An American scientist says the ice cap at the North Pole has melted. Dr James McCarthy, an oceanographer, says he found a mile-wide stretch of open ocean on a recent trip to the pole.

Some experts say the ice cover could disappear altogether by the end of the 21st century. They point to it as further evidence of global warming - but other scientists say movements in polar ice regularly create gaps in the ice cap - including at the North Pole itself.

On a cruise on a Russion icebreaker, palaeontologist Dr Malcolm C McKenna, said the ship was able to sail all the way to the North Pole through only a thin crust of ice, and arrived on the spot to discover no ice at all.

"I don't know if anybody in history ever got to 90 degrees north to be greeted by water, not ice," Dr McKenna was quoted as saying. "Some folks who pooh-pooh global warming might wake up if shown that even the pole is beginning to melt at least sometimes."

Dr McCarthy, who is working on studies for the Intergovernmental Panel on Climate Change (IPCC), says has previously found the North Pole covered in some 3 metres (9 feet) of ice during the summer.

Some scientists say it could disappear altogether by the end of the 21st century.

The hole in the ozone layer over the Antarctic is expected to increase in size this year as early measurements show significant ozone depletion, the United Nations weather agency said Tuesday. Four observation stations in the Antarctic this month reported a decrease in ozone of between 20 and 35 percent compared with the period between 1964 and 1976, before the "ozone hole" was observed, said Taysir al-Ghanem, spokesman for the World Meteorological Organization.

"We cannot be optimistic with these latest measurements," al-Ghanem said. "We are expecting that the ozone hole this year is going to be quite large, probably more than last year." Ozone depletion in the region starts in July and intensifies during August. WMO says the biggest hole yet was recorded in 1998, when it reached some 4.63 million square miles, partly helped by strong polar winds. Last year, the hole reached 3.86 million square miles. The protective ozone layer shields the earth from damaging ultraviolet rays. Reduction of the ozone layer can let rays from the sun reach the earth"s surface. Too much UV radiation can cause skin cancer and destroy tiny plants at the beginning of the food chain.

One cause of ozone depletion is chlorine and bromine released by manmade chemical compounds such as chlorofluorocarbons, contained in some aerosols. WMO has said those chemicals have leveled off thanks to the Montreal Protocol, which commits countries to eliminating production and use of ozone-depleting substances. But the agency says it could be 20 years before ozone levels recover noticeably. Full recovery can be expected around 2050.

MIYAKEJIMA, Japan - When Prime Minister Yoshiro Mori sounded the alarm for Japan's annual mock earthquake drill Friday, more people than usual may have been listening.

Some 70,000 quakes have rattled this Izu islands chain about 120 miles south of Tokyo this summer and a volcano on one of the isles has blown its top, prompting many to wonder if a major quake is about to strike the capital.

But despite some headline-grabbing predictions of doom in weekly Japanese tabloids and other media, the scientific consensus is that the latest seismic activity says little about whether Tokyo is poised for a rerun of the 1923 Great Kanto Earthquake which left 140,000 dead in its wake. Friday marks the anniversary of that temblor, one of the worst natural disasters to strike anywhere in the 20th century.

Major media have quoted experts, some with impressive credentials, as saying the quakes jolting the Izu chain could signal a big one is heading for Tokyo.

``The quake on the Izu island of Niijima (on July 15) was a dangerous indicator of a Tokyo region quake,'' Kyodo news agency quoted Megumi Mizoue, head of a group of professors who advises the Meteorological Agency on earthquake prediction, as saying.

Other experts, however, dismiss the notion of a scientific link between Izu's jolts and looming disaster in Tokyo. Japan rests atop one of the most complicated geographical structures in the world and is prone to quakes because it sits at the meeting point of several key tectonic plates, massive slabs that make up the earth's crust.

The plates are so large and their movements so complex that many geologists say there is no scientific basis for saying that the rather shallow Izu island events will lead to a cataclysmic disaster somewhere else along the plate.

New York and the entire East Coast of the United States obliterated by an apocalyptic sea wave? We've seen it in Hollywood blockbuster "Deep Impact," but surely it couldn't really happen?

