A new wrinkle in ancient ocean chemistry

UC Riverside's Chris Reinhard analyzes metal content in 2.5 billion-year-old black shale using a mass spectrometer seen to his left. -  UCR Strategic Communications.
UC Riverside’s Chris Reinhard analyzes metal content in 2.5 billion-year-old black shale using a mass spectrometer seen to his left. – UCR Strategic Communications.

Scientists widely accept that around 2.4 billion years ago, the Earth’s atmosphere underwent a dramatic change when oxygen levels rose sharply. Called the “Great Oxidation Event” (GOE), the oxygen spike marks an important milestone in Earth’s history, the transformation from an oxygen-poor atmosphere to an oxygen-rich one paving the way for complex life to develop on the planet.

Two questions that remain unresolved in studies of the early Earth are when oxygen production via photosynthesis got started and when it began to alter the chemistry of Earth’s ocean and atmosphere.

Now a research team led by geoscientists at the University of California, Riverside corroborates recent evidence that oxygen production began in Earth’s oceans at least 100 million years before the GOE, and goes a step further in demonstrating that even very low concentrations of oxygen can have profound effects on ocean chemistry.

To arrive at their results, the researchers analyzed 2.5 billion-year-old black shales from Western Australia. Essentially representing fossilized pieces of the ancient seafloor, the fine layers within the rocks allowed the researchers to page through ocean chemistry’s evolving history.

Specifically, the shales revealed that episodes of hydrogen sulfide accumulation in the oxygen-free deep ocean occurred nearly 100 million years before the GOE and up to 700 million years earlier than such conditions were predicted by past models for the early ocean. Scientists have long believed that the early ocean, for more than half of Earth’s 4.6 billion-year history, was characterized instead by high amounts of dissolved iron under conditions of essentially no oxygen.

“The conventional wisdom has been that appreciable atmospheric oxygen is needed for sulfidic conditions to develop in the ocean,” said Chris Reinhard, a Ph.D. graduate student in the Department of Earth Sciences and one of the research team members. “We found, however, that sulfidic conditions in the ocean are possible even when there is very little oxygen around, below about 1/100,000th of the oxygen in the modern atmosphere.”

Reinhard explained that at even very low oxygen levels in the atmosphere, the mineral pyrite can weather on the continents, resulting in the delivery of sulfate to the ocean by rivers. Sulfate is the key ingredient in hydrogen sulfide formation in the ocean.

Timothy Lyons, a professor of biogeochemistry, whose laboratory led the research, explained that the hydrogen sulfide in the ocean is a fingerprint of photosynthetic production of oxygen 2.5 billion years ago.

“A pre-GOE emergence for oxygenic photosynthesis is a matter of intense debate, and its resolution lies at the heart of understanding the evolution of diverse forms of life,” he said. “We have found an important piece of that puzzle.”

Study results appear in the Oct. 30 issue of Science.

“Our data point to oxygen-producing photosynthesis long before concentrations of oxygen in the atmosphere were even a tiny fraction of what they are today, suggesting that oxygen-consuming chemical reactions were offsetting much of the production,” said Reinhard, the lead author of the research paper.

The researchers argue that the presence of small amounts of oxygen may have stimulated the early evolution of eukaryotes – organisms whose cells bear nuclei – millions of years prior to the GOE.

“This initial oxygen production set the stage for the development of animals almost two billion years later,” Lyons said. “The evolution of eukaryotes had to take place first.”

The findings also have implications for the search for life on extrasolar planets.

“Our findings add to growing evidence suggesting that biological production of oxygen is a necessary but not sufficient condition for the evolution of complex life,” Reinhard said. “A planetary atmosphere with abundant oxygen would provide a very promising biosignature. But one of the lessons here is that just because spectroscopic measurements don’t detect oxygen in the atmosphere of another planet doesn’t necessarily mean that no biological oxygen production is taking place.”

To analyze the shales, Reinhard first pulverized them into a fine powder in Lyons’s laboratory. Next, the powder was treated with a series of chemicals to extract different minerals. The extracts were then run on a mass-spectrometer at UC Riverside.

“One exciting thing about our discovery of sulfidic conditions occurring before the GOE is that it might shed light on ocean chemistry during other periods in the geologic record, such as a poorly understood 400 million-year interval between the GOE and around 1.8 billion years ago, a point in time when the deep oceans stopped showing signs of high iron concentrations,” Reinhard said. “Now perhaps we have an explanation. If sulfidic conditions could occur with very small amounts of oxygen around, then they might have been even more common and widespread after the GOE.”

