Running short of worries? Then ponder the super-volcanoes — earth-bombs that can vomit 10 or 100 or 1,000 cubic kilometers of molten rock. Super-volcanoes can change history by creating rivers of red-hot ash moving at highway speed, spreading dust across hundreds of kilometers and spewing vapors that block the sun, destroy crops and start famines.

A volcano may go dormant for thousands of years after such a huge eruption, so they may be even harder to predict than smaller ones — which are also unpredictable at this point…

But this week, Nature published a new analysis of Santorini, a Mediterranean monster, that shows the movement of molten rock that preceded the eruption.

Santorini’s sudden release of 40 to 60 cubic kilometers of rock and ash was followed by a giant collapse that left a characteristic ring of hills called a caldera. Thousands may have died in the eruption, which laid down a 60-meter layer of ash and rock.

Eruptions of this general size happen about every 300 years, says Timothy Druitt, a volcanologist at the Université Blaise Pascal in France, who lead the current study. The most recent was in 1815 at Tambora, in Indonesia.

Druitt’s new analysis of crystals within the frozen magma offers a rough schedule for the entry of molten magma into a holding tank — the magma chamber — below the volcano, which is a precursor to eruption.

Caldera-forming eruptions rival earthquakes and tsunamis as the deadliest natural disasters. “People who work in the field know these volcanoes are not rare, even on a human time scale,” says Druitt, but “we have never been able to monitor one of these big eruptions during the long buildup phase, so we are not really sure how that happens.”

The crystal analysis detects microscopic changes in chemical composition, offering a unique, after-the-fact picture of the gestation of eruption.

In the crystals

As crystals grow in the cooling magma, atoms of trace elements diffuse within them, and both growth and diffusion are affected by conditions within the hot magma, says Druitt. “These crystals grow progressively, and as they do, their chemical composition changes according to the composition of the magma around them, and the temperature and amount of water in the magma.”

The crystals revealed that a big gob of magma — perhaps 10 percent of the magma chamber’s total contents — entered in the decades before the eruption. “Looking at the crystals in this magma, we were able to reconstruct very crudely events taking place in the last few decades prior to the eruption,” Druitt says.

That final addition probably made the magma chamber unstable, leading to the eruption, Druitt explains.

If such a late, large magma movement proves typical of super-volcanoes, that could contribute to a distant early warning system for mega-eruptions, based on more conventional methods, such as seismic monitoring.

Distant early warning

But the findings also carried a caution, Druitt says, since Santorini was apparently dormant for about 18,000 years before the last apoplectic outburst. “That is a slightly alarming result. There are lot of these big caldera systems, but most are in a stage of repose.”

The upshot is more proof that a dormant volcano can still be a dangerous one, he adds. “We can imagine that a big caldera in a remote region of the world, such as the Andes, which is not monitored very well, could reawaken pretty quickly on a human time scale.”

The crystal method gives after-the-fact data on an eruption. Current attempts to anticipate eruptions rely on data about earth shaking, deformation of the crust, and release of gases.

“It’s a very timely topic, and solid science in terms of the measurements and observations,” says Bradley Singer, a volcanologist and professor of geoscience at University of Wisconsin-Madison. “They admit that there are issues about the time scales,” largely because the diffusion of strontium and titanium is imperfectly understood in the hot magma.

The study’s title, however, specifies that the final growth of the magma chamber occurs on “Decadal to monthly timescales,” Singer notes. “It could be centuries or even longer, which implies that we’d have a longer time prior to the eruption” to worry about the effects of the rising magma.

Singer concurs on the importance of understanding the relationship of magma flows, instability and eruption, and says the crystal analysis is gaining traction in volcanology.

That’s just as well, since giant caldera-forming volcanoes may be frighteningly common. The one at Yellowstone, for example, released 1,000 cubic kilometers of rock 640,000 years ago. Wouldn’t you want to know if something like that was building on your continent?

The seas’ most sought-after fish are swimming between a rock and a hard place: the fisherman’s net and an encroaching mass of suffocating water.

A recent study has uncovered a new dose of bad news for ocean fish and the fishing industry. Areas of the deep ocean with little dissolved oxygen, called dead zones, are expanding and, thus, shrinking many fishes’ watery homes.

One driving force behind the predicament is none other than that pesky climate problem.

“Climate change is actually working in tandem with overexploitation of the animals to push these populations into a real dangerous place in terms of population collapse,” said Eric Prince, a fisheries biologist with the National Oceanic and Atmospheric Administration’s Southeast Fisheries Science Center and co-author of the study.

For example, Prince and his colleagues calculated that the Atlantic blue marlin, an economically valuable fish that was a focus of their study, has lost about 15 percent of its habitat from expanding dead zones since 1960. Dwindling habitat threatens not only the lives of fishes, but also the sustainability of the already ailing fishing industry.

Breathing room

Like their above-water brethren, fish need oxygen, which is dissolved in the water. Big, predatory fish, such as the blue marlin, need more dissolved oxygen than most, because they require lots of energy to grow and survive. Without sufficient oxygen, they’ll suffocate.

The level of oxygen in the water thus partly delineates fish habitat boundaries. Dead zones often draw these borders.

As climate change causes open ocean dead zones to balloon, fish habitat deflates.

Diagram modified from one originally published in Deep Sea Research Part I: Oceanographic Research Papers, Vol 57, Issue 4, Lothar Stramma, Sunke Schmidtko, Lisa A. Levin, & Gregory C. Johnson. Ocean oxygen minima expansions and their biological impacts, 587-595, Copyright Elsevier (2010).

Technically known as oxygen minimum zones, dead zones are actually a natural occurrence. Found at depths of between 200 and 1000 meters, they are caused partly by seawater circulation and partly by the decomposition of organic matter, namely deceased sea critters that sink from surface waters.

As aerobic bacteria nosh on the organic matter, they use up the oxygen in the water. Eventually, hypoxia happens—the water becomes so depleted of oxygen that many creatures can’t survive.

Since deep-sea dead zones are insulated from the ocean’s surface, where the water borrows oxygen from the atmosphere, they can only reload with oxygen if currents make a long-distance delivery, according to Sunke Schmidtko, an oceanographer at the University of East Anglia, the other co-author of the study.

Deep-sea dead zones are different from their coastal cousins like the one in the Gulf of Mexico. Coastal dead zones form due to a buildup of agricultural fertilizer that rivers, such as the Mississippi, collect and then flush out to sea, causing abnormal blooms of plant life.

De-fizzing the ocean

But climate change is turning what Mother Nature does normally into a big problem. As the air is getting hotter, so is the water, and warmer water can hold less oxygen than colder water.

This is similar to what happens to a soft drink on a hot day. After sitting in the heat and sun, the fizz fizzles, and you are left with a flat, carbon dioxide-depleted beverage.

Also, warmer surface waters are less likely to sink to the ocean’s lower layers, because warm water is lighter than the colder water below, Schmidtko explained. In other words, as the oxygen-rich surface layers heat up, they could have a harder time delivering oxygen to the deeper ocean.

Schmidtko clarified that oceanographers are still trying to determine how exactly climate change is affecting the ocean, but with their knowledge of how water works, these represent their current speculations.

The rock below

With less oxygen to go around, oxygen minimum zones are swelling and intruding on many fishes’ living zones.

For example, marlins often dive deep to feed, sometimes as far down as 800 meters. However, in the eastern Atlantic’s growing dead zone, which is already one of the largest in the world, Prince found that marlins can’t dive as deep as their west-side counterparts.

