ThursdayNovember 17,

2011(The Precambrian

Era; Continue Lab – The Geologic Time

Scale )

The Launch PadThursday, 11/17/11

Describe the process by which continents were formed in the

Precambrian Eon.1. Volcanic island arcs and oceanic plateaus rose up in the ancient seas due to the upwelling of

magma from the upper mantle.

3. The crustal provinces then accreted into cratons.4. The cratons then accreted to form the

foundations of the modern continents.

2. The action of plate tectonics caused the arcs to accrete into crustal provinces.

Assignment Currently Open

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Last Day

Project – Moon Features F1 10/18 10/21

Quiz 9 S (last 6-wks) 11/2 11/2 11/3 11/17

Video WS – Fearless Planet – Earth Story F2 11/3 11/10 11/16 11/18

Quiz 10 S1 11/10 11/10 11/11 12/2

Activity – The Geologic Time Scale “Cheat Sheet”

F4 11/11 11/15

Lab – The Geologic Time Scale F5 11/15 11/18

AnnouncementsI will be here today

until 5:00 PM.

We will have a Quiz tomorrow!

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.

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.

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.

The Precambrian Eon

The first primitive prokaryotic single-celled organisms appeared in the

oceans in the form of bacteria

(eubacteria or Achaea).

The earliest life forms were prokaryotes

that evolved in the seas, possibly as early as 3.8 Ga.

The Precambrian Eon Earth’s first living organisms were probably

chemotrophs existing in an anoxic world and producing H2S or CO2.

The Precambrian Eon Nearly 3.5 Ga, photosynthezing

cyanobacteria began releasing oxygen into the atmosphere as a by-product of the

process of photosynthesis.

The Precambrian Eon The first multi-cellular organisms appeared

toward the end of the Precambrian Eon, sometime prior to 542 Ma.

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.

The Precambrian Eon With the eukaryotes comes sexual

reproduction, enabling genetic diversity and the concomitant ability to adapt to and

survive environmental changes.

LabThe Geologic Time Scale

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.