100 Million Years AD

Jan Zalasiewicz, a lecturer in geology at the University of Leicester, has published a new study looking at the lasting impression made by mankind -- 100 million years hence.

He takes the perspective of alien explorers arriving on Earth -- their geologists study the layers of rock, using the many clues to piece together its history over several billion years

A story unfolds of moving and changing continents, rising and falling oceans, ice ages, and evidence of life going back many millions of years. They grow familiar with its phases of change, the rise of great new ecosystems, and occasional catastrophic collapses of life, according to an announcement of the project.

But then they stumble on something quite different in a thin layer of rock: a striking signal of climate changes, extinctions and strange movements of wildlife across the planet. Following this trail, decoding clues in the rocks takes them to the petrified remains of cities, and finally to the fossilized bones of those, long dead, who built them.

Zalasiewicz says: "From the perspective of 100 million years in the future–a geologist's view–the reign of humans on Earth would seem very short: we would almost certainly have died out long before then. What footprint will we leave in the rocks? What would have become of our great cities, our roads and tunnels, our cars, our plastic cups in the far distant future? What fossils would we leave behind?

"My study shows how scientists put together clues from the rocks to understand the past, its landscapes and climate, and the nature of the creatures that inhabited it," he adds. "A thin layer of silt here, a trace formed by a crawling worm there–the clues are often subtle and difficult to read. But by such clues would future geologists–whether hyper-evolved rat or alien visitor–work out our story. My study explores which of our structures are likely to leave traces, and what future explorers might make of us and the impact we made on our environment.

"Looking to the distant future gives us a warning for the present: our activities have already left a significant footprint on the planet, and not a flattering one. It is not too late to limit it. We would not wish to be dubbed by future explorers the 'amazingly clever and utterly foolish two-legged ape'."

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New Deep-Sea Hydrothermal Vents, Life Form Discovered

A new "black smoker"--an undersea mineral chimney emitting hot springs of iron-darkened water--has been discovered at 8,500-foot depths by an expedition funded by the US National Science Foundation (NSF) to explore the Pacific Ocean floor off Costa Rica.

Scientists from Duke University, the Universities of New Hampshire and South Carolina, and the Woods Hole Oceanographic Institution in Massachusetts have named their discovery the Medusa Hydrothermal Vent Field.

The researchers chose that name to highlight the presence there of a unique pink form of the jellyfish order stauromedusae. The jellyfish resemble "the serpent-haired Medusa of Greek myth," says expedition leader Emily Klein, a geologist at Duke University.

The bell-shaped jellyfish sighted near the vents may be of a new species "because no one has seen this color before," says Karen Von Damm, a geologist at the University of New Hampshire.

According to Von Damm, stauromedusae are usually found away from high-temperature hydrothermal vents, where the fluids are a little bit cooler, not close to the vents as these are.
Aboard the Research Vessel (R/V) Atlantis, the researchers are studying ocean floor geology of the East Pacific Rise, one of the mid-ocean ridge systems where new crust is made as the earth spreads apart to release molten lava.

"Each new vent site has the potential to reveal new discoveries in interactions between hot rocks beneath the seafloor, the fluids that interact with those rocks and the oceans above, as well as a rich biosphere that depends on vent processes," says Adam Schultz, program director in NSF's Division of Ocean Sciences, which funded the expedition through its Ridge 2000 program. "This discovery has implications for understanding the origin of Earth's crust, its evolution over time and how living organisms adapt to extreme environmental conditions."

Jason II, a remotely-controlled robotic vehicle the scientists are using to probe the vent field, logged water temperatures of 330 degrees Celsius (626 degrees Fahrenheit) at the mouth of one of the vents. Jason II subsequently found a second vent about 100 yards away.

Von Damm said that heat-tolerant tubeworms found living on Medusa's chimneys, a type known as alvinellids, are commonplace in the equatorial Pacific and thrive on high-iron fluids. Jason also has retrieved two other types of tubeworms--tevnia and riftia--from the vent area.

In addition, the camera-studded robot, which can collect biological specimens with the aid of the mechanical arms it uses to remove rock samples, has gathered samples of mussels from the vent area.


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Scientists Use Seismic Waves To Locate Missing Rock Under Tibet

Geologists at the University of Illinois at Urbana-Champaign have located a huge chunk of Earth's lithosphere that went missing 15 million years ago. By finding the massive block of errant rock beneath Tibet, the researchers are helping solve a long-standing mystery, and clarifying how continents behave when they collide.