“They need to go where the food is and where they can breathe,” he said.

With less breathing room below, the floor of their habitat rises, and they are pinned to the surface layers. With nowhere to go but up, marlins become squished into tighter, testier quarters with other predatory fish and their prey. They also find it harder to dodge a waiting fishing hook or net.

“Concentrating them makes it much easier for overexploitation by [humans],” said Prince.

The increasing concentration of animals at the top could also lead to a boost in the amount of sinking organic matter, which would further worsen the oxygen shortage below.

Softening the hard place above

As a prized catch, Atlantic blue marlins are already victims of overharvesting. In fact, their populations have dropped 60-64 percent over the past three fish generations (14-18 years).

But the growing dead zones can actually fool scientists and fishermen into thinking fish populations are doing just fine, since more fish are squeezed into a smaller area. Thus, to ensure the dead zone-fishing vise does not become their demise, Prince said scientists must more carefully monitor fish populations, as well as the expansion of the dead zones.

While fish stock assessments are starting to incorporate this information, Prince warned the pace needs to quicken.

And if the Earth is to continue warming, as most scientists predict, Schmidtko added that humans should chill out on fishing.

After all, we will never be capable of “ventilating the ocean,” he said.

Interested in waterfront property in Southern California? A new study of a continental schism running east of Los Angeles offers a clear “buy” signal for the long-term investor: The North American continent is splitting apart along a rift, and if you got the patience, we have the real-estate-appreciation potential!

In just a few million years, as the North American continent sunders in a weak zone called the Salton Trough, the Gulf of California will stretch further north.

On our unstable Earth, not even the continents are rock solid. Instead, they shift around like blocks of sea ice that join, fissure and separate once again — over millions of years.

Geologists know the process is occurring in the Southern California desert, and we’ve just read a sophisticated analysis that finds an ominous thinning of the strong crustal layer in the Salton Trough.

Ominous, that is, unless you are planning a waterfront resort here, with a grand opening in, say, 2,002,011.

The study helps to fill a gap in our understanding of the earth, says first author Vedran Lekic, a National Science Foundation post-doctoral fellow at Brown University. “The main question is, how do continents come to break apart? This process is really fundamental to shaping how the Earth looks; if not for rifting, once Pangaea formed, it would never have broken apart and we would have only one continent.”

Pangaea is a giant agglomeration of continents that broke up about 150 million years ago, creating our current collection of continents.

Scoping out the Earth

The lithosphere, Earth’s crust and the rigid rock beneath it, essentially floats on the asthenosphere, the soft and hot outer layer of the mantle that is located tens of kilometers belowground.

As a continental rift grows, one would expect to find a thinned lithosphere at the Salton Trough. But Lekic says the actual thinning was more dramatic than expected — as much as a 50 percent reduction compared to adjacent areas.

By studying earthquake waves passing through Earth, Lekic and colleagues measured the thickness of the lithosphere by locating its lower border. They knew that one type of wave converts to a faster wave type as it passes up from the asthenosphere into the lithosphere, so the conversion could be used to mark the base of the lithosphere.

It turned out that the lithosphere measured about 40 kilometers thick beneath the Salton Trough, compared to 60 to 80 kilometers on nearby areas. That thinning translates into a weakening that will eventually allow open water into the Trough, and myriad real-estate opportunities along the new shoreline.

Previous efforts to estimate the lithosphere’s depth have relied mainly on surface data, says Lekic, and that limited our knowledge of how the continental splitsville takes place. From relying on “surface observations of faults, topography, heat flow, and some studies of the crustal structure, we have not been able to image the detailed topography of the base of the tectonic plate, as it looks during rifting.”

Rift terrific

Although the study relied on the interest in Southern California seismology that is a response to extreme seismic activity, the finding says little about earthquake probabilities.

But earthquakes are not the only tectonic game in town, says Eugene Humphreys, a professor of geophysics at the University of Oregon. “While most people know southern California is being sheared by the San Andreas and related faults, most people are not aware that the region also is being pulled apart as the Pacific plate also moves slowly away from North America. These researchers have imaged the deep structure of the plate where it is being torn apart by this process, and contrary to what many have thought, the tears go through the entire plate right where the surface expression of this rifting is seen. It’s exciting work.”

The study provides insight into deep structure and processes of fluid migration up into the plate, says Humphreys. “These lower-plate interfaces were not expected to exist at all, and the scientific community is excited but struggling to determine what could create relatively sharp interfaces.”

Although Earth warms with depth, that is unlikely to explain the weakness, Humphreys says, “so the search for other causes is on. By associating the position and shape of these interfaces with a specific deformation history, this study provides important information on the origin of these interfaces.”

Lekic, who worked with co-author Karen Fischer of Brown, on the study, says that “Even at great depth, we see the same stretching and deformation that we see near the surface. At the bottom of the lithosphere, there is this persistent weakness, in a zone that runs more or less vertically, and that’s surprising.”

But as scientists wrestle with the geological goulash that is Southern California, we suggest you send a down payment to Rift ‘n Grift Realty on the ocean-front lot of your dreams – and wait a few million years!

— David J. Tenenbaum

We approach the Cave of the Mounds, a landmark (so to speak) in Southwest Wisconsin, along a walkway painted with fossils and markings that start at the Ordovician era (450 million years ago), when the limestone beneath our feet was deposited as a rain of sea shells on an ocean floor. Finally, at the cave’s entry, the asphalt calendar enters the last million years, when the cave started to be excavated by flows of acidic water.

The geological markings under our feet are one indication that the cave-men and -women who operate this site are intent on linking past and present, above- and below-ground.

Cave of the Mounds was discovered in 1939 by workers blasting in a limestone quarry on one of the highest spots in southern Wisconsin. Today, it is a tourist destination with a message — a cool, underground mecca, strategically illuminated, where tour guides leave the nettlesome lectures above ground, and offer easy-to-digest science along the cave’s alleyways.

The above ground section of the site features resurrected prairies and oak savannas, but the main attraction is the stalactites hanging over stalagmites, flowstone, the fossils embedded in ancient limestone, and the rare opportunity to see geology at work as you observe the earth from the inside out.

Aftermath of a flood unparalleled

What caused the huge erosion features, ancient shorelines, and scoured potholes in the “channeled scablands” in Eastern Washington state? In 1923, J. Harlen Bretz coined that ominous moniker and proposed that the features had been created by a gigantic flood.

During this time, geology was ruled by a “uniformitarianism” dogma, which highlighted gradual processes like deposition and erosion, and discounted the power of sudden events like floods (and perhaps even earthquakes, tsunamis and volcanoes).

Skeptics demanded to know the source of all that water in an arid region, and Bretz had a reputation as a kook. Then, geologists gradually realized that the ice-age flood had originated to the east, in glacial Lake Missoula, which had been plugged by the lobe of a glacier emanating from Canada.

In the 1950s, the idea that this huge lake had eaten through an ice dam and then coursed downstream with phenomenal power started gaining acceptance, and in 1979, Bretz, age 96, received the highest award from Geological Society of American for solving this great Earth riddle. Today, scientists believe the floods may have recurred every few years or decades as the ice age was waning, around 14,000 years ago.

