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Intro to Earth Sciences II
Midterm Review Topics and Brief Notes
Summer 2004

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The Earth Environment

insolation and climate
uneven distribution of solar radiation striking Earth's surface
heat distributed by atmospheric and oceanic circulation
large scale atmospheric convection modified by coriolis effect
general atmospheric circulation, prevailing winds
the dominant low pressure (rising air) zones and high pressure (sinking air) zones
climate belts simplified: equatorial, tropical deserts, mid-latitude temperate belt, polar
ocean surface currents (clockwise flow in northern hemisphere, counterclockwise in southern hemisphere)
bottom water currents, cause of sinking water, important locales of deep water formation
ocean conveyor belt and climate
how could the conveyor belt slow? (global warming, increased melting in Greenland, decreased ocean salinity)
how could that possibly affect regional climates (e.g., NW Europe)?

Sedimentary Environments

equatorial: (hot, wet) aerially extensive coal
deserts: sand dunes -> large scale cross-bedded sandstone, frosted sand grains
glacial deposits: poorly sorted glacial sediments, terminal moraines
stream deposition
point bar sand (sandstones) and overbank muds (shales); current ripples, terrestrial fossils, etc.
coastal deposition
coastal marsh -> dunes and beach -> offshore muds -> farther offshore reefs (if warm & clear)
marsh: mud and/or peat -> shale and/or coal
dunes and beach sand and gravel -> sandstone & conglomerate
nearshore sand -> sandstone
offshore silt and clay (mud) -> shales
in warm water beyond where most mud is deposited coral reefs may grow -> limestone
marine sandstones and shales contain fossils of marine (ocean) life
off the continental shelf (continental rise, continental slope)
turbidites (chaotic, fining-upward sedimentary layers); formed from turbidity currents
deep abyssal plains finely laminated shales, limestone, and chert
limestone from calcareous oozes from single-cell, microscopic organisms with calcite shells (e.g. foraminifera)
chert from siliceous oozes from single-cell, microscopic organisms with silica shells (e.g. radiolaria)
pelagic (open ocean) clays from windblown dust from the continents and oceanic volcanoes

Stratigraphy and Correlation

formations: group, formation, member, bed
changes of sedimentation resulting related to sea level
lateral differences in sedimentation due to position relative to sea level (on land, beach, offshore)
sea level rise yields fining of sedimentation, sea level fall yields coarsening of sedimentation
transgression-regression
correlation
based on lithology (rock characteristics), sequence of beds, and fossils
geophysical methods: e.g., magnetostratigraphy
unconformities (erosion surfaces, time missing): nonconformities, angular unconformities, disconformity 

Geologic Time

sequence of geologic events
Steno's Principles (1669): original horizontality, superposition, lateral continuity
crosscutting relations, baked contacts, inclusions, fossils, unconformities
- know how to interpret a geologic cross section of the sort in the homework exercise
the fossil succession:
William Strata Smith, first geologic map, England and Wales (1790s to 1815)
Cuvier & Brogniart, geologic map of Paris basin, 1811
development of the geologic timescale
Sedgewick, Murchison, and the Cambrian and Silurian (plus the Ordovician)
finishing up: Devonian (from Devonshire), Carboniferous (coal measures), etc.
absolute time - how old is the Earth?
Bishop Ussher and the generations since Adam - ~6000 yr
Werner (18th ct) and Catastrophism (rocks formed by precipitation from primeval sea [as in Genesis?]
Hutton, Lyell (18th & 19th ct.) and uniformitarianism - OLD (millions of years?)
Darwin: many hundreds of millions to account for evolution
British geologists (latter 19th ct.) and time required to deposit all sedimentary layers - ~100 m.y.
Joly (1899) - time required to make the oceans salty - ~100 m.y.
Lord Kelvin (latter 19th ct.) and the cooling Earth - 20 - 40 m.y. to 100 m.y.
Becquerel, Curie, and the discovery of radioactivity (1896)
Rutherford and Soddy (1902), radioactive decay proportional to amount of unstable isotope;
parent/daughter ratio might be useful for dating natural materials
B.B. Boltwood (1907), "first man to date a rock," after estimating decay rate of uranium into lead;
samples ranged in age from 410 m.y. to 2.2 b.y.
radiometric dating
unstable parent atoms decay to stable daughter atoms at known rate (half-life)
measuring ratio of parent to daughter yields the age of crystallization
- know how to determine a radiometric age like in the homework exercise
oldest preserved rocks that formed on Earth are about 4 b.y. old
     (oldest preserved individual minerals (zircon crystals) are 4.3 to 4.4 b.y. old)
oldest rocks formed in the solar system (meteorites, moon rocks) are 4.5 to 4.6 b.y. old 

The Carbon Cycle and Climate

atmospheric composition
the greenhouse effect
greenhouse gases: CO₂, H₂O, CH₄, etc.
the carbon cycle
photosynthesis <-> respiration (exchange (CO₂) and oxygen (O₂) with the atmosphere)
     burial in sediments of organic matter produced by photosynthesis
weathering of rocks draws atmospheric CO₂ to produce carbonic acid
     carbon storage in carbonate rocks on the deep ocean seafloor and continental shelves
outgassing from arc volcanoes of CO₂ released by metamorphism of subducted carbonate rocks
outgassing from midocean ridges of CO₂ stored in the mantle
rate considerations
     changes in the rate of such things as seafloor spreading (CO2 outgassing)
     and mountain building (and weathering of freshly uplifted and exposed rocks)
     what is their direct affect on climate?
negative feedbacks in the carbon cycle
     how are rate changes in the carbon cycle and their climate effects
     countered by the carbon cycle so as to that buffer (moderate) climate change?

Origin of the Universe, Solar System, and Earth

Big Bang theory for the formation of the universe
the redshift of light coming from distant galaxies: the universe is expanding
the microwave background radiation: predicted remnant of the early days of the universe
the only elements produced by Big Bang was lots & lots of hydrogen plus a little helium
stellar evolution and the formation of the elements
star formation: gravitational contraction of nebula (cloud) of hydrogen
main stage energy production by fusion of hydrogen into helium
secondary contraction when decreasing hydrogen fuel content slows rate of fusion
     small stars will slowly fade
     sun-size stars will become red giants: fuse helium into elements up to iron
     large stars (10x sun) will go supernova, producing all elements of periodic table and spread them into space
     (giant stars (100x sun) become black holes)
solar nebula theory of how the solar system and Earth formed
the sun is at least a second generation star
     it formed after at least one generation of large stars formed and then went supernova
     otherwise we wouldn't have elements beyond hydrogen and helium in our solar system (no rock, metal, or life)
the sun formed as any star (see above)
how did the planets form?
difference between terrestrial (Earth-like) planets and Jovian (Jupiter-like) planets and the reason why
what is the asteroid belt that lies between Mars and Jupiter?

Early Earth History