Said Lyons, “This is important because oxygen-poor and sulfidic conditions almost certainly impacted the availability of nutrients essential to life, such as nitrogen and trace metals. The evolution of the ocean and atmosphere were in a cause-and-effect balance with the evolution of life.”

Fortuitous research provides first detailed documentation of tsunami erosion

In the summer of 2006, this area strewn with rocks and logs near the shore of Ainu Bay on Matua Island in the Kurils was covered by about 6 feet of sand and soil, about even with the top of the 6-foot-6 white rod in the center of the photo. When researchers had excavated there previously they did not encounter any of the boulders they later found exposed by the tsunami. -  Breanyn MacInnes
In the summer of 2006, this area strewn with rocks and logs near the shore of Ainu Bay on Matua Island in the Kurils was covered by about 6 feet of sand and soil, about even with the top of the 6-foot-6 white rod in the center of the photo. When researchers had excavated there previously they did not encounter any of the boulders they later found exposed by the tsunami. – Breanyn MacInnes

Tsunamis are among the most-devastating natural calamities. These earthquake-generated waves can quickly engulf low-lying land and bring widespread destruction and death. They can deposit sand and debris far inland from where they came ashore.

Now, for the first time, a group of scientists working in the Kuril Islands off the east coast of Russia has documented the scope of tsunami-caused erosion and found that a wave can carry away far more sand and dirt than it deposits.

The fortuitous observations resulted because the Kuril Biocomplexity Project had made detailed surveys of some Kuril Island coastlines during the summer of 2006, and then returned for additional work in the summers of 2007 and 2008. That provided a unique opportunity for before-and-after comparisons following a magnitude 8.3 earthquake and accompanying tsunami on Nov. 15, 2006, and an 8.1 quake and resulting tsunami on Jan. 13, 2007.

When the scientists revisited coastlines they had surveyed in 2006, they found that in some places the amount of sand and soil removed by tsunami erosion was nearly 50 times greater than the amount deposited.

“It was so extreme. I was really surprised,” said Breanyn MacInnes, a University of Washington doctoral student in Earth and space sciences.

The team observed shorelines stripped of vegetation, small hills of soil and volcanic cinders washed away to expose boulders and, in one place, the unearthed rusty remnants of military equipment left behind at the end of World War II.

“We were there the year before and it had been completely covered with vegetation, and there were ridges closer to shore that had been completely removed when we returned,” MacInnes said.

She is the lead author of a paper describing the observed differences in erosion and deposition, published in the November issue of the journal Geology. Co-authors are Joanne Bourgeois, a UW professor of Earth and space sciences and MacInnes’ doctoral adviser, and Tatiana Pinegina and Ekaterina Kravchunovskaya of the Far East Branch of the Russian Academy of Sciences. The work was funded by the National Science Foundation and the Russian Academy of Sciences Institute of Marine Geology and Geophysics.

The Nov. 15, 2006, Kurils earthquake was large enough to raise alarms about the potential for a tsunami throughout the Pacific basin. Only very tiny waves were recorded on the Japanese island of Hokkaido, relatively near the Kurils. However, a tsunami nearly 6 feet high did more than $10 million damage to the harbor at Crescent City, Calif., some 4,500 miles away.

The Kurils themselves were hit by tsunami waves more than 70 feet high in some places, and changes in topography were dramatic.

The amount of erosion from a tsunami depends somewhat on the topography of the land, but definitely is related to the force of the wave, the scientists found. They noted that an area called South Bay on Matua Island lost about 50 cubic meters, or about 1,765 cubic feet, of sediment per meter of width, while an area called Ainu Bay lost an astounding 200 cubic meters, or about 7,060 cubic feet, of sediment per meter of width because of tsunami-induced erosion.

At a spot called Dushnaya Bay, where the tsunami was at a relatively low elevation at its greatest distance from shore, the biggest change occurred on the sandy beach, with about 5 cubic meters, or about 177 cubic feet, of sediment eroded per meter of width.

In other areas, relatively fine volcanic sand from the shore and much coarser volcanic cinders unearthed from ridges were deposited well inland, but the amount of sediment deposited was far less than the amount eroded, the researchers found.

