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






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.





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.