Why Is The Ocean Salty?

Pacific Ocean at dawn. Today's ocean salt has ancient origins. As the earth formed, gases spewing from its interior released salt ions that reached the ocean via rainfall or land runoff. (Credit: Michele Hogan)
Pacific Ocean at dawn. Today’s ocean salt has ancient origins. As the earth formed, gases spewing from its interior released salt ions that reached the ocean via rainfall or land runoff. (Credit: Michele Hogan)

The saltiness of the sea comes from dissolved minerals, especially sodium, chlorine, sulfur, calcium, magnesium, and potassium, says Galen McKinley, a UW-Madison professor of atmospheric and oceanic sciences.

Today’s ocean salt has ancient origins. As the earth formed, gases spewing from its interior released salt ions that reached the ocean via rainfall or land runoff.

Now, the ocean’s salinity is basically constant. “Ions aren’t being removed or supplied in an appreciable amount,” McKinley says. “The removal and sources that do exist are so small and the reservoir is so large that those ions just stay in the water.” For example, she says, “Each year, runoff from the land adds only 0.00005 percent of total ocean salts.”

In lakes, relatively rapid turnover of water and its dissolved salts keeps the water fresh – a water droplet and its ions will stay in Lake Superior for about 200 years, compared to roughly 100 to 200 million years in the ocean. “Even if you did have any accumulation of an ion in a lake, it would be washed out quickly,” McKinley explains.

Ocean salts, however, have no place to go. “The ions that were put there long ago have managed to stick around,” McKinley says. “There is geologic evidence that the saltiness of the water has been the way that it is for at least a billion years.”

Researchers monitor glaciers for long-haul study

Michael O'Neal, an assistant professor of geography at the University of Delaware, and his students spent two weeks in August studying glaciers in the Cascade Mountain Range in the Pacific Northwest.
Michael O’Neal, an assistant professor of geography at UD, and his students spent two weeks in August studying glaciers in the Cascade Mountain Range in the Pacific Northwest.

Michael O’Neal, an assistant professor of geography at UD who recently returned from a two-week field trip studying glaciers in the Cascade Mountain Range, describes a typical day of research: A five-mile vertical hike kicks things off. Careful note-taking fills most of the daylight hours. The hike back to camp (at an elevation of 3,000 feet) completes the cycle. And at the end of the trip, the thoroughgoing data will be inconclusive. Two weeks in the life of millennia-old glaciers is a very short span, after all.

But O’Neal, who’s spearheading a decade-long study monitoring glaciers in the Pacific Northwest, isn’t motivated by instant results. In fact, it’s the monumental challenge and scale of the systems he studies, he says, that he enjoys.

“There are as many as 10,000 glaciers in the Cascades region,” O’Neal said, “and realizing that as one person I can only study a few, or a few dozen, in my lifetime makes it a trick.

“A lot of time is spent trying to figure out exactly where the glaciers that you’re studying were in recent history–primarily the last 200 years,” he added, describing the nature of the fieldwork that he, two colleagues and 10 students from UD’s Department of Geography conducted on the Aug. 12-21 trip. “And that’s no easy task.

“For the last 10,000 years, alpine glaciers in the mid latitudes in the northern hemisphere have fluctuated back and forth,” he said, “and what we’re studying now are how changes in precipitation and temperatures over a span of years are affecting the larger valley glaciers in the region.”

Starting from the Canadian border and ending in Oregon, O’Neal’s August expedition with Brian Hanson, glaciologist and chairperson of UD’s Department of Geography; Daniel Leathers, climatologist and professor of geography at UD; and seven UD graduate and three undergraduate students, included visits to some of the larger valley glaciers in the Cascade range and tracked data being charted for the 10-year study.

Now in its second year, the monitoring process will include summertime field trips to Iceland, Greenland, Alsaka and the Canadian Rockies, as well, and will trace how patterns in precipitation and temperature affect glaciers over time.

“One of the things that the Department of Geography specializes in is especially cold climates, so in this study we’re trying to understand how glaciers vary naturally, and we’re particularly interested in recent glacier fluctuation in the Cascades,” O’Neal said. “We’re one of just a handful of groups working in that area of the country, so that makes the region all the more appealing.”

Adding that the study, at its conclusion, will leave some room for the growing debate over global warming, O’Neal emphasized that the primary goal is to better understand the natural variations of glaciers over time.

