From ‘Finding Nemo’ to minerals — what riches lie in the deep sea?

Left: The first species ever recovered from the deep sea. Center: Rockfish use deep-sea carbonate formations at Hydrate Ridge, US, as a refuge. Right: Deep-sea corals such as the one pictured are a source of jewelery and other riches. -  SERPENT Project/D.O.B. Jones, L. Levin, UK's BIS Department
Left: The first species ever recovered from the deep sea. Center: Rockfish use deep-sea carbonate formations at Hydrate Ridge, US, as a refuge. Right: Deep-sea corals such as the one pictured are a source of jewelery and other riches. – SERPENT Project/D.O.B. Jones, L. Levin, UK’s BIS Department

As fishing and the harvesting of metals, gas and oil have expanded deeper and deeper into the ocean, scientists are drawing attention to the services provided by the deep sea, the world’s largest environment. “This is the time to discuss deep-sea stewardship before exploitation is too much farther underway,” says lead-author Andrew Thurber. In a review published today in Biogeosciences, a journal of the European Geosciences Union (EGU), Thurber and colleagues summarise what this habitat provides to humans, and emphasise the need to protect it.

“The deep sea realm is so distant, but affects us in so many ways. That’s where the passion lies: to tell everyone what’s down there and that we still have a lot to explore,” says co-author Jeroen Ingels of Plymouth Marine Laboratory in the UK.

“What we know highlights that it provides much directly to society,” says Thurber, a researcher at the College of Earth, Ocean and Atmospheric Sciences at Oregon State University in the US. Yet, the deep sea is facing impacts from climate change and, as resources are depleted elsewhere, is being increasingly exploited by humans for food, energy and metals like gold and silver.

“We felt we had to do something,” says Ingels. “We all felt passionate about placing the deep sea in a relevant context and found that there was little out there aimed at explaining what the deep sea does for us to a broad audience that includes scientists, the non-specialists and ultimately the policy makers. There was a gap to be filled. So we said: ‘Let’s just make this happen’.”

In the review of over 200 scientific papers, the international team of researchers points out how vital the deep sea is to support our current way of life. It nurtures fish stocks, serves as a dumping ground for our waste, and is a massive reserve of oil, gas, precious metals and the rare minerals we use in modern electronics, such as cell phones and hybrid-car batteries. Further, hydrothermal vents and other deep-sea environments host life forms, from bacteria to sponges, that are a source of new antibiotics and anti-cancer chemicals. It also has a cultural value, with its strange species and untouched habitats inspiring books and films from 20,000 Leagues Under the Sea to Finding Nemo.

“From jewellery to oil and gas and future potential energy reserves as well as novel pharmaceuticals, deep-sea’s worth should be recognised so that, as we decide how to use it more in the future, we do not inhibit or lose the services that it already provides,” says Thurber.

The deep sea (ocean areas deeper than 200m) represents 98.5% of the volume of our planet that is hospitable to animals. It has received less attention than other environments because it is vast, dark and remote, and much of it is inaccessible to humans. But it has important global functions. In the Biogeosciences review the team shows that deep-sea marine life plays a crucial role in absorbing carbon dioxide from the atmosphere, as well as methane that occasionally leaks from under the seafloor. In doing so, the deep ocean has limited much of the effects of climate change.

This type of process occurs over a vast area and at a slow rate. Thurber gives other examples: manganese nodules, deep-sea sources of nickel, copper, cobalt and rare earth minerals, take centuries or longer to form and are not renewable. Likewise, slow-growing and long-lived species of fish and coral in the deep sea are more susceptible to overfishing. “This means that a different approach needs to be taken as we start harvesting the resources within it.”

By highlighting the importance of the deep sea and identifying the traits that differentiate this environment from others, the researchers hope to provide the tools for effective and sustainable management of this habitat.

“This study is one of the steps in making sure that the benefits of the deep sea are understood by those who are trying to, or beginning to, regulate its resources,” concludes Thurber. “We ultimately hope that it will be a useful tool for policy makers.”