The evidence for the floods comes in all sizes. Alternating stacks of coarse gravel and fine sand show gravel left by flood currents under sand left by slower water when the floods receded. A dry river bed called the Grand Coulee, in Eastern Washington, was gouged by the astonishing flow of uncorked glacial melt water. The periodic cascades that shaped Dry Falls, now in Sun Lakes State Park are considered the largest known waterfalls in Earth’s history.

The unbearable whiteness of being

The world’s largest field of gypsum dunes, at White Sands National Monument in south-central New Mexico, could arouse anybody’s inner drywaller, as gypsum is the mineral basis for both drywall and plaster. But here, where 275 square miles of gypsum dunes have built a hot, severe and scorchingly beautiful landscape, there’s not a sheet of drywall in sight.

Set aside as a national monument by President Herbert Hoover in 1933, the dunes trace their origin to vast deposits of hydrated calcium sulfate — gypsum — that were laid down on an ancient lake a quarter-billion years ago. After a geological uplift, they were exposed roughly 10 million years ago, and eventually moved to the present site in a geologic eye-blink — the last 7,000 years.

Mammoth tracks have been seen in the dunes, but they could get buried with time: Some dunes are moving 30 feet a year, as the wind piles them up on the windward side and gravity avalanches them down the lee.

The gypsum dunes are said to be the largest in the world, but what’s most amazing is not the geology, but the evolutionary adaptations life has used to survive these harsh conditions. At least seven species of animals, including three lizards, that are closely related to darker varieties living in the surrounding desert have turned white for camouflage in this bleached world. (The drywalling lizard or the plastering mouse must be here somewhere!)

Visiting the Sands? Ponder a trip to Trinity, the site of the first test of the atomic bomb.

Science museums: Try the trifecta!

The Windy City boasts not just one, but three cool science destinations, all next door to each other on the Museum Campus along the shore of Lake Michigan.

To explore some of the world’s biological and cultural wonders, spend the day at the Field Museum of Natural History, a collision of anthropology, botany, geology, paleontology and zoology. The permanent exhibits include the DNA Discovery Center, a journey through four billion years of earthly life, and Sue, the largest (and most expensive?) complete skeleton of the ferocious T. rex. Among the temporary exhibits was a recent one on the horse and its deep relationship with humans (an exhibit that particularly excited one horse-crazy Why Filer).

If your palate is whetted for a wetter world, walk to the Shedd Aquarium to explore underwater life from the Amazon, the Caribbean and both poles. Green sea turtles, beluga whales, moray eels, piranhas and penguins will be among your hosts.

If otherworldly science is more your thing, visit the Adler Planetarium. Chat about the stars with real space scientists at their Space Visualization Laboratory, or just sit back and watch the star show. Adler’s centerpiece is the Doane Observatory, the largest publicly accessible telescope in the Chicago vicinity. While you can only peer through the lens after dark, this could make for a great conclusion to your trip.

Discover a life aquatic

An Australian freshwater crocodile grows in Baltimore. Seriously. The National Aquarium Baltimore boasts more than 660 species of fish, birds, amphibians, reptiles and mammals, totaling around 16,500 marine creatures.

In addition to its rich marine menagerie, the aquarium has a collection of special exhibits and interactive oceanic enjoyment. See the world through a dolphin’s eyes at Our Ocean Planet, a show that teaches visitors about dolphins and the connections between people and their seafaring friends. Or soak in ocean sensations with a movie at the 4-D Immersion Theater, where you can experience sea life in multiple dimensions, including the smell and feel of (simulated) mist and wind. Or take an expert-led tour, including behind-the-scenes peek of the sharks’ quarters.

The aquarium is also a center for conservation. For example, its Marine Animal Rescue Program tracks the progress of rescued animals after release. Other conservation projects include restoring wetlands and investigating the impacts of mercury on the marine food chain. After all, protecting the life that sustains the ocean ecosystem benefits everyone—not just aquarium visitors.

An excursion exotic to Melville

What’s more breathtaking than seeing the world’s largest animals in the wild? Whale watching puts you up close and personal with these magnificent marine mammals. Since the 1950s, in a 180° turnaround from Herman Melville’s day, people have been flocking by the boatloads to glimpse whales doing what they do rather than to kill them.

Both the U.S. east and west coasts have whales to watch, though you must catch them in the right season during their migration. There’s no guarantee, but on the western seaboard, you could spot orcas and gray whales. The east is home to the right, fin and sei whales. Humpbacks, minkes, and blue whales troll both coastlines.

Several cetaceans (a scientific category including whales, dolphins and porpoises) are endangered, including the North Atlantic right, blue, fin, sei and gray whales. In any case, marine mammals are heavily protected by law, so whale watching should be done with professionals who obey the rules.

Celebrating, protecting southern nature

With more than 500 full-time employees and an annual budget exceeding $30-million, Audubon Nature Institute sounds more like a business than a private, non-profit organization dedicated to explaining and preserving the wonders of nature with a Cajun flavor. The group operates a zoo, aquarium and assorted parks in and around New Orleans. The Aquarium of the Americas focuses on the Caribbean, Amazon, Gulf of Mexico (complete with oil-drilling replica) and Mississippi River.

A primate exhibit in the Audubon Zoo shows dozens of our opposable-thumbed relatives. Its 360 species of animals include a jaguar shown in a replica Amazon jungle. The “Embraceable Zoo” is devoted to full-contact animal admiration, and you can also eyeball, if not pet, a prickly Indian crested porcupine. Audubon maintains two locations that focus on captive breeding and survival of endangered species; these are closed to the public, but we expect to see you at the new insectarium, located in the old Federal customs house, for the beetle races on Sept. 3.

North Carolina: decapitation capitol

Every summer, vacationers flock to North Carolina’s coast for a beach getaway. But beach vacations would have been a hard sell early in the 18th century, as the coast was the stomping grounds of the South’s most feared pirate, Edward Teach, otherwise known as Blackbeard.

Nowadays, the area is proud of its sordid past, attracting pirate-curious tourists and archaeologists alike. In 1996, Blackbeard’s biggest and final ship, Queen Anne’s Revenge, was found off the coast of Beaufort, where it had been hiding for more than 270 years. While the dives did not uncover much treasure, archaeologists estimate the wreckage holds up to 750,000 artifacts, some of which are displayed at Beaufort’s North Carolina Maritime Museum.

Blackbeard is a primary local industry. Ocracoke Island, a favored Blackbeard anchorage, was where he met his fate at the hands of what he mocked as a rabble of “cowardly puppies.” Bath has the legendary ball of light, presumed to be Blackbeard’s ghostly severed head.

So why watch Johnny Depp impersonate a pirate at the multiplex when you can check out the history of this famous scoundrel? Like we said, this old, dead, head-free pirate is a godsend for small business…

Tar is my name. Fossils are my fame

If you’re stuck for a scientific sojourn in Southern California, head for the pits. Since long before there was a Los Angeles, the La Brea Tar Pits have been an oozing, 3-D flypaper for animals, now with that all-too-trendy urban accent. Asphalt, we learn, is not just good for roads, but also for trapping live animals and preserving their fossils. Since their first description in a scientific publication in 1875, the pits have produced prodigious prizes for paleontology. The onsite Page Museum houses more than 650 species of plants and animals, all removed from the black goo, and dating back 11,000 to 50,000 years.

The tar pits were a graveyard for thousands of carnivores, including the dire wolf, coyote and saber-toothed cat, and a smaller number of herbivores, including mammoth and bison. In an effort to transcend the “heroic” era of paleontology and flesh out (if we can put it that way) a comprehensive picture of life in the era of ice, researchers have recently shifted their focus to fossils of plants and smaller animals, including millipedes, 31 species of mollusks, and 25 species of beetles.

