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History Of Earth

Earth's History and How humans might alter its future

 Dr. Abhinandan Bhardwaj PhD

 Earth is about 4.5 billion years old. Earth Scientists have grouped  this time into eons, eras, and periods. The most basic unit is period. The Geologic timescale table below shows what various Era's, Periods and Epochs are and how long did they lasted ( in Million Years)

Geologic Timescale

Era

Period

Epoch

Duration

Number of years ago

Cenozoic

Quaternary

Holocene

10,000 - present

 

Pleistocene

2

.01

Tertiary

Pliocene

11

2

Miocene

12

13

Oligocene

11

25

Eocene

22

36

Paleocene

71

58

Mesozoic

Cretaceous

 

71

65

Jurassic

 

54

136

Triassic

 

35

190

Paleozoic

Permian

 

55

225

Carboniferous

 

65

280

Devonian

 

60

345

Silurian

 

20

405

Ordovician

 

75

425

Cambrian

 

100

500

Precambrian

 

 

3,380

600

 How Earth & Other Planets of our Solar System Formed:

According to nebular theory the Earth and the other planets of our solar system were formed from a large gaseous cloud. The fragments formed the planets while the centre developed in to the sun. The Earth in this stage did not have atmosphere and was in a molten state.

What latest Research Says about Earth's Early Days  ?

According to latest research, scientists now are trying to understand how Earth might have looked soon after it formed 4.56 billion years ago, based on clues within the oldest grains of mineral zircon (zirconium silicate crystals).
 
 Zirconium silicate crystals found in ancient stream deposits indicate that Earth developed continents and water,  perhaps even oceans and environments in which microbial life could emerge 4.3 billion to 4.4 billion years ago, remarkably soon after our planet was formed.

The findings by two research groups, one in Australia and the other in the United States, suggest that "liquid water stabilizes early on Earth-type planets," according to  Stephen Mojzsis, a member of the NASA Astrobiology Institute's University of Colorado, Boulder, team. "This increases the likelihood of finding life elsewhere in the universe" because conditions conducive to life can evidently develop faster and more easily than once thought.

It also "gives us a new view of the early Earth, where the Earth cooled quickly" after gas and dust in the newborn solar system congealed to form planets, says geologist William Peck, of Colgate University in Hamilton, New York. "There were continents and water really early  and maybe oceans and life, all to be obliterated later by meteorites, with almost no record left except these zircons."

Until roughly 3.9 billion years ago, swarms of comets and meteorites whacked the young Earth often enough to occasionally vaporize the surface zones of the oceans and erase any life residing there. The earliest known evidence of microbial life on Earth comes from carbon isotope patterns investigated by Mojzsis and colleagues in 3.85-billion-year-old Greenland sediments.

Now, the zircons from Western Australia demonstrate that continents and water existed 4.3 billion to 4.4 billion years ago. "Life could have had the opportunity to start 400 million years earlier than previously documented,"  according to these scientists.
Mojzsis and Peck belong to separate research teams, one that found a 4.4-billion-year-old zircon in 1999 and another team that unearthed a pair of 4.3-billion-year-old zircons last year from the same area of Western Australia's Jack Hills rock formation. Both groups had published their studies in the Jan. 11, 2001, issue of the British journal Nature.

According to these scientists liquid water existed at some point before 4.4 billion years ago. They also say that oceans existed because "to make continents, you need to have water."

Peck said that before there were oceans, giant plates of Earth's crust already could have started moving and colliding with each other, causing large blocks of rock to dive downward in a process called subduction. Without oceans, that rock could not have melted to form continental rock like granite.

Oceans, atmosphere and continents were in place by 4.3 billion years ago," says these scientists.

According to them, the first oceans might have formed from water brought to Earth by comets or have been emitted during early volcanic eruptions from what became mid-ocean ridges.
 

Life Might have existed 4.3 billion years ago:
The zircons suggest that life could have existed on Earth 4.3 billion years ago,  because three key factors necessary for life to take hold were present: energy, organic material (from incoming comets and atmospheric reactions) the zircons and liquid water.

Earth's  Balanced Atmosphere

Like many of the other planets, Earth's axis of rotation is titled to its orbit, so instead of spinning around the Sun in an upright position, our planet is instead titled over at an angle of 23.5 degrees from vertical. The Earth's tilt points in the same direction in space regardless of its position on its orbit round the Sun, so different regions of the planet receive differing amounts of sunlight throughout the year. This gives rise to the seasons on Earth. In order for life to flourish Earth needed different seasons. And in order to sustain all kind of life a well balanced atmosphere with right amount of gases was needed. The combination of continents, oceans, and atmosphere makes it unique among all the planets in the solar system. These features also create the conditions for life in all its diversity.
 

Carbon Oxygen Cycle:

Trees helps maintaining this cycle. Animals need oxygen to survive and trees need carbon dioxide to make their food. We might imagine leaves of trees having an arrangement with humans and animals. We both use oxygen from the air and return carbon dioxide. The leaves take in the carbon dioxide, keep the carbon to build up the wood, and release oxygen into the air for us all to use.
Acting as an enormous "carbon sink", trees soak up carbon dioxide from the air, producing life-giving oxygen in return. In fact, a medium-sized tree generates the same amount of oxygen as each one of us needs to breathe. Trees have been helping keeping carbon oxygen balance for millions of years. If we do not have this balance we will not have the kind of life we have on this planet.

 

How Humans are impacting the delicate balance of Nature:

 

Earth took millions of years to create a necessary  balanced atmosphere for life to survive and evolve on this planet. But Human's indiscriminate use of natural resources and fossil fuel is jeopardizing all that now. Humanity is facing one of its biggest challenges in its history "the global warming" a human induced climate change. One of the main offenders contributing to rapidly increasing temperature isn't carbon itself, it's increased carbon dioxide (C02) emissions, methane and deforestation, all caused by human actions.
Trees ingest carbon dioxide and turn it into carbon which they store - the problem is that there's simply not enough trees left to deal with the massive carbon load we put on our ecosystem. Unless we all do something to increase the number of trees on this planet and find ways to reduce the carbon dioxide load on this planet, there is every possibility that we are all responsible for altering the very fabric of nature which is necessary for the life to survive on this planet and indeed this would lead us to our own destruction.

 

References:

Source: Courtesy NASA Astrobiology Institute.

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