Some of the landscape scars will remain visible for decades, or even centuries, the scientists reported. For example, along Ainu Bay ridges were removed, depressions were scoured into the topography and a lake was breached and drained.

“One thing we really noticed was that anywhere there had been human disturbance, like the remnants of a military base or even just a fencepost, there was always some sort of blowout or deeper erosion,” MacInnes said.

She noted that geologists have long considered erosion to be an important factor in studying tsunamis.

“There are a lot of papers that describe erosion but they can’t really quantify it. Our study is the first to say, ‘This much sand was removed from the coast,'” she said.

“This emphasizes that erosion is something to consider when assessing a community’s risks and vulnerability.”

Volcanoes played pivotal role in ancient ice age, mass extinction

Researchers at Ohio State University have discovered that volcanoes played a pivotal role in a deadly ice age that occurred nearly half a billion years ago. This photograph shows volcanic ash beds -- formed around 455 million years ago -- layered in the rock of the Nashville Dome area in central Tennessee. -  Photo by Matthew Saltzman, courtesy of Ohio State University.
Researchers at Ohio State University have discovered that volcanoes played a pivotal role in a deadly ice age that occurred nearly half a billion years ago. This photograph shows volcanic ash beds — formed around 455 million years ago — layered in the rock of the Nashville Dome area in central Tennessee. – Photo by Matthew Saltzman, courtesy of Ohio State University.

Researchers here have discovered the pivotal role that volcanoes played in a deadly ice age 450 million years ago.

Perhaps ironically, these volcanoes first caused global warming — by releasing massive amounts of carbon dioxide into the atmosphere.

When they stopped erupting, Earth’s climate was thrown off balance, and the ice age began.

The discovery underscores the importance of carbon in Earth’s climate today, said Matthew Saltzman, associate professor of earth sciences at Ohio State University.

The results will appear in the journal Geology, in a paper now available online.

Previously, Saltzman and his team linked this same ice age to the rise of the Appalachian Mountains. As the exposed rock weathered, chemical reactions pulled carbon from Earth’s atmosphere, causing a global cooling which ultimately killed two-thirds of all species on the planet.

Now the researchers have discovered the other half of the story: giant volcanoes that formed during the closing of the proto-Atlantic Ocean — known as the Iapetus Ocean — set the stage for the rise of the Appalachians and the ice age that followed.

“Our model shows that these Atlantic volcanoes were spewing carbon into the atmosphere at the same time the Appalachians were removing it,” Saltzman explained. “For nearly 10 million years, the climate was at a stalemate. Then the eruptions abruptly stopped, and atmospheric carbon levels fell well below what they were in the time before volcanism. That kicked off the ice age,” he said.

This is the first evidence that a decrease in carbon from volcanic degassing — combined with continued weathering of the Appalachians — caused the long-enigmatic glaciation and extinction in the Ordovician period.

Here is the picture the researchers have assembled: 460 million years ago, during the Ordovician, volcanoes along the margin of what is now the Atlantic Ocean spewed massive amounts carbon dioxide into the atmosphere, turning the world into a hothouse. Lava from those volcanoes eventually collided with North America to form the Appalachian Mountains.

Acid rain — rich in carbon dioxide — pelted the newly exposed Appalachian rock and wore it away. Chemical reactions trapped the carbon in the resulting sediment, which formed reefs in the vast seas that covered North America.

For about 10 million years, the volcanoes continued to add carbon to the atmosphere as the Appalachians removed it, so the hothouse conditions remained stable. Life flourished in the warm oceans, including abundant species of trilobites and brachiopods.

Then, 450 million years ago, the eruptions stopped. But the Appalachians continued weathering, and atmospheric carbon levels plummeted. The Earth swung from a hothouse to an icehouse.

By 445 million years ago, glaciers had covered the south pole on top of the supercontinent of Gondwana (which would eventually break apart to form the continents of the southern hemisphere). Two-thirds of all species had perished.

When they started this research, Saltzman and his team knew that Earth’s climate must have changed drastically at the end of the Ordovician. But they didn’t know for certain that volcanoes were the driving force, explained Seth Young, who did this research for his doctoral degree at Ohio State. He is now a postdoctoral researcher at Indiana University.

“This was not necessarily what we expected when we started investigating, but as we combined our data sources, the story began to fall into place,” Young said.

Using a computer model, they drew together measurements of isotopes of chemical elements — including strontium from rocks in Nevada and neodymium from rocks in Virginia and Pennsylvania — with measurements of volcanic ash beds in the same locations. Then they factored in temperature models developed by other researchers.

