December 31, 2009

Circumhorizontal Arc

circumhorizontal arc

Circumhorizontal Arc
, (sometimes known as Fire Rainbow for its flame-like appearance) is the rarest of all naturally occurring atmospheric wonder. It is an optical phenomenon, an ice-halo formed by plate shaped ice crystals in high level cirrus clouds.

For a circumhorizon arc to be visible, the sun must be at least 58 degrees high in a sky. Cirrus clouds containing relatively large plate shaped ice crystals must also be pCircumhorizontal Arc - Fire Rainbowresent. The arc is produced by this plate oriented crystals. Sunlight enters a near vertical side face and leaves via the lower near horizontal face (check the source for diagram). The refraction of the almost parallel solar rays through faces inclined at 90 degree produces the pure, bright and well separated prismatic colors. The colors are purer than those of the rainbow.


November 20, 2009

Grand Canyon

Grand canyon

"Grand" does not tell how truly incomprehensible this canyon is. Most people use such words as "marvelous" or "fantastic" but no word is really adequate to describe this amazing wonder of nature. The scene continually changes as light plays off the rocks and clouds, creating shadows and contrasts. The world seems larger here with sunrises, sunsets, and storms taking on an added dimension to match the landscape. The permutations are unceasing, and the moods are without end. This is a land to humble the soul.

Grand Canyon is in the northwest corner of Arizona, close to the borders of Utah and Nevada. The Colorado River, which flows through the canyon, drains water from seven states, but the feature we know as Grand Canyon is entirely in Arizona. Most of Grand Canyon lies within Grand Canyon National Park and is managed by the National Park Service. It was first protected in 1893 as a forest reserve in which mining, hunting and lumbering were permitted; upgraded to a game reserve in 1906, giving protection to the wildlife; and declared a national park on 26 Feb 1919 by Act of Congress. The climate at Grand Canyon is classified as semi-arid (south rim receives 15 inches of precipitation each year, only 8 inches each year reaches the canyon bottom). Many people consider Grand Canyon National Park the world’s premiere geologic landscape and a "geologic wonder". Grand Canyon contains many important geologic resources, including a vast fossil record ranging from Precambrian stromatolites to Ice Age mammal bones and dung found in caves; a potentially active volcanic field in the western Grand Canyon; a geologic history ranging more than 1.7 billion years; and the canyon landscape itself as the greatest example of arid land erosion. Grand Canyon owes its unique shape to the fact that the different rock layers in the canyon walls each respond to erosion in different ways: some form slopes, some form cliffs, some erode more quickly than others. The vivid colors of many of these layers are mainly due to small amount of various minerals, most containing iron, which impart subtle shades of red, yellow or green to the canyon walls. Climate plays an important role, too. If the climate at Grand Canyon were wetter, the planes and trees that grow there would be very different, and the canyon walls might be covered with lush vegetation.

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August 5, 2009

Mariana Trench

Mariana TrenchMariana Trench - It is the deepest part of the earth's ocean and the deepest location of the earth itself. Mariana Trench is located in the Pacific ocean, just east of the 14 Mariana Islands near Japan. The trench is about 1580 miles long with the mean width of only 43 miles. It reaches a maximum depth of about 10,924 meters at the Challenger Deep, a small slot-shaped valley in its floor, at its southern end.

Mariana TrenchMariana Trench was created by ocean-to-ocean subduction, a phenomena in which a plate topped by oceanic crust is subducted beneath another plate topped by oceanic crust. The deepest part of the Mariana Trench is the Challenger Deep, so named after the British exploration vessel HMS Challenger II. So how come the Challenger Deep is so deep? - Well, the earth's crust is not one solid piece of rock, its really pretty thin. In fact its made up of huge plates of thin crust that float on the molten rock of the earth's mantle. While floating around the mantle the edges of these plates slide past each other, bump into each other and sometimes even crash. The oceanic crust is much heavier than the continental crust so when the plates crash into each other, the oceanic plate plunges downward toward the molten mantle, while the lighter continental plate rides up over the top. The forces driving the two plates are really intense so the underlying oceanic plate creates a trench where it drags the edge of the continental crust down as it descends underneath. This is what is happening on the bottom of the Pacific ocean off the Marianas Islands.