“Everybody has heard that glaciers are retreating,” he said, “and in a general sense that’s true. But understanding how much glaciers have retreated and when and how they have retreated is very difficult, and the data is very complex. In our fieldwork, we’re trying to understand how glaciers vary naturally. Glaciologists have observed–just in recent history–that these systems can advance by as much as 300 meters in a very short span of years, as they did in the 1980s. So knowing how and why they do this is vital for making any sweeping predictions of climate change.”

Given this scholarly angle, as well as the leisurely timeframe, the study, O’Neal said, allows for in-depth research and affords students the rare opportunity to take what they’ve learned beyond the classroom.

“If I’m excited about one thing, it’s that students from our department are getting the opportunity to do something they’d probably never do on their own,” he said. “We camp at about 3,000 feet and hike every day to about 7,000 or 8,000 feet. Students get exposed to icy, alpine landscapes, and getting to these locations is no small feat. It’s a physical challenge to study them on top of a mental challenge, and students get a real vision of what it means to be in these environments and why it’s so hard to study them. At the end of two weeks, there are enough scrapes and bruises for me to be glad that I’ve limited the trip to 10 days and 10 students, but the value of the experience is lasting.”

Two independent projects, launched during the summer’s trip, reflect this. One, by master’s candidate Adam Goldstein, a geology major from Wayne, N.J., will examine how heavy deforestation affects local summertime mountain temperatures (and, by extension, glaciers). The other, by senior Janine Howard, an environmental conservation major from Ridgefield, Conn., will draw on data she collected this summer for a presentation she’ll give with O’Neal at the annual conference of the Association of American Geographers in Boston next spring.

“Geography students at UD do work on ice and climate, so being involved in fieldwork is important for them, and in terms of their collaboration, we’re going to look for National Science Foundation funding,” O’Neal said.

Explaining the complex and long-term nature of the study, he added that most students who want to participate in the summertime field trips get the chance.

“There are warm periods, not unlike the one we’re in now, that have occurred frequently on 100-year time scales during the last 10,000 years,” O’Neal said, “and part of what we want to understand is how often they occurred and how many times in the past few thousand years glaciers retreated to their farthest extent. That is the kind of information we are trying to establish even before we try to tweak out how recent patterns of precipitation and temperature have affected glaciers in the Cascades.”

Fitting data collected from the study into a larger framework of glacier research is an even bigger goal, he added.

“The Pacific Northwest is a small region of the planet, and relating our data to research conducted in other regions–there are tens of thousands of glaciers on earth–will be tricky,” O’Neal said.

“One of the things we do believe–and one of the reasons we are studying glaciers in the Pacific Northwest, where there are decades-old precipitation patterns that last–is that precipitation and temperature are equally important in affecting the larger valley glaciers in the Cascade Range. In a lot of regions, that’s not true. But in the Pacific Northwest, the precipitation patterns tell at least half the story on how the glaciers out there behave. So the statement we can make from our research that hasn’t been made before is that understanding the role precipitation plays on glaciers in Cascades region is critical,” he said.

As a larger framework gets laid and the science community draws further evidence for global warming, O’Neal said that having conclusive data will be especially useful.

“I think that most of the people in this department would agree that if you look at the statistics of recent climate, the planet does seem to be warming,” he said. “But climate is the statistics of weather, and weather is noisy, and glaciers are poor proxies of climate change in general. They take a long time to respond. Their behavior is complicated and the natural variations of the systems are poorly understood. So while we hope that we’re a contributor to the global thought that global warming is affecting glaciers, we are really gathering data with the intent that it will go to the scientific community to give us all better tools for understanding the natural variations of glacial systems.”

Geologist Discovers Three New Minerals

On a geological expedition along the windswept slopes of the Larsemann Hills in Antarctica, UMaine geologist Edward Grew collected samples of the area’s unique rock formations that would later reveal three minerals previously unknown to science. The minerals, stornesite-(Y), chopinite and tassieite, are extremely rare and represented only by microscopic samples collected by Grew.

The unique mineralogy of the Larsemann Hills, located on the eastern shore of Prydz Bay in Princess Elizabeth Land, inspired Grew and his fellow researcher Chris Carson (now at Geoscience Australia) to make the four-month expedition in 2003 – 2004, which was funded by the National Science Foundation and made possible by the Australian Antarctic Division.

Grew and his colleagues identified and characterized the minerals using cutting edge technologies. Martin Yates used the powerful electron microprobe at UMaine to image the new minerals and measure their chemical compositions. Next, the minerals were sent to Olaf Medenbach at the Ruhr University (Bochum, Germany) and Thomas Armbruster at the University of Bern (Switzerland), who determined the new minerals’ optical properties and crystal structures, respectively. Then Grew submitted a complete dataset for each mineral to a special commission of the International Mineralogical Association, which formally approved them as valid new species. Grew has discovered a total of ten new minerals, and sees each as an opportunity to expand scientific understanding of the Earth and its complex geological processes.

