Sun and moon trigger deep tremors on San Andreas Fault

The faint tug of the sun and moon on the San Andreas Fault stimulates tremors deep underground, suggesting that the rock 15 miles below is lubricated with highly pressurised water that allows the rock to slip with little effort, according to a new study by University of California, Berkeley, seismologists.

"Tremors seem to be extremely sensitive to minute stress changes," said Roland Bürgmann, UC Berkeley professor of earth and planetary science.

Marine scientists discover deepest undersea erupting volcano

An explosion at the West Mata Volcano throws ash and rock, with molten lava glowing below. Photo: NSF/NOAAScientists funded by the National Science Foundation (NSF) and NOAA have recorded the deepest erupting volcano yet discovered – West Mata Volcano – describing high-definition video of the undersea eruption as "spectacular."

"For the first time we have been able to examine, up close, the way ocean islands and submarine volcanoes are born," said Barbara Ransom, program director in NSF's Division of Ocean Sciences. "The unusual primitive compositions of the West Mata eruption lavas have much to tell us."

Fault weaknesses, the centre cannot hold for some geologic faults

This is a view of the Zuccale Fault, Elba, Italy from a distance. Photo: Cristiano Collettini, Universita degli Studi di Perugia, Italy,Some geologic faults that appear strong and stable, slip and slide like weak faults. Now an international team of researchers has laboratory evidence showing why some faults that "should not" slip are weaker than previously thought.

"Low-angle normal faults – faults that dip less than 45 degrees – are a problem," said Chris Marone, professor of geosciences, Penn State. "Standard analysis shows that these faults should not slip because it is easier to form a new fault than to slip on this orientation."

Pre-eruption earthquakes offer clues to volcano forecasters

Like an angry dog, a volcano growls before it bites, shaking the ground and getting "noisy" before erupting. This activity gives scientists an opportunity to study the tumult beneath a volcano and may help them improve the accuracy of eruption forecasts, according to Emily Brodsky, an associate professor of Earth and planetary sciences at the University of California, Santa Cruz.

Brodsky will present recent findings on pre-eruption earthquakes on, December 16, at the fall meeting of the American Geophysical Union in San Francisco.

Story of 4.5 million-year-old whale unveiled in Huelva

These are vertebra colonised by bivalves. Photo:Esperante et al.In 2006, a team of Spanish and American researchers found the fossil remains of a whale, 4.5 million years old, in Bonares, Huelva. Now they have published, for the first time, the results of the decay and fossilisation process that started with the death of the young cetacean, possibly a baleen whale from the Mysticeti group.

This is not the first discovery of the partial fossil remains of a whale from the Lower Pliocene (five million years ago) in the Huelva Sands sedimentary formation, but it is the first time that the results of the processes of fossilisation and fossil deposition following the death of a whale have been published.

Paleoasian Ocean disappeared about 251 million years ago

The collision between the Siberian Plate and North China Plate was a significant geological event in earth history, which led to the final closure of the Paleoasian Ocean and the formation of the Eurasian continent. Despite numerous research efforts in recent decades, the precise time of this event has remained a puzzle until now. New evidence in helping settle this issue is provided by Prof. Deng Shenghui and his colleagues in their paper newly published in Science in China.

Geological studies have demonstrated that during the early Paleozoic, an interval from 450-300 million year ago, the Siberian paleo-land was thousands kilometers away from the North China paleo-land, which is very different from their present situation.

Lower rate of quakes along some subduction zones

Most earthquakes occur along fault lines, which form boundaries between two tectonic plates. As the relative speed of the plates around a fault increases, is there a corresponding increase in the number of earthquakes produced along the fault? According to this study published in the December issue of BSSA, the answer depends upon the type of tectonic boundary. On certain types of boundary, the efficiency of earthquake production actually depends on the fault slip rate.

Seismic hazard assessments consider many factors, including relative plate velocity. It is important to understand whether there is a linear relationship between relative plate velocity along a fault and the production of earthquakes in order to estimate risk to populations and manmade structures from seismic activity.

