EVOLUTION OF EARTH

 

The Universe 13 – 16 Billion Years old

 

Big Bang – Time Begins.

 

Formation of 1st 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 1st generation stars the “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

 

Different Materials for Inner and Outer Planets

 

 

 

Condensation of Materials vs. Distance from Sun

 

 

 

 

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Accretion of Planetesimals

 

 

 

4.6 to 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

 

 

 

Watch This Video - How the Moon Was Formed - Another Mechanism Earth Melted

YouTube Video

Collision Graphics

 

 

 

 

 

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 came and went due to plate motions.

 

Living organisms changed the atmosphere by adding free oxygen.

 

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