The ash deposits demonstrated when the volcanoes stopped erupting; the strontium levels indicated that large amounts of volcanic rock were being eroded and the sediment was flooding Earth’s oceans during this time; and the neodymium levels pinpointed the Appalachians as the source of the sediment.

The new findings mesh well with what scientists know about these ancient proto-Atlantic volcanoes, which are thought to have produced the largest eruptions in Earth’s history. They issued enough lava to form the Appalachians, enough ash to cover the far ends of the earth, and enough carbon to heat the globe. Atmospheric carbon levels grew 20 times higher than they are today.

This study shows that when those volcanoes stopped erupting, carbon levels dropped, and the climate swung dramatically back to cold. The timing coincides with today’s best estimates of temperature fluctuations in the Ordovician.

“The ash beds start building up at the same time the Appalachian weathering begins, but then the record of volcanism ends, and the temperature drops,” Saltzman said. “Knowing these details can help us understand how carbon in the atmosphere is changing Earth’s climate today.”

Next, the researchers will examine the role of the ancient volcanic ash more closely. While the ash was in the atmosphere — before it settled around the globe — it might have blotted out the sun, and cooled the earth somewhat. Saltzman and his team want to make some estimate of this short-term cooling effect to refine their computer model.

Meanwhile, Young is just starting to re-analyze the same rock samples, this time looking for a different isotope — sulfur. This, he hopes, will offer clues to how much oxygen was in the oceans, and how that oxygen may have affected life in the Ordovician.

Tsunami waves reasonably likely to strike Israel

There is a likely chance of tsunami waves reaching the shores of Israel,” says Dr. Beverly Goodman of the Leon H. Charney School of Marine Sciences at the University of Haifa following encompassing geoarchaeological research at the port of Caesarea. “Tsunami events in the Mediterranean do occur less frequently than in the Pacific Ocean, but our findings reveal a moderate rate of recurrence,” she says.

Dr. Goodman, an expert geo-archaeologist, exposed geological evidence of this by chance. Her original intentions in Caesarea were to assist in research at the ancient port and at offshore shipwrecks. “We expected to find the remains of ships, but were surprised to reveal unusual geological layers the likes of which we had never seen in the region before. We began underwater drilling assuming that these are simply local layers related to the construction of the port. However, we discovered that they are spread along the entire area and realized that we had found something major,” she explains.

Geological drilling – in areas of 1-3 meters in length and at various depths – enabled Dr. Goodman to date the underwater layers using two methods: carbon-14 dating and OSL (optically stimulated luminescence). She found evidence of four tsunami events at Caesarea: in 1500 BC, 100-200 CE, 500-600 CE, and 1100-1200 CE.

In an article published in Geological Society of America Bulletin, Dr. Goodman explains that the earliest of these tsunamis resulted from the eruption of the Santorini volcano, which affected the entire Mediterranean region. The later, more local tsunami waves, Dr. Goodman assumes, were generated by underwater landslides caused by earthquakes. “‘Local’ does not necessarily imply ‘small’. These could have been waves reaching 5 meters high and as far as 2 km onshore. Coastal communities within this range would have undoubtedly been severely damaged from such a tsunami. While communities onshore clear the ground after such an event and return to civilization, tsunami evidence is preserved under the water,” she explains.

Geologists studying groundwater arsenic levels in India empower Bengali women, children

A Kansas State University geologist and graduate student are finding that the most important tools in their fieldwork on groundwater arsenic pollution are women and children armed with pamphlets and testing kits.

“When going into a foreign land, you need the common people’s help, support and understanding of the work you are doing,” said Saugata Datta, a K-State assistant professor of geology.

Datta’s research examines arsenic levels in the groundwater in Bangladesh and West Bengal, India. In his quest to understand how and why the naturally occurring arsenic gets into groundwater, Datta is helping Bengalis identify contaminated water sources so they can make more informed decisions about where to dig wells as they look for cleaner water. At K-State, Datta is joined by Andrew Neal, a master’s student in geology from Byron, Ga.

“We are targeting the women and children 13 to 15 years old, because they are the most available people, more so than the men of the family,” Datta said. “These women are not formally educated, but when it comes to this type of suffering, they have a huge voice and they can really articulate the message very clearly to their neighbors and their own families.”