“When new minerals are identified, some have little significance, and some end up being tremendously important,” said Grew. “They all tell us something about how rocks form. Ultimately, discoveries like these contribute to our understanding of the origin of rocks, plate tectonics and other processes, and give us valuable insights into temperature, pressure and other conditions within the Earth at different points of its history.”

Climate research gives clues to human expansion out of tropical Africa

New research that involves a University of Nebraska-Lincoln scientist has shed light on an important, but previously little-understood period in Africa’s climate history that has implications for understanding human evolution and the expansion of Homo sapiens out of tropical Africa.

In a paper published this week in the online version of the Proceedings of the National Academy of Sciences, a team headed by Andrew Cohen of the University Arizona and including UNL’s Jeffery Stone as the second author, reported findings from sediment cores recovered from one of the world’s deepest lakes, Lake Malawi in East Africa’s Great Rift Valley. Cohen, Stone and colleagues reported finding evidence of two extended periods of extreme aridity between 135,000 and 70,000 years ago, an important time in human pre-history.

“Prior to this research, there was not a really good terrestrial record of climate that stretched back through the period of human development and migration from the tropical region of Africa,” said Stone, an adjunct faculty member in the UNL Department of Geosciences who also has a research appointment at Arizona.

“Most of the previous records basically stretch back to the last glacial maximum, maybe 20,000 years. They show some really dry conditions and it’s assumed that that had a huge impact on human populations in Africa, but nobody really had a sense of what was going on before that.”

The scientists studied a variety of fossils and other sediments that settled to the lake bottom over the millennia and used them as proxies to interpret the climate at various times during the last 140,000 years. For example, diatoms, Stone’s specialty, are one-celled organisms having a silica skeleton that fossilizes readily. Different species of diatoms flourish or fail during different climatic conditions, so their relative abundance or absence provides a good indication of contemporary climate conditions.

What the diatoms and other proxies indicate is a Lake Malawi basin between 135,000 and 70,000 years ago that looked a lot different from the lush conditions found there today. Modern Lake Malawi has a surface area of 29,500 square kilometers (more than 11,000 square miles) and reaches a depth of 706 meters (more than 2,300 feet). Annual rainfall in its watershed varies from 800 to 2,400 millimeters a year (31-93 inches; for comparison, Lincoln averages 27.8 inches of rainfall per year).

But records from the sediment cores reveal two periods of megadrought, from 135,000 to 127,000 and 115,000 to 95,000 years ago, when the level of Lake Malawi fell 550 to 600 meters (1,800-1,970 feet) below present-day levels. The surrounding watershed was a semidesert that received less than 400 millimeters (16 inches) of rain per year, creating much drier conditions than occurred during the last glacial maximum, 35,000 to 15,000 years ago, when Lake Malawi’s level fell by only 30 to 200 meters.

There is little archaeological evidence of human habitation in tropical Africa during the megadroughts, a period that coincides with the earliest evidence of humans outside the region — about 125,000 years ago in North Africa and the Middle East.

The research by Stone and colleagues, however, indicates that tropical Africa’s climate became wetter after 70,000 years ago and reached conditions comparable to today by about 60,000 years ago. That period coincided with increased evidence of human habitation in the area, and closely coincided with increased aridity in other parts of the continent.

Cohen said the new finding provides an ecological explanation for the “Out-of-Africa” hypothesis that suggests that all humans descended from just a few people living in Africa sometime between 150,000 and 70,000 years ago. He said it’s possible that the human population crashed during the megadroughts, but rebounded when the climate became more hospitable. The growing human population eventually expanded down the Nile valley and dispersed around the globe.

The PNAS paper concluded that this timing is “consistent with the idea that the earlier (approximately 125,000 years ago) documented occurrence of modern humans in North Africa and the Levant represents ultimately unsuccessful ‘excursions’ out of Africa.”

The article is scheduled for publication in the Oct. 16 print edition of PNAS. The National Science Foundation, the International Continental Drilling Program and the Smithsonian Institution funded the research.

Carbon Dioxide Did Not End The Last Ice Age, Study Says

Lowell Stott, professor of earth sciences at the University of Southern California, examines a sediment core. (Credit: Dietmar Quistorf)
Lowell Stott, professor of earth sciences at the University of Southern California, examines a sediment core. (Credit: Dietmar Quistorf)

Carbon dioxide did not cause the end of the last ice age, a new study in Science suggests, contrary to past inferences from ice core records.

