Oceanography 16.5 - 17

Due to the Coriolis Affect,

currents in the Northern Hemisphere are deflected to the right.

The Earth’s first atmosphere, 

contained no oxygen 

Smog is produced

when sunlight reacts with automobile exhaust

What were Earth’s first atmospheric gases?

Hydrogen and helium.

Why did hydrogen and helium disappear?

They boiled away or were blown off by solar winds.

Where did the next gases come from?

From comets and bolides that brought CO₂, H₂O, and N₂

When did cyanobacteria start producing oxygen?

About 2.7 billion years ago

When was the First Great Oxidation Event? 

Around 2.4 billion years ago.

When was the Second Great Oxidation Event?

About 600 million years ago.

What formed during the First Great Oxidation Event?

Banded Iron Formations (BIFs)

What are BIFs and why are they important?

Layers of iron-rich rock formed when oxygen reacted with dissolved iron; 90% of Earth’s iron comes from them

What are the main gases in today’s atmosphere?

Nitrogen (78%), oxygen (21%), and small amounts of argon, CO₂, and others.

How is atmospheric pressure measured?

With a barometer.

What is the standard pressure at sea level?

760 mm Hg = 1 bar = 1013 mbar = 1 atm

What happens in the troposphere?

Weather and clouds; temperature decreases with height

What is the tropopause? 

The top of the troposphere (~17 km); limits mixing with the stratosphere

What happens in the stratosphere?

Ozone forms and temperature increases with altitude

What happens in the mesosphere?

Thin air, very cold, temperature decreases.

What happens in the thermosphere?

High-energy reactions, temperature increases again

What caused the Donora Smog Disaster? 

Air pollution trapped by weather conditions in 1948.

What law began addressing air pollution?

The Clean Air Act of 1963

How does acid rain form?

Burning fossil fuels releases SO₂ and NOₓ, which combine with water vapor.

What are some effects of acid rain?

Damage to humans, property, and ecosystems.

What is smog and ozone in the troposphere caused by? 

Chemical reactions between sunlight, vehicle emissions, and pollutants

Where is the ozone layer found?

In the stratosphere.

How is ozone formed?

Sunlight breaks O₂ molecules; single O atoms join O₂ to make O₃

Why is ozone important?

It absorbs harmful ultraviolet (UV) radiation.

What destroys ozone? 

CFCs and halons that release chlorine and bromine atoms.

What is the ozone hole?

A region of low ozone concentration over Antarctica, discovered in 1985.

When were CFCs banned?

1996