Earth and Ozone hole

Ozone is an unstable molecule made up of three oxygen atoms (O3). It is found at two levels in the atmosphere. Near the ground  , it is toxic , notably for the respiratory tract and mucosa.This ozone is generated by pollution , mainly from motor vehicles. Ozone is also found at high altitude in the stratosphere.

Here , there is a "layer" some 20 to 25 km above the Earth , wich is formed through equilibrium between its formation and destruction under the effect of solar radiation, from temperature changes and from presence of other chemical substances. This layer protects us from some of the harmful rays of the sun , such as ultraviolet radiation.

When we talk about the hole in the ozone layer it is in this stratospheric ozone.The discover of a hole in the ozone layer goes back to the 1980s. It was in the Antartic that the first ground measurements of ozone levels produced some surprising results. As early as 1985 , Joseph Farman , from the British Antarctic Survey, published the results of his observations in Nture. A "hole" , or a drop in concentration , albeit temporary but very marked, appeared each spring in the stratospheric ozone layer above the Antartic. This phenomenon mainly occured in the lower stratosphere. What is the situation today ? The next year , his phenomenon was investigated by NASA , the American Space Agency. A report drawn up with the help of some hundred or so experts from all over the world suggested that stratospheric ozone concentration had fallen on average by 1.7 to 3% in the northern hemisphere between 1969 and 1986 , despite major annual variations.However , by the end of the 1980s , the scientific community had reached agreement about the cause of this depletion in both the Antarctic and Arctic regions : halogenated hydrocarbons, and particulary the notorious CFCs ( chlorofluorocarbons).

The Gulf Stream stopped ?

For most people , slowing or even stopping the Gulf Stream could only be a sci-fi story.This vast oceanic current on the surface of the Atlantic , wich runs from  the intertropical zone towards the shores of Europe (thus ensuring our mild winters and temperate summer) cannot simply "break down".

However , a reduction in its intensity , or even its coming to a complete halt , is not impossible.The climatic history of our planet shows this.The Gulf Stream has already seen some major disturbances to its "flow".Canadian , American and British researchers , whose work was partly funded by the European Union's 5th Framework Research Programme , reckon that over the past ten years , the global warming of our planet has modified the salinity of ots oceans , wich in turn may disturb the circulation of marine currents ( know as thermohaline circulation).

If the Gulf Stream malfunctions , then Europe , deprived of ots effects , will in turn lurch towards a new era of lower temperatures. In other word , winters in Lisabon may become as rigurous as those in New York. Fact or fiction ? The climatic history of our planet shows that such a development in the past - a considerable  influx of fresh water in the North Atlantic resulting from a massive offloading of ice from the American ice sheet - has already seen the Gulf Stream mechanism put "out of order".A question of salinity It is the increased evaporation of surface water in  temperate regions , generating a significant surplus of water vapour in the atmosphere and more precipitation of fresh water at higher  latitudes , that could be briging about  such a change in the salinity of the North Atlantic.

Mystery of Machu Picchu

It was in July, 1911, that we first entered that marvelous canyon of the Urubamba, where the river escapes from the cold regions near Cuzco by tearing its way through gigantic mountains of granite. From Torontoy to Colpani the road runs through a land of matchless charm. It has the majestic grandeur of the Canadian Rockies, as well as the startling beauty of the Nuuanu Pali near Honolulu, and the enchanting vistas of the Koolau Ditch Trail on Maul. In the variety of its charms and the power of its spell, I know of no place in the world which can compare with it.

