Earth evolution      


After the Big Bang, matter forms first galaxies. After its initial expansion, the universe cooled sufficiently to allow the formation of subatomic particles, and later atoms.  These primordial elements—mostly hydrogen, with some helium and lithium—later coalesced through gravity, forming early stars and galaxies. Astronomers observe the gravitational effects of an unknown dark matter surrounding galaxies. Most of the gravitational potential in the universe seems to be in this form, and the Big Bang models and various observations indicate that this excess gravitational potential is not created by  normal atoms. In addition, measurements of the redshifts of supernovae indicate that the expansion of the universe is accelerating, an observation attributed to an unexplained phenomenon known as dark energy.[9]

Within galaxies, the stars have their own life cycles, Clouds of Hydrogen in the galaxies collapse and spin up until fusion is ignited to form the sun. Debry is the spinning disk accrete driven by gravity, until they are pulled spherical and form planets. The star fusion reaction uses up  its fusion fuel and creates heavier elements.   Eventually it collapses leading to black holes, neutron stars and supernovae depending on size.



The earth forms with "tectonic plates" of crust floating on a molten core. On earth, a massive collision with a meteor creates the moon. Around 200M years ago,  land masses were merged to form "Pangea".




Periods of stable oceans leads to erosion of the land mass and the deposition of a layer of sandstone.  As the plates move, uplift changes the oceans and different layers are formed. These layers can be clearly  seen in the Grand Canyon, Zion and the parks of the Grand Staircase covering the time from 500M to 50M years ago.

The corpses of life in the oceans also created layers of carbon containing material that converted to layers of limestone. Under particular circumstances  oil was formed from 400M to 300M years ago.

The most famous meteor impact was  66M years ago that ended the dinosaurs and formed the K-T boundary.








 The layers are often modified by pressure from subsequent layers, mountain building and volcanic activity occur primarily at the junctions between plates.

Throughput most of time, earth has had more carbon dioxide than today and hence  significantly hotter than today. The peak occurred around 100M years ago at 10C hotter, no ice caps, and sea levels 70 meters higher than today.







As the continents moved to  todays locations, ice caps have formed and the earth has cooled.

The distance of the earth to the sun changes roughly every 100K year (Milkantivitch) cycles, and these have led to 4 ice ages over the last 400K years.  

In the last 100 years, human use of half the available fossil fuels has started to change the climate, and has forced a fundamental change in the way we live on the planet.