What Is an Earthquake?

The expression “on solid ground” is often used to describe something as stable. Usually the solid ground underfoot seems very stable. But sometimes it is not.

"The ground seemed to twist under us like a top while it jerked this way and that, and up and down and every way," wrote a person describing the experience of being in the large 1906 earthquake in San Francisco, CA.

Earthquakes happen as large blocks of the Earth’s crust move suddenly past one another because of the force of plate tectonics. These blocks of the Earth’s crust meet at cracks called faults. Sometimes those pieces do not slide smoothly past one another. There can be friction along the fault – jagged edges that snag the blocks of rock. This makes it difficult for them to move past each other. Sometimes they get stuck together temporarily. When the pieces of rock overcome the snags, energy is released. The release of energy causes shaking at the ground surface.

The location inside the Earth where an earthquake begins is called the focus. The point at the Earth’s surface directly above the focus is called the epicenter. The strongest shaking happens at the epicenter.

Each year, more than a million earthquakes occur worldwide. Most of these are so small that people do not feel the shaking. But some are large enough that people feel them, and a few of those are so large that they cause significant damage.

Earthquakes can cause damage to things like buildings, bridges, and roads. Earthquakes can cause landslides and mudslides, too. If a large earthquake happens under the ocean it can cause a tsunami – a giant ocean wave or series of waves.

Scientists can figure out whether an earthquake is likely to happen in a place by studying plate tectonics, the faults underground, and the history of the area’s earthquakes. However, unlike weather events, earthquakes can not be forecast ahead of time.

Source : windows2universe

Japan under nature attack

Date : 11 March 2011
Place: Japan


Cars, ships and buildings were swept away by a wall of water after the 8.9-magnitude tremor, which struck about 400km (250 miles) north-east of Tokyo.

A state of emergency has been declared at a nuclear power plant, where pressure has exceeded normal levels.

Officials say 350 people are dead and about 500 missing, but it is feared the final death toll will be much higher.

In one ward alone in Sendai, a port city in Miyagi prefecture, 200 to 300 bodies were found.

The quake was the fifth-largest in the world since 1900 and nearly 8,000 times stronger than the one which devastated Christchurch, New Zealand, last month, said scientists.

Thousands of people living near the Fukushima nuclear power plant have been ordered to evacuate.

Japanese nuclear officials said pressure inside a boiling water reactor at the plant was running much higher than normal after the cooling system failed.

Officials said they might need to deliberately release some radioactive steam to relieve pressure, but that there would be no health risk.

US Secretary of State Hillary Clinton had earlier said the US Air Force had flown emergency coolant to the site.

But US officials later said no coolant had been handed over because the Japanese had decided to handle the situation themselves.

The UN's nuclear agency said four nuclear power plants had shut down safely.

Measured at 8.9 by the US Geological Survey, it struck at 1446 local time (0546 GMT) at a depth of about 24km.

The tsunami rolled across the Pacific at 800km/h (500mph) - as fast as a jetliner - before hitting Hawaii and the US West Coast, but there were no reports of major damage from those regions.

Thousands of people were ordered to evacuate coastal areas in the states of California, Oregon and Washington.

The biggest waves of more than 6-7ft (about 2m) were recorded near California's Crescent City, said the Pacific Tsunami Warning Centre.

A tsunami warning extended across the Pacific to North and South America, where many other coastal regions were evacuated, but the alert was later lifted in most parts, including the Philippines, Australia and China.

Strong waves hit Japan's Miyagi and Fukushima prefectures, damaging dozens of coastal communities.

A 10m wave struck Sendai, deluging farmland and sweeping cars across the airport's runway. Fires broke out in the centre of the city.

Video :

Source :BBC News

Titanic in the grave

The story of the Titanic and the iceberg has grown into a legend of the sea. It took her discovery in 1985 to begin to find the truth behind the myth. One of the things that makes the Titanic so fascinating is that she represented the best of technology when she set sail on her ill-fated voyage in 1912, and it took the best of technology in the form of sonar, satellite tracking, and deep-dive technology to locate her grave 73 years later. In the early 1900's, waterborne transportation was the norm; today, satellites are taken for granted by our society. But we tend to forget the immense effort that these two technologies require to operate to their maximum potential. Until recently, the technology did not exist to locate, photograph, and explore this ship that rested two and a half miles down on the ocean floor.

On April 10, 1912, the RMS Titanic set sail from Southampton on her maiden voyage to New York. At that time, she was the largest and most luxurious ship ever built. At 11:40 PM on April 14, 1912, she struck an iceberg about 400 miles off Newfoundland, Canada. Although her crew had been warned about icebergs several times that evening by other ships navigating through that region, she was traveling at near top speed of about 20.5 knots when one grazed her side.