Listen hard: Hear the galaxies?

Love big? Dig distant, mysterious and unfathomably old? At the Very Large Array, in western New Mexico, you can gawk at 27 giant antennas used by astronomers to “listen” to radio signals from the universe. When you’re done rubber-necking the hardware, check out exhibits at the visitor center.

Then climb an observation tower to get another view of the world’s premier radio telescope zoo. Notice how every single antenna has silently and inexorably changed its orientation, and is now pointing to another invisible spot in the heavens? You are looking at visual proof of our planet’s normally insensible rotation.

It takes a lot of work, and some hefty equipment, to pry loose the secrets of the universe, and here, the scale of the operation is written across the desert. Since 1980, the VLA has, alone or in tandem with other telescopes, been collecting the astrophysical evidence for the formation and destruction of stars and galaxies. The new “enhanced VLA” can “hear” three times as many radio bandwidths as the VLA and is 10 times more sensitive. How sensitive is that? They say it could hear a cellphone calling from Jupiter…

Go under cover in the capital city

Explore life under cover (and the technology that allows a spy to hide in plain sight) at the International Spy Museum, the only public museum of its kind in the United States. With the largest public collection of international espionage artifacts, the museum provides a unique global perspective of this covert profession — said to be the second oldest — and how it has shaped the past and present.

Before you start your mission, you are challenged to adopt a secret identity. As you snoop about, you’ll discover the Secret History of History, which highlights the influence of spies through the ages; gadgets and stories of espionage during the American Civil War, World War II, and Cold War; and a gallery of spy technology. You can even see if you have what it takes to be an agent in the Operation Spy interactive experience, in which you must find a missing nuclear trigger before it ends up in the wrong hands. Just don’t blow your cover!

Visit the “Boneyard”

Warplanes go to the desert to die, and there, for a fee, you can tour thousands of mothballed fighters, bombers and helicopters at the 309th Aerospace Maintenance and Regeneration Center. Bus tours run from the Pima Air and Space Museum, on the outskirts of Tucson, Ariz. With more than 4,200 planes, the “boneyard” is the ultimate in aerial combat nostalgia.

Some of these planes will be scrapped, others may be sold or salvaged for parts, or pressed back into service during future wars. Seldom celebrated, but perhaps more important from a technological point of view, the site also stores 350,000 tools used to make these machines, including, we presume, the one-of-a-kind tools and dies used to shape jet engines, wings and fuselages.

Ogling killing machines may seem macabre, but then, if you are a U.S. taxpayer, you’ve already paid for this stuff… might as well check it out, and witness how the technology of aerial warfare has changed over the decades!

Edison’s Garden of Invention

In 1887, after he had patented the first practical electric light bulb, mega-inventor Thomas Edison invented an inventor’s playground in West Orange, N.J., just outside Manhattan. Edison stocked the lab with every resource needed to crank out movie cameras and projectors, teletypes, recording and playback devices, batteries and countless other electric gadgets for the fast-modernizing nation.

With labs focusing on chemistry and physics, and with shops devoted to woodworking and metal-working, Edison could concentrate on his strong points: cranking out ideas and masterminding publicity stunts that helped ensure his commercial success. During World War I, 10,000 people cranked out electrical devices for the military at the factories clustered around the lab. Edison worked at the West Orange lab until his death in 1931.

Think of Edison as primarily an inventor? Then you have to wonder how his name wound up on the companies selling electricity to New York and Chicago. God may have made the Garden of Eden, but Thomas Edison made the garden of invention in north Jersey, and it awaits your visit.

– David J. Tenenbaum & Jenny Seifert

The death toll from the May 22, 2011 tornado in Joplin – now 122 — is the latest tragedy of a horrific year for tornadoes. On April 27, twisters in Alabama and nearby states killed 314, the fourth highest in U.S. history. The 480 deaths in 2011 are already the highest number since 1953, and tornado season continues through mid-August.

The Why Files asked Jonathan Martin, an expert on the large atmospheric disturbances that form tornadoes, some questions about tornado prediction. We edited the answers of Martin, a professor of atmospheric and oceanic sciences at the University of Wisconsin-Madison, after the interview.

The Why Files: What must we know to make a good tornado prediction?

The Why Files: Are predictions getting more accurate?

The Why Files: Why so much damage and death this year? Is this a result of climate change?

Japan, a world leader in earthquake engineering, has been paralyzed by a series of giant waves that followed one of the most violent earthquakes in a century.

Although the magnitude 9.0 quake on Mar. 11, 2011, apparently did not collapse high-rise buildings, the ensuing tsunamis flattened vast areas along the northeast coast. The death toll is swelling steadily as bodies wash in on the surf, and citizens and Japan’s Self Defense Forces scour a landscape turned upside down by inconceivably powerful waves.

The news recalls the estimated 250,000 people who perished, mainly on the Indonesian island of Sumatra, in the 2004 “Christmas tsunami” that followed a huge, offshore quake. (Both Japan and Indonesia are volcanic lands in the Ring of Fire, which partly surrounds the Pacific Ocean in a giant series of subduction zones and volcanoes.)

Shortly after Japan stopped shaking at 2:46 pm local time on Friday, March 11, we began hearing about troubles at a series of nuclear plants. After the reactors automatically shut down during the quake, emergency systems for removing heat still being generated in the reactors were routinely switched on.

But because the electric grid was down and the standby generators were damaged — perhaps by seawater — the emergency cooling failed. By Tuesday, March 15, three reactors had exploded, a fourth was burning, radioactive material was airborne, reactor workers were being evacuated, electricity was growing short in Tokyo, and the crucial containment vessels were under severe threat if not already breached.

With the first nuclear meltdowns since Chernobyl, in 1986, under way, global stock markets were crashing.

What causes tsunamis?

As Japan licks its wounds, The Why Files wants to know what causes tsunamis. How do they travel across the ocean? How they have impacted coastal people through history? Can we reduce our vulnerability to nature at its most cataclysmic?

Graphic: Anthony Liekens

Movement of the sea floor translates into waves at the surface.

Tsunamis — once slangily called tidal waves — are extremely powerful waves caused by large undersea disturbances. (“Tsunami” derives from Japanese for “harbor wave,” reflecting the fact that harbors can concentrate their energy. True tidal waves are the slow oscillations that drive ocean tides in response to solar and lunar gravity.)

Although landslides and volcanoes cause some tsunamis, probably 95 percent result from underwater earthquakes that contain a strong vertical motion. Such quakes often occur where one of Earth’s tectonic plates dives, or “subducts,” beneath another.

Like the Sunda trench near Sumatra, the subduction zone in the Japan trench is notorious for large earthquakes, says Timothy Masterlark, an associate professor of geological science at the University of Alabama. Although the timing is always uncertain, he says, “The history was known, big earthquakes were known, and even though the people and government went to great lengths to prepare, at some level … there is simply nothing they can do.”

Lessons from Sumatra

Masterlark, who has studied the giant, 2004 earthquake and tsunami in Sumatra, says the magnitude 9.0 earthquake in Japan likely broke a fault stretching at a shallow angle from the sea floor roughly 150 kilometers beneath Japan, along a trench several hundred kilometers in length.

