In nature, repetitive events like this are rare, says the U.S. Geological Survey's Richard Iverson, who led the study team.

"So it seemed to me that whatever was causing this had to be something where the physics was quite simple."

Boing, Boing

Iverson likens the process to trying to push a block of wood across a table with a spring.

"If conditions are right, the spring can cause the block to move in a jerky fashion as tension is built up and released."

Specifically, magma, or molten rock, is rising at a steady rate, pushing against the base of the plug until it lurches upward. The lurches are so small-only about a quarter of an inch (0.5 centimeter)-that they can't be seen by video cameras that monitor the crater.

For the process to have continued for so long, new magma must be solidifying against the bottom of the plug at the same average rate at which the plug is rising.

Otherwise, the mountain should pop its cork and spew lava-or the plug should seal the lava strongly enough that the quakes would temporarily halt.

No one knows how long the current eruption will continue, but nobody expects it to stop soon. As long as magma continues to rise from below, Iverson said, "the chances are that it'll keep coming out at the top."

The new research on the tiny quakes, which have magnitudes of less than 2.0, will be published in tomorrow's issue of the journal Nature.

Not all geologists are convinced. One of them is Bernard Chouet of the U.S. Geological Survey office in Menlo Park, California.

Chouet doubts that the plug's tiny motions can cause quakes within Mount St. Helens.

In an effort to pinpoint the location of the quakes, Chouet and colleagues examined data from 19 seismometers installed on the mountain in 2005. Seismometers measure ground movement.

Chouet's team concluded that the drumbeats were not being created by rock sliding against rock in the magma channel.

Rather, they say, vibrations in a steam-filled horizontal fracture about 330 feet (100 meters) beneath the crater floor are causing the drumbeats.

"This mechanism has nothing to do with stick/slip," he said.

In his scenario, the pressure probably comes from steam, as water inside the volcano is heated by the rising magma.

"There's plenty of water in the ground, and there's plenty of heat," Chouet said.

"It looks like Mount St. Helens is huffing and puffing and basically behaving like a steam engine," Chouet said.

Steam engine or not, none of the scientists are predicting that Mount St. Helens is about to explode like it did in 1980.

Study leader Iverson said in an email, "Large explosions at Mount St. Helens are certainly possible, as they are at any volcano.

"But with the current style and level of volcanic activity at Mount St. Helens, we believe the probability of large explosions is very low."

Stephen Scherer, senior scientist at the Hospital for Sick Children, has found new kinds of genetic variations hidden within the genome, which scientists say could change their entire understanding of inheritance of disease and evolution.

The study, published yesterday in the journal Nature, also reveals that genetic variation between humans is much greater than previously thought.

"We have a common heritage through our common humanity, but we also have a lot of differences that make us unique," says Scherer, who is also a professor of medicine at the University of Toronto. "Now we have more biology to explain the differences between brothers or cousins or spouses."
The map will soon be used in 20,000 labs around the world, says Tom Hudson, president and scientific director of the new Ontario Institute for Cancer Research.

In the six years since scientists mapped the human genome, researchers continue to find new information hidden deep within our genes. Scherer and his team discovered many hundreds of genetic variations called copy number variants (CNVs), large segments of DNA that either have an extra or missing part, as opposed to a single pair.

Scherer and his colleagues at several different research centres in the United States, Japan and Europe, used state-of-the-art technology to locate CNVs within the human genome, creating a new map that shows 1,477 new locations for this form of genetic variation.

This is a big leap forward from the Human Genome Project that helped identify millions of base-pair changes in the DNA code. These single nucleotide polymorphisms (SNPs) have been mapped in more detail and scientists have long thought that they were the primary source of genetic variation within humans.

But as Scherer continued to build on his research, the team found that CNVs had a much wider reach.

They compared chunks of DNA from 270 people with African, Asian or European ancestry and found nearly 1,500 CNV regions, which covers 12 per cent of the human genome.