Less than three hours later, the Titanic plunged to the bottom of the sea, taking more than 1500 people with her. Only a fraction of her passengers were saved. The world was stunned to learn of the fate of the unsinkable Titanic. It carried some of the richest, most powerful industrialists of her day. Together, their personal fortunes were worth $600 million in 1912! In addition to wealthy and the middle class passengers, she carried poor emigrants from Europe and the Middle East seeking economic and social freedom in the New World.

The remains of the Titanic were found in 1985 by Dr. Robert Ballard, an oceanographer and marine biologist with the Woods Hole Oceanographic Institution. When he located the Titanic, he saw that, as some survivors reported, the ship had broken apart. He believed the weight of the water-filled bow raised the stern out of the water and snapped the ship in two just before it sank. Debris falling out of the ship was strewn over a 1/2 mile across the sea floor. The bow and the stern were found nearly 2000ft. apart.

Keeping her location a secret, Bob Ballard used GPS to find theTitanic again when he returned the next year. He hoped to prevent treasure seekers from finding her and plundering the ship for booty such as coffee cups inscribed with RMS Titanic. On this second expedition, he visited the ship several times by submarine. On his last descent, he left a plaque honoring the 1500 victims and asking that subsequent explorers leave their grave undisturbed.
Find the Titanic again!

1. Eventually Bob Ballard released the coordinates of the Titanic's location. He recorded her coordinates as, stern section sits on ocean floor at 41o43'35" N, 49o56'54" W, boilers at 41o43'32" N, 49o56'49" W, bow at 41o43'57" N, 49o56'49" W. Find these coordinates and trace the outline of the sunken pieces of the Titanic on a chart of the North Atlantic.

2. How far is it from its plotted course? At the time of the accident, the ship was reported to be at 41o46' N, 50o 14' W. (She was found 13½ miles southeast of the position given in her lastdistress call.)

3. Discuss the fact that satellite technology through GPS can pinpoint any position on Earth to within 30 feet. In 1912, navigation techniques of dead reckoning and celestial navigation could only give one an approximate location within several miles of one's true position.If the Titanic had had better navigational aids, could its passengers have all been saved? Could it even have avoided the iceberg?

4. Track the route she took from England to New York in April, 1912.


She started from Southampton, England, and stopped at Cherbourg, France and Queenstown, Ireland to pick up passengers. Her destination was New York. She sank 1000 miles due east of Boston, Massachusetts, and 375 miles southeast of St. John's, Newfoundland.
Unsinkable challenge

Build an unsinkable boat. What would it be made of? How would it be shaped? How will you test your hypothesis? How much weight ("passengers") could it carry? How far can it tip to the side before it flips?
Reliving the moment

Draw a picture of the Titanic on that fateful night, using literature connection references. Information that should be incorporated into the work: It was night. There were icebergs. As the bow sank, the stern lifted farther and farther out of the water."Just before the ship disappeared entirely," according to Bob Ballard,"Many eyewitnesses agreed that the ship in fact broke in two, the bow plunging down while the stern briefly righted itself before turning almost vertical and sinking a few moments later."

Detail what it might have been like aboard the Titanic between 11:40PM (when the ship gently grazed the iceberg) to 2:18 AM when it disappeared below the sea.

Or draw an illustration of Jason finding the bow of the Titanic at the bottom of the sea at a depth of 12,460 ft. The ship was found in several pieces. Draw what the Titanic might look like after another 100 years on the ocean floor.
Lifeboats

How many lifeboats were needed? TheTitanic was owned by the British White Star Line, flew the British flag,and thus was under the rules and regulations of the British government. Although she was originally designed to carry 42 lifeboats, the ship carried only 20 lifeboats (four more than were required at the time by British regulations) for the 2,228 passengers and crew. (That number could supposedly hold 1,178 people.) The original designer of theTitanic had proposed 50 lifeboats, but the British owners of the White Star Line had decided against it. (If it had been under US Government regulation at the time, 42 lifeboats, enough to accommodate 2,367 persons would have been required for a ship that size.)

Only 705 people were rescued; 1523 drowned or froze to death in the icy water. Ironically, most of those who drowned were Americans. Assuming that each lifeboat could hold 65 people, how many lifeboats did they need? Unfortunately, the 20 lifeboats on board were launched in panic before they were filled to capacity, so the number of people rescued was even fewer than could have been accommodated.

Only 705 of 2,227 people on board survived. What percentage is that?
Women Men Total
& Children
First class 94% 31% 60%
Second class 81% 10% 44%
Steerage 47% 14% 25%
Crew 87% 22% 24%

Analyze these statistics. What do these figures tell you about the policy of saving women and children first, how social standing and wealth influenced who was rescued, and the tradition that the crew usually went down with the ship? Many of the poorest people were not aware of the seriousness of the damage to the Titanic until shortly before it sank.