“There has been this continual reference to the correspondence between CO2 and climate change as reflected in ice core records as justification for the role of CO2 in climate change,” said USC geologist Lowell Stott, lead author of the study, slated for advance online publication Sept. 27 in Science Express.

“You can no longer argue that CO2 alone caused the end of the ice ages.”

Deep-sea temperatures warmed about 1,300 years before the tropical surface ocean and well before the rise in atmospheric CO2, the study found. The finding suggests the rise in greenhouse gas was likely a result of warming and may have accelerated the meltdown — but was not its main cause.

The study does not question the fact that CO2 plays a key role in climate.

“I don’t want anyone to leave thinking that this is evidence that CO2 doesn’t affect climate,” Stott cautioned. “It does, but the important point is that CO2 is not the beginning and end of climate change.”

While an increase in atmospheric CO2 and the end of the ice ages occurred at roughly the same time, scientists have debated whether CO2 caused the warming or was released later by an already warming sea.

The best estimate from other studies of when CO2 began to rise is no earlier than 18,000 years ago. Yet this study shows that the deep sea, which reflects oceanic temperature trends, started warming about 19,000 years ago.

“What this means is that a lot of energy went into the ocean long before the rise in atmospheric CO2,” Stott said.

But where did this energy come from” Evidence pointed southward.

Water’s salinity and temperature are properties that can be used to trace its origin — and the warming deep water appeared to come from the Antarctic Ocean, the scientists wrote.

This water then was transported northward over 1,000 years via well-known deep-sea currents, a conclusion supported by carbon-dating evidence.

In addition, the researchers noted that deep-sea temperature increases coincided with the retreat of Antarctic sea ice, both occurring 19,000 years ago, before the northern hemisphere’s ice retreat began.

Finally, Stott and colleagues found a correlation between melting Antarctic sea ice and increased springtime solar radiation over Antarctica, suggesting this might be the energy source.

As the sun pumped in heat, the warming accelerated because of sea-ice albedo feedbacks, in which retreating ice exposes ocean water that reflects less light and absorbs more heat, much like a dark T-shirt on a hot day.

In addition, the authors’ model showed how changed ocean conditions may have been responsible for the release of CO2 from the ocean into the atmosphere, also accelerating the warming.

The link between the sun and ice age cycles is not new. The theory of Milankovitch cycles states that periodic changes in Earth’s orbit cause increased summertime sun radiation in the northern hemisphere, which controls ice size.

However, this study suggests that the pace-keeper of ice sheet growth and retreat lies in the southern hemisphere’s spring rather than the northern hemisphere’s summer.

The conclusions also underscore the importance of regional climate dynamics, Stott said. “Here is an example of how a regional climate response translated into a global climate change,” he explained.

Stott and colleagues arrived at their results by studying a unique sediment core from the western Pacific composed of fossilized surface-dwelling (planktonic) and bottom-dwelling (benthic) organisms.

These organisms — foraminifera — incorporate different isotopes of oxygen from ocean water into their calcite shells, depending on the temperature. By measuring the change in these isotopes in shells of different ages, it is possible to reconstruct how the deep and surface ocean temperatures changed through time.

If CO2 caused the warming, one would expect surface temperatures to increase before deep-sea temperatures, since the heat slowly would spread from top to bottom. Instead, carbon-dating showed that the water used by the bottom-dwelling organisms began warming about 1,300 years before the water used by surface-dwelling ones, suggesting that the warming spread bottom-up instead.

“The climate dynamic is much more complex than simply saying that CO2 rises and the temperature warms,” Stott said. The complexities “have to be understood in order to appreciate how the climate system has changed in the past and how it will change in the future.”

Stott’s collaborators were Axel Timmermann of the University of Hawaii and Robert Thunell of the University of South Carolina. Stott was supported by the National Science Foundation and Timmerman by the International Pacific Research Center.

Stott is an expert in paleoclimatology and was a reviewer for the Intergovernmental Panel on Climate Change. He also recently co-authored a paper in Geophysical Research Letters tracing a 900-year history of monsoon variability in India.

The study, which analyzed isotopes in cave stalagmites, found correlations between recorded famines and monsoon failures, and found that some past monsoon failures appear to have lasted much longer than those that occurred during recorded history. The ongoing research is aimed at shedding light on the monsoon’s poorly understood but vital role in Earth’s climate.

