geology

Standing at the summit of one of the Alps’ tallest mountain passes in the fall of 218 B.C., Hannibal peered into enemy territory: Italy’s Po River Valley. The panorama was reassuring. Hannibal’s plan — a sneak attack of the Romans on their own soil — was at last within reach. As his army trudged along a snow-covered path, Hannibal, Carthage’s greatest military leader, used the sight of Italy to encourage his ailing troops to keep going.

They needed the encouragement.

The revolution started with a bang in 1980. For some, this revolution became a religion, even an orthodoxy. The true believers became proselytes and began to see signs supporting their viewpoint everywhere. But each time the proselytes claimed to have found yet another example in support of their “religion,” naysayers and doubters emerged. Two sides formed, each loudly castigating and questioning their opponents.

This back-and-forth ideological debate describes both the historical and still-ongoing struggle over a purported cause of mass extinctions: the meteor impact theory.

At the close of the Permian, 252 million years ago, conditions on Earth took a turn for the worse, nearly wiping out life on land and at sea in the planet’s most severe extinction event. Now, eons later, geologists are implicating a coal seam that dates to the “Great Dying” at the Permian-Triassic boundary in one of the modern world’s worst cancer epidemics.

In U.S. policy, the past year was dominated by discussions of energy and climate change issues, at least in the earth sciences realm. In the first year of his administration, President Barack Obama focused on his top campaign priorities — but between discussions of healthcare reform, trying to rejuvenate the economy and setting up his cabinet, he still found time to discuss the sciences.

Burying carbon dioxide in underground geologic formations is an attractive option for dealing with increasing carbon dioxide in the atmosphere. But before employing such schemes, researchers need to be sure that the greenhouse gas will actually stay put. Scientists have done everything from computer modeling to pumping vast amounts of carbon dioxide into the subsurface to find out if — and how — the gas might be trapped, but gauging how sealed the formations are over geologic time scales is difficult.

David Harwood’s geology field course for future teachers is not a network reality show — but it should be. The three-week course has all the humor, drama, exacting challenges and bleepable moments of “Survivor.” But in contrast to the staged setups of TV “reality” shows, Geology 160 offers billions of years’ worth of authentic geological history that students see, taste and scrape from under their fingernails.

David Harwood’s field geology course gives future teachers an introduction to several of geology’s most fundamental principles, including the stratigraphic basics described by Nicholas Steno in 1669. Go to the head of the class with this quick primer.

Reconstructing the history of supercontinents requires careful detective work. A variety of geological processes wipes the evidence clean, like a burglar who smears away his fingerprints. Yet even the most cautious criminals leave clues behind — and so do supercontinents.

What the planet’s past mass extinctions tell us about the future of life on Earth

The crash-landing of a 10-kilometer-wide asteroid 65 million years ago made for a very bad day for dinosaurs — or one very lucky day for mammals.

About 505 million years ago, the continent that would become North America straddled the equator. With no terrestrial plants or animals, the land was a barren landscape. The warm, shallow sea bordering the continent, however, hosted a carbonated reef teeming with a diverse array of organisms, most of which were relatively small bottom-dwellers. Periodically, the animals would get washed over the reef and deposited at its base, where their bodies accumulated in the muddy sediments. Today, these creatures are beautifully preserved in the Burgess Shale.

About four years ago, a group of scientists proposed that a series of giant, wedge-shaped sandy deposits found along the shores of southern Madagascar might be evidence of a giant tsunami — a “mega-tsunami” — generated by an asteroid that may have blasted into the Indian Ocean sometime in the last 10,000 years. Furthermore, the scientists said, such impacts and the resulting tsunamis may have occurred fairly frequently during this period. To search for evidence of these impacts, the researchers formed the Holocene Impact Working Group.

The Inca knew there was something sinister about the cinnabar they hauled out of the ground at Huancavelica in Peru hundreds of years ago. They called the mine the Mine of Death. Now, a new study has exposed a 3,500-year history of mercury pollution from the cinnabar mines, a much longer legacy than researchers had previously realized.

Lunar exploration is once again in full swing. Japan’s Kaguya and India’s Chandrayaan-1 satellites are currently in orbit around the moon. China’s Chang’e spacecraft, after a successful mission, has been intentionally crashed on the moon. And the United States’ Lunar Reconnaissance Orbiter is preparing to launch. These are all unmanned missions; humans haven’t been to the moon in more than 30 years. But we will probably return in the next decade, and when we do, we hope to dig even deeper to uncover the moon’s secrets.

Blogging on EARTH

The Quaternary Period — the geologic time period that includes human evolution up to the present — is now a bit longer than it used to be.

Blogging on EARTH

After months of threatening and rumbling, Mount Redoubt finally erupted late Sunday night.

Redoubt began to exhibit increasing unrest last fall, with seismic activity becoming markedly increased in January, and expectations of an imminent eruption were growing. On March 15, researchers detected four hours of continuous volcanic tremor and observed of a brief plume of gas and ash, according to the U.S. Geological Survey's Alaska Volcano Observatory.

In 1702, Francis Chadsey and his family bought 200 hectares of meadow and upland on the banks of the Brandywine Creek in southeastern Pennsylvania. Within a year, he built a mill for grinding wheat, oats and barley. Like other landowners in the region, Chadsey also built a small dam on the creek. He most likely used local stone to erect the 2.5- to 3.5-meter-high structure, behind which a small pond sprang up. From the pond, a conduit carried water that spilled over a wheel to produce power to run the mill.

Millions of years ago, the first animals emerged from their watery habitat to live on dry land. After becoming fully adapted to a terrestrial environment, however, some animals, such as whales, ultimately returned to the ocean. But the evolutionary steps involved in that watery return have long been a mystery. Now, some exceptional fossils — and one really old baby — are shedding some light on how whales went back to the sea.

Any gardener can tell you that earthworms play a major role in soil ecology. But that information hasn’t always been common knowledge. Charles Darwin was one of the first to study earthworms, and in 1881, he discovered the curious fact that many species leave behind calcite crystals as they work their way through the soil. Now, new research might shed some light on the enduring mystery of how and why earthworms produce the crystals.

Even before the birth of the planets, our solar system was hardly a lonely place. Small rocky bodies, called planetesimals, filled the inner solar system, eventually colliding together to form the planets. Now a new look at a group of ancient meteorites shows that at least some planetesimals generated their own magnetic fields — a feat many scientists thought extremely difficult for such small astronomical bodies. The work also has scientists rethinking how planets formed.

Mars may be mythologically known as the Red Planet, but its topography can be as captivating as its celestial glow. Several striking features stand out with only a glance at a topographic map of Mars: the odd distribution of land on its surface and the equatorial string of giant volcanoes known as the Tharsis Rise. Since Mars has no plate tectonics, how these unique features formed has been a longstanding mystery.