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June 12, 2009

Great Blue Hole

Great Blue Hole
Great Blue Hole - A feature attraction of Diving, lies approximately 60 miles off the mainland out of Belize City, Central America. It is one of the astounding dive sites to be found anywhere on earth and an amazing natural wonders of the world. Its a part of the Lighthouse Reef System, and right in its center is a large, almost perfectly a circular hole approximately one quarter of a mile across. Inside the hole the water is 480 feet deep and it is the dept of water which gives the deep blue color. Hence the name Blue Hole. The blue hole is a perfectly circular limestone sinkhole more than 300 feet across and 412 feet deep. The array of bizarre stalactites and limestone formation which mould its inner wall seems to become more intricate and intense the deeper one dives. The hole is surrounded by circular reefs, that stretches for about 1000 feet and provide an ideal habitat for corals to attach and flourish. The hole itself is the opening to a system of caves and passageway that penetrate this undersea mountain. In various places, massive limestone stalactites hang down from what was once the ceiling of air filled caves before the end of the last Ice age. When the ice melted the sea level rose, flooding the caves.
Little light reaches the depths of the hole and water does not circulate freely. As a result the deeper areas inside the blue hole dont have the profusion of life associated with most drop-offs.

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May 15, 2009

Coral Reefs

coral reef
Corals are extremely ancient animals that evolved into modern reef building forms over the last 25 million years.
Corals are anthozoans, the largest class of organism within the phylum cnidaria. Stony corals make up the largest order of anthozoans, and are the group primarily responsible for laying the foundation of, and building up the reef structures. Stony corals are colonial organisms composed of hundreds to hundreds of thousands of individual, called polyps. The massive reef structures are formed when each stony coral pholyp secrets a skeleton of calcium carbonate. Although all corals secretes calcium carbonate, not all are reef builders.
Colonies of reef building corals exhibit a wide range of shapes but most can be classified within ten genral forms. They are 1. Branching corals 2. Digitate corals 3. Table corals 4. Elkhorn coral 5. Foliose corals 6. Encrusting corals 7. Submassive corals 8. Massive corals 9. Mushroom corals 10. Cup corals.
Coral Reefs grow optimally in water temperatures between 23 degree and 29 degree centigrade, but some can tolerate temperatures as high as 40 degree centigrade for a limited period of time. Most require very salty water ranging from 32 to 42 parts per thousand. The water must also be clear to permit high light penetration. Hence the number of species of corals on a reef declines rapidly in the deeper water.

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February 27, 2009

Dead Sea

Dead Sea 

 The Dead sea, one of the most spectacular natural and spiritual landscape is a salt lake between Israel and Jordan. It is almost six times as salty as ocean and hence nothing lives in it. The Dead Sea is completely landlocked and it gets saltier with increasing depth. Down to about 40 meters, the seawater comprises about 300 grams of salt per kilogram of seawater. That is about 8.6 times saltier than ocean. This salinity makes for a harsh environment where animals cannot survive. Fish accidentally swimming into the sea are killed instantly, their bodies are quickly coated with a preserving layer of salt crystals and are tossed onto shore by wind and waves. As well as there is no seaweed or plants of any kind in and around the water.
The shores of the sea is covered with white crystal of salts. The salts found in the Dead Sea are mineral salts, just like you find in the oceans of the world, only in extreme concentrations. There are more than 35 different types of mineral that are essential for the health and care of the body skin including Magnesium, Calcium, Potassium, Bromine, Sulfur, and Iodine. They are well known for relieving pains and sufferings caused by arthritis, rheumatism, psoriasis, eczema, headache and foot-ache, while nourishing and softening the skin. Because of the extremely high concentration of dissolved mineral salts in the water its density is more than that of plain fresh water. And human bodies are more buoyant in dead sea (which actually makes very tough to swim), so you bob like a cork.
It is 422 meters below the sea level and its shores are the lowest point on the surface of the earth. Scientist figure that the Dead Sea lowers by as much as 13 inches per year.