Not only has it great snow peaks looming above the clouds more than two miles overhead; gigantic precipices of many-colored granite rising sheer for thousands of feet above the foaming, glistening, roaring rapids; it has also, in striking contrast, orchids and tree ferns, the delectable beauty of luxurious vegetation, and the mysterious witchery of the jungle. One is drawn irresistibly onward by ever-recurring surprises through a deep, winding gorge, turning and twisting past overhanging cliffs of incredible height. Above all, there is the fascination of finding here and there under the swaying vines, or perched on top of a beetling crag, the rugged masonry of a bygone race; and of trying to understand the bewildering romance of the ancient builders who ages ago sought refuge in a region which appears to have been expressly designed by Nature as a sanctuary for the oppressed, a place where they might fearlessly and patiently give expression to their passion for walls of enduring beauty. Space forbids any attempt to describe in detail the constantly changing panorama, the rank tropical foliage, the countless terraces, the towering cliffs, the glaciers peeping out between the clouds.

We had camped at a place near the river, called Mandor Pampa. Melchor Arteaga, proprietor of the neighboring farm, had told us of ruins at Machu Picchu.

The morning of July 24th dawned in a cold drizzle. Arteaga shivered and seemed inclined to stay in his hut. I offered to pay him well if he would show me the ruins. He demurred and said it was too hard a climb for such a wet day. When he found that we were willing to pay him a sol, three or four times the ordinary daily wage in this vicinity, he finally agreed to guide us to the ruins. No one supposed that they would be particularly interesting. Accompanied by Sergeant Carrasco I left camp at ten o'clock and went some distance upstream. On the road we passed a venomous snake which recently had been killed. This region has an unpleasant notoriety for being the favorite haunt of “vipers.” The lance-headed or yellow viper, commonly known as the fer-de-lance, a very venomous serpent capable of making considerable springs when in pursuit of its prey, is common hereabouts. Later two of our mules died from snake-bite.
After a walk of three quarters of an hour the guide left the main road and plunged down through the jungle to the bank of the river. Here there was a primitive “bridge” which crossed the roaring rapids at its narrowest part, where the stream was forced to flow between two great boulders. The bridge was made of half a dozen very slender logs, some of which were not long enough to span the distance between the boulders. They had been spliced and lashed together with vines. Arteaga and Carrasco took off their shoes and crept gingerly across, using their somewhat prehensile toes to keep from slipping. It was obvious that no one could have lived for an instant in the rapids, but would immediately have been dashed to pieces against granite boulders. I am frank to confess that I got down on hands and knees and crawled across, six inches at a time. Even after we reached the other side I could not help wondering what would happen to the “bridge” if a particularly heavy shower should fall in the valley above. A light rain had fallen during the night. The river had risen so that the bridge was already threatened by the foaming rapids. It would not take much more rain to wash away the bridge entirely. If this should happen during the day it might be very awkward. As a matter of fact, it did happen a few days later and the next explorers to attempt to cross the river at this point found only one slender log remaining.

Taj Mahal - Indian beauty

Agra, once the capital of the Mughal Empire during the 16th and early 18th centuries, is one and a half hours by express train from New Delhi. Tourists from all over the world visit Agra not to see the ruins of the red sandstone fortress built by the Mughal emperors but to make a pilgrimage to Taj Mahal, India’s most famous architectural wonder, in a land where magnificent temples and edificies abound to remind visitors about the rich civilization of a country that is slowly but surely lifting itself into an industrialized society.

The postcard picture of Taj Mahal does not adequately convey the legend, the poetry and the romance that shroud what Rabindranath Tagore calls "a teardrop on the cheek of time". Taj Mahal means "Crown Palace" and is in fact the most well preserved and architecturally beautiful tomb in the world. It is best described by the English poet, Sir Edwin Arnold, as "Not a piece of architecture, as other buildings are, but the proud passions of an emperor’s love wrought in living stones." It is a celebration of woman built in marble and that’s the way to appreciate it.

Mumtaz MahalShah JahanTaj Mahal stands on the bank of River Yamuna, which otherwise serves as a wide moat defending the Great Red Fort of Agra, the center of the Mughal emperors until they moved their capital to Delhi in 1637. It was built by the fifth Mughal emperor, Shah Jahan in 1631 in memory of his second wife, Mumtaz Mahal, a Muslim Persian princess. She died while accompanying her husband in Burhanpur in a campaign to crush a rebellion after giving birth to their 14th child. The death so crushed the emperor that all his hair and beard were said to have grown snow white in a few months.

