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Environment
Who is going to be
the Next!
by VK
Joshi
The 4.5
billion year old evolutionary history of the earth has seen many a
vicissitudes in terms of natural disasters. Fortunately we were not
there, but since times immemorial, the cradle that holds the humanity
has been facing the brunt of the nature's ire. Today, when the vast
areas are marooned by the floods or kilometers of coastal stretches are
devastated by a tsunami, often the blame is put on the global warming.
Well no doubt the global warming is responsible for many events of
floods, droughts etc.
But question
is what causes global warming? Mere industrialization cannot warm the
entire weather system. Similarly industrialization might raise some smog
and make the sunlight dull, but it cannot cause such a haze which would
disrupt the solar heat to cool the earth so much that it is wrapped in
an ice sheet. Then who is behind all such phenomenon? To get answer,
just read on:
A bolt from the blue and the dinosaurs perished some 65 million years
ago (Ma). Likewise there have been four major extinctions in the past
around 251 Ma, 256 Ma, and 204 Ma and of course the latest one around 65
Ma that changed the course of the evolutionary history of the present
day life. Similarly we know that our earth was often shrouded under a
cover of ice or it had become so hot that Svante Arrhenius (1896), a
Swedish Nobel Laureate called it a "Hot House earth". Who was behind all
these upheavals? Was it due to merely earth bound processes as commonly
thought or was it due to some 'external hand'?
Researches since 1980 have put forth facts which point towards 'some
galactic forces' of Milky Way, our home galaxy were behind the major
turmoil like recurring mass extinctions of both terrestrial and marine
species, global ice ages, major tectonic impacts, periodic boosts in
fossil diversity, formation of large igneous provinces (LIP), climatic
changes causing perturbations to global climate cycle leading to carbon
isotope excursions (CIE), says, octogenarian scientist and free lance
science writer A.V. Sankaran, in the September 2008 issue of Current
Science.
What has the galaxy to do with the turmoil on the Planet? Well the
answer to 'external hand' appears to lie in the galaxy! Our home galaxy,
the Milky Way has four major arms arranged in a spiral, viz.
Cygnus-Norma, Crux-Scutum, Carina-Sagittarius and Perseus. Before
understanding the 'might' of the 'external hand' one must know the
dimensions of our galaxy. It is 100,000 light years (l y) (One l
y=9460730472580.0 km) in diameter with an average thickness of 1000 l y.
Compared to the galaxy our Solar system is a minuscule located in a
smaller arm Orion between Perseus and Sagittarius arms.
The galactic arms rotate around the galactic centre and so do the Sun,
albeit at a slightly higher speed and completes one rotation in about
250 million years (m. y.). Besides, the solar system is also known to
oscillate up and down the galactic plane; each of these motions and
locations relative to the galactic centre correlate with some of the
geological events in the earth's history says Sankaran.
The scientists synthesized the so far available galactic, geological,
biological and atmospheric data and the conclusion was amazing! It was
found that the geologic events occur at an approximate interval of 176
m. y., which is incidentally the time taken by the solar system to
travel from one arm of the galaxy to the same position on the other.
The Solar system of which our planet, the Earth is a part makes an orbit
of all the four galactic arms in 250 m. y. While the solar system
traverses across a galactic arm, there is a marked turbulence on our
planet in the form of catastrophic geologic events; whereas during the
passage of the solar system through the inter-arm space there is a
'quieter phase', free from cosmic ray flux (CRF) and geomagnetic
reversals. The quieter phase called as Superchron, lasts for about 20 m.
y. or more. Sankaran says that three such superchrons in the earth's
geologic past are now well established. The latest was during the
Cretaceous period of the earth's history lasting for 36 m. y. between
120 and 84 Ma. There were two other older superchrons, one lasting for
48 m. y. between 312 and 264 Ma and for 22 m. y. between 485 and 463 Ma.
The 'quieter phase' is not that quiet as understood from the term. It is
a period of volcanic eruptions on a large scale, leading to large
igneous provinces (LIPs). The Panjal igneous province (250-160 Ma) and
Deccan igneous province 60 Ma are the two examples of such LIPs from
India. The former is present as the Pir Panjal range that separates the
Kashmir valley from Jammu and the later forms the Deccan Plateau. In
addition there are many other LIPs, world over through different
geological periods, they are: Emeishan (China) (250-260 Ma); Central
Atlantic, Karoo-Ferrar (South Africa) (180-200 Ma); Parana-Etendeka
(Brazil and Namibia), Ontong-Java (Papua New Guinea) (120-130 Ma) and
Caribbean (90 Ma).
The superchrons are also catalysts to great biological diversity,
because they offer ideal conditions for the proliferation of life. For
example, the Cambrian explosion of life that took place as early as 542
Ma had occurred during the inter-arm passage after the Solar system
crossed Perseus arm. Amongst the four mass extinctions of the geologic
past the latest, extinction of the dinosaurs took place during the
transit of the Sun across Carina-Sagittarius arm of the galaxy.
There are other impacts, like geomagnetic reversals and quasi-periodic
gravitational perturbations on the Oort cloud too faced by the earth
during the inter-arm crossing of the solar system. The Oort cloud is a
hypothetical spherical cosmic cloud lying about a light year away from
the Sun, responsible for earth impacting materials. There are evidences
to suggest that an asteroid hit the earth some 65 million years ago
which was responsible for wiping off the dinosaurs.
Similarly the galactic triggers like CRF and geomagnetic reversals are
thought to be powerful enough to modulate the earth's climate. It is
also believed that an increased CRF in the vicinity of the earth
promotes extensive cloud formation and consequent reduction in global
temperatures, leading to Ice ages. The presence of certain isotopes of
beryllium, carbon and oxygen found only in the space are found in the
sediments of the past ice ages gives credence to the thought that there
is an 'external hand in triggering the ice ages!
It is apparent that the galactic forces are much more powerful than
thought and need to be carefully studied. As far as the galactic
influence on mankind is concerned, Dr Sankaran says, "If the galactic
forces had swayed various earth processes in past geological periods,
mankind as well as other life as part of the plant can be affected, if
not in one's life time, but certainly in geological time scales."
Only time
will tell who is going to be the next victim of the galactic forces!
February 15,
2009
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