How DO Cyclone Form??????

Mechanism of a Tropical Cyclone Formation :-

Cyclones are large revolving tropical storms caused by winds blowing around a central area of low atmospheric pressure. In the southern hemisphere these tropical storms are called cyclones and rotate in a clockwise direction, while in the northern hemisphere cyclones are called hurricanes or typhoons and rotate in an anti-clockwise direction.
Cyclones develop over warm waters in the tropical regions of the oceans where areas of very low pressure are created by air being heated by the sun. This causes the air to rise very rapidly and becomes saturated with moisture that condenses into large thunderclouds.

Cool air rushes in to fill the void and is bent inwards and spirals upwards with a great force caused by the coriolis effect of the earth spinning on its axis. The result of all this is – the winds begin to rotate faster and form a large rotating weather system, in some cases up to several thousand km in diameter

Wind Power

Wind Power – ‘When Nature Gets Angry’ – The Worst Natural Disasters Caused By Wind ----This is a visualized report about the worst wind disasters in the world, the Power of Windand the disastrous destruction a major wind storm can cause.
Wind disasters have an affect on the world’s billions of people and more than often, when disaster strikes, it hits the poorest of the poor

You are in a city or town hit by a cyclone, typhoon or hurricane. The first breeze – the ones that make the trees bend – arrives quite slowly but increases in intensity either in a matter of hours or days.
In the sophisticated western world, warnings and forecasts are published early and all affected will know what is to be expected and can make precautious arrangements, yet in remoter, poor and rural areas in Asia lets say, there are no such communication facilities and residents are left to their own devices.
…and then the full force of nature strikes home to devastating affect. Full scaled Hurricanes, Typhoons, Cyclones ravage across your land and takes everything with it which is in its way.

How Do Diamonds Form?

How Do Diamonds Form?

Contrary to what many people believe, most diamonds do not form from coal.
Methods of Diamond Formation


Many people believe that diamonds are formed from the metamorphism of coal. That idea continues to be the "how diamonds form" story in many science classrooms.

Coal has rarely played a role in the formation of diamonds. In fact, most diamonds that have been dated are much older than Earth's first land plants - the source material of coal! That alone should be enough evidence to shut down the idea that Earth's diamond deposits were formed from coal.

Another problem with the idea is that coal seams are sedimentary rocks that usually occur as horizontal or nearly horizontal rock units. However, the source rocks of diamonds are vertical pipes filled with igneous rocks.

Four processes are thought to be responsible for virtually all of the natural diamonds that have been found at or near Earth's surface. One of these processes accounts for nearly 100% of all diamonds that have ever been mined. The remaining three are insignificant sources of commercial diamonds.

These processes rarely involve coal.


1) Diamond Formation in Earth's Mantle


Geologists believe that the diamonds in all of Earth's commercial diamond deposits were formed in the mantle and delivered to the surface by deep-source volcanic eruptions. These eruptions produce the kimberlite and lamproite pipes that are sought after by diamond prospectors. Diamonds weathered and eroded from these eruptive deposits are now contained in the sedimentary (placer) deposits of streams and coastlines.

The formation of natural diamonds requires very high temperatures and pressures. These conditions occur in limited zones of Earth's mantle about 90 miles (150 kilometers) below the surface where temperatures are at least 2000 degrees Fahrenheit (1050 degrees Celsius) (1). This critical temperature-pressure environment for diamond formation and stability is not present globally. Instead it is thought to be present primarily in the mantle beneath the stable interiors of continental plates (2).
Diamonds formed and stored in these "diamond stability zones" are delivered to Earth's surface during deep-source volcanic eruptions. These eruptions tear out pieces of the mantle and carry them rapidly to the surface (3), See Location 1 in the diagrams above and at right. This type of volcanic eruption is extremely rare and has not occurred since scientists have been able to recognize them.