The researchers give women and children information about how sediment traits like color and texture may indicate arsenic contamination. They also arm them with arsenic testing kits to use when wells are being drilled in their communities. If these water testing kits indicate high levels of arsenic, they can send a sample to a laboratory in the city for further testing before more contaminated water is distributed to the community. These tests are being done for both shallow and deep aquifers in those districts.

Although much research and action has been done to mitigate arsenic contamination in Bangladesh, the researchers said the process has been slower in India.

“They are very nice people in West Bengal, but when you talk to them you see that they are very frustrated,” Neal said. “They want to have some way of knowing how they can get rid of this problem. They want to know where to get clean water to drink so their kids don’t get sick.”

Datta said that some of the wells that the researchers tested have 30 times more arsenic than is accepted by the World Health Organization and the U.S. Environmental Protection Agency. Datta said the effects of arsenic in groundwater aren’t apparent immediately but rather build up over time. It causes skin lesions and skin cancer that spreads to other parts of the body. It can lead to paralysis and organ failure.

“Technically this is a natural source of pollution,” Datta said. “The major hypothesis is that the Himalayan river systems that feed the Ganges-Brahmaputra-Meghna delta have been carrying down sediments that are the major source of arsenic. These sediments in the form of specific minerals and in the right environmental conditions trigger the release of arsenic into the groundwater.”

The researchers suggest that as the arsenic-rich water enters the river, the chemistry causes it to precipitate and adhere to iron-bearing minerals in the sediments.

In effect, they said, the sediments form an “iron curtain” to keep the arsenic out of surface water in the river. But recycling of these arsenic-laden sediments to the Ganges-Brahmaputra-Meghna delta aquifer may lead to further groundwater contamination.

Datta is collaborating with Karen Johannesson at Tulane University and John F. Stolz at Duquesne University.
Results of studies by Datta and Columbia University researchers in the Meghna River in Bangladesh appeared Oct. 6 in the journal Proceedings of the National Academy of Sciences. Neal presented their research at the Geological Society of America meeting Oct. 18-21 in Portland, Ore.

Glacial melting may release pollutants in the environment

Pollutants from melting glaciers may help explain an increase in persistent organic pollutants in certain lakes since the 1990s, despite decreased used of pesticides. -  Wikimedia Commons
Pollutants from melting glaciers may help explain an increase in persistent organic pollutants in certain lakes since the 1990s, despite decreased used of pesticides. – Wikimedia Commons

Those pristine-looking Alpine glaciers now melting as global warming sets in may explain the mysterious increase in persistent organic pollutants in sediment from certain lakes since the 1990s, despite decreased use of those compounds in pesticides, electric equipment, paints and other products. That’s the conclusion of a new study, scheduled for the Nov. 1 issue of ACS’ Environmental Science & Technology, a semi-monthly journal.

In the study, Christian Bogdal and colleagues focused on organic pollutants in sediment from a model body of water — glacier-fed Lake Oberaar in the Bernese Alps, Switzerland — testing for the persistent organic pollutants, including dioxins, PCBs, organochlorine pesticides and synthetic musk fragrances. They found that while contamination decreased to low levels in the 1980s and 1990s due to tougher regulations and improvements in products, since the late 1990s flow of all of these pollutants into the lake has increased sharply. Currently, the flow of organochlorines into the lake is similar to or even higher than in the 1960s and 1970s, the report states.

The study attributed the most recent spike in the flow of pollutants into Lake Oberaar to the accelerated release of organic chemicals from melting Alpine glaciers, where contaminants were deposited earlier and preserved over decades. “Considering ongoing global warming and accelerated massive glacial melting predicted for the future, our study indicates the potential for environmental impacts due to pollutants delivered into pristine mountainous areas,” Bogdal said.

Seismic noise unearths lost hurricanes

Seismologists have found a new way to piece together the history of hurricanes in the North Atlantic-by looking back through records of the planet’s seismic noise. It’s an entirely new way to tap into the rich trove of seismic records, and the strategy might help establish a link between global warming and the frequency or intensity of hurricanes.

“Looking for something like hurricane records in seismology doesn’t occur to anybody,” said Carl Ebeling, of Northwestern University in Evanston. “It’s a strange and wondrous combination.”

The research is attempting to address a long-standing debate about whether the warming of sea-surface waters as a result of climate change is producing more frequent or more powerful hurricanes in the North Atlantic. It’s a tough question to answer.

