FROM THE BIG BANG TO THE PRESENT:
EVOLUTION OF THE UNIVERSE AND EARTH

Universe 13 – 16 Billion Years old

Big Bang – Time Begins.

Formation of 1^st generation stars and galaxies

6,000,000,000 years after big bang

(7 to 10 billion years before present)

Formation of the Sun

5,000,000,000 years ago

Solar system ~4.5 billion years old?

Condensed from gas/dust clouds (nebula) left over from supernovas of 1^st generation stars –NEBULAR HYPOTHESIS

Formation of our solar system

Formed from accretion of many smaller boulder-to-mountain-to continent sized objects, under the influence of gravity.

Summary Image

Details of Process

Formation of Accretion Disk

Different Materials for Inner and Outer Planets

Condensation of Materials vs. Distance from Sun

Accretion of Planetesimals

4.6 – 3.5 Billion years before present

Earth Melted - Heat Sources:

(1) residual heat of formation - gravitational compression

(2) impacts from planetesimals,

(3) internal radioactivity

(4) friction and angular momentum - conversion to heat

Examples of Cratering

Differentiation occurred- producing the core/mantle/crust structure

An atmosphere formed from outgassing of volcanoes: carbon dioxide, nitrogen, water, etc.

Cooling of crust permitted oceans to form

Continental land masses formed

from lighter rocks (e.g,, granite)

Plate tectonics started, driven by interior heat

Life originated in early oceans.

NEXT 3.5 BILLION YEARS:

Continents drift across globe, floating on and powered by mantle convection currents.
Continents collide, mountains are built, they erode and continental drift continues
.
EPISODES OF MOUNTAIN BUILDING ACCELERATE REMOVAL OF CO₂ FROM ATMOSPHERE
as erosion of lofty mountains increases and limestone (primarily CaCO₃) is buried in the sea.
At the same time volcanic activity increases the level of CO₂.

Living organisms changed the atmosphere
Green plants evolve and photosynthesis removes C0₂from the atmosphere.
Blue Green Algae were first about 3.5 BYBP then
multi-cellular eukaryotes about 2.5 BYBP.
RESULT: CO₂ LEVEL FALLING, O₂LEVEL RISING.

Cambrian Explosion, vast increase in the number of organisms with hard parts
especially CaCO₃ (calcium carbonate) shells.
RESULT: ACCELERATION OF REMOVAL OF CO₂.

Geologic cycle established—erosion by water, wind, and ice, new crust formed by volcanic activity.

NOW: Once again life is modifying the atmosphere on a global scale
Since the beginning of the Industrial Revolution CO₂ levels have doubled because of human activity.
Stratospheric Ozone is being depleted by chloroflourocarbons.

On a local and regional scale, acid enhanced rainfall is
having a devastating effect on soil and vegetation health. .