The Tibetan Plateau and adjacent Himalayan Mountains were created by the movements of vast tectonic plates that make up Earth's outermost layer of rocks, the lithosphere. About 55 million years ago, the Indian plate crashed into the Eurasian plate, forcing the land to slowly buckle and rise. Containing nearly one-tenth the area of the continental U.S., and averaging 16,000 feet in elevation, the Tibetan Plateau is the world's largest and highest plateau.

Tectonic models of Tibet vary greatly, including ideas such as subduction of the Eurasian plate, subduction of the Indian plate, and thickening of the Eurasian lithosphere. According to this last model, the thickened lithosphere became unstable, and a piece broke off and sank into the deep mantle.

"While attached, this immense piece of mantle lithosphere under Tibet acted as an anchor, holding the land above in place," says Wang-Ping Chen, a professor of geophysics at the University of Illinois. "Then, about 15 million years ago, the chain broke and the land rose, further raising the high plateau."

Until recently, this tantalizing theory lacked any clear observation to support it. Then doctoral student Tai-Lin (Ellen) Tseng and Chen found the missing anchor.

"This remnant of detached lithosphere provides key evidence for a direct connection between continental collision near the surface and deep-seated dynamics in the mantle," Tseng says.
"Moreover, mantle dynamics ultimately drives tectonism, so the fate of mantle lithosphere under Tibet is fundamental to understanding the full dynamics of collision."

Through a project called Hi-CLIMB -- an integrated study of the Himalayan-Tibetan Continental Lithosphere during Mountain Building, Tseng analyzed seismic signals collected at a number of permanent stations and at many temporary stations to search for the missing mass.
Hi-CLIMB created a line of seismic monitoring stations that extended from the plains of India, through Nepal, across the Himalayas and into central Tibet. "With more than 200 station deployments, Hi-CLIMB is the largest broadband (high-resolution) seismic experiment conducted to date," says Chen, who is one of the project's two principal investigators.

Using high-resolution seismic profiles recorded at many stations, Tseng precisely measured the velocities of seismic waves traveling beneath the region at depths of 300 to 700 kilometers. Because seismic waves travel faster through colder rock, Tseng was able to discern the positions of detached, cold lithosphere from her data. "We not only found the missing piece of cold lithosphere, but also were able to reconstruct the positions of tectonic plates back to 15 million years ago," Tseng says. "It therefore seems much more likely that instability in the thickening lithosphere was partially responsible for forming the Tibetan Plateau, rather than the wholesale subduction of one of the tectonic plates."

Other evidence, including the age and the distribution of volcanic rocks and extrapolation of current ground motion in Tibet, the researchers say, also indicates the remnant lithosphere detached about 15 million years ago.


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Diamonds from Outer Space

If indeed "a diamond is forever," the most primitive origins of Earth's so-called black diamonds were in deep, universal time, geologists have discovered. Black diamonds came from none other than interstellar space.

In a paper published online on December 20, 2006, in the journal Astrophysical Journal Letters, scientists Jozsef Garai and Stephen Haggerty of Florida International University, along with Case Western Reserve University researchers Sandeep Rekhi and Mark Chance, claim an extraterrestrial origin for the unique black diamonds, also called carbonado diamonds.

Infrared synchrotron radiation at Brookhaven National Laboratory was used to discover the diamonds' source.

"Trace elements critical to an 'ET' origin are nitrogen and hydrogen," says Haggerty. The presence of hydrogen in the carbonado diamonds indicates an origin in a hydrogen-rich interstellar space, he and colleagues believe.

The term carbonado was coined by the Portuguese in Brazil in the mid-18th century; it's derived from its visual similarity to porous charcoal. Black diamonds are found only in Brazil and the Central African Republic.

"Conventional diamonds are mined from explosive volcanic rocks [kimberlites] that transport them from depths in excess of 100 kilometers to the Earth's surface in a very short amount of time," says Sonia Esperanca, program director in the National Science Foundation's Division of Earth Sciences, which funded the research. "This process preserves the unique crystal structure that makes diamonds the hardest natural material known."

From Australia to Siberia, from China to India, the geological settings of conventional diamonds are virtually identical, said Haggerty. None of them are compatible with the formation of black diamonds.

Approximately 600 tons of conventional diamonds have been mined, traded, polished and adorned since 1900. "But not a single black/carbonado diamond has been discovered in the world's mining fields," Haggerty says.

The new data support earlier research by Haggerty showing that carbonado diamonds formed in stellar supernovae explosions. Black diamonds were once the size of asteroids, a kilometer or more in diameter when they first landed on Earth.


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