Before satellite observations began in the 1960s, weather monitoring was spotty. Ships, planes, and land-based monitoring stations probably missed some hurricanes, which tend to last for about a week or so, Ebeling said. This type of uncertainty poses a problem for scientists, who can’t identify trends until they know what the actual numbers were.

To fill in the historical blanks, Ebeling and colleague Seth Stein are looking to seismic noise, an ever-present background signal that bathes the surface of the Earth. Seismic noise derives its energy from the atmosphere and then gets transmitted through the oceans into the solid earth, where it travels as waves. Seismometers record the noise as very low-amplitude wiggle patterns with much larger, obvious signals that come from earthquakes. Subtle changes in seismic noise frequency and amplitude have long been ignored.

Ebeling and Stein analyzed digital seismograms dating back to the early 90s from two monitoring stations: one in Harvard, Mass., and one in San Juan, Puerto Rico. For this study, the researchers looked at seismograms recorded during known hurricanes in an attempt to see whether patterns produced during hurricanes look predictably different from patterns produced during regular storms or when there are no storms at all.

Their preliminary results suggest that hurricanes do indeed produce recognizable patterns, and the waves generated by hurricanes travel large distances. The Harvard station recorded signals from Hurricane Andrew more than a thousand kilometers away.

“There’s definitely something there that shows this can be workable,” Ebeling said. “This is something new and interesting.”

At least one major hurdle remains before scientists will be able to pull together a complete hurricane history out of the seismic records. For most of the 20th century, seismograms recorded data on rolls of paper. Those records, which contain hundreds of thousands of hours of data, will need to be digitized. Ebeling is looking for an efficient way to do that.

As Greenland melts

This is a drill drilling for an ice core sample in Northwest Greenland.  The North Greenland Eemian ice-drilling project hopes to reach ice layers just above Greenland's bedrock, where ice as much as 130,000 years old may hold clues to the impact climate change could have in the next few decades.
This is a drill drilling for an ice core sample in Northwest Greenland. The North Greenland Eemian ice-drilling project hopes to reach ice layers just above Greenland’s bedrock, where ice as much as 130,000 years old may hold clues to the impact climate change could have in the next few decades. – www.climatecentral.org

Not that long ago – the blink of a geologic eye – global temperatures were so warm that ice on Greenland could have been hard to come by. Today, the largest island in the world is covered with ice 1.6 miles thick. Even so, Greenland has become a hot spot for climate scientists. Why? Because tiny bubbles trapped in the ice layers may help resolve a fundamental question about global warming: how fast and how much will ice sheets melt?

Monday night on The NewsHour with Jim Lehrer (PBS), a report by Climate Central’s Dr. Heidi Cullen explores efforts by an international group of scientists looking for answers. Their method: drill down through 130,000 years of accumulated ice to unlock the secrets of climate history from what geologists call the Eemian period. That was the last time the average global temperature was significantly warmer than it is today, and tiny bubbles trapped in the ice preserve key planetary conditions from that time period.

Scientists from 14 nations are participating in the North Greenland Eemian Ice drilling project, or NEEM. Dr. Cullen, Senior Research Scientist for Climate Central (climatecentral.org), a non-profit, non-advocacy group of journalists and scientists dedicated to communicating about climate change, along with a television crew from StormCenter Communications, was invited to report the story. In July she accompanied scientists to North Western Greenland where she observed ice core drilling firsthand.

“Securing a pristine ice core dating back 130,000 years will provide a snapshot of conditions on Greenland when the average global temperature was 5 to 9 degrees Fahrenheit warmer than today,” says Dr. Cullen. “The Eemian provides a very realistic scenario of what we might see in the coming centuries.”

Climate Central scientists calculate that in 2007, Greenland shed ice at a rate that, melted, equals the equivalent of draining San Francisco Bay – once a week – all year long. Some climate models suggest that if greenhouse emissions are not reduced, Earth’s average temperature could approach Eemian era levels when today’s children reach their 70’s and 80’s. Another key question the ice samples may help answer: how long would temperatures have to remain at those levels – or higher – to trigger a major rise in sea level?

Ice cores have been a tool for science since the Cold War, after it was discovered that air bubbles trapped in ice are science rich time capsules. Each layer of ice is a world unto itself. As Jeff Severinghaus, of Scripps Institution of Oceanography, tells Dr. Cullen, “The beautiful thing about an ice core is that it has all of these different indicators: atmospheric composition, mean ocean temperature, dust.”

