WednesdayNovember 9, 2011

(Origin of the Atmosphere and

Oceans )

The Launch PadWednesday, 11/9/11

Briefly describe the following components of Earth’s

structure:crustupper mantlelower mantleouter coreinner core

Brittle, oceanic & continental, thinSolid but mobile, asthenosphereSolid, hot, dense rocky materialLiquid, metallic, iron & nickel, creates magnetic fieldSolid metallic, iron & nickel, extremely

high pressure

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Project – Moon Features F1 10/18 10/21

Quiz 8 S (last 6-wks) 10/26 10/26 10/27 11/10

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

Activity – Draw Earth’s Internal Structure

F3 11/8 11/9

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Figure 12.6Over 4 billions years ago volcanic activity

was producing Earth’s primitive atmosphere and

oceans.

Stromatolite bacteria mounds

Figure 12.7Earth’s primitive

atmosphere, which consisted mainly of H2O vapor and CO2,

was formed by a process called

“outgassing”, in which gases trapped

in the planet’s interior are released

by volcanic eruptions.

This process continues

today.

Origin of the Atmosphere and Oceans Water vapor

condensed to form

clouds and

rainwater that formed

the oceans.

Origin of the Atmosphere and Oceans

About 3.5 billion years ago,

photosynthesizing bacteria began

to release oxygen.

Origin of the Atmosphere and Oceans

Oxygen levels steadily increased

Origin of the Atmosphere and Oceans Eventually oxygen levels were sufficient for ozone to develop in the atmosphere.

These layered, iron-rich rocks, called banded

iron formations, were deposited during the

Precambrian. Much of the oxygen generated

as a by-product of photosynthesis was readily consumed by

chemical reaction with iron to produce these

rocks.

Origin of the Atmosphere and Oceans Outgassing produced acidic conditions

that caused an accelerated rate of weathering of Earth’s rocky surface.

Origin of the Atmosphere and Oceans

Products of this

weathering were

carried to the oceans,

thus increasing the salinity

of the oceans..

Origin of the Atmosphere and Oceans The oceans also served as a depository for carbon dioxide, which is readily soluble in

water.

CO2 reacts with other substances in seawater to form calcium carbonate (limestone.) Eventually, marine organisms would removed calcium carbonate from the seawater to make their shells. When these organisms died, their remains were deposited on the

seabed in the form of chalk. These chalk beds later became exposed, as in this picture of the White Cliffs of Dover, in southern England.