We asked Masterlark how, if the slip was mainly horizontal, the rocks had enough vertical movement to cause a tsunami. “In Sumatra, we found a shallow slip created some vertical movement because the rock at the surface was softer, so the fault became more vertical, which changed the slip from mostly horizontal to mostly vertical.”

To imagine how vertical movement of the seafloor causes a tsunami, imagine making waves by throwing a stone in a pond. Even though earthquakes disturb the bottom of the water, the analogy works: just as a larger stone, thrown faster, makes a larger wave, the size of the tsunami depends on extent and speed of the ocean-floor movement.

The tsunami is usually most intense close to the earthquake: as waves spread from the epicenter in a typical arc-shaped pattern, their energy also spreads out.

Spread out, but still powerful

One factor that distinguishes tsunamis from more familiar waves is their extreme wavelength. On the open ocean, the peaks of waves may be 300 kilometers apart, and they may travel at 500 to 600 miles per hour. Even though they can keep pace with a jetliner, you wouldn’t see a tsunami from the cockpit of a jet. A killer tsunami may be only 2 feet tall in mid-ocean — far too small to be noticed from an airplane or even a ship, yet it can carry huge amounts of energy across the Pacific.

All that kinetic energy can hide in waves we can barely see because long-wavelength waves are extremely deep, and the massive amount of water moving beneath the surface contains enormous energy.

In deep water, boats can ride the worst tsunamis without noticing them; but when they reach shallow water and “run aground,” these waves become dangerous.

Like all waves, tsunamis slow when the lower part of the wave encounters the upward-sloping ocean floor. But while the front of the wave slows, the wave behind is still moving faster, causing a giant pile-up at the front, and the kinetic energy that was spread through the ocean depth concentrates in a towering wave at the surface.

Wild waves

It is these surface waves — which can be 10 meters high or taller as they cross the beach — that cause the utter destruction of tsunamis. Like all waves, tsunamis have both a rising and a falling motion, says Masterlark. “Depending on where you are with respect to the earthquake, you may first see a wall of water, or the opposite, the sea retreating.” In 2005, during a research cruise to Sumatra, “We were told that the tourists had heard that the ocean was retreating, and saw this as a great holiday, ‘Let’s walk on the seashore,” and this wall of water came in and killed them. This was a great warning, when they saw the water retreat, they should have headed away from the shore.”

Tsunamis have other quirks. They can be spaced as much as one hour apart, so subsequent waves can kill those who return to help victims of earlier waves.

In 1998, Harry Yeh, a civil engineering professor now at the University of Oregon, told us that tsunamis can have decidedly unconventional behavior. In one case, he said, a tsunami destroyed houses in a cove without damaging a house on an unprotected headland: “It’s the exact opposite of what a storm wave would do.”

A warning

Modified from original image by NASA

Location of foreshocks, aftershocks and the March 11 Japan earthquake (M 9.0). Circle size represents quake magnitude. Dotted lines = foreshocks; solid lines = aftershocks

The Pacific Tsunami Warning Center, established in Hawaii in the wake of the deadly 1946 tsunami, is a nexus in the global warning network. Since almost all tsunamis originate in earthquakes, the warning centers rely on data from seismographs, many of them located on the unstable ring of fire.

Tsunami warnings are now triggered automatically, says Masterlark, based on measurements of earth movement. “Seismographs are excellent because in seconds they can tell that a quake of some magnitude, big enough to trigger a tsunami, has occurred. This information can automatically trigger a warning in seconds.”

In tsunamis, seconds saved can translate into lives saved.

Researchers are working to use global positioning system (GPS) data to refine size estimates, Masterlark adds, to give “a more refined view of the potential risk, but this takes a little longer and is still in a research mode.”

Further confirmation of the size of the wave may come from special purpose ocean buoys, if they are in the right place, Masterlark says. “But they only work once the tsunami has already arrived, so they can only confirm or help refine the warning.”

Tricks of the tsunami trade

In terms of generating tsunamis, not all underwater earthquakes are created equal, says Andrew Newman, assistant professor of earth and atmospheric sciences at Georgia Tech. “A few times a decade, we have what we call ‘tsunami earthquakes’ that create a tsunami that’s much larger than would be expected for the magnitude of the earthquake,” largely due to a shallow rupture. “Usually a magnitude 7.8 earthquake would create a tsunami that might rise only 20 centimeters to 1 meter [when it reaches land], but one in Sumatra last year created a 17-meter tsunami.”

These large tsunamis come from a smaller break in the ocean floor, and so contain relatively little energy and do not travel well across the ocean, Newman says. But they also offer less warning because local people do not feel the massive shaking associated with a major tsunami.

Newman and colleagues have developed software to detect the peculiar signature of the tsunami earthquake, and are now running it on a research basis. “We get an earthquake or tsunami warning within four or five minutes, our algorithm starts processing, and a few minutes after that, the system sends email to the Pacific Tsunami Warning Center and the U.S.G.S. [Geological Survey],” Newman says.

Although the Japanese had little time between the earthquake and the tsunami, Newman says the national warning system did work. “In some ways, you have to look at real success in Japan. They have developed a substantial tsunami warning system, and it worked in as quickly as three minutes. People did evacuate, for the large part. Much of the video you see is from helicopters, or people watching from two or three stories up in buildings. There is only so much you can do with these events; this is a massive force.”

But the rising casualty counts highlights the deadly role of proximity to the quake, says Masterlark. “The very sad part is that because the quake was so close to the coast, they had very little warning; the time between the earthquake and the tsunami was minutes.”

More distant regions had adequate warning, Masterlark adds. “We had several hours before the wave reached Hawaii, and so were prepared. But Japan, unfortunately, even if you knew it was coming, you had only minutes, and that’s not enough time for many people to get to higher ground.”

Photo: Sarah Ruth

Basic tsunami safety

Public education and quick personal action remain the only ways to reduce the tsunami death toll:

1. Be on guard for strong earthquakes, which can spark a tsunami. If you feel one near the water, run inland.

2. Heed the warnings, and stay tuned to emergency radio stations.

3. Never go down to the beach to watch for tsunamis — they move much faster than you can run. People die doing this.

4. Most structures in the danger zone provide no protection. However, the upper stories of tall, reinforced concrete hotels can provide refuge if you have no time to move inland or to higher ground.

5. A tsunami is a series of waves. Don’t go near the water until you hear the all-clear from emergency authorities.

Following fatal footsteps?

Seismologists are loathe to predict earthquakes, but in the past decade or two, they have recognized that earthquakes occur in series along major faults in Turkey and Sumatra, as big quakes place extra stress on the adjacent fault. In Sumatra, a violent series of quakes began in 2004 with a magnitude 9.1, a magnitude 8.7 in 2005, a magnitude 7.6 in 2009, and a magnitude 7.7 in 2010.

The large quake in 2005 did not cause a major tsunami, but its timing, just three months after the Dec. 26 monster, suggests a compelling reason to focus intensively on the earthquake zone in the Japan trench, says Masterlark. “I am not trying to be alarmist, but I’m trying to look at where earthquakes have occurred along nearby faults to identify faults at risk. We’ll bring in numerical modeling and try to predict this as fast as possible. Time is of the essence, as we saw in Sumatra.”

For decades, scientists have thought that the pre-historic Antarctic climate was governed by events at the other end of the planet — in the Arctic. That’s because variations in solar radiation in the northern summer tracked nicely with the temperature record from sediment cores and ice cores taken on or around Antarctica.