Jeju Island is a live volcano

These are pictures of the sedimentary layer containing charcoal found on a stony mountain developing site in Sangchang-ri, and the carbonized wood sample used for the radiocarbon dating. Thick lava covers the upper gravel layer. -  KIGAM
These are pictures of the sedimentary layer containing charcoal found on a stony mountain developing site in Sangchang-ri, and the carbonized wood sample used for the radiocarbon dating. Thick lava covers the upper gravel layer. – KIGAM

In Jeju, a place emerging as a world-famous vacation spot with natural tourism resources, a recent study revealed a volcanic eruption occurred on the island. The Korea Institute of Geoscience and Mineral Resources (KIGAM) indicated that there are the traces that indicated that a recent volcanic eruption was evident 5,000 years ago. That is the first time to actually find out the date when lava spewed out of a volcano 5,000 years ago in the inland part of the island as well as the one the whole peninsula.

The research team led by Dr. Jin-Young Lee confirmed in results from radiocarbon dating for carbonized wood (charcoal) found below the basaltic layer located in Sangchang-ri, Seogwipo-si, Jeju-do it dated back to 5,000 years ago; which means the time when the basalt on the upper layer was formed took place relatively recently, i.e. 5,000 years ago, and which demonstrates that the island has experienced a volcanic eruption fairly recently.

The latest volcanic eruption occurring on Jeju Island was volcanic activity known to have spewed around 7,000 years ago at Mt. Songak. The basaltic layer in Sangchang-ri is known to be formed due to the eruption in the vicinity of Byeongak Oreum 35,000 years ago; though, this study revealed that the layer is a product of the most recent volcanic activity among those known ever. Volcanic activity at Mt. Songak was limited hydro volcanic activity out of which a great deal of volcanic ash was released while it is evident that Sangchang-ri was a dynamic active volcano out of which lava was spewed and then flowed down in all directions along the inland slope.

It is also remarkable that the research team enhanced the accuracy of the findings in the radiocarbon dating technique using carbonized wood, consequently raising the reliability of the findings. Until now, previous research used the dating method for rocks covering the upper sedimentary layer, in which such dating method with the relatively longer half-life period shows limitations in determining the time the basalt was formed about 10,000 years ago.


In order to overcome the limitations of the dating method for the rocks covering the upper sedimentary layer, the research team led by Dr. Jin-Young Lee concurrently used radiocarbon dating and optically stimulated luminescence dating (OSL), using such cross-validation of which raised the accuracy of tracing the past volcanic activities.

Judging from the findings, Jeju Island is not an extinct volcano, but seems to rather be a potentially live volcano because a volcano that has erupted within 10,000 years is defined to be a live volcano on a geological basis.

Not remaining complacent for the findings, the research team plans to continuously conduct the studies on the time the volcanic rocks were formed in several regions on the island in order to identify the latest volcanic activity.

How much magma is hiding beneath our feet?

Molten rock (or magma) has a strong influence on our planet and its inhabitants, causing destructive volcanic eruptions and generating some of the giant mineral deposits. Our understanding of these phenomena is, however, limited by the fact that most magma cools and solidifies several kilometres beneath our feet, only to be exposed at the surface, millions of years later, by erosion. Scientists have never been able to track the movements of magma at such great depths? that is, until a team from the University of Geneva (UNIGE) discovered an innovative technique, details of which will be published in the next issue of the journal Nature.

It is a story of three scientists: a modelling specialist, an expert in a tiny mineral known as “zircon”, and a volcanologist. Following a casual conversation, the researchers stumbled upon an idea, and eventually a new method to estimate the volume and flow of magma required for the construction of magma chambers was shaped. The technique they developed makes it possible to refine predictions of future volcanic eruptions as well as identifying areas of the planet that are rich in magma-related natural resources.

