EESA01H3 Lecture Notes - Lecture 8: Great Unconformity, Devonian

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21 Apr 2012
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EESA06 Lecture 8 Page 1
EESA06 Lecture 8
Japan Earthquake:
- Pacific plate going beneath the Philippine plate both going underneath
Japanese mainland (Tokyo is dangerous)
- Tsunami wave height was low but…
- Japan as a whole moved east 25metres normal is 2.5-3cm/year
o plates were locked build up of stress and energy
o recurrence interval plates locked for 1000years (superquakes)
- vertical uplift is what killed people tsunami and lowered shoreline
Geologic Time and Stratigraphy
- The Earth is 4.56 Billion Years Old
How did we find this out?
1) Early idea on stratigraphy (the study of rock layers as in a book)
2) How layers get bent & broken (lost chapters)
3) Relative age of rocks (this one is older than…)
4) Absolute age (isotopic age dating ex: 50 million years)
5) The Geological Timescale: 4.56 to today (similar to a book)
Ancient Greeks recognized fossils embedded in rocks now on top of mountains
- How did they get there? uplifted
- Strata beds, older at bottom, deposition and accumulation of older layers
o Can use these to correlate rocks from one location to another
o Aliogeography trying to find out what it was like in ancient times
“Diluvium” (Meaning ‘of a flood’) Africa was moving towards North America, collided with east coast
- Strict biblical interpretation of earth’s history – rocks and landscapes result from Noah’s Flood
- More than one flood recognized new life created each time so each layer contains different
life forms
Archbishop Ussher (1581-1625)
- Declared in 1625 that “Earth formed at 9am on October 26th, 4004BC” only 6,000 years old
- Based on counting generation in the Bible
- But…
Georgius Agricola (1494-1555)
- “father of mining geology”
- Recognizes that fossil remains are of marine organisms in 1531
Nicolas Steno (1631-86)
- “mountains can be raised and lowered, land can be conveyed from one place to another”
The “Scottish Enlightment” (c1730-1830) Industrial Revolution, more rational beliefs
- Joseph Black (Pioneer Chemist), James Hutton (Farmer, interest in soil formation), Adam Smith
(Economist, Free Trade), James Watt (Steam Engine, Energy), Walter Scott (Writer)
- An English visitor to Edinburgh remarked: “here I stand at what is called the Cross of Edinburgh,
and can, in few minutes, take 50 of genius and learning by the hand”
- Rational outlook science based
- Industrialization - Mapping of Oil shale rocks, building of canals
-
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EESA06 Lecture 8 Page 2
James Hutton (1726-97) “Father of modern day geology”
- Recognized “unconformities” within layer of rock and the
igneous origin of granite gaps in geological record
- Proposed concept of “uniformitarianism” (the present is
the key to the past) actualism, same processes observed today
- Came into conflict with Abram Werner and “diluvialism” and
catastrophism catastrophic floods, 6k years old earth
- Facies means “appearance of
o Geologists speak of rock facies
- Arthur’s Seat – distinctive shape, igneous intrusion, sill
o First identification of igneous rocks forms in molten state
- Hutton’s Unconformity at Siccar Point in Scotland ->
John Playfair, geologist (1747-1819)
- The concept ofDeep Time”
- “the mind grows giddy gazing so far back into the abyss of time”
- Layers in earth
o Secondary Strata second layer, contained fossils
o Unconformity gap, earth experienced multiple events
o Primary Strata first layer
The Great Unconformity at Marmora, Ontario
- Peterborough, hwy7
- Old Iron at bottom, limestone on top with fossils
An Angular Unconformity: 500 million missing years
- Kingston
- Flat lying rocks on top of steeply dipping rocks
The Taconic Unconformity in New York State about 440Ma
- Africa collide with North America
The Igneous Original of Granite
- From Charles Lyell’s geology textbook ‘Principles of Geology’ 1830
The Big Debate of the 19th Century
- Catastropism and Creationism vs. Uniformitarianism and Evolution
- Louis Agassiz (1807-73) vs. Charles Darwin (1809-82)
- Ice Ages suggested by Agassiz
The Industrial Revolution (1790-1820)
- Watt’s Steam Engine need for coal
- Scientific Revolution
- Great Demand for Resources and Geologists
Discovery of the origin of coal (1830):
- Formed in situ from plant debris growing in swamps
- Confirmed by discovery of in situ lithified tree trunk in coal seams
o Logan’s trees in Swansea, Wales
One of the first Geological Society in 1807
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