Wednesday, December 31, 2008

Extinct dinosaurs

Dinosaurs are animals that lived on earth several million years ago. They lived during the mesozoic era which is also known the age of dinosaurs. Some are herbivores while others ate flesh of other dinosaurs. But the question is how did they become extinct?

About 65 million years ago, at the end of Cretaceous period, all the dinosaurs had become extinct. There are many theories about the extinction of dinosaurs. It is believed that a massive asteroid may have crashed into the earth. This caused an enormous explosion that formed a huge cloud of dust.This blocked the sun's rays. Because of it the temperature got lowered and the plants died. The herbivores that fed on them also died. The carnivore have fed on there flesh but they may have also perished.

There is also another theory that a massive volcano that erupted, blasting lava into the atmosphere. These theories where developed from the layer of iridium in late cretaceous period. This metal is only present in the core of earth and in asteroids. Hence the theories.

But the disappearance of the dinosaurs gave an opportunity for mammals to became dominant on land and for the birds to rule the air supreme.

Remains of dinosaurs were first discovered in England in the 1820. Then they where discovered in many parts of the world.The name dinosaur was suggested by Richard Owen which means terrible reptiles!!!!

Wednesday, December 24, 2008

What causes Hail?

One of the unusual weather conditions we can experience is a hailstorm. It is quite a thing to see and hear hailstones coming down, sometimes with such force that great damage is done. Animals, and even men, have been killed by hail!

A hailstorm usually occurs during the warm weather and is accompanied in many cases by thunder, lightning and rain. Hail is formed when raindrops freeze while passing through a belt of cold air on their way to earth.

Hailstorm lashes Lismore

Single raindrops form very small hailstones. It is interesting to note when a raindrop falls as a hailstone, it may meet with a strong rising current of air. so, it is carried up again to the level where the raindrops are falling. New drops begin to cling to the hailstone. And as it falls once more through the cold belt, these new drops spread into a layer around it and freeze, and now we have larger hailstones.

Hailstones, in size of a tennis-ball

This rising and falling of the hailstone may be repeated time after time until it has added so many layers that its weight is heavy enough to overcome the force of the rising current of air. Now it falls to the ground.

A field littered with large hailstones right after a summer hailstorm.

Hailstones measuring three or four inches in diameter and weighing as much as a pound are sometimes built up. Snow too freezes around hailstones when they are carried into regions where it is forming. Thus, the hailstones are frequently made up of layers of ice and snow.

Largest Hailstone ever measured (17.8 cm in diameter and a 47.6 cm in circumference)

Hailstorm in Bogota, Colombia

On 20 April 1888 in Moradabad, India, 246 people (along with more than 1,600 sheep and goats) were killed by hailstones, some as big as cricket balls. Hailstones can be a dangerous hazard, especially if they get very large. They can do tremendous damage to property and have even been know to kill cattle!

A larger hailstone has broken the win shield

Friday, December 19, 2008

Stalactites and Stalagmites

A stalactite or dripstone, is a type of speleothem that hangs from the ceiling or wall of limestone caves.

Stalactites come in a variety of forms, some of which have their own classification, such as deflected stalactites. Another much rarer form is the elephant's foot stalactite, which is flat, rather than pointed, on the bottom. An image of these is in the lower table, second image from the left

Stalactites appear in many caves or caverns. The Carlsbad Caverns in New Mexico, is made up of limestone, which is a fairly soft rock that can be dissolved by a weak acid. The acid that dissolves limestone comes from the rainwater. These raindrops combine with the carbondioxide from the air and the soil, and thus changes into carbonic acid.

About one million years ago, the rainwater dripped into the ceiling of the caves, they formed, tiny rings of lime, which crystallized in the ceiling. As time passed, these rings of lime formed a little stone "icicle". It kept on growing. As the time passed, thousands of drops fell on the same spot. The specks of lime formed, looked like a stubby stone candle. The "candle" kept on growing.

The icicle of stone on the ceiling is called a stalactite. The stubby candle on the floor is a stalagmite. Each stalactite and stalagmite grows at a different rate, depending on the wetness of the cave, the temperature of the room, and the thickness of the limestone bed above it.

Stalagmites take on a variety of forms, from tall, spindly "broomsticks" to ornate, multi-tiered towers.

Shape is determined largely by drip rate, ceiling height, cave atmosphere conditions, and the carbonate chemistry of the drip water solution.

Ice Stalagmites

Thursday, December 11, 2008

Mumbai Terror Attack

The Mumbai Terror attack on November 2008 were a series of coordinated terrorists attack across Mumbai, the financial capital of India. The attacks were carried over by the armed men using automated weapons and grenades. The attacks started on 26 November and ended on 29 November, when the Indian security forces, in Operation Black Tornado, brought under control all the attack sites.

Locations of the attack

More than eight attacks took place in the site of South Mumbai: the Chhatrapati Sivaji Terminus, the Oberoi Trident, the TajMahal Palace and Tower, Leopold Cafe, Cama Hospital, the Jewish centre Nariman House, the Metro Cinema, and the lane behind the Times of India Building behind St. Xavier's College. There were also explosions heard around the Mumbai's port area and a taxi blast at Vile Parle.

The attackers traveled by sea from Karachi, Pakistan, across the Arabian Sea to Mumbai. They entered via speed boats that were on board trawlers. The trawlers left Pakistan and stopped at Porbandar, India, before landing in Mumbai.

Some people trapped in the hotels were forced to climb down using curtains or jump to safety.

Mumbai's main railway station was also hit. People fled the huge terminus leaving their luggage when gunmen opened fire.

Security forces managed to free some people from the hotels, but the stand-off continued throughout the day. The attacks were condemned by governments around the world, including the US and UK, whose citizens were among those apparently targeted by the gunmen.

