Mr joseph vempeny Posted on : 29/01/2008 13:18:58

Geomorphology

The Unique Planet

Joseph vempeny

About nine billion years after it all began, that is, around five billion years before the present, one of the second-generation stars ended up its life after having spent all its nuclear fuel in creating heavy elements. During this explosive event this dying star turned itself into what is called a supernova. This explosion sent the heavier elements in the star hurtling far out into space while the lighter ones, mostly hydrogen and small quantities of helium and lithium, remained at the centre of this dispersed mass of matter. The space around this also contained plenty of gases and dust just as in other spaces between stars.

Whether it was evolution by chance or creation by design, the lighter matter in the central region of this swirling disc gathered into one huge ball of gas. The tremendous force of gravity caused the temperature to soar and nuclear fusion again took over. A new, third- generation star was born. We call it the sun and it remains in one corner of our galaxy, the milky way, which consists of a hundred billion other stars as well as supernovae, black holes, neutron stars, white dwarfs and red giants.

Once it was thought that the planets were created simultaneously with the sun. But the opinion of the scientific community of today is that the planets formed only a couple of million years after the birth of the sun. During this period, the matter that today forms the planets and asteroids was a disc-shaped cloud of dust and gas called a nebula. This nebula progressed round our infant sun like a giant record player in slow motion, until something happened - something that looked natural in the past but seems inexplicable today. The matter of the cloud gradually condensed into bigger and bigger lumps until the asteroids and planets were formed, shall we say, created. Creation of the earth was not something that happened with the birth of the sun nor something that is quite normal in the process of cosmic evolution. The sun could have had its entire life with just a nebula of dust and gases around it for all that we know. Many stars have such nebulae around them throughout their lifespan. What happened a few million years after the creation of the sun was a separate act of creation, the creation of the planets, the creation of the earth, a home for us.

The Icy Planet

The earth started probably as a ball of molten rock of uniform density. As it cooled the gravity brought the heavier metals to the centre, with concentric layers of varying density and composition. It consisted of a central core of solid nickel-iron surrounded by the outer core of molten nickel-iron. Over this were the semi-solid mantle, partially molten asthenosphere, and the solid crust or lithosphere. The lithosphere consisted of the silicates and oxides of metals as well as quartz, the oxide of silicon. The lightest oxide, water, formed the outermost layer called the hydrosphere and above this was the atmosphere of gases, mostly nitrogen and carbon dioxide. The water on the surface of the earth was in the frozen state because, the sun in those days, was not as hot as it is today. This state of affairs did not last long. The heat produced by the constant bombardment of meteorites, the heat of the sun as well as the heat emitted from the radioactive elements of the earth from inside it thawed most of the ice and at least the tropics were covered with water in the liquid form. Still there was no dry land.

Land Ahoy

Meanwhile there was constant flow of heat from the very hot interior to the exterior. This was not conducted away to the outside, as the lithosphere was a poor conductor. Hence the excess energy found outlet through vents of volcanism. This gradually built mid oceanic ridges and in the southern hemisphere some of the lithosphere rose above the water, creating the first islands or an archipelago. Still there was no continent or a landmass of any considerable size. For more than three billion years our planet remained a huge ocean, with some islands and frozen water around the pole. The first super continent was formed some 700 million years ago, most of the land being in the southern hemisphere. Geologists call this landmass Pangaea.

A Jigsaw Puzzle

We have got used to the idea that the earth is rotating on its axis rather fast and flying round the sun every year. And now comes this notion that the surface of the earth is not at rest at all. The continents are always moving ever so slightly, some very slow, others comparatively fast. The branch of geomorphology called plate tectonics dealing with the movements of continental plates and ocean plates was born in the fifties. About 200 million years ago the single continent of Pangaea started breaking up. 180 million years ago there were two landmasses the northern one called Laurasia and the southern one Gondwanaland. These two were still nominally joined at Gibraltar. Then Gondwanaland began breaking up. About 130 million years ago, Africa, retaining South America, Arabia and Madagascar began moving north, away from the southern most landmass comprising of Antarctica and Australia as a single piece. Later the Indian plate also had broken up from Africa and began moving north. The present island of Madagascar was joined with the Indian plate.

65 million years ago South America broke off from Africa. The Madagascar separated from the Indian plate. The Indian plate reached the equator in its flight to join Asia. Africa disengaged from Europe at Gibraltar but a new link to Asia was made at Suez, though Arabia was still part of the African landmass. Australia was still joined to Antarctica though the Australian section had moved further north. While all these changes were happening in the southern hemisphere, the northern part, Laurasia seemed to have undergone very little change. Though this part began breaking up, the Canadian section was still fully joined to the western European section. The various pieces of the Jig saw puzzle on the earth’s crust was placed in their present positions during the last 50 million years. There were some very remarkable events in this relatively short span of time in earth’s history.

During this period:

• North America broke off from Europe and joined up with South America.

• Australia broke off from Antarctica and moved further north.

• The fault line that created east African rift valley system also created the red sea separating Arabia from Africa except for the Suez connection.

• This period also saw the birth of many of the present islands including all the islands of the South-East Asia, the British Isles and Sri Lanka. One of the youngest islands is the Hawaii.

• The Indian plate moving up north joined up with the Asian landmass.

Of all these the most dramatic event was the fusion of the Indian plate with the Asian continental mass. The force of this collision gave birth to the rise of the greatest mountain range in the world, the Himalayas. It was also this event that gave rise to a new climatic phenomenon, the monsoons. According to some geologists, the Indian plate is still moving northwards at a rate of something like 2 cm per year. Is this going to push the Himalayas and Everest still higher than it is now. Not likely. They suggest that the Indian plate is sliding under the continental mass and the result could be catastrophic earthquakes that could affect many densely populated areas from Kashmir to the Ganges delta.