Our record of temperatures in the deep south is carried in the ratios of oxygen and hydrogen isotopes (atoms with different masses) contained in ice cores. But Thomas Laepple, of the Alfred Wegener Institute for Polar and Marine Research in Germany, has just published an article maintaining that because the Antarctic ice cores did not accumulate at a steady pace, they have not been interpreted correctly.

Today, more snow (the source of ice), gathers in winter. Because that likely also happened in the past, ice cores from Antarctic tell us more about winter than summer, says Laepple.

And God created winter!

Photo 1: Hans Oerter, Alfred Wegener Institute, Germany, Photo 2: Eric Cravens, National Ice Core Lab

This 150,000-year-old piece of Antarctic ice is 10 centimeters in diameter, and was taken from a depth of 2,250 meters. After researchers clean, measure and catalog this core, it may be stored in a giant freezer like the one in the next image (rollover).

When Laepple and his colleagues factored in this seasonal effect, the level of sunlight in the southern hemisphere suddenly began to explain Antarctic temperatures. Although the orbital cycles still globally affect solar radiation, there was no longer a need to look at the other end of the Earth to explain rhythms in Antarctic temperatures.

The orbital cycles in question are named for Serbian engineer Milutin Milankovitch, who, about a century ago, sought to understand how three slow shifts in Earth’s orbit would affect the amount of sunshine in different regions, different seasons and years.

These orbital variations, which are influenced by gravity of the moon, sun, Jupiter and Saturn, are the basis of the “Milankovitch cycle:”

As scientists examined ocean sediments and then ice cores, the Milankovitch influence on solar radiation in the Northern hemisphere became the accepted explanation for the changing global climate. But when Laepple factored in the seasonal nature of Antarctic snowfall, he found that Milankovitch could explain the climate on the southern continent more directly. “I don’t question that the Milankovitch cycle has an influence on climate,” says Laepple, “but I question that its influence on the Antarctic is coming through the Artic.”

The adjustment was needed because more ice accumulates during winter and does not affect the overall climate record, Laepple says, “but it completely changes the recording of the signal stemming from the precession of the earth axis, which was the evidence for the remote North-South connection.”

Photo 1: Steven Profaizer, Photo 2: Sepp Kipfstuhl, Alfred Wegener Institute, Germany

Scientists use massive drills to uncover the stories about past climates told in ice cores (roll over for to see a core from a depth of 2,668 meters).

How would you explain it?

Climate is never simple, notes Richard Alley, a climate expert and professor of earth science at Penn State, who was not involved in the research. The Milankovitch cycle, he says, “shifts sunshine around on the planet, with more in some places and less in others, changing the length of seasons, the total sunshine during seasons … so it is not surprising that multiple hypotheses can be advanced to explain a given climate record. Ultimately, the mere fact of correlation is not the answer; we seek understanding of the physical linkages. … The new paper provides a clever new idea for a physical linkage, and I anticipate it will get people discussing and studying.”

Any new study concerning climate processes could get sucked into the political vortex enmiring global warming, so we asked if Laepple’s study of Antarctic conditions should lead us to question the widely-accepted theory that burning fossil fuels and changing land use have altered the climate.

Laepple reminded us that he’s studying changes that occur over periods of 10,000 years. He also insists that the new analysis “will not change the basic record of glacial and interglacial periods — the march of ice ages over the past million years. We are focusing on the precession cycle [the 21,000-year cycle affecting the location of Earth's axis], as this provides the evidence showing where and how the climate is affected by radiation changes, and might hold the key to the mechanism of slow climate change.”

Years ago, scientists began to revise their interpretation of Greenland ice to account for the seasonality in snowfall, Laepple says. “This new study is part of a long discussion. As we interpret the climate record, we have to focus more on how the climate signal gets recorded in the climate record.”

Photo: Oct. 7, 2010, friedrich glorian

With red sludge still visible, women survey the damage in Hungary. Eight died when a dike burst at a factory that processed ore into alumina, a raw material for aluminum.

Have you seen the photos of aluminum sludge surging through villages in Hungary, heading for the Danube River? With eight people dead, and new cracks appearing in the wall containing a pond-ful of alkaline sludge, we’re left to hope that the toxic crud is defanged by dilution before it does too much damage to the mighty Danube.

Still, the spill got us to thinking about the plight of the world’s rivers. Rivers are our foremost source of freshwater, used for drinking, industry and agriculture. Their wetlands and floodplains clarify water, temper floods, and provide an irreplaceable habitat for countless plants and critters, many of which are the major source of protein for hundreds of millions of people.

But a new study in the journal Nature shows that the globe’s rivers are being lambasted by pollution and invasive species. Heavy burdens of artificial fertilizer have created dead zones at the mouth of hundreds of rivers. Rivers are being over-fished, channeled into barge canals, and drained for irrigation, industry and drinking water.

Graphic: Barry Carlsen, copyright University of Wisconsin Board of Regents

A new analysis of 23 threats to global water security and biodiversity shows many regions with a high cumulative level of threats.

When the study¹ assessed river health in terms of pollution, biological change, watershed disturbance and water resource development, rivers carrying 65 percent of the total amount of water that rivers bring to the ocean “is moderately to severely threatened on a global basis,” says study co-author Peter McIntyre, a professor of zoology and freshwater expert at the University of Wisconsin-Madison.

Dam difficult

Both human water supplies and the natural world are endangered, McIntyre says. “One-quarter of the world’s vertebrate species live in fresh waters, and hundreds of thousands of plants and animals are at risk because they live in places where threats are high.” In total, biodiversity is more threatened in freshwater than it is in saltwater or on land, McIntyre says; ominous declines are being seen in fish, turtles, mussels and plants.

Lest “biodiversity” sound frivolous, estimates suggest that the value of “ecosystem services” like clean air and clean water exceeds the global economic output. The necessity of clean water is obvious, but we are also utterly reliant on plants, above and below water, to convert carbon dioxide into oxygen.

And these ecosystem services are best served by stable ecosystems.

Managing freshwater is a delicate balancing act, and some experts anticipate that tightening supplies will lead to disputes or even water wars later in the century. The U.S. government says if current trends continue, “by 2025, one-third of all humans will face severe and chronic water shortages,” with the first and worst problems appearing in Africa and the Middle East.

Already, the Colorado River in the United States, and the Yellow River in China, are so thoroughly exploited that they scarcely reach the ocean. Low flows and massive pollution plague rivers in China, India, the Middle East and Africa.

Nile denial

Photo: Bionet

The Nile River supplies virtually all water in Egypt (notice how fields cluster along the river?) and major portions in Uganda, Sudan and Ethiopia. The Nile is polluted by sewage and agricultural chemicals, and is failing to supply growing populations along its dry lower stretches with enough water for a good standard of living. With a watershed that includes parts of 11 nations, disputes over the Nile’s water could devolve into war.

Water security vs. environment: Inevitable tension?

Although pollution, invasive species and overfishing play major roles in declining freshwater biodiversity, dams and associated water diversions are a fundamental part of the tension between environment and river development.

Dams are built to store and divert water, supply hydroelectric power and prevent floods. Dams, and the locks that allow ships to traverse them, remain a keystone of river management in Western Europe and the United States, which is home to an estimated 75,000 dams.

While dam construction is largely over in Europe and North America (where some dams are even being removed), the 20th century was epic for dam building, says Bradley Udall, director of the Western Water Assessment at the University of Colorado. Udall notes that the volume of water stored behind dams has risen 350 times since 1900, to 5,000 cubic kilometers.