Zircon: a valuable mineral for scientists

Professor Urs Schaltegger has been studying zircon for more than ten years in his laboratory at UNIGE, one of the world’s few labs in this field. «The zircon crystals that are found in solidified magma hold key information about the injection of molten rock into a magma chamber before it freezes underground,» explains the professor. Zircon contains radioactive elements that enable researchers to determine its age. As part of the study, the team from the Section of Earth and Environmental Sciences of UNIGE paired data collected using natural samples and numerical simulation. As Guy Simpson, a researcher at UNIGE further explains: «Modelling meant that we could establish how the age of crystallised zircon in a cooled magma reservoir depends on the flow rate of injected magma and the size of the reservoir.»

Applications for society and industry


In the Nature article, the researchers propose a model that is capable of determining with unprecedented accuracy the age, volume and injection rate of magma that has accumulated at inaccessible depths. As a result, they have established that the formation of Earth’s crust, volcanic super eruptions and mineral deposits occur under very specific yet different conditions. Professor Luca Caricchi adds: «When we determine the age of a family of zircons from a small sample of solidified magmatic rock, using results from the mathematical model we have developed, we can tell what the size of the entire magma chamber was, as well as how fast the magma reservoir grew». The professor continues: «This information means that we can determine the probability of an explosive volcanic eruption of a certain size to occur. In addition, the model will be of interest to industry because we will be able to identify new areas of our planet that are home to large amounts of natural resources such as copper and gold.»

New Oso report, rockfall in Yosemite, and earthquake models

From AGU’s blogs: Oso disaster had its roots in earlier landslides

A research team tasked with being some of the first scientists and engineers to evaluate extreme events has issued its findings on disastrous Oso, Washington, landslide. The report studies the conditions and causes related to the March 22 mudslide that killed 43 people and destroyed the Steelhead Haven neighborhood in Oso, Washington. The team from the Geotechnical Extreme Events Reconnaissance (GEER) Association, funded by the National Science Foundation, determined that intense rainfall in the three weeks before the slide likely was a major issue, but factors such as altered groundwater migration, weakened soil consistency because of previous landslides and changes in hillside stresses played key roles.

From this week’s Eos: Reducing Rockfall Risk in Yosemite National Park

The glacially sculpted granite walls of Yosemite Valley attract 4 million visitors a year, but rockfalls from these cliffs pose substantial hazards. Responding to new studies, the National Park Service recently took actions to reduce the human risk posed by rockfalls in Yosemite National Park.

From AGU’s journals: A new earthquake model may explain discrepancies in San Andreas fault slip

Investigating the earthquake hazards of the San Andreas Fault System requires an accurate understanding of accumulating stresses and the history of past earthquakes. Faults tend to go through an “earthquake cycle”-locking and accumulating stress, rupturing in an earthquake, and locking again in a well-accepted process known as “elastic rebound.” One of the key factors in preparing for California’s next “Big One” is estimating the fault slip rate, the speed at which one side of the San Andreas Fault is moving past the other.

Broadly speaking, there are two ways geoscientists study fault slip. Geologists formulate estimates by studying geologic features at key locations to study slip rates through time. Geodesists, scientists who measure the size and shape of the planet, use technologies like GPS and satellite radar interferometry to estimate the slip rate, estimates which often differ from the geologists’ estimations.

In a recent study by Tong et al., the authors develop a new three-dimensional viscoelastic earthquake cycle model that represents 41 major fault segments of the San Andreas Fault System. While previous research has suggested that there are discrepancies between the fault slip rates along the San Andreas as measured by geologic and geodetic means, the authors find that there are no significant differences between the two measures if the thickness of the tectonic plate and viscoelasticity are taken into account. The authors find that the geodetic slip rate depends on the plate thickness over the San Andreas, a variable lacking in previous research.

The team notes that of the 41 studied faults within the San Andreas Fault system, a small number do in fact have disagreements between the geologic and geodetic slip rates. These differences could be attributed to inadequate data coverage or to incomplete knowledge of the fault structures or the chronological sequence of past events.

