Solar SystemSolar System

CHAPTER 9

The Living Earth

CHAPTER 9

The Living Earth

Tellus (Greek Gaia)

Hesiod's Theogony tells how, after Chaos, arose broad-breasted Gaia the everlasting foundation of the gods of Olympus. She brought forth Uranus, the starry sky, her equal, to cover her, the hills (Ourea), and the fruitless deep of the Sea, Pontus, "without sweet union of love," out of her own self through parthenogenesis. But afterwards, as Hesiod tells it-she is a great god of nature

9-1 What powers the motions of the Earth’s atmosphere, oceans, and land surfaces

9-2 How scientists have educed the layered structure of our planet’s interior

9-3 The evidence that the continents are being continuously moved and reshaped

9-4 How life on Earth is protected from subatomic particles emitted by the Sun

9-5 How the evolution of life has transformed the Earth’s atmosphere

9-6 Why Earth keeps its atmosphere9-7 How human civilization is causing dramatic and adverse

changes to our planetary habitat

By reading this chapter, you will learn

¾ of Earth’s Surface Covered with liquid H2O

Earth has a troposphere … “held” to within about 12 K above surface

Geological forces folded terrain and ‘rotated’ the layers into a vertical orientation

1994-Volcano on KamchatkaBoundary of Eurasia and Pacific plates

What Temperature Means

SpeedIncreases with temperature –

Decreases with larger mass

Planetary Atmospheres-Why?Stronger Gravity requires larger escape velocity

Higher temperatures increase molecular speed – lighter molecules move faster

The Greenhouse Effect

• Initially: Earth too hot for ANY atmosphere

• Planet ‘outgas’ … blow off gas directly when surface hot … thru volcanic activity as surface cools and solidifies

• Gasses mostly H2O and CO2 with some N2 and SO2

• Surface cools more-rainfall generates oceans and washes out CO2

H2O Freezing Point

Sun’s Luminosity increases with time

Earth’s Temperature:• Tng (No atmosphere – no greenhouse effect)

• Tg (Assuming current atmosphere and greenhouse effect)

Life caused major change in our atmosphere - Oxygen

Photosynthesis:Carbon dioxide + water + sunlight yields Sugar + Oxygen

2 2 6 12 6 26 6 6CO H O energy C H O O

Younger than 2.2 billion years

Older than 2.2 billion years

The CO2 Cycle

‘Drives’ the CO2 c

CO2 cycle operates on 400,000 year timescale!

Plate Tectonics drives the CO2 cycle – regulates global temp!

So why worry about “global warming?”

What’s changed the picture?

You and me … and 6+ billion like us!

Deforestation of Amazonia – 20,000 km2 / yr

Burning Fossil Fuel

USA fossil fuel energy usageCoal-fired power plant

High Temperature Can Cause a Planet to Lose H2O – Why?

…If it’s too hot – H20 molecules rise high in atmosphere where they are “attacked” by uv, broken apart and bye bye H!

The Ozone Cycle

UV + O3 → O2 + O + IRReaction releases heat (IR) into stratosphere causing a global temperature inversion!

Ozone Hole Over Antarctica

1 Chlorine (Cl) molecule in stratosphere catalyzes breakup of 1 billion ozone (O3) molecules!

Earth’s Magnetosphere

False color spacecraft image of aurora over north pole

Aurora Australis over Antarctica-Space Shuttle image

Aurora Borealis – Visual from Alaska

Green color due to Oxygen excitation and emission

Another way to lose H2O … as well as the rest of its atmosphere!

Did a Planet Ever Have H2O?

Check H/D Ratio

Look out Venus…here we come!

Key Ideas

The Earth’s Energy Sources: All activity in the Earth’s atmosphere, oceans, and surface is powered by three sources of energy.

Solar energy is the energy source for the atmosphere. In the greenhouse effect, some of this energy is trapped by infrared absorbing gases in the atmosphere, raising the Earth’s surface temperature.

Tidal forces from the Moon and Sun help to power the motion of the oceans.

The internal heat of the Earth is the energy source for geologic activity.

Key Ideas The Earth’s Interior: Studies of seismic waves

(vibrations produced by earthquakes) show that the Earth has a small, solid inner core surrounded by a liquid outer core. The outer core is surrounded by the dense mantle, which in turn is surrounded by the thin low-density crust.

The Earth’s inner and outer cores are composed of almost pure iron with some nickel mixed in. The mantle is composed of iron rich minerals.

Both temperature and pressure steadily increase with depth inside the Earth.

Key Ideas

Plate Tectonics: The Earth’s crust and a small part of its upper mantle form a rigid layer called the lithosphere. The lithosphere is divided into huge plates that move about over the plastic layer called the asthenosphere in the upper mantle.

Plate tectonics, or movement of the plates, is driven by convection within the asthenosphere. Molten material wells up at oceanic rifts, producing seafloor spreading, and is returned to the asthenosphere in subduction zones. As one end of a plate is subducted back into the asthenosphere, it helps to pull the rest of the plate along.

Key Ideas Plate tectonics is responsible for most of the major features

of the Earth’s surface, including mountain ranges, volcanoes, and the shapes of the continents and oceans.

The Earth’s Magnetic Field and Magnetosphere: Electric currents in the liquid outer core generate a magnetic field. This magnetic field produces a magnetosphere that surrounds the Earth and blocks the solar wind from hitting the atmosphere.

Some charged particles from the solar wind are trapped in two huge, doughnut-shaped rings called the Van Allen belts. An excess of these particles can initiate an auroral display.

Key Ideas

The Earth’s Atmosphere: The Earth’s atmosphere differs from those of the other terrestrial planets in its chemical composition, circulation pattern, and temperature profile.

The Earth’s atmosphere evolved from being mostly water vapor and carbon dioxide. A strong greenhouse effect kept the Earth warm enough for water to remain liquid and to permit the evolution of life.

Plate tectonics has created a geology that caused most of the early era CO2 to get locked up in the Earth as carbonate rock.

Key Ideas

The appearance of photosynthetic living organisms led to our present atmospheric composition, about four-fifths nitrogen and one-fifth oxygen.

Plate Tectonics drives the CO2 cycle that regulates the CO2 concentration and the temperature of our atmosphere.

The Earth’s atmosphere is divided into layers called the troposphere, stratosphere, mesosphere, and thermosphere. Ozone molecules in the stratosphere absorb ultraviolet light and protect us from losing our liquid H2O!

Key Ideas

The Biosphere: Human activity is changing the Earth’s biosphere, on which all living organisms depend.

Industrial chemicals released into the atmosphere have damaged the ozone layer in the stratosphere.

Deforestation and the burning of fossil fuels are increasing the greenhouse effect in our atmosphere and warming the planet. This can lead to destructive changes in the climate.