At the same time, Udall notes, due to such alterations as damming, draining, levees and development, “We have destroyed one-half of wetlands worldwide, which are very important for all kinds of ecological services, including water purification.” (Watch 23,000-plus large dams spread across the world.)

Chinese (river) checkers

Dam building is booming in developing countries, as an answer to floods and shortages of water and electricity. China’s Three Gorges Dam was essentially completed in 2008, after more than 1 million people were moved away from a new lake that is expected to cover 400 square miles. With a planned electrical output equal to more than 20 large nuclear plants (about 10 times greater than Niagara Falls), Three Gorges was also intended to halt disastrous flooding on the Yangtze River.

The series of dams that China is building or planning along the Yangtze and its tributaries will generate even more electricity than Three Gorges.

Yangtze River in When, China

Photo: Doris Antony

The river, shows intense pollution and human habitation in a city of about 9 million.

Dams can raise issues in any location. As Three Gorges proved, they displace riverside villages and cities and drown archeological sites. As is happening at the Glen Canyon dam in the United States, reservoirs can fill with silt, losing storage capacity and causing erosion as downstream areas are deprived of their normal silt supplies.

Dams also divert money that could be used for other purposes.

Granted, dams are a critical source of usable water, but they can also be a scourge of native plants and animals. “There is definitely a tension between human infrastructure and biodiversity conservation,” says Laurence Smith, a professor of geography at the University of California at Los Angeles, and author of a new book on environmental trends².

China is embarked on the largest water project in history, a 50-year program to move water from the Yangtze toward population centers in the drier north. Designed to move 50 cubic kilometers per year, the project aims to reduce sandstorms and water shortages while bolstering sinking aquifers in North China.

U.S. Fish and Wildlife Service

Rivers in the North, like Alaska’s Koyukuk, are far less impacted by pollution, diversion and damming.

Failing fish

Courtesy Peter B. McIntyre

A man fishes at Igamba Falls, on the Malagarasi River, Tanzania, site of a proposed hydroelectric dam. Fish are a major source of protein — and dams are a major cause of fish declines.

Altering rivers with dams enacts fundamental changes in ecosystems, says Smith. “A lot of the most biologically diverse riverine environments are seasonally flooded wetlands and flood plains. Biodiversity is not found in a big reservoir behind a dam… It is more the episodic flooding [of natural rivers] that gives this diverse habitat.”

Dams block the migration of important fish species, including the salmon, which is vanishing along the Atlantic and Pacific coasts of the United States, where dams block the upstream spawning journey.

That problem is widespread, says McIntyre. “In the tropics, species like big catfish, and the family known as the tetras, are very intensively fished. You have regions where people depend on these migratory fish, and if you put in a dam to stop the migration — rivers are aquatic highways — you profoundly change the system. There’s a real concern that if fisheries collapse, hundreds of millions of people worldwide who get a majority of their protein from freshwater fish could go hungry.”

In the central United States, massive dams and engineering projects on rivers like the Illinois, Missouri, Mississippi, Tennessee, Wisconsin and Ohio have also been blamed for ecosystem destruction.

For example, locks and dams north of St. Louis on the Mississippi stabilize the water level so large barges can traverse the river. But that stability, combined with extensive levees on the banks, has eliminated vast wetlands that once bordered the river. When the river no longer surges in the spring and subsides in the fall, remaining flat land along the river turns to muck that can no longer support native plants and animals.

Photo: Jason Sturner

Massive engineering projects along the upper Mississippi River have essentially changed the river into a barge canal.

Biodiversity black hole

One reason to foster biodiversity in rivers and watersheds is this: Biological systems with many interacting species tend to be more stable, and people, like other animals, have adapted to a fairly stable environment. “In experiments with bacteria, if you strip away species, you eventually hit a point where the basic properties change,” says zoologist Peter McIntyre. “It can be on a plateau of high function for a while, but there is a threshold, and we can’t predict where it occurs, things start to fall apart.”

The classic analogy, McIntyre says, “is popping rivets on the wing of an airplane; you pop one too many, and boom! down you go. In the global river context, we are rolling the dice, we know we are losing species. The rates of extirpation and extinction are highest in freshwater; and that is where we are seeing the worst human impacts.”

Scientists who are looking more broadly at the health of river ecosystems are hampered by a lack of information. “There are no global data sets” that would support an exact measurement on the biological health of rivers around the world, says Carmen Revenga, a freshwater scientist at the Nature Conservancy.

Still, new evaluations of biodiversity are delineating the difficulties. Revenga says a recent assessment listed 253 endemic species of freshwater fish in the Mediterranean — meaning they are found nowhere else — and 56 percent of them are threatened with extinction. Another survey found severe declines among 40 percent of the 300 species of freshwater turtles, she adds. “Nobody would have guessed it was that bad.”

The inevitable tension between environment and human water use is growing more intense in dry places such as Africa and Australia, with heavy population pressure and intense land usage.

When farms, people or industry get thirsty, “Freshwater biodiversity has not tended to play role in discussions about water security,” Revenga says. “Usually there is a lot of focus on providing water that is secure and safe. Irrigation took precedence at first, and now cities take precedence, but the ecosystem hardly gets included.”

The sad, dry Aral Sea

Photo: Gilad Rom

The Aral Sea in Central Asia dried up after the rivers that fed it were diverted to irrigate vast cotton farms.

And that leaves less water for ecological purposes, Revenga adds. “When we calculate the amount of runoff in a basin, we assume we can tap all the water that’s available” for human uses. “The conservation and environmental community has not interacted with the water supply community, and the environment is almost forgotten.”

Mono Lake in California, whose water was diverted to Los Angeles in the 1940s, is one example showing that cities and farms have come first in American water management. According to the Mono Lake Committee:

In recent decades, California has been pressured to allot some water to environmental purposes, part of a gradual rebalancing of water use in the dry, densely populated American Southwest.

We’ll explore evidence of progress in water management in the next Why Files, but note that cities like New York rely on watershed protection to ensure a clean, adequate water supply. “It’s a very good strategy to protect upland forest, and reduce siltation and runoff into streams, but a lot of projects don’t look at biodiversity in the river,” Revenga says. Watershed protection is rare, and in any case the ecological benefits are secondary to the need to provide clean water to cities, she adds.

Climate change

As more people look to rivers to supply more water, there’s one final factor to consider: the climate. Brad Udall of the University of Colorado, an expert on the waters of the West, told us that climate change is not just about temperature. “You could make a compelling argument that it’s about changes to water cycles; changes in the quantity, quality and timing, almost all of which are detrimental” to freshwater supplies.

In general, Udall says, studies of ancient climate show that “wet areas get wetter and dry areas get drier.” In the Colorado River basin, where climate change has been intensely studied, “we can expect a 10 percent to 20 percent reduction in runoff by 2050.”

Photo: Laslovarga

Hoover Dam and its reservoir Lake Mead are major factors in Western water management, but at what environmental cost?

Because so many rivers in the American West are fed by melting snow, warmer winters already have a major impact, Udall says, with the earlier spring causing earlier runoff in the rivers. Studies project that the floods could happen as much as 60 days earlier in the spring, “and we are already seeing 20-day advances, especially in lower-level snow-dominated systems, like in the Pacific Northwest.”