About Oceanography

The science of the sea; including physical oceanography (the study of the physical properties of sea water and its motion in waves, tides, and currents), marine chemistry, marine geology, and marine biology. The need to know more about the impact of marine pollution and possible effects of the exploitation of marine resources, together with the role of the ocean in possible global warming and climate change, means that oceanography is an important scientific discipline.

Improved understanding of the sea has been essential in such diverse fields as fisheries conservation, the exploitation of underwater oil and gas reserves, and coastal protection policy, as well as in national defense strategies. The scientific benefits include not only improved understanding of the oceans and their inhabitants, but important information about the evolution of the Earth and its tectonic processes, and about the global environment and climate, past and present, as well as possible future changes.
The modern discipline. The traditional basis of modern oceanography is the hydrographic station. Hydrographic studies are still carried out at regular intervals, with the research vessel in a specific position. Seawater temperature, depth, and salinity can be measured continuously by a probe towed behind the ship.

The revolution in electronics has provided not only a new generation of instruments for studying the sea but also new ways of collecting and analyzing the data they produce. Computers are employed in gathering and processing data in all fields, and are also used in the creation of mathematical models to aid in understanding. Much information can also be gained by remote sensing using satellites, which are also a valuable navigational aid. These provide data on sea surface temperature and currents, and on marine productivity. Satellite altimetry gives information on wave height and winds and even bottom topography (because this affects sea level). Scientists look forward to a day when observations can be made in the deep sea by autonomous vehicles. However, the ship remains a fundamental tool for many observations.

Physical oceanography. Physical oceanography, and in particular ocean circulation studies, forms the core of oceanographic research. The movements of seawater—ocean currents—are powerful agents in the distribution of heat throughout the world, influencing both weather and climate. The continual renewal of water bearing dissolved nutrients is essential to most marine organisms, which will be abundant only where such supplies are available.
Twentieth-century dynamical oceanographers have shown how the deflecting effect of the Earth's rotation influences water movements. Geostrophic forces are responsible for the intensification of surface currents, such as the Gulf Stream, on the western sides of oceans (western boundary currents).

In the 1950s the existence of a southward-flowing counter current under the Gulf Stream was predicted. Neutrally buoyant floats, to be tracked by radio signals picked up by hydrophones on board ship, were deployed to confirm this prediction. However, further out in the Atlantic the floats moved unexpectedly fast, with frequent changes in direction. This was the first indication of vigorous eddies in the ocean that have since been shown to be comparable to atmospheric weather systems. Further investigations of these phenomena, studies of equatorial currents and undercurrents, and transport between oceans are the principal topics occupying physical oceanographers in the latter part of the twentieth century. The World Ocean Circulation Experiment, a large-scale international program of cooperation on research projects and data-collecting expeditions, was designed to throw further light on the ocean's influence on world climate. Among the techniques being employed are the use of Swallow floats, arrays of current meters, that can be moored to the sea bed for a period of time to measure deep-water movements and then released for retrieval by acoustic signals, and the use of geochemical tracers, including chlorofluorocarbons, to obtain data on the distribution and age of water masses.

