GEO 303 Lecture Notes - Lecture 11: Afar Region, Strontium, Rubidium

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10 May 2016
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Geology Notes Chapter 11:
In lab: Chapter 8
Exam 1 Wed Sep 30th (Know details from lectures)
oReview material on canvas
oLectures 1-9
oOptional review mon 7:30
Next Lecture: Origin of life (12 to 194)
Telling Geologic Time
Deep Time
oEarth’s history, how its unfolded
oOrigin of Life, chemical and physical changes throughout history
oRock record: rocks at the bottom
Law of superposition, in a horizontal stack of sedimentary
rocks
oUnconformity: missing time in rock record
Telling Geo Time
oDiscovering deep time
oEarly geologic clocks: hourglass methods
oThe radioactivity clock
Properties of decay
Parent decay and daughter growth
oUseful parent-daughter pairs
oCalculating an Isotopic age
oThe meaning of isotopic ages
Discovering Deep Time
oHave no idea how old earth is, several guesses (Biblical guesses to
NASA)
oPeople made observations, and then Hutton hit on an idea that was
revolutionary. His unconformity discovery of figuring out how
everything is related meant that the process of what acts on the planet
now (beach moves sediment, earthquakes, etc.) IF the rock is the
record, there is no vestige of a beginning, and no prospect of an end.
oUniformitarianism: natural laws and processes that operate in the
universe now have always operated in the universe in the past and
apply everywhere in the universe.
Previous idea, catastrophism, was the idea that deep time
depends on having 4.5 billion years of earth history occurring
to make everything make sense
oLyell had an idea to measure the rate of sediment, varve (lake
sediment deposited through the years) in a light-dark pattern every
year (depends on summer/winter)
Count them like tree rings
One lake: 215 meters thick*15
varves/cm*100cm/meter*1year/varve=322,500 years.
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