mantles

Jovian planets (Jupiter, Saturn, Uranus, Neptune) formed in the cooler outer reaches
gaseous giants: hydrogen, ammonia, methane, and helium

segregation of the Earth's iron core and (ultramafic) silicate mantle

early Earth history

early Earth very hot: three heat sources:
gravitational compression as Earth grew in size
frictional heating from meteor bombardment
five times as much radioactive heat produced as compared to today

formation (and composition) of the Earth's core and mantle
Earth formed as a hodgepodge accumulation of metallic and silicate meteorites
early Earth was partly to mostly molten
heavy iron liquids sank to form core - lighter silicate liquids rose to form mantle
late additions from continuing bombardment allowed some iron to remain in the mantle

formation and evolution of Earth's atmosphere

atmosphere outgassed from mantle from volatiles placed there during planetary accretion

early atmosphere had no free oxygen

early atmosphere rich in water vapor and carbon dioxide plus a little nitrogen

the oceans formed by precipitation of the abundant water vapor that outgassed from mantle

carbon dioxide eventually was exchanged for oxygen via photosynthesis,

nitrogen continued to accumulate

formation of stable crust and the first continents

the Hadean eon
earliest "crust" was ultramafic solidified mantle
oldest existing crust is 4 b.y. old (all older - Hadean eon - crust destroyed)
end of heavy meteor bombardment by 4-3.8 b.y.

the Archean eon
to form true crust, Earth needed to cool sufficiently to allow partial melting (not complete melting)
paired metamorphic belts: greenstone belts vs. granite/tonalite/gneiss belts
microcontinents
Algoman/Kenoran orogenies: the first minicontinents

the Proterozoic eon
Hudsonian orogeny, Laurentia
Grenville orogeny, Rodinia, Gondwana
passive margin subsidence