Cave Records Provide Clues To Climate Change

A close up of one of the stalagmites analyzed in the study. (Credit: Jud Partin)
A close up of one of the stalagmites analyzed in the study. (Credit: Jud Partin)

When Georgia Tech Assistant Professor Kim Cobb and graduate student Jud Partin wanted to understand the mechanisms that drove the abrupt climate change events that occurred thousands of years ago, they didn’t drill for ice cores from the glaciers of Greenland or the icy plains of Antarctica, as is customary for paleoclimatolgists. Instead, they went underground.

Growing inside the caves of the tropical Pacific island of Borneo are some of the keys to understanding how the Earth’s climate suddenly changed – several times – over the last 25,000 years. By analyzing stalagmites, the pilar-like rock formations that stem from the ground in caves, they were able to produce a high-resolution and continuous record of the climate over this equatorial rainforest.

“These stalagmites are, in essence, tropical ice cores forming over thousands of years,” said Partin. “Each layer of the rock contains important chemical traces that help us determine what was going on in the climate thousands of years ago, much like the ice cores drilled from Greenland or Antarctica.”

The tropical Pacific currently plays a powerful role in shaping year-to-year climate variations around the globe (as evidenced by the number of weather patterns influenced by the Pacific’s El Nino), but its role in past climate change is less understood. Partin and Cobb’s results suggest that the tropical Pacific played a much more active role in some of the abrupt climate change events of Earth’s past than was once thought and may even have played a leading role in some of these changes.

Polar ice cores reveal that the Northern Hemisphere and the Southern Hemisphere each have their own distinct patterns of abrupt climate change; the tropical Pacific may provide the mechanistic link between the two systems. Understanding how the climate changes occurred and what they looked like is important to helping scientists put into context the current trends in today’s climate.

The research team collected stalagmites from the Gunung Buda cave system in Borneo in 2003, 2005 and 2006. Analyzing three stalagmites from two separate caves allowed the pair to create a near-continuous record of the climate from 25,000 years ago to the present. While this study is not the first to use stalagmites to examine climate over this time period, it is the first to do so in the tropical Pacific. Typically, in these types of studies, only one stalagmite is analyzed, but Partin and Cobb compared their three stalagmite records to isolate shared climate-related signals.

Stalagmites are formed as rain water, mixed with calcium carbonate and other elements, makes its way through the ground and onto the cave floor. As this solution drips over time, it hardens in layers, creating a column of rock.

Partin and Cobb cut open each stalagmite and took 1,300 measurements of their chemical content to determine the relative moisture of the climate at various periods in history starting from the oldest layers at the bottom to the present at the top. They dated the rocks by analyzing the radioactive decay of uranium and thorium, and determined the amount of precipitation at given times by measuring the ratio of oxygen isotopes.

“Our records contain signatures of both Northern and Southern Hemisphere climate influences as the Earth emerged from the last ice age, which makes sense given its equatorial location,” said Cobb. “However, tropical Pacific climate was not a simple linear combination of high-latitude climate events. It reflects the complexity of mechanisms linking high and low latitude climate.”

For example, Partin and Cobb’s records suggest that the tropical Pacific began drying about 20,000 years ago and that this trend may have pre-conditioned the North Atlantic for an abrupt climate change event that occurred about 16,500 years ago, known as the Heinrich 1 event.

“In addition, the Borneo records indicate that the tropical Pacific began to get wetter before the North Atlantic recovered from the Heinrich 1 event 14,000 years ago. Perhaps the tropical Pacific is again driving that trend,” said Partin.

“Currently our knowledge of how these dramatic climate changes occurred comes from just a few sites,” said Cobb. “As more studies are done from caves around the world, hopefully we’ll be able to piece together a more complete picture of these changes. Understanding how the dominoes fell is very important to our understanding of our current warming trend.”

These findings are published in the Sept 27, 2007 issue of the journal Nature.

Eruption debris may extend snow seasons

Debris-covered snow and ice on Mt Ruapehu, in New Zealand
Debris-covered snow and ice on Mt Ruapehu, in New Zealand

Skiers and snowboarders may have the recent eruption to thank for an extended ski season, says Massey University glaciologist Dr Martin Brook.

Dr Brook is a lecturer in physical geography who has specialised in the study of glaciers. On hearing of the eruption last Tuesday, he and a team headed up Mt Ruapehu to install monitoring equipment to assess the glaciological response.