Carbon and oxygen in tree rings can reveal past climate information

Photo:Martin Male/WikimediaIsotope analysis provides accurate information

The analysis of carbon and oxygen isotopes embedded in tree rings may shed new light on past climate events in the Mackenzie Delta region of northern Canada. Scientists have long looked at the width of tree rings to estimate temperature levels of past years.Larger rings indicate more tree growth in a season, which translates into warmer summer temperatures.

New research uncovers deep origins of the 'Hawaiian Hotspot'

PLUME ocean-bottom seismometer being retrieved off Hawaii in January 2006. Photo:Horst Rademacher.Findings suggest hotspot is the result of a lower-mantle plume

A new study by an international research team has opened up a window into the earth to reveal Hawaii's deep roots and the best picture yet of a plume originating from the lower mantle. The findings suggest that the Hawaiian hot spot is the result of an upwelling high-temperature plume from the lower mantle.

Big freeze plunged Europe into ice age in months

In the film, The Day After Tomorrow the world enters the icy grip of a new glacial period within the space of just a few weeks. Now new research shows that this scenario may not be so far from the truth after all.

William Patterson, from the University of Saskatchewan in Canada, and his colleagues have shown that switching off the North Atlantic circulation can force the Northern hemisphere into a mini 'ice age' in a matter of months. Previous work has indicated that this process would take tens of years.

Past regional cold and warm periods linked to natural climate drivers

Intervals of regional warmth and cold in the past are linked to the El Niño phenomenon and the so-called "North Atlantic Oscillation" in the Northern hemisphere's jet stream, according to a team of climate scientists. These linkages may be important in assessing the regional effects of future climate change.

"Studying the past can potentially inform our understanding of what the future may hold," said Michael Mann, Professor of meteorology, Penn State.

Small faults in southeast Spain reduce earthquake risk of larger ones

A team of Spanish scientists, studying recent, active deformations in the Baetic mountain range, have shown that the activity of smaller tectonic structures close to larger faults in the south east of the Iberian Peninsula partially offsets the risk of earthquakes.

"There are large faults in the eastern part of the Baetic mountain range, which are active and occasionally cause moderate, low magnitude earthquakes (measuring less than 5 on the Richter scale)", Antonio Pedrera, lead author of the study and a researcher in the Department of Geodynamics at the University of Granada (UGR), tells SINC.

Oceanic crust formation is dynamic after all

Imagine the Earth's crust as the planet's skin: Some areas are old and wrinkled while others have a fresher, more youthful sheen, as if they had been regularly lathered with lotion.

Carry the metaphor a little further and a good picture emerges of the geological processes leading to the creation of the planet's crust. On land, continental crust, once created, can remain more or less unaltered for billions of years. But the oldest oceanic crust is only about 200 million years old, as new crust is continually forming at mid-ocean ridge spreading centres.

Cave study links climate change to California droughts

Moaning Cave. Photo:Dave Bunnell/WikimediaCalifornia experienced centuries-long droughts in the past 20,000 years that coincided with the thawing of ice caps in the Arctic, according to a new study by UC Davis doctoral student Jessica Oster and geology professor Isabel Montañez.

The finding, which comes from analysing stalagmites from Moaning Cavern in the central Sierra Nevada, was published online Nov. 5 in the journal Earth and Planetary Science Letters.

The sometimes spectacular mineral formations in caves such as Moaning Cavern and Black Chasm build up over centuries as water drips from the cave roof. Those drops of water pick up trace chemicals in their path through air, soil and rocks, and deposit the chemicals in the stalagmite.

"They're like tree rings made out of rock," Montañez said. "These are the only climate records of this type for California for this period when past global warming was occurring."

At the end of the last ice age about 15,000 years ago, climate records from Greenland show a warm period called the Bolling-Allerod period. Oster and Montanez's results show that at the same time, California became much drier. Episodes of relative cooling in the Arctic records, including the Younger Dryas period 13,000 years ago, were accompanied by wetter periods in California.

The researchers don't know exactly what connects Arctic temperatures to precipitation over California. However, climate models developed by others suggest that when Arctic sea ice disappears, the jet stream – high-altitude winds with a profound influence on climate – shifts north, moving precipitation away from California.

"If there is a connection to Arctic sea ice then there are big implications for us in California," Montañez said. Arctic sea ice has declined by about 3 per cent a year over the past three decades, and some forecasts predict an ice-free Arctic ocean as soon as 2020.