The bend in the Appalachian mountain chain is finally explained

A dense, underground block of volcanic rock (shown in red) helped shape the well-known bend in the Appalachian mountain range. -  Graphic by Michael Osadciw/University of Rochester.
A dense, underground block of volcanic rock (shown in red) helped shape the well-known bend in the Appalachian mountain range. – Graphic by Michael Osadciw/University of Rochester.

The 1500 mile Appalachian mountain chain runs along a nearly straight line from Alabama to Newfoundland-except for a curious bend in Pennsylvania and New York State. Researchers from the College of New Jersey and the University of Rochester now know what caused that bend-a dense, underground block of rigid, volcanic rock forced the chain to shift eastward as it was forming millions of years ago.

According to Cindy Ebinger, a professor of earth and environmental sciences at the University of Rochester, scientists had previously known about the volcanic rock structure under the Appalachians. “What we didn’t understand was the size of the structure or its implications for mountain-building processes,” she said.

The findings have been published in the journal Earth and Planetary Science Letters.

When the North American and African continental plates collided more than 300 million years ago, the North American plate began folding and thrusting upwards as it was pushed westward into the dense underground rock structure-in what is now the northeastern United States. The dense rock created a barricade, forcing the Appalachian mountain range to spring up with its characteristic bend.

The research team-which also included Margaret Benoit, an associate professor of physics at the College of New Jersey, and graduate student Melanie Crampton at the College of New Jersey-studied data collected by the Earthscope project, which is funded by the National Science Foundation. Earthscope makes use of 136 GPS receivers and an array of 400 portable seismometers deployed in the northeast United States to measure ground movement.

Benoit and Ebinger also made use of the North American Gravity Database, a compilation of open-source data from the U.S., Canada, and Mexico. The database, started two decades ago, contains measurements of the gravitational pull over the North American terrain. Most people assume that gravity has a constant value, but when gravity is experimentally measured, it changes from place to place due to variations in the density and thickness of Earth’s rock layers. Certain parts of the Earth are denser than others, causing the gravitational pull to be slightly greater in those places.

Data on the changes in gravitational pull and seismic velocity together allowed the researchers to determine the density of the underground structure and conclude that it is volcanic in origin, with dimensions of 450 kilometers by 100 kilometers. This information, along with data from the Earthscope project ultimately helped the researchers to model how the bend was formed.

Ebinger called the research project a “foundation study” that will improve scientists’ understanding of the Earth’s underlying structures. As an example, Ebinger said their findings could provide useful information in the debate over hydraulic fracturing-popularly known is hydrofracking-in New York State.

Hydrofracking is a mining technique used to extract natural gas from deep in the earth. It involves drilling horizontally into shale formations, then injecting the rock with sand, water, and a cocktail of chemicals to free the trapped gas for removal. The region just west of the Appalachian Basin-the Marcellus Shale formation-is rich in natural gas reserves and is being considered for development by drilling companies.

NMR under pressure: Reproducing deep-Earth chemistry

A new pressure cell invented by UC Davis researchers makes it possible to simulate chemical reactions deep in the Earth’s crust. The cell allows researchers to perform nuclear magnetic resonance (NMR) measurements on as little as 10 microliters of liquid at pressures up to 20 kiloBar.

“NMR is our window into the chemical world,” said Brent Pautler, a postdoctoral researcher in chemistry at UC Davis and first author on the paper published July 2 in the online edition of the journal Angewandte Chemie. “It lets us see chemical reactions as they are happening.”

The new device allows researchers for the first time to study chemical reactions in liquid water under pressure, without it freezing into a solid.

“We were able to get to the point where we could no longer ignore the compressibility of the water molecules,” Pautler said. “This is the first time this has ever been reported.”

Geochemists want to know what kind of chemistry is happening deep in the Earth’s crust, beyond the reach of boreholes. These chemical reactions could affect water and minerals that eventually migrate to the surface, or the behavior of carbon cycling between the Earth’s depths and the surface.