Nor is this the final picture, the geologists tell us. Plate movements shall continue. Geologists predict a possible scenario for 50 million years from now which could include the following changes if not more.

• On the western side of North America, the California plate will break off from the mainland completely and stay as a long island.

• North and South America will again separate, replacing the man-made Panama Canal with a natural link between Pacific and Atlantic.

• Even the Suez will open up and give natural link between red sea and the Mediterranean.

• The great lakes of East Africa will join up and form a sea like the red sea, separating much of East Africa from the mainland.

• The Persian Gulf will disappear when Arabia joins up with Asia.

• Most of the landmass except the Antarctica will move further north.

• Atlantic and Indian Oceans will become larger at the expense of the Pacific.

These predictions for the future regarding the changes in the continental structure cannot in any way give any view of the distribution of life 50 million years from now, not even 5000 years from now.

Uniqueness of the Earth

Life, as we know it, cannot exist everywhere. Certain preconditions are necessary for its origin and survival. The earth and the solar system have met these conditions and that is one of the things that makes this part of the universe so unique. There are many facts that make the earth a very unique place. Let me try to get a general picture of this based on the most recent findings or conclusions of cosmologists.

Our galaxy itself is unique. There are many galaxies and globular clusters where life cannot exist in any part of them because of the nature of star distribution as well as the intensity of radiation levels in these. There could be other galaxies similar to ours. We are not sure of this. In our galaxy itself all parts are not ‘habitable’. The astronomers have charted a ring in the galaxy, which they call the ‘galactic habitable zone’. Sun happens to be in this ring. This is far from the centre of the galaxy but not quite at the edge. We are privileged to be in the residential area. Within the solar system also there is a ring of ‘habitable zone’. This includes only three planets – Venus, earth and mars. Any closer to the sun, and it will be too hot. Any farther from the sun and it will be too cold. And we know that our earth is at the centre of this residential area.

The presence of the very heavy elements like iodine, gold and uranium is quite an intriguing aspect unique to our solar system. Such heavy weights cannot be produced by the nuclear fusion processes that take place even in the largest of stars. These are manufactured during the collision of two neutron stars. Neutron star collisions are so rare and the fact that our star, the sun, was born in the area of the cosmos where this rare occurrence had taken place also makes our home a unique one. It is not just the luster of Gold or the fissibility of uranium that will be missing in most other planets of other solar systems but the presence of many elements like iodine that are necessary for life.

The speed and period of rotation and revolution of the earth, the tilt of the earth on its axis in the solar orbit, all these makes the days and nights, seasons and years as well as climatic conditions conducive to life on the planet. Imagine the earth always facing the sun with perpetual daylight for one half and everlasting night for the other half. Or imagine the same weather conditions all the 365 days of the year. How unbearable it all could be! The size of the planet is also significant. If it were much smaller or lighter there would have been no atmosphere. If it was much bigger or heavier the atmospheric pressure would have been too much and all undesirable gases would have been here. This is because gravity determines the escape velocity that decides whether the gases will fly away or stay. The earth is the right size. Not too large, not too small. Some other mysteries that surround our earth include the magnetic field, the ionosphere, the Van-Allen belt and the ozone layer. These are the protective shields that prevent harmful and lethal radiations from reaching the earth. These radiations could be detrimental to life or could have inhibited the origin of life.

The Mystery of Water

Every one knows that liquid water is essential for life. But we take for granted the various special properties that make it possible for water to remain in the liquid state forming our oceans. Its density, the boiling point and freezing point are all so ideal. But what is most mysterious is a property called the anomalous expansion. Every substance contracts on cooling and thus the density increases. Water also does so till it cools from 100 to 4 degree Celsius. On further cooling, instead of contracting the liquid expands causing a decrease in density. Thus water at 4 degree Celsius has a maximum density. When the water of the oceans or lakes cools down in winter the water at the bottom of the sea or lake will be at 4 degree. From the bottom to the surface there will be a temperature gradient from four to zero degrees. This allows the water to remain liquid at the bottom even when the surface is frozen. But for this unique property the densest water must be at zero degree and freezing will start at the bottom of the oceans and not at the top. This will cause the whole of the ocean, even if they are a few kilometers deep, to freeze in a very short time. Once this happens to thaw all his ice and to get the water back into the liquid form will almost be impossible.

Two other properties supplement this one property and allow the oceans to remain liquid at the bottom even during the worst of ice ages. One is the fact that water expands on freezing. This makes ice to float on the surface. Most other substances like iron expand on melting. In other words, usually the solid form is denser than the liquid form. If ice were denser than water the frozen ice would sink to the bottom and soon the whole body of water would be frozen. Yet another property is the poor conductivity of ice. This prevents the extreme cold of the atmosphere penetrating to the bottom layers. These three properties of water – the anomalous expansion, expansion on freezing and poor conductivity of ice – allow us to have water in the oceans even in the harshest of winters and prevents the oceans from freezing completely thereby destroying all the aquatic life. And life was purely marine for the first 3 billion years or so.

We do not know if there is life elsewhere in the universe or not. But when every fact is taken into account the probability of finding life anywhere else is rather very low. We are actually unique and can be happy and proud of it. I do not in any way imply that there is no life elsewhere. If there is life anywhere else in the universe is this going to affect my beliefs? Not at all. The fact that there are other places with life or intelligent life will in no way affect our belief in God. It is all the more reason to wonder at His ways.