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.
How Earth
Was Formed ?
Courtesy: National Film Board of Canada
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