“Aqueous fluids deep in the Earth are the great unknown for geochemists,” said Chris Colla, a graduate student in Earth & Physical Sciences at UC Davis and co-author on the paper. “By doing NMR we can get an inside view of what is occurring deep in the Earth’s crust.”

For example, Pautler, Colla and colleagues have already looked at calcium ions in solution. Dissolved calcium ions can be surrounded by four, six or eight water molecules. High pressure forces dissolved calcium into an eight-water state, they found.

The high-pressure measurements could also shed light on chemical processes involved in hydraulic fracturing, or “fracking,” and the behavior of buried nuclear waste over long periods of time. Fracking is the process of extracting oil and gas by injecting liquids under high pressure into rocks.

The high-pressure NMR cell was built in the machine shop at the Crocker Nuclear Laboratory with the help of Peter Klavins, research specialist in the Department of Physics, and Steve Harley, a former UC Davis graduate student now at the Lawrence Livermore National Laboratory.




Video
Click on this image to view the .mp4 video
Chemists want to understand chemical reactions that happen in solutions under high pressure in the Earth’s crust. A new device invented at UC Davis allows chemists to make nuclear magnetic resonance measurements of chemical solutions up to pressures of 20 kiloBar. – Video by Andy Fell/UC Davis Strategic Communications.

New view of Rainier’s volcanic plumbing

This image was made by measuring how the ground conducts or resists electricity in a study co-authored by geophysicist Phil Wannamaker of the University of Utah Energy & Geoscience Institute. It  shows the underground plumbing system that provides molten and partly molten rock to the magma chamber beneath the Mount Rainier volcano in Washington state. The scale at left is miles depth. The scale at bottom is miles from the Pacific Coast. The Juan de Fuca plate of Earth's Pacific seafloor crust and upper mantle is shown in blue on the left half of the image as it dives or 
'subducts' eastward beneath Washington state. The reddish orange and yellow colors represent molten and partly molten rock forming atop the Juan de Fuca plate or 'slab.' The image shows the rock begins to melt about 50 miles beneath Mount Rainier (the red triangle at top). Some is pulled downward and eastward as the slab keeps diving, but other melts move upward to the orange magma chamber shown under but west of Mount Rainier. The line of sensors used to make this image were placed north of the 14,410-foot peak, so the image may be showing a lobe of the magma chamber that extends northwest of the mountain. Red ovals on the left half of the page are the hypocenters of earthquakes. -  R Shane McGary, Woods Hole Oceanographic Institution.
This image was made by measuring how the ground conducts or resists electricity in a study co-authored by geophysicist Phil Wannamaker of the University of Utah Energy & Geoscience Institute. It shows the underground plumbing system that provides molten and partly molten rock to the magma chamber beneath the Mount Rainier volcano in Washington state. The scale at left is miles depth. The scale at bottom is miles from the Pacific Coast. The Juan de Fuca plate of Earth’s Pacific seafloor crust and upper mantle is shown in blue on the left half of the image as it dives or
‘subducts’ eastward beneath Washington state. The reddish orange and yellow colors represent molten and partly molten rock forming atop the Juan de Fuca plate or ‘slab.’ The image shows the rock begins to melt about 50 miles beneath Mount Rainier (the red triangle at top). Some is pulled downward and eastward as the slab keeps diving, but other melts move upward to the orange magma chamber shown under but west of Mount Rainier. The line of sensors used to make this image were placed north of the 14,410-foot peak, so the image may be showing a lobe of the magma chamber that extends northwest of the mountain. Red ovals on the left half of the page are the hypocenters of earthquakes. – R Shane McGary, Woods Hole Oceanographic Institution.

By measuring how fast Earth conducts electricity and seismic waves, a University of Utah researcher and colleagues made a detailed picture of Mount Rainier’s deep volcanic plumbing and partly molten rock that will erupt again someday.