Oster's analysis of the past is rooted in a thorough understanding of the cave in the present. Working with the cave owners, she has measured drip rates, collected air, water, soil and vegetation samples, and studied what happens to the cave through wet and dry seasons to determine how stalagmites are affected by changing conditions.

Oster collected stalagmites and cut tiny samples from them for analysis. The ratio of uranium to its breakdown product, thorium, allowed her to date the layers within the stalagmite. Isotopes of oxygen, carbon and strontium and levels of metals in the cave minerals all vary as the climate gets wetter or drier.

"Most respond to precipitation in some way," Oster said. For example, carbon isotopes reflect the amount of vegetation on the ground over the cave. Other minerals tend to decrease when rainfall is high and water moves through the aquifer more rapidly.

Oxygen-18 isotopes vary with both temperature and rainfall. Measuring the other mineral compositions provides more certainty that the changes primarily track relative rainfall.

The stalagmite records allowed Oster and Montañez to follow relative changes in precipitation in the western Sierra Nevada with a resolution of less than a century.

"We can't quantify precipitation, but we can see a relative shift from wetter to drier conditions with each episode of warming in the northern polar region," Montañez said.

Other authors on the paper are Warren Sharp, a geochronologist at the Berkeley Geochronology Centre, and Kari Cooper, associate professor of geology at UC Davis. The research was funded by the National Science Foundation.

African desert rift confirmed as new ocean in the making

Image: ChelysGeologists show that seafloor dynamics are at work in splitting African continent

In 2005, a gigantic, 35-mile-long rift broke open the desert ground in Ethiopia. At the time, some geologists believed the rift was the beginning of a new ocean as two parts of the African continent pulled apart, but the claim was controversial. Now, scientists from several countries have confirmed that the volcanic processes at work beneath the Ethiopian rift are nearly identical to those at the bottom of the world's oceans, and the rift is indeed likely the beginning of a new sea.

The new study, published in the latest issue of Geophysical Research Letters, suggests that the highly active volcanic boundaries along the edges of tectonic ocean plates may suddenly break apart in large sections, instead of little by little as has been predominantly believed. In addition, such sudden large-scale events on land pose a much more serious hazard to populations living near the rift than would several smaller events, says Cindy Ebinger, professor of earth and environmental sciences at the University of Rochester and co-author of the study.

"This work is a breakthrough in our understanding of continental rifting leading to the creation of new ocean basins," says Ken Macdonald, professor emeritus in the Department of Earth Science at the University of California, Santa Barbara, and who is not affiliated with the research. "For the first time they demonstrate that activity on one rift segment can trigger a major episode of magma injection and associated deformation on a neighbouring segment. Careful study of the 2005 mega-dike intrusion and its aftermath will continue to provide extraordinary opportunities for learning about continental rifts and mid-ocean ridges."

"The whole point of this study is to learn whether what is happening in Ethiopia is like what is happening at the bottom of the ocean where it's almost impossible for us to go," says Ebinger. "We knew that if we could establish that, then Ethiopia would essentially be a unique and superb ocean-ridge laboratory for us. Because of the unprecedented cross-border collaboration behind this research, we now know that the answer is yes, it is analogous."

Atalay Ayele, professor at the Addis Ababa University in Ethiopia, led the investigation, painstakingly gathering seismic data surrounding the 2005 event that led to the giant rift opening more than 20 feet in width in just days. Along with the seismic information from Ethiopia, Ayele combined data from neighbouring Eritrea with the help of Ghebrebrhan Ogubazghi, professor at the Eritrea Institute of Technology, and from Yemen with the help of Jamal Sholan of the National Yemen Seismological Observatory Centre. The map he drew of when and where earthquakes happened in the region fit tremendously well with the more detailed analyses Ebinger has conducted in more recent years.

Ayele's reconstruction of events showed that the rift did not open in a series of small earthquakes over an extended period of time, but tore open along its entire 35-mile length in just days. A volcano called Dabbahu at the northern end of the rift erupted first, then magma pushed up through the middle of the rift area and began "unzipping" the rift in both directions, says Ebinger.