Bombarded by images of Turkish cities razed by earthquakes or Indian shantytowns swept away by cyclone and flood, we become inured to natural disasters. We feel we have seen it all and it wouldn't affect us anyway—would it? We couldn't be further from the truth. For the last few millennia Mother Nature has been unnaturally quiet, amusing herself with the odd flood, earthquake, or volcanic eruption, but nothing too big.

She can and will, however, make things considerably more unpleasant for us. The crucial questions are when and how.

In 1883 when the Indonesian volcano Krakatoa blew itself apart, it produced immense waves known as tsunami that ended the lives of 36,000 fishermen and their families along the coasts of neighboring islands. In 1998 an earthquake-triggered submarine landslide generated tsunami three times the height of a London bus that battered the north coast of New Guinea, wiping out four villages and killing more than 3,000 people.

Some of the biggest tsunami are caused by landslides or volcanic eruptions, but most are triggered by earthquakes, and around the Pacific Rim these have killed over 50,000 people during this century alone.

Tsunami are insidious, hurtling across the oceans as innocuous waves barely a meter high before building as they approach a coastline into towering walls of water. Tsunami propagate in excess of 800 km an hour in deep water and can cross an ocean in 24 hours or less, losing very little of their destructive potential. Those formed by the great Chilean quake of 1960 retained sufficient energy to wreak death and destruction as far away as Hawaii and Japan.

They are hundreds of kilometers across. When they hit land, they just keep on coming, perhaps for half an hour or more, before taking the same length of time to retreat. Very few people carried away by the waves survive.

The Pacific is the Mecca for earthquake-generated tsunami, but it is to the Atlantic that we should look for the next megatsunami.

In 1949 an eruption occurred on the unspoiled Canary Island of La Palma. As magma inflated the volcano, the entire western flank—an immense pile of rock totaling 200 cubic kilometers—dropped four meters seaward then stopped. This huge rock mass still hangs over the western Atlantic, ready to slide into the sea at any moment.

The legacy of this collapse will herald calamity for all living around the margins of the Atlantic Basin, as colossal waves—initially up to 200 meters high—fan out from the island.

Thousand-ton boulders hurled 20 meters above sea level and kilometer-long wedges of sand rammed between the islands testify to what happened when tsunami from the last Canary Island collapse pounded into the Bahamas, eons ago. Next time, the Caribbean and the east coast of the U.S. will suffer the same fate, and the destruction will be on a scale never before experienced.

What we must remember is that this is not science fiction. It is a question of when, not if, part of La Palma collapses into the Atlantic.

Scientists have discovered cracks in the ocean floor off the East Coast that they say could trigger a tsunami, sending 18-foot waves toward the mid-Atlantic states.

In this month's issue of the journal Geology, the three researchers say they discovered the cracks along a 25-mile section of the continental shelf off the Virginia and North Carolina coasts.

Those areas would be at the highest risk for wave heights similar to the storm surge of a category 4 hurricane, which is characterized by top sustained winds of 131 mph to 155 mph.

Neal Driscoll of the Woods Hole Oceanographic Institution on Cape Cod, Jeffrey Weissel of Columbia University and John Goff of the University of Texas said the recently discovered cracks could mean the continental shelf is unstable. The cracks indicate the sea floor could slide down like an avalanche, triggering giant waves.

El Trebol refugee camp perches on a shorn hilltop overlooking Tegucigalpa, Honduras. More than 400 families shelter in this cluster of plywood shacks that was hastily erected between two motorway junctions more than a year ago. Among them are Marita Fonseca and her six children, who consider themselves lucky to have any sort of roof over their heads. The Fonsecas are among the three million people across Guatemala, Nicaragua, Honduras, El Salvador and Belize still reeling from the devastation of Hurricane Mitch seventeen months ago.

Most of the residents displaced by the hurricane were poor and now cope stoically as emergency measures become daily routine. Aid pledges came from around the world in the wake of Hurricane Mitch and its 180-mph winds that nearly blew away the economic future of Central America, but as new disasters grab headlines, the funds are slow to materialize. To repair most of the damage from Hurricane Mitch would cost $5 billion in Honduras alone, where the gross domestic product is just $7 billion. "We’ll just have to do what we can with the little that we have," said the Finance Minister, Gabriela Nunez.