“The eruption dumped a lot of volcanic material on the upper snowfields at Ruapehu, which act as source accumulation areas collecting snow,” he says. “This is in turn turns into firm snow and then glacier ice for the Whakapapa Glacier in particular. As we are now moving into the spring and summer melting season, where the sun is at a higher angle, and the days are longer, snow and glacier ice on Ruapehu usually melts rapidly until the following autumn. However, this year, there is now debris cover on the ice of varying thickness, so this will protect the snow and ice from melting in the accumulation area, keeping a base of snow and ice in place for a longer than usual. That also gives us the tantalising prospect of enhanced snow at the beginning of the autumn ski season in 2008.”

Were the layer of debris thinner – or thicker – it would have a different impact.

“Melting is enhanced under debris up to about 8mm thick, due to absorption of shortwave radiation from the sun. The debris re-emits this as long-wave radiation into the adjacent snow and ice. This is because dark colours have a low reflectivity, and do not reflect sunlight like lighter colours do. However, with a debris cover thicker than about eight to 10mm, this actually acts to insulate the ice and snow below, as the debris is too thick for any radiation received at the surface to be transmitted downwards to the snow below.”

Dr Brooks says New Zealand is unusual in glaciological terms. “It’s doubly intriguing; New Zealand’s glaciers are not your average glaciers. Those on the west coast of the South Island (Fox, Franz Josef) respond to snowfall, which appears to overprint the effect of temperature.

“Hence, we have a situation in New Zealand, with global warming heating the oceans, evaporating more sea water into the atmosphere, leading to enhanced precipitation on the West Coast of the South Island, and a short seven-minute volcanic eruption perhaps leading to insulation of parts of the Ruapehu glaciers and snowfields on the North Island.”

Dr Brooks and his team have a permit application with the Department of Conservation to install an automatic weather station and an array of ablation stakes in the summit snowfield, and the top of the Whakapapa Glacier. They hope to return to install the equipment with the assistance of Mt Ruapehu ski field staff this week.

Geologists Recover Rocks from San Andreas Fault

For the first time, geologists have drilled into the San Andreas Fault. - Credit: Zina Deretsky, National Science Foundation
For the first time, geologists have drilled into the San Andreas Fault. – Credit: Zina Deretsky, National Science Foundation

For the first time, geologists have extracted intact rock samples from two miles beneath the surface of the San Andreas Fault, the infamous rupture that runs 800 miles along the length of California.

Never before have so-called “cores” from deep inside an actively moving tectonic boundary been available to study. Now, scientists hope to answer long-standing questions about the fault’s composition and properties.

Altogether, the geologists retrieved 135 feet of 4-inch diameter rock cores weighing roughly 1 ton. They were hauled to the surface through a borehole measuring more than 2.5 miles long.

“Now we can hold the San Andreas Fault in our hands,” said Mark Zoback, a geologist at Stanford. “We know what it’s made of. We can study how it works.”

Zoback is one of three co-principal investigators of the San Andreas Fault Observatory at Depth (SAFOD) project, which is establishing the world’s first underground earthquake observatory. William Ellsworth and Steve Hickman, geophysicists with the U.S. Geological Survey in Menlo Park, Calif., are the other co-principal investigators.

SAFOD, which first broke ground in 2004, is a major research component of EarthScope, a National Science Foundation (NSF)-funded program to investigate the forces that shape the North American continent and the physical processes controlling earthquakes and volcanic eruptions.

“This is a tremendously exciting discovery,” said Kaye Shedlock, EarthScope program director at NSF. “Obtaining cores from the actively slipping San Andreas Fault is unprecedented and will allow for far-reaching, transformative research and discoveries.”

Scientists seeking to understand how the margins of tectonic plates evolve and generate earthquakes have had to settle for working with samples of ancient faults uncovered at the Earth’s surface by millions of years of erosion, along with computer simulations and laboratory experiments approximating what they think might be happening at the depths at which earthquakes occur.

“To an earthquake scientist, these cores are like the Apollo moon rocks,” Hickman said. “Scientists from around the world are anxious to get their hands on them in the hope that they can help solve the mystery of how this major, active plate boundary works.”

Drilling through the fault was completed in 2005. Next, the science team will install a host of seismic instruments in the 2.5-mile-long borehole that runs from the Pacific plate on the west side of the fault into the North American plate on the east. By placing sensors next to a zone that has been the source of many small quakes, scientists will be able to observe the earthquake generation process in unprecedented ways.

Studying the San Andreas Fault is important because, as Zoback said, “the really big earthquakes occur on plate boundaries like the San Andreas Fault.”