Since the 2005 event, Ebinger and her colleagues have installed seismometers and measured 12 similar – though dramatically less intense – events.

"We know that seafloor ridges are created by a similar intrusion of magma into a rift, but we never knew that a huge length of the ridge could break open at once like this," says Ebinger. She explains that since the areas where the seafloor is spreading are almost always situated under miles of ocean, it's nearly impossible to monitor more than a small section of the ridge at once so there's no way for geologists to know how much of the ridge may break open and spread at any one time. "Seafloor ridges are made up of sections, each of which can be hundreds of miles long. Because of this study, we now know that each one of those segments can tear open in a just a few days."

Ebinger and her colleagues are continuing to monitor the area in Ethiopia to learn more about how the magma system beneath the rift evolves as the rift continues to grow.

Additional authors of the study include Derek Keir, Tim Wright, and Graham Stuart, professors of earth and environment at the University of Leeds, U.K.; Roger Buck, professor at the Earth Institute at Columbia University, N.Y.; and Eric Jacques, professor at the Institute de Physique du Globe de Paris, France.

Geologist analyses earliest shell-covered fossil animals

Cambrothyra fossil.Photo: UCSBThe fossil remains of some of the first animals with shells, ocean-dwelling creatures that measure a few centimetres in length and date to about 520 million years ago, provide a window on evolution at this time, according to scientists. Their research indicates that these animals were larger than previously thought.

John Moore, a Ph.D. student in the Department of Earth Science at UC Santa Barbara, and his collaborators, analysed fossils from the epoch called the Early Cambrian. During this important time in the history of the earth, there was a tremendous diversification of animal life in the oceans. Many of the major animal groups that are still alive today appeared at this time, as well as many unusual groups that went extinct.

In particular, the Cambrian marked the first widespread occurrence of animals with shells or other hard parts. Many of these early animals had complex external armours containing dozens to thousands of tiny pieces. When the animals died, the armour fell apart. From the resulting jumbled puzzle pieces, Moore and his research team discerned what the animals were like, and how they are related to other animals.

"In our study, we focused on a strange Cambrian creature, called Cambrothyra," said Moore. He explained that Cambrothyra fossils look like tiny jars or vases, a few tenths of a millimetre long. They have been found in only a few locations in central China. The research team collected rocks from China's Shaanxi Province and brought them back to the lab where they extracted the fossils from the host rocks.

"While some scientists once thought that each little jar-like structure of Cambrothyra was the shell of a tiny single-celled protist, our work instead supports the hypothesis that Cambrothyra was an animal, probably a few centimetres long, that was covered with an armor that was made up of hundreds of separate tiny, jar-shaped pieces," said Moore. "In particular, Cambrothyra seems to be related to another unusual Cambrian animal, the chancelloriids, which were attached to the sea floor and looked a bit like barrel cacti – although they were animals rather than plants which suggests that Cambrothyra may have been a relative."

Cambrothyra also shares similarities with a different Cambrian group, the halkieriids. This animal looked like a slug covered with armour. It travelled around the sea floor and thus may help support the idea that chancelloriids and halkieriids are closely related to each other, despite very different appearances.

Moore presented his findings at the annual meeting of the Geological Society of America in Portland, Ore., today. He completed the work in collaboration with his advisor Susannah Porter, assistant professor in the Department of Earth Science at UCSB; Michael Steiner of the Freie Universität, Berlin; and Guoxiang Li of the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences.

Himalayan fault, subduction zone fully in picture

The Hi-CLIMB (Himalayan-Tibetan Continental Lithosphere during Mountain Building) seismic station at the Mt. Everest base camp in Tibet. Photo: John Nabelek, OSUAn international team of researchers has created the most complete seismic image of the Earth’s crust and upper mantle beneath the rugged Himalaya Mountains, in the process discovering some unusual geologic features that may explain how the region has evolved.

Their findings, published this week in the journal Science, help explain the formation of the world’s largest mountain range, which is still growing.The researchers discovered that as the Indian and Eurasian tectonic plates collide, the Indian lower crust slides under the Tibetan crust, while the upper mantle peels away from the crust and drops down in a diffuse manner.