Relatives of victims of the attacks grieved as they waited to pick up bodies from a hospital.

The ten attackers and their home towns in Pakistan have been identified by Mumbai police: Ajmal Amir from Fardikot, Ismail Khan from Dera Ismail Khan, Hafiz Arshad and Babr Imran from Multan, Javed from Okara, Shoaib from Narowal, Nazih and Nasr from Faisalabad, Abdul Rahman from Arifwalla, and Fahad Ullah from Dipalpur Taluka, Ismail Khan is in the North West Frontier Province, the rest of the towns are in Pakistani Punjab.

Ajmal Amir is the only gunman captured alive by police and is currently in Indian custody.

Wednesday, December 10, 2008

Mount Everest

People used to think that Kangchenjunga was the world's highest mountains. Then, in 1852, the Great Trigonometrical Survey, of India, was completed, which measured all the countries land features. The Survey showed that Mount Everest(then called Peak XV) was the world's highest mountain. The mountains name was suggested in 1865, as a tribute to the Surveyor General of India at that time, that is, Sir George Everest, who led the Survey.

The height of Mount Everest reckoned to be 8840 metre, which has since been adjusted as improved measuring methods have been used.

Mt. Everest is a part of the Great Himalayan Range, and forms a natural border, between China and Nepal. It is believed that the mountain rises its height 4 metre every year.

The mountain range is young-fold mountain range. It is formed when the Eurasian and Indian techtonic plates collided 30 to 50 million years ago.

Mount Everest is also called as a Mountain of Junk. The people and their teams who have climbed Mt. Everest have dropped more than 50 tonnes of rubbish. In 2001, local guides collected more than 6 tonnes of paper bags, tents, ropes, clothes, aluminium ladders, batteries, oxygen bottles and plastic cans. Nepal, now charges 3,000 euros deposit which is returned only if they remove all their rubbish.

Hillary, Sir Edmund Percival, mountain climber and Antarctic explorer, who, with the Nepalese Sherpa Tenzing Norkay, was the first to reach the summit of Mount, the world’s highest peak.

Mount Everest is Southern Tibet

More than 1,000 people have climbed Mount Everest, since it was conquered in 1953.

Climbing activity continues to increase, however, and the environmental future of the Mount Everest area remains uncertain.

Monday, December 8, 2008

Lightning and Thunderstorms

Clouds are made up of water droplets together with the dust in the atmosphere at an altitude of 1 to 16 km. These droplets move downward while the air currents upwards. These movements cause different charges. Lightning occurs when the oppositely charged clouds collide with each other. Lightning can be seen as a streak of bright light and sound. There are of very high voltage(minimum 2 million) and they rush towards the ground through the moisture filled air.

Lightning strike could destroy life and property. It is therefore necessary to take measures to protect ourselves. During lightning and thunderstorm a house or a building is safe place. If you are travelling by car or by bus, you are safe inside with windows and doors of the vehicle shut.
Lightning can strike telephone cords, electric wires and metal pipes. Avoid bathing suring thunderstorms so that you can avoidcontact with the running water.

Lightning Strikes the Capitol Building in Washington

Perhaps 90 percent of the lightning flashes are said to be negative and the remaining, positive. The average interval between successive lightning strokes is 0.02 sec and the average flash lasts 0.25 sec.

It is said that lightning flashes consist of multiple events.There are 42 flashes which are preceded by a leader stroke.Ball lightning is a rare phenomenon in which the discharge takes the form of a slowly moving, luminous ball that sometimes explodes.

The lightning surges in there own path towards the earth, can strike power lines and antenna and pass through wires to the terminal equipments such as TV.the huge voltage current, even through of short life,can damage the electrical components and electronic circuits which are usually designed for low power.

Nearly 40 percent of all farm fires and 75,000 forest fires are started due to lightning. However, lightning enriches the soil. This is by forming nitrogen-dioxide which dissolves in rain water and forms nitric acid, which is and essential nutrient for plant growth.

Saturday, December 6, 2008


Meteors are tiny meteoroids that burn up as they travel through the earth's atmosphere producing tiny streaks of light. Meteorites are meteoroids that reach the surface of earth without being fully burnt. The meteoroid material is left by comets as they pass close to the Sun.

More than 3,000 meteorites land on Earth every year. Most fall in the sea, but a handful are seen to fall on the land.

The fragmentation of the meteorite causes a visual effect called a shooting star.

Willamette Meteorite

Meteorites from mars

Atleast eight meteorites have fallen on theEarth from the Mars. The Nakhla meteorite fell in Egypt in 1911. Those meteorites tell us that the Mars had once running water.

There are atleast three main types of meteorites: stony, iron, or stony-iron.
The stony meteorites contain silicate minerals.They are subdivided into Chondrites and Achondrites meteorites

Chondrite meteorite

Achondrite Meteorite

The Iron meteorites contain a high percentage of iron and nickel. They are created in the rupture of asteroids.

Iron meteorite

Stony-iron meteorite

Gao Meteorite

The Hoba meteorite, the largest in the world was found in Nambia in 1920. It measures 2.73x 2.43 and is 82 percent iron and 16 percent nickel. It weighs more than 60 tonnes.

Hoba Meteorite

The Tent, found in Greenland in 1894, originally known by its Eskimos name, as Ahnighito. This meteorite weighs about 57.3 tonnes. One can view this meteorite, it the New York Museum of Natural History.


Large meteorites can form a crater when they strike the Earth.

Vredefort, South Africa

Chicxulub, Yucatan, Mexico

The collisionof the meteorite compresses and excavates the ground, leaving a crater.

The Popigai crater in Siberia, Russia is the fourth largest impact crater on the earth.

Popigai, Russia

Today about 150 impact craters can be identified including the Wolfe Crater of Australia.