Is coal involved? Coal is a sedimentary rock, formed from plant debris deposited at Earth's surface. It is rarely buried to depths greater than two miles (3.2 kilometers). It is very unlikely that coal has been moved from the crust down to a depth well below the base of a continental plate. The carbon source for these mantle diamonds is most likely carbon trapped in Earth's interior at the time of the planet's formation.


2) Diamond Formation in Subduction Zones


Tiny diamonds have been found in rocks that are thought to have been subducted deep into the mantle by plate tectonic processes - then returned to the surface (4). (See Location 2 in the diagrams above and at right.) Diamond formation in a subducting plate might occur as little as 50 miles (80 kilometers) below the surface and at temperatures as low as 390 degrees Fahrenheit (200 degrees Centigrade) (1). In another study, diamonds from Brazil were found to contain tiny mineral inclusions consistent with the mineralogy of oceanic crust. (8)

Is coal involved? Coal is a possible carbon source for this diamond-forming process. However, oceanic plates are more likely candidates for subduction than continental plates because of their higher density. The most likely carbon sources from the subduction of an oceanic plate are carbonate rocks such as limestone, marble and dolomite and possibly particles of plant debris in offshore sediments.


3) Diamond Formation at Impact Sites
Throughout its history, Earth has been repeatedly hit by large asteroids. When these asteroids strike the earth extreme temperatures and pressures are produced. For example: when a six mile (10 kilometer) wide asteroid strikes the earth, it can be traveling at up to 9 to 12 miles per second (15 to 20 kilometers per second). Upon impact this hypervelocity object would produce an energy burst equivalent to millions of nuclear weapons and temperatures hotter than the sun's surface (5).

The high temperature and pressure conditions of such an impact are more than adequate to form diamonds. This theory of diamond formation has been supported by the discovery of tiny diamonds around several asteroid impact sites. See Location 3 in the diagrams above and at right.

Tiny, sub-millimeter diamonds have been found at Meteor Crater in Arizona. Polycrystalline industrial diamonds up to 13 millimeters in size have been mined at the Popigai Crater in northern Siberia, Russia. [7]

Is coal involved? Coal could be present in the target area of these impacts and could serve as the carbon source of the diamonds. Limestones, marbles, dolomites and other carbon-bearing rocks are also potential carbon sources.


4) Formation in Space
NASA researchers have detected large numbers of nanodiamonds in some meteorites (nanodiamonds are diamonds that are a few nanometers - billionths of a meter in diameter). About three percent of the carbon in these meteorites is contained in the form of nanodiamonds. These diamonds are too small for use as gems or industrial abrasives, however, they are a source of diamond material (6), See Location 4 in the diagrams above and at right.

Smithsonian researchers also found large numbers of tiny diamonds when they were cutting a sample from the Allen Hills meteorite (7). These diamonds in meteorites are thought to have formed in space through high speed collisions similar to how diamonds form on Earth at impact sites.

Is coal involved? Coal is not involved in the creation of these diamonds. The carbon source is from a body other than Earth.


The Most Convincing Evidence
The most convincing evidence that coal did not play a role in the formation of most diamonds is a comparison between the age of Earth's diamonds and the age of the earliest land plants.

Almost every diamond that has been dated formed during the Precambrian Eon - the span of time between Earth's formation (about 4,600 million years ago) and the start of the Cambrian Period (about 542 million years ago). In contrast, the earliest land plants did not appear on Earth until about 450 million years ago - nearly 100 million years after the formation of virtually all of Earth's natural diamonds.

Since coal is formed from terrestrial plant debris and the oldest land plants are younger than almost every diamond that has ever been dated, it is easy to conclude that coal did not play a significant role in the formation of Earth's diamonds.

Novarupta : The Most Powerful Volcanic Eruption of the 20th Century.