Dr. Cullen also reports that the Greenland project employs a new field technique – cutting a thin slab of the ice core, melting it, and conducting a millimeter-by-millimeter analysis of the drip water. When drilling ended for the 2009 summer season samples from one mile down had been retrieved, dating back over 38,000 years. Scientists hope to reach Eemian ice in the summer of 2011.

None of this is to suggest that a massive, accelerated melting of Greenland is in the offing any time soon – but as the San Francisco Bay analogy highlights -the melting in Greenland demands careful attention be paid.

Bedrock of a holy city: the historical importance of Jerusalem’s geology

Jerusalem’s geology has been crucial in molding it into one of the most religiously important cities on the planet, according to a new study.

It started in the year 1000 BCE, when the Jebusite city’s water system proved to be its undoing. The Spring of Gihon sat just outside the city walls, a vital resource in the otherwise parched region. But King David, in tent on taking the city, sent an elite group of his soldiers into a karst limestone tunnel that fed the spring. His men climbed up through a cave system hollowed out by flowing water, infiltrated beneath the city walls, and attacked from the inside. David made the city the capital of his new kingdom, and Israel was born.

In a new analysis of historical documents and detailed geological maps, Michael Bramnik of Northern Illinois University will add new geological accents to this pivotal moment in human history in a presentation Tuesday, October 20 at the annual meeting of the Geological Society of America in Portland.

“The karst geology played a major role in the city’s selection by David for his capital,” Bramnik said.

It proved to be a wise decision. One of David’s successors, King Hezekiah watched as the warlike Assyrian horde, a group of vastly superior warriors toppled city after city in the region. Fearing that they’d soon come for Jerusalem, he too took advantage of the limestone bedrock and dug a 550 meter-long (1804 feet) tunnel that rerouted the spring’s water inside the city’s fortified walls.

The Assyrians laid siege to the city in 701 BCE, but failed to conquer it. It was the only city in history to successfully fend them off.

“Surviving the Assyrian siege put it into the people’s minds that it was because of their faith that they survived,” Bramnik said. “So when they were captured by the Babylonians in 587, they felt it was because their faith had faltered.”

Until then, the Jewish religion had been loosely associated. But that conviction united the Jews through the Babylonian Captivity, “and so began modern congregational religion,” Bramnik said.

In an arid region rife with conflict, water security is as important today as it was during biblical times. While the groundwater for Jerusalem is recharged surface waters in central Israel, other settlements’ water sources are not publicly available for research. Bramnik’s efforts to find detailed hydrological maps were often rebuffed, or the maps were said to be non-existent.

“I think Jerusalem’s geology and the geology of Israel is still significant to life in the region, perhaps even reaching into the political arena,” he said.

Geologists point to outer space as source of the Earth’s mineral riches

According to a new study by geologists at the University of Toronto and the University of Maryland, the wealth of some minerals that lie in the rock beneath the Earth’s surface may be extraterrestrial in origin.

“The extreme temperature at which the Earth’s core formed more than four billion years ago would have completely stripped any precious metals from the rocky crust and deposited them in the core,” says James Brenan of the Department of Geology at the University of Toronto and co-author of the study published in Nature Geoscience on October 18.

“So, the next question is why are there detectable, even mineable, concentrations of precious metals such as platinum and rhodium in the rock portion of the Earth today? Our results indicate that they could not have ended up there by any known internal process, and instead must have been added back, likely by a ‘rain’ of extraterrestrial debris, such as comets and meteorites.”

Geologists have long speculated that four and a half billion years ago, the Earth was a cold mass of rock mixed with iron metal which was melted by the heat generated from the impact of massive planet-sized objects, allowing the iron to separate from the rock and form the Earth’s core. Brenan and colleague William McDonough of the University of Maryland recreated the extreme pressure and temperature of this process, subjecting a similar mixture to temperatures above 2,000 degrees Celsius, and measured the composition of the resulting rock and iron.

Because the rock became void of the metal in the process, the scientists speculate that the same would have occurred when the Earth was formed, and that some sort of external source – such as a rain of extraterrestrial material – contributed to the presence of some precious metals in Earth’s outer rocky portion today.

“The notion of extraterrestrial rain my also explain another mystery, which is how the rock portion of the Earth came to have hydrogen, carbon and phosphorous – the essential components for life, which were likely lost during Earth’s violent beginning.”