The SAFOD site, located about 23 miles northeast of Paso Robles near the tiny town of Parkfield, sits on a particularly active section of the fault that moves regularly. But it does not produce large earthquakes.

Instead, it moves in modest increments by a process called creep, in which the two sides of the fault slide slowly past one another, accompanied by occasional small quakes, most of which are not felt at the surface.

This drilling rig was used to retrieve samples of rock from the San Andreas Fault. - Photo Credit: EarthScope
This drilling rig was used to retrieve samples of rock from the San Andreas Fault. – Photo Credit: EarthScope

One of the big questions the researchers are working to answer is how, when most of the fault moves in violent, episodic upheavals, there can be a section where the same massive tectonic plates seem, by comparison, to gently tiptoe past each other.

“There have been many theories about why the San Andreas Fault slides along so easily, none of which could be tested directly until now,” Hickman said. Some posit the presence of especially slippery clays, called smectites. Others suggest there may be water along the fault plane, lubricating the surface. Still others note the presence of a mineral called serpentine exposed in several places along the surface trace of the fault, which–if it existed at depth–could both weaken the fault and cause it to creep.

In 2005, when the SAFOD drill pierced the first zone of active faulting, mineralogist Diane Moore of the USGS detected talc in the rock cuttings brought up to the surface. This finding was published in the Aug. 16, 2007, issue of the journal Nature.

“Talc is one of the slipperiest, weakest minerals ever studied,” Hickman said.

Might this mineral be smoothing the way for the huge tectonic plates? Chemically, it’s possible, for when serpentine is subjected to high temperatures in the presence of water containing silica, it forms talc.

Serpentine might also control how faults behave in other ways. “Serpentine can dissolve in ground water as fault particles grind past each other and then crystallize in nearby open pore spaces, allowing the fault to creep even under very little pressure,” Hickman said.

The SAFOD borehole cored into two active traces of the fault this summer, both contained within a broad fault “zone” about 700 feet wide. The deeper of the two active fault zones, designated 10830 for its distance in feet from the surface as measured along the curving borehole, yielded an 8-foot-long section of very fine-grained powder called fault gouge.

Such gouge is common in fault zones and is produced by the grinding of rock against rock. “What is remarkable about this gouge is that it contains abundant fragments of serpentine that appear to have been swept up into the gouge from the adjacent solid rock,” Hickman said. “The serpentine is floating around in the fault gouge.”

The only way to know what role serpentine, talc or other minerals play in controlling the behavior of the San Andreas Fault is to study the SAFOD core samples in the laboratory.

The second fault zone, called 10480, contains 3 feet of fault gouge. It also produces small earthquakes from a location 300 feet below the borehole. “Remarkably, we observe the same earthquake rupturing at the same spot on the fault year after year,” Ellsworth said. This repeating earthquake, always about a magnitude 2, will be the focus of the observatory to be installed inside the fault in 2008.

Sensitive seismometers and tiltmeters to be installed in the SAFOD borehole directly above the spot that ruptures will observe for the first time the birthing process of an earthquake from the zone where the earthquake energy accumulates. Preliminary observations made in 2006 already have revealed the tiniest earthquakes ever observed–so small they have negative magnitudes.

In addition to funding from NSF, USGS and Stanford University, the SAFOD project has also been supported by the International Continental Drilling Program.

Geologist discovers Martian mineral

Geology professor Ron Peterson discovered natural crystals in a frozen BC pond similar to ones that he grew in his garage -- and are also believed to exist on Mars. - Photo Courtesy: Ron Peterson
Geology professor Ron Peterson discovered natural crystals in a frozen BC pond similar to ones that he grew in his garage — and are also believed to exist on Mars. – Photo Courtesy: Ron Peterson

A Queen’s University researcher’s surprising discovery – made first in his garage and later verified through field work – has resulted in the naming of a new mineral species that may exist on Mars, and has caught the attention of the NASA space program.

Geologist Ron Peterson’s findings will be reported in the October issue of the journal, American Mineralogist. Dr. Peterson, who was invited to Houston last fall to present his original findings at the Johnson Space Center, continues to work with NASA scientists on Mars research.

The new mineral, meridianiite, is unusual because it is a planetary mineral and also thought to exist on the moons of Jupiter.

Also on the research team are Bruce Madu from the B.C. Ministry of Energy, Mines, and Petroleum Resources, Queen’s Chemistry Professor Herb Shurvell, and high school student Will Nelson, from Ascroft, B.C.

The Queen’s discovery was inspired by information sent back from Mars by the Mars Exploration Rover (MER), Opportunity, indicating that magnesium sulfate is present on that planet’s surface. The rover also sent back photographs of voids in rocks that are thought to have originally contained crystals.