Novarupta

The Most Powerful Volcanic Eruption of the 20th Century.
June 6th, 1912
People in Juneau, Alaska, about 750 miles from the volcano, heard the sound of the blast – over one hour after it occurred.
The morning of June 6th arrived on the Alaska peninsula to find the area which is now Katmai National Monument being shaken by numerous strong, shallow earthquakes. The most powerful volcanic eruption of the 20th Century was about to begin – but very few people knew about it. The Alaska peninsula has a low population density today, but in 1912 it was even lower. Beyond the land shaken by the earthquake activity, the beginnings of this event were almost unnoticed.
Volcanic Monitoring - 1912 vs. Today


Today the stirring of an important volcano draws enormous global attention. Weeks or even months before most large eruptions, a buzz circulates through an electronically-connected community of volcano scientists as clusters of small earthquakes are detected by a global array of seismographs. Many scientists working at diverse global locations interpret this data and begin to collaborate about an awakening volcano and the eruption that might follow. Reports are posted on the internet and news stories communicate the volcano's activity to millions of people. Often it is a false alarm – the volcano is simply stirring.

If the earthquakes strengthen and begin moving upwards, many of these scientists will travel to the area of potential eruption to make observations and set up a local network of data-gathering instruments.

However, in 1912, Alaska was not a US state, very few scientists were supported to do volcanic studies and a worldwide network of seismic monitoring was not in place. Scientists were just starting to understand the mechanics of volcanic eruptions.
Impact of the Eruption


Forty years after the eruption, investigators finally realized that Novarupta - and not Katmai - was the source of the tremendous blast.
The inhabitants of Kodiak, Alaska, on Kodiak Island, about 100 miles away, were among the first people to realize the severity of this eruption. The noise from the blast would have commanded their attention and the visual impact of seeing an ash cloud rise quickly to an elevation of 20 miles then drift towards them would have been terrifying.

Within just a few hours after the eruption a thick blanket of ash began falling upon the town - and ash continued falling for the next three days, covering the town up to one foot deep. The residents of Kodiak were forced to take shelter indoors. Many buildings collapsed from the weight of heavy ash on their roofs.

Outside, the ash made breathing difficult, stuck to moist eyes and completely blocked the light of the sun at midday. Any animal or person who was caught outside probably died from suffocation, blindness or an inability to find food and water.


Pyroclastic Flow


Back on the peninsula, heavy pyroclastic flows swept over 20 kilometers down the valley of Knife Creek and the upper Ukak River. (A pyroclastic flow is a mixture of superheated gas, dust, and ash that is heavier than the surrounding air and flows down the flank of the volcano with great speed and force.)

These flows completely filled the valley of Knife Creek with ash, converting it from a V-shaped valley into a broad flat plain. By the time the eruption was over, the world’s most extensive historic ignimbrite (solidified pyroclastic flow deposit) would be formed. It covered a surface area of over 120 square kilometers to depths of over 200 meters thick near its source. (The satellite image at right shows the original geographic extent of pyroclastic flow deposits as a yellow line.)


Volcanic Ash


Immediately after the June 6th blast, an ash cloud rose to an elevation of about 20 miles. It was then carried by the wind in a westerly direction, dropping ash as it moved. The ash deposits were thickest near the source of the eruption and decreased in thickness downwind. (The satellite image above/right has red contour lines showing the thickness of the ash deposits in the area of the eruption. Measurable thickness of ash fell hundreds of miles beyond the one meter contour line.)

When the eruption stopped on June 9th, the ash cloud had spread across southern Alaska, most of western Canada and several U.S. states. Winds then carried it across North America. It reached Africa on June 17th.

Although the eruption had these far-reaching effects, most people outside of Alaska did not know that a volcano had erupted. More surprising is that no one knew for sure which of the many volcanoes on the Alaska peninsula was responsible. Most assumed that Mount Katmai had erupted but they were wrong.

What Can We Do About It?


People can not prevent this type of eruption. They can assess the potential impact, develop with the possibility of loss in mind, plan a response, educate the public and key decision makers, and monitor the region where it might occur.

The more you know about a natural hazard, the greater your chances of avoiding injury or loss. We are lucky to have this record of the past.