At the same time, river flow is likely to diminish earlier in the late summer, and the water will also be warmer, Udall says, which poses problems for life. “Many critters in the water are stressed in high temperature, which also carries less dissolved oxygen.”

Dry conditions in late summer also contribute to a longer wildfire season in the West.

Climate change may be even more catastrophic where drinking water comes from rivers sourced in melting glaciers, Udall warns. Large cities like Bogotá and Lima in South America, “could go from having a glacier upstream one day to not having it the next. The United States does not have that problem, but in the Andes, there is potential for very harsh consequences.”

The Ganges: A river or a sewer?

Photo: Daniel Bachhuber

Worshippers leave heaps of offerings alongside the Ganges river in Varanasi. It’s easy enough to hose away the dregs into the river, but that just adds more pollution to the “Mother Ganges.” Says Science Daily, the Ganges “contains untreated sewage, cremated remains, chemicals and disease-causing microbes. … Cows wade in the river. People wash their laundry in it and drink from it. … The Ganges River is a major source of disease.”
If this can happen to a sacred river…

Summary judgment

Rivers collect runoff from their watersheds, and therefore carry messages about conditions from most of the land on our planet. As the authors of the recent Nature study found, trying to assess the health of rivers around the world is not for the data-shy. Differences in economy, history, geography and culture all affect how we view rivers, and how we decide whether to use, alter or preserve them.

Photo: Steve Dewey, Utah State University, Bugwood.org

Purple loosestrife is striking, but it invades wetlands near rivers, reducing biodiversity, destroying habitat for native species, and reducing the ability to filter water.

But most “decisions” that affect rivers, like allowing them to be polluted with chemicals, topsoil or fertilizer, or building a dam to store water for the dry season, are made not with rivers in mind, but with another goal, like growing more food or getting people something to drink.

“You don’t miss your water ’til your well runs dry,” pertains to rivers as well as groundwater, says Peter McIntyre, one author of the recent global river survey. “In the industrialized world, we go home at night, turn on the faucet and get beautiful, clear water, it’s safe to drink and bathe; it poses no risk to us and our kids. Mass investments in engineering and infrastructure have granted us this water security.”

As developing countries, where people struggle to find water for faucets, farms and factories, embark on the dam-building that was so crucial to European and American water supplies, saying “don’t do what we did” seems hypocritical at best and repugnant at worst.

And yet experience shows that dams can damage or destroy plants and animals in rivers and their floodplains. We’ll concede that questions about biodiversity, the environment and the long term seldom interest people who are hungry or thirsty. But they may still be worth asking. Will a proposed dam harm an essential fishery? Will it produce benefits over the long term, or will it silt up in a decade because trees have been stripped from its watershed?

There are lessons to be learned from the water-management experience in Europe and North America, and one of the most significant one is to expect a continual tension between human water use and biodiversity. “I am not pretending there is an easy answer,” McIntyre says, “or that I should have the right to dictate to that person whether they build a dam or not.”

Coming Oct. 28: Part II : The Why Files will discuss some river-management ideas for balancing human and environmental needs.

Why do some rocks break so easily once an earthquake begins? In a giant quake, the fracture, where the two sides of the fault grind against each other, can extend dozens or hundreds of miles. The question has met several answers over the years.

According to one theory, rocks get hot enough at the break to form a slippery layer of glassy rock along the fault. But that is not entirely satisfactory, says Ze’ev Reches, a professor of geoscience at the University of Oklahoma, because large earthquakes can form where the rocks are too cool to form glass.

“For some reason, friction seems to decline during a break, but what is the mechanism?” he asks.

In a laboratory study in this week’s Nature, Reches and David Lockner of the U.S. Geological Survey showed that a thin layer of rock powder that forms at the break causes a rapid drop in friction, which allows the break to spread further and faster down the fault. “The powder itself is a lubricant and it reduces the friction when it forms,” he says.

• Haiti. January 12, 2010. Magnitude: 7.0.

  Photo: United Nations Development Programme
  

• San Francisco, CA. April 18, 1906. Magnitude: 7.8

  Photo: Chadwick, H. D./NARA National Archives and Records Administration
  

• Chile. February 27, 2010. Magnitude: 8.8, and March 5, 2010. Magnitude: 6.6.

  Photo: Nico Ibieta
  

• Indonesia. September 30, 2009. Magnitude: 7.5.

  Photo: United Nations Development Programme
  

• Turkey. August 17, 1999. Magnitude: 7.6.

  Photo: yolalmis
  

Rock ‘n rotate

To test rock samples, the researchers used a press that rotated one sample against another, producing a motion that was more representative of actual earthquakes, and also much longer and faster than previous researchers have studied. The study showed that a thin layer of rock powder can weaken the fault by at least 50 percent, Reches says.

The results concern how rock can slip once a fault breaks. It would be nice to know how the first rupture occurs, Reches says, but conditions in fault zones are so varied “that there is always a place where it’s significantly weaker, or is under a significantly higher load, so it starts moving. The question becomes, how far will this movement go?”

And the answer depends on how much friction remains in the broken portion, he says.

The rotary rock-grinder also showed that the powder, called gouge, ceases to lubricate within hours or days. “Everybody has seen the powder in faults and in experiments, but it was always taken for granted that the gouge does not change its properties,” Reches says. “What we have discovered is fundamentally different: The gouge has to be formed fresh, each time, to obtain this lubrication.”

Courtesy Ze’ez Reches

A close-up of the test apparatus shows lubricating powder that formed when rocks were ground against each other to simulate earthquake movement.

Break, dancing

The original powder is composed of grains that are “a few tens of nanometers across, but then because of adhesion between the grains it starts forming much larger clusters,” Reches says. The small grains can slip against each other, “but once they form these clusters, it takes a lot of energy to break them, so friction rises.”

“The internal workings of earthquake faults is one of the great unsolved problems of geophysics,” says Harold Tobin, a fellow fan of faults who is professor of geoscience at the University of Wisconsin-Madison. “Understanding the friction and mechanisms inside a fault, as it suddenly goes from hundreds of years of building up tremendous stress to rupturing in an earthquake, would help us understand why, where and when earthquakes occur. Experiments like the ones reported by Reches and Lockner are a key tool for getting at how earthquake faults slip.”

The study, Tobin says, is “a window on how an initial cracking turns into an earthquake. In my view, the study is not a game-changer in terms of our understanding of earthquake faults, but it does provide some solid data that will feed into better theories and models.”

Bearing it out

The study could help explain why the many tiny quakes that occur each day do not set off major quakes, Reches says. “In Oklahoma, we have magnitude 2 or 3 quakes but they don’t grow, because the conditions surrounding the break are not suitable. Why an earthquake occurs is not related to the initiation, but to the weakness that allows it to propagate.”

Photo: Scott Haefner/U.S. Geological Survey

The San Andreas Fault in California is active and deadly.

The phenomenon could also explain the “creeping section” of the San Andreas Fault, near Parkfield, California. Beyond both ends of the 120-mile section, the fault produces lethal, magnitude 8 quakes, Reches says, yet quakes in between release less than 10,000 times as much energy. “Although it’s on such a major active fault, the creeping section accommodates the motion in a very different mode. It might be that the rocks in this zone are not capable, once the motion starts, of creating the gouge that would lubricate it.”

With medium- and large-size earthquakes, Reches says, “the fundamental issue is, what is the mechanism of the weakening? What we have found is that once it starts moving, the formation of gouge makes it much weaker than before the movement started.”

– David J. Tenenbaum