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Thursday November 17, 2011

Thursday November 17, 2011. (The Precambrian Era; Continue Lab – The Geologic Time Scale ). The Launch Pad Thursday , 11/17/11. Describe the process by which continents were formed in the Precambrian Eon.

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Thursday November 17, 2011

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  1. ThursdayNovember 17, 2011 (The Precambrian Era; Continue Lab – The Geologic Time Scale )

  2. The Launch Pad Thursday, 11/17/11 Describe the process by which continents were formed in the Precambrian Eon. Volcanic island arcs and oceanic plateaus rose up in the ancient seas due to the upwelling of magma from the upper mantle. The action of plate tectonics caused the arcs to accrete into crustal provinces. The crustal provinces then accreted into cratons. The cratons then accreted to form the foundations of the modern continents.

  3. Announcements I will be here today until 5:00 PM. We will have a Quiz tomorrow!

  4. Latest News The Leonid meteor shower peaks tonight (Nov. 17), but bright moonlight is threatening to wash out this year's light display. The annual Leonid meteor shower is expected to reach peak activity tonight at approximately 10:40 p.m. EST (0340 GMT on Nov. 18), but a luminous third quarter moon could outshine even the brightest meteors, said Bill Cooke, head of the Meteoroid Environments Office at NASA's Marshall Space Flight Center in Huntsville, Ala. "The moon is going to be a major interference, but we could see a rate of about 20 per hour," Cooke told SPACE.com. Meteor showers occur when Earth orbits through clouds of particles and dust on its path around the sun. Meteors are often referred to as "shooting stars," because of how they streak across the sky, but these dazzling streaks of light are really triggered by pieces of debris that hit Earth's atmosphere and burn up.

  5. The Precambrian Eon It was during the Precambrian Eon that life first began on the Earth. Although the Precambrian Eon contains some 88% of Earth's history, its fossil record is poor because organism were soft-bodied during this time, resulting in little remaining evidence.

  6. The Precambrian Eon The majority of Precambrian fossils are stromatolites that are often heavily metamorphosed or deeply buried. However, preserved cells have been discovered at selective sites, such as the 2.0 Ba Gunflint Formation Jasper stromatolites from Gunflint Formation near Mackies, northern Ontario.

  7. The Precambrian Eon The earliest life forms were prokaryotes that evolved in the seas, possibly as early as 3.8 Ga. • The first primitive prokaryotic single-celled organisms appeared in the oceans in the form of bacteria (eubacteria or Achaea).

  8. The Precambrian Eon Earth’s first living organisms were probably chemotrophs existing in an anoxic world and producing H2S or CO2.

  9. The Precambrian Eon Nearly 3.5 Ga, photosynthezing cyanobacteria began releasing oxygen into the atmosphere as a by-product of the process of photosynthesis.

  10. The Precambrian Eon The first multi-cellular organisms appeared toward the end of the Precambrian Eon, sometime prior to 542 Ma.

  11. The Precambrian Eon When the eukaryotes (single-celled organisms with a nucleus) evolved through endosymbiosis is disputed, with claims as early as 3.4 Ga, but with less equivocal fossils dating from 1.8 to .8 Ga.

  12. The Precambrian Eon With the eukaryotes comes sexual reproduction, enabling genetic diversity and the concomitant ability to adapt to and survive environmental changes.

  13. Lab The Geologic Time Scale

  14. Activity • Get your tape from the Lab on the Geologic Time Scale. • On the front side (from Part 1), divide the Precambrian Eon into Eras. • Research what caused the Eras to change and note this on the tape. • On the back side (from Part 2), if you have not done so already, divide the Phanerozoic Eon into eras, periods, and epochs. • Research what caused the all of the changes and note this on the tape.

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