This supports the team’s theory that regions of Mars were once covered with water, which later froze and then evaporated, leaving a residue of crystal molds in the sediment.

Based on these observations, in the winter of 2005, Dr. Peterson left a solution of drugstore epsom salts (hydrated magnesium sulfate) to crystallize in his unheated garage for several days. He then rushed the frozen crystals to a Queen’s chemistry lab, where experiments showed them to be an unusual form of magnesium sulfate that displayed some of the same properties reported earlier by Mars rovers.

Dr. Peterson wondered whether the same mineral might be found on Earth. In the fall of 2006 he located some ponds near Ashcroft in the Okanagan Valley of B.C., from which magnesium sulfate had once been mined. He then enlisted the help of a local high-school chemistry student to send him mineral samples from the ponds, by mail, throughout the fall.

In February 2007 Dr. Peterson visited the frozen ponds himself, and brought back crystals in a cooler packed with dry ice. These natural crystals were put through a series of tests, and in June meridianiite was approved as a new valid mineral species by the Commission on New Mineral names and Mineral Nomenclature of the International Mineralogical Association.

-The name was chosen to reflect the locality on Mars where a rover had observed crystal molds in sedimentary rock that are thought to be caused by minerals that have since dehydrated or dissolved,- says Dr. Peterson. -Observations obtained by using the rover wheels to dig trenches into the Martian soil show that magnesium sulfate minerals have been deposited below the surface.-

Between 20 and 30 new minerals are identified each year, the researcher notes, but -these often involve rare elements.- Meridianiite, on the other hand, is formed from the common materials magnesium, sulfate and water.

A geologist who normally studies mine waste, Dr. Peterson admits he has been a -space geek- since childhood, and says that working on this project has been exciting. -It began with a moment of insight – based on my previous geological experience – and now I have the chance to collaborate with experts from around the world who are studying the geology of the Martian surface.-

Deepest ever scientific ocean drilling could hold key to understanding earthquakes

CHIKYU sailing in Tokyo Bay
CHIKYU sailing in Tokyo Bay

One of the most ambitious earth science expeditions yet mounted to gain a better understanding of the earthquake process, has begun off the coast of Japan.

Dr Lisa McNeill, of the University of Southampton’s School of Ocean & Earth Science, based at the National Oceanography Centre, Southampton, and Joanne Tudge, of the Department of Geology, University of Leicester, are taking part in the multi-disciplinary study of a ‘subduction’ zone off the Japanese coast, aboard the deep-sea drilling vessel Chikyu (which means ‘Planet Earth’ in Japanese). This is the maiden scientific voyage of this vessel, which has unique capabilities enabling it to access new regions of the Earth’s crust.

Large-scale subduction earthquakes are the world’s most powerful seismic events and the cause of major catastrophes, such as the 2004 Boxing Day earthquake and tsunami in the Indian Ocean.

Japan, which has endured devastating earthquakes in cities such as Kobe in 1995, has made major investments in technology, including Chikyu, to learn more about seismic activity near its shores.

Lisa, a lecturer at Southampton, joins the Nankai Trough Seismogenic Zone Experiment (or NanTroSEIZE) expedition, part of the Integrated Ocean Drilling Program (IODP), as a scientific participant, but will also serve as a co-chief scientist on a later phase of the experiment in 2009.

PhD student Joanne Tudge is part of the Geophysics and Borehole Research Group in the Department of Geology at Leicester, which has a long-standing history of providing logging services and expertise for the IODP. Her research focuses on interpreting data from the borehole to better understand the sediments. On this NanTroSEIZE expedition she will be working to classify the rocks and understand the physical properties of the sediments in the subduction zone.

The project is ambitious in scale – the first phase alone is the longest period of scientific ocean drilling ever attempted in one area. In the second phase, colleagues will attempt to break the scientific ocean-drilling depth record by targeting a fault around 3500 m below the sea floor.

During the third phase, the drill ship aims to reach the main plate boundary at 6 km and place long-term monitoring tools. The experiment will take samples and install observatories to assess, for example, how strain is building up on the fault, the effects of fluid on rocks and the physical properties of sediments as they are deformed.

Dr McNeill said, “The scale of this experiment is unprecedented and I am very excited to be taking part. This is an extremely challenging expedition but the results should give us a much greater understanding of the processes responsible for generating earthquakes and tsunami.”

The ship sailed from Japan on 21 September and the experiment can be followed on the JAMSTEC website.