"We were shocked at the number of these things that we found," says Scherer, who adds that the team spent six months checking and double-checking their data to make sure it was valid. "We knew they existed, but we never predicted this many of them."

Roderick McInnes, scientific director of the Institute of Genetics at the Canadian Institutes for Health Research, says that Scherer and colleagues were right in concluding that scientists will have to incorporate CNV analysis in every new study on genomes. Last month, Scherer released the CNV map to the scientific community via his website, and scientists from all over the world, working in clinical science, evolutionary biology and basic science, began using the new database.

Hudson, a founding member of the Human Genome Project, says the CNV study is a significant step forward because the techniques and tools are immediately available to the research community. Hudson is now leading a new project called Assessment of Risk for Colorectal Tumours in Canada to find ways of predicting a person's genetic susceptibility to colon cancer. He is eager to see if CNVs can push his research forward.

Scherer says that CNVs could influence how genetic tests and personalized genome sequencing methods are developed, and may be used in the field of pharmacogenetics to explain the body's response to different drugs. CNVs could also provide clues to evolutionary biologists about how chromosomes evolved between species, he says. Scientists have found CNVs in the genome of other animal species, including mice and chimpanzees.

For Scherer, the next step is to look for CNVs at an even higher resolution to create a second-generation map and a more complete database. There are likely many, many more.

"We would like to sample 1,000 people from around the world to get a better survey of the characteristics and content of CNVs," he says.

"We want to know where all of them are in a human population and fully understand their implications in development and disease."

At least 70 species of frogs, mostly mountain-dwellers that had nowhere to go to escape the creeping heat, have gone extinct because of climate change, the analysis says. It also reports that between 100 and 200 other cold-dependent animal species, such as penguins and polar bears are in deep trouble.

"We are finally seeing species going extinct," said University of Texas biologist Camille Parmesan, author of the study. "Now we've got the evidence. It's here. It's real. This is not just biologists' intuition. It's what's happening."

Her review of 866 scientific studies is summed up in the journal Annual Review of Ecology, Evolution and Systematics.

Parmesan reports seeing trends of animal populations moving northward if they can, of species adapting slightly because of climate change, of plants blooming earlier, and of an increase in pests and parasites.

Parmesan and others have been predicting such changes for years, but even she was surprised to find evidence that it's already happening; she figured it would be another decade away.

Just five years ago biologists, though not complacent, figured the harmful biological effects of global warming were much farther down the road, said Douglas Futuyma, professor of ecology and evolution at the State University of New York in Stony Brook.

"I feel as though we are staring crisis in the face," Futuyma said. "It's not just down the road somewhere. It is just hurtling toward us. Anyone who is 10 years old right now is going to be facing a very different and frightening world by the time that they are 50 or 60."

While over the past several years studies have shown problems with certain species, animal populations or geographic areas, Parmesan's is the first comprehensive analysis showing the big picture of global-warming induced changes, said Chris Thomas, a professor of conservation biology at the University of York in England.

While it's impossible to prove conclusively the changes are the result of global warming, the evidence is so strong and other supportable explanations are lacking, Thomas said, so it is "statistically virtually impossible that these are just chance observations."

The most noticeable changes in plants and animals have to do with earlier springs, Parmesan said. The best example can be seen in earlier cherry blossoms and grape harvests and in 65 British bird species that in general are laying their first eggs nearly nine days earlier than 35 years ago.

Parmesan said she worries most about the cold-adapted species, such as emperor penguins that have dropped from 300 breeding pairs to just nine in the western Antarctic Peninsula, or polar bears, which are dropping in numbers and weight in the Arctic.

The cold-dependent species on mountaintops have nowhere to go, which is why two-thirds of a certain grouping of frog species have already gone extinct, Parmesan said.

Populations of animals that adapt better to warmth or can move and live farther north are adapting better than other populations in the same species, Parmesan said.

"We are seeing a lot of evolution now," Parmesan said. However, no new gene mutations have shown themselves, not surprising because that could take millions of years, she said.