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EVOLUTION OF EARTH 

 

 

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]

https://en.wikipedia.org/wiki/Big_Bang

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.

 

 

 When the Earth formed, it would have been  entirely molten due

to the release of gravitational energy. It  has cooled so the earth

has "tectonic plates" of crust floating on a molten mantle. It is kept molten by radioactive atoms release energy in the mantle.  

Around 4B years ago, volcanic activity decomposed rock, pumping CO2, methane, water vapor into the atmosphere, eventually the earth cooled and water condensed. Bacteria evolved producing oxygen which started the "great oxidation event" that trapped metals out of the water as oxides producing red rocks. As bacteria evolved into plants, the continued oxygen emissions then allowed the first oxygen consuming animals to evolve. The planet itself had evolved with clean water and atmosphere of  oxygen and nitrogen.

 

Between 1.26B and 700 M years ago, the supercontinent " Rhodinia assembled. The break up produced large amounts of basalt lava that when rained on created acid silicates that removed CO2 from the atmosphere which then cooled  produced iceberg earth. Thawing of iceberg earth with a burst of oxygen to the atmosphere produced the first evolutionary jump to macroscopic life. 

Around 500-400 M years ago, the continents had assembled into Gondwanaland and Laurasia. 

Around 200M years ago,  land masses were re-merged to form a single mega-continent "Pangea". As the dinosaurs ruled, carbon dioxide levels were 3 times today, temperatures were 10C higher and there were no ice caps so sea level were 100 meters (300 ft) higher. 

NASA model &

http://www.actforlibraries.org/types-of-climates-the-dinosaurs-lived-in


Water and ice causes erosion of the land mass leaving features such as the Grand Canyon, and Yosimite. The products of erosion leads to  deposition of layers of sandstone. 

 

As the plates move, uplift changes the oceans and different layers are formed. These layers can be clearly  seen in the walls  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.

Volcanic activity at the plate boundaries are thought to have caused multiple mass extinction events at 252 M years ago and 205 M years ago. The event 252 M year is though to be caused by  the Siberian traps a massive igneous rock outflow covering 7 M squ km.  The event elevated global temperatures, and in the oceans led to widespread anoxia and acidification.

The most famous meteor impact was  66M years ago  which formed 180 km (112 mi) Chicxulub crater in the Gulf of Mexico's Yucatán Peninsula. The impact  that ended the dinosaurs and formed the K-T boundary. The explosion, likely caused by an object about 10 km  across, would have released as much energy as 100 trillion tons of TNT, more than a billion times more than the atom bombs that destroyed Hiroshima and Nagasaki.  The impact would have created a dust cloud that blocked sunlight for up to a year, inhibiting photosynthesis.[120] Freezing temperatures probably lasted for at least three years.[156] At Brazos section, the sea surface temperature dropped as much as 7 °C (13 °F) for decades after the impact.[158] It would take at least ten years for such aerosols to dissipate, and would account for the extinction of plants and phytoplankton, and subsequently herbivores and their predators

 

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

The temperature profile over time illustrates the impact of geological events on the environment. Throughput most of time, earth has had more carbon dioxide than today and hence significantly hotter than today.  Temperature spikes at 250 M years and 66 M years coincide with extinctions. As the continents moved to  todays locations, ice caps have formed and the earth has cooled. In the last 50 M years there has been a steady decline, with cycles of ice ages every 100 K years. 

 

The isthmus of Panama is thought to have been formed around 3 million years ago, separating the Atlantic and Pacific Oceans and causing the creation of the Gulf Stream. This was first suggested in 1910 by North American paleontologist Henry Fairfield Osborn. He based the proposal on the fossil record of mammals in Central America. This conclusion provided a foundation for Alfred Wegener when he proposed the theory of continental drift in 1912. 

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.  When the planet's orbit reaches its most elliptical stage, about 100,000 years from now, that difference will result in 23% more sunlight reaching Earth's atmosphere.

The last ice age reached its maximum 18 K years ago. 

Today, the earth continues to evolve through the motion of tectonic plates. The map shows volcanos scattered along the junctions between plates, as well as stationary hot pots in Hawaii and the Galapagos Islands. The "Ring of Fire" surrounding the Pacific Ocean shows up clearly in the volcano pattern. 

The earthquakes emit huge amounts of energy.  Measured by the Richter Scale, a log base 10 scale. San Francisco sized quakes (Mag 8) occur somewhere once a year with an energy release of 100 Hiroshima's.  A magnitude 7 such as Loma Prieta does limited damage in a community that has effective building codes. 

Explosive volcano's cause much more damage, as measured by 

Volcano Explosivity Index another log base 10 scale.  

VEI 8 every 50,000 yrs - Yellowstone basin  20B tons TNT

VEI 7 every 1000 yrs - Santorini 2B tons TNT  

VEI 6 every 250 yrs - Mt Pinatubo, Krakatoa 200M tons TNT

Data from https://volcano.si.edu/E3/

For comparison, the fission bomb in Hiroshima was 20K tons TNT, and H bombs 1M tons TNT.

The climate impact of Krakatoa  is well documented. The blast led to a "lost summer" and  global air temperatures  dropped by as much as 1.2 degrees Celsius. According to a 2006 article in the journal Nature, the volcano caused oceans to cool for as much as a century, offsetting the effect of human activity on ocean temperatures. If the volcano had not erupted, the authors argue, our sea levels might be much higher than they are today.

A Santorini event (every 1000 years), was 10x larger and would significantly affect life. There have been two well documented VEI 7 events in recent history.

1812  Mount Tambora is a volcano on the island of Sumbawa in present-day Indonesia. This brief period of significant climate change (0.5C)  triggered extreme weather and harvest failures in many areas around the world.

 

In 1257, a catastrophic eruption occurred at the Samalas volcano on the Indonesian island of Lombok. Recent proxy data indicate that a temperature drop of 0.7 °C (1.3 °F) occurred in 1258 and of 1.2 °C (2.2 °F) in 1259, but with differences between various geographical areas. Medieval chronicles say that in 1258, the summer was cold and rainy, causing floods and bad harvests,[60] with cold from February to June.[196] Frost occurred in the summer 1259 according to Russian chronicles.[101] In Europe and the Middle East, changes in atmospheric colors, storms, cold, and severe weather were reported in 1258–1259,[197] with agricultural problems extending to North Africa.[198] In Europe, excess rain, cold and high cloudiness damaged crops and caused famines followed by epidemics.

The Yellowstone basin explosion (every 50,000 yrs) was another 10x larger and would cause majority disruption and species loss. For reference, the KT meteor was 1000x larger than Yellowstone.

The cycles of uplift and volcanism caused by continental drift, followed by erosion, deposition, and further drift is responsible for the huge variety of landscapes on todays earth. 

For the first time human activity is now affecting or "terraforming" the planet. We are at a warm point in the ice age cycle. By 2100, it is projected that temperatures could be 5-6C higher, half way to the carbon dioxide level and temperatures of the age of

the dinosaurs. In the last 100 years, humans have  used  half the available fossil fuels and  started to change the climate, and  forcing a fundamental change in the way we live on the planet.

 

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