“The building of Tibet is not a simple process,” said John Nabelek, an Oregon State University geophysicist and lead author on the Science study. “In part, the mountain building is similar to pushing dirt with a bulldozer except in this case, the Indian sediments pile up into a wedge that is the lesser Himalayan mountains.

“However, an important component of the mass transfer from the upper crust of India to the Himalayas also occurs at depth through viscous processes, while the lower crust continues sliding intact farther north under the Tibet plateau,” Nabelek added.

The findings are important because there has been clear scientific consensus on the boundaries and processes for that region’s tectonic plates. In fact, the piecemeal images gathered by previous research have led to a series of conflicting models of the lithospheric structure and plate movement.

In this study, the international research team – called Hi-CLIMB (Himalayan-Tibetan Continental Lithosphere during Mountain Building) – was able to create new in-depth images of the Earth’s structure beneath the Himalayas.

The interface between the subducting Indian plate and the upper Himalayan and Tibetan crust is the Main Himalayan thrust fault, which reaches the surface in southern Nepal, Nabelek said. The new images show it extends from the surface to mid-crustal depths in central Tibet, but the shallow part of the fault sticks, leading to historically devastating mega-thrust earthquakes.

“The deep part is ductile,” Nabelek said, “and slips in a continuous fashion. Knowing the depth and geometry of this interface will advance research on a variety of fronts, including the interpretation of strain accumulation from GPS measurements prior to large earthquakes.”

Nabelek, an associate professor in OSU’s College of Oceanic and Atmospheric Sciences, said the lower part of the Indian crust slides about 450 kilometres under the southern Tibetan plate and the mantle appears to shear off and break into sub-parallel segments.

The researchers found evidence that subduction in the fault zone has been occurring from both the north and south sides – likely at different times in its geologic history.

In this project, funded primarily by the National Science Foundation, the researchers deployed and monitored about 230 seismic stations for a period of three years, cutting across 800 kilometers of some of the most remote terrain in the world. The lowest-elevation station was at 12 meters above sea level in Nepal; the highest, nearly 5,500 meters in Tibet. In fact, 30 of the stations were higher than 5,000 meters, or 16,400 feet.

“The research took us from the jungles of Nepal, with its elephants, crocodiles and rhinos, to the barren, wind-swept heights of Tibet in areas where nothing grew for hundreds of miles and there were absolutely no humans around,” Nabelek said. “That remoteness is one reason this region had never previously been completely profiled.”

Other authors on the Science study include Gyorgy Hetenyi and Jerome Vergne of Ecole Normale Superieure in France; Soma Sapkota and Basant Kafle, Department of Mines and Geology in Kathmandu, Nepal; Mei Jiang and Heping Su, Chinese Academy of Geologic Sciences; John Chen, Peking University in Beijing; Bor-Shouh Huang, Academia Sinica in Taiwan; and the Hi-CLIMB Team.

Earth science made easier

Instead of an ice-covered South Pole, picture sub-tropical temperatures and flowering plants. That’s what parts of Antarctica looked like 85 million years ago. How long ago was that? If you’re drawing a blank you’re not alone.

Thinking on geologic time scales does not come easily for many people, and that’s a challenge in teaching earth science, says Lamont-Doherty oceanographer Kim Kastens, in a recent cover story in EOS, a weekly newspaper published by the American Geophysical Union.

Our resistance to taking the long view of time is not surprising, Kastens and her colleagues explain. On the timeline of our planet, human history is but a tiny blip. Events like glaciations and mountain formation happen over thousands and millions of years, and at monumental scales. To make sense of Earth’s evolution, exponential numbers, ratios and proportional reasoning are required.

For nearly two decades Kastens has looked at ways to make learning about Earth more intuitive. Currently, she is leading an effort to synthesise research from psychology, philosophy and other disciplines. One technique for helping students understand geologic time, she writes, is to think about events in Earth’s past as a story, with pictures. Focusing on the narrative, rather than numerical ages, allows students to draw from their own experience of how earlier events shape later events.

She says that a “systems approach” to teaching earth science can be effective, by showing how the atmosphere, hydrosphere and other systems influence each other. She also recommends field-work to help students become better observers. “Like a criminal investigator at a crime scene, a geoscientist in the field sees differently than a novice at the same scene,” she writes.