Marine biology. Biologists seek to classify the great diversity of life, from microscopic bacteria and phytoplankton to the great whales. To learn how the food web operates, they must examine the constraints on marine productivity and the distribution of species in the surface and mid water layers, and the vertical migrations between them, and in the bottom-living (benthic) fauna. Deep-sea cameras and submersibles now permit visual evidence of creatures in these remote depths to be obtained. Marine geology. Since the early 1900s, all recorded ocean depths have been incorporated in the General Bathymetric Chart of the Ocean. The amount of data available increased greatly with the introduction of continuous echo sounders; subsequently, side-scan sonar permitted very detailed topographical surveys to be made of the ocean floor. The features thus revealed, in particular the mid ocean ridges (spreading centers) and deep trenches (subduction zones), are integral to the theory of plate tectonics. An important discovery made toward the end of the twentieth century was the existence of hydrothermal vents, where hot mineral-rich water gushes from the Earth's interior. The deposition of minerals at these sites and the discovery of associated ecosystems make them of potential economic as well as great scientific interest. Possibly life on Earth began in similar situations in the remote past. Investigation of such areas can be made directly by scientists using submersibles and by underwater cameras, as well as by instrumentation. Even the sediments and other rocks of the sea floor are being sampled by the international deep-sea drilling program to provide information on how the present oceans evolved and on past climate change.
Reference : McGraw - Hill Encyclopedia of Science and Technology

Volcanoes - Silent killer

A volcano is an opening in the Earth's crust through which molten lava, ash, and gases erupt. In many cases, lava and ash form a mountain around the opening.

It used to be thought that volcanoes leaked molten rock and gases directly from the Earth's core. That is not the case. As hot, solid rock rises in the mantle, the pressure drops and a small part of the rock begins to melt. This liquefied rock, called magma, is less dense than solid rock. It squeezes out from the solid like water from a sponge. The rising magma creates wide channels in the crust as it forces its way to the surface. When it breaks through the surface, the pressure drops. Gases dissolved in the magma force it to erupt through the opening as lava.

TYPES OF VOLCANOES

The behavior of a volcano depends on the type of magma that fuels it. Volcanoes such as those near Hawaii and Iceland are sitting on top of a rising plume of hot mantle rock, called a hot spot. The lava that erupts from these volcanoes comes from great depths, sometimes more than 90 mi. (150km) into the mantle. Its

composition is not the same as the mantle, because only a tiny fraction of the mantle rock melts. This lava is runny when molten and sets as dense, black basalt. Because the lava is so runny, it can pour out through fissures at vast rates and flow across the land at speeds of up to 31 mph (50kph). Where this type of volcano erupts underwater, the lava cools quickly and

builds volcanic islands as it sets. Where gas bubbles through it, the runny lava erupts in spectacular fountains. Because this type of lava flows freely, eruptions are smooth rather than explosive.
A different type of volcano is found where ocean crust dives under the edge of a continent. The ocean crust partly melts to form a sticky lava that is rich in silica and contains some water. During an eruption, the sudden drop in pressure causes the water to turn to steam. This results in an explosion of fine ash and hot gases. This mixture, which can race down the sides of a volcano at 125 mph (200kph), is called a nuée ardente, French for "glowing avalanche."

LIVING WITH VOLCANOES

With their combinations of red-hot lava, toxic gases, and suffocating ash. volcanic eruptions can be deadly phenomena. But people continue to live on the sides of volcanoes despite the danger. This is because volcanic soil is often fertile, and eruptions can be few and far between, giving a false sense of security. The consequences can be disastrous. In 1902, when Mount Pelee on the Caribbean island of Martinique erupted, a nuee ardente raced down the mountain and engulfed the port of San Pierre- More than 29,000 people were killed. The only survivor was a prisoner in an underground cell. In A.D. 79, a similar eruption from Mount Vesuvius smothered the Roman towns of Boscoreale, Herculaneum, Pompeii, and Stabiae with mud and ash.

It is possible to predict at least some eruptions by monitoring volcanic gases and measuring changes in gravity as molten lava rises inside a volcano Sometimes, the whole mountain bulges. When Mount St. Helens, in Washington, started to bulge in 1980, most people were evacuated before the mountain blew its top. A huge landslide removed part of the volcano, exposing the pressurized molten lava. The lava then exploded sideways and upward. The blast hurled about half a cubic mile of rock into the air and flattened trees up to 19 mi. (30km) away.
Reference : The Kingfisher Science Encyclopedia De Charles Taylor