“This is the most direct image yet capturing the melting process that feeds magma into a crustal reservoir that eventually is tapped for eruptions,” says geophysicist Phil Wannamaker, of the university’s Energy & Geoscience Institute and Department of Civil and Environmental Engineering. “But it does not provide any information on the timing of future eruptions from Mount Rainier or other Cascade Range volcanoes.”

The study was published today in the journal Nature by Wannamaker and geophysicists from the Woods Hole Oceanographic Institution in Massachusetts, the College of New Jersey and the University of Bergen, Norway.

In an odd twist, the image appears to show that at least part of Mount Rainier’s partly molten magma reservoir is located about 6 to 10 miles northwest of the 14,410-foot volcano, which is 30 to 45 miles southeast of the Seattle-Tacoma area.

But that could be because the 80 electrical sensors used for the experiment were placed in a 190-mile-long, west-to-east line about 12 miles north of Rainier. So the main part of the magma chamber could be directly under the peak, but with a lobe extending northwest under the line of detectors, Wannamaker says.

The top of the magma reservoir in the image is 5 miles underground and “appears to be 5 to 10 miles thick, and 5 to 10 miles wide in east-west extent,” he says. “We can’t really describe the north-south extent because it’s a slice view.”

Wannamaker estimates the reservoir is roughly 30 percent molten. Magma chambers are like a sponge of hot, soft rock containing pockets of molten rock.

The new image doesn’t reveal the plumbing tying Mount Rainier to the magma chamber 5 miles below it. Instead, it shows water and partly molten and molten rock are generated 50 miles underground where one of Earth’s seafloor crustal plates or slabs is “subducting” or diving eastward and downward beneath the North America plate, and how and where those melts rise to Rainier’s magma chamber.

The study was funded largely by the National Science Foundation’s Earthscope program, which also has made underground images of the United States using seismic or sound-wave tomography, much like CT scans show the body’s interior using X-rays.

The new study used both seismic imaging and magnetotelluric measurements, which make images by showing how electrical and magnetic fields in the ground vary due to differences in how much underground rock and fluids conduct or resist electricity.

Wannamaker says it is the most detailed cross-section view yet under a Cascades volcanic system using electrical and seismic imaging. Earlier seismic images indicated water and partly molten rock atop the diving slab. The new image shows melting “from the surface of the slab to the upper crust, where partly molten magma accumulates before erupting,” he adds.

Wannamaker and Rob L. Evans, of the Woods Hole Oceanographic Institution, conceived the study. First author R Shane McGary – then at Woods Hole and now at the College of New Jersey – did the data analysis. Other co-authors were Jimmy Elsenbeck of Woods Hole and Stéphane Rondenay of the University of Bergen.

Mount Rainier: Hazardous Backdrop to Metropolitan Seattle-Tacoma

Mount Rainier, the tallest peak in the Cascades, “is an active volcano that will erupt again,” says the U.S. Geological Survey. Rainier sits atop volcanic flows up to 36 million years old. An ancestral Rainier existed 2 million to 1 million years ago. Frequent eruptions built the mountain’s modern edifice during the past 500,000 years. During the past 11,000 years, Rainier erupted explosively dozens of times, spewing ash and pumice.

Rainier once was taller until it collapsed during an eruption 5,600 years ago to form a large crater open to the northeast, much like the crater formed by Mount St. Helens’ 1980 eruption. The 5,600-year-old eruption sent a huge mudflow west to Puget Sound, covering parts or all of the present sites of the Port of Tacoma, Seattle suburbs Kent and Auburn, and the towns Puyallup, Orting, Buckley, Sumner and Enumclaw.

Rainier’s last lava flows were 2,200 years ago, the last flows of hot rock and ash were 1,100 years ago and the last big mudflow 500 years ago. There are disputed reports of steam eruptions in the 1800s.

Subduction Made Simple – and a Peek beneath a Peak

The “ring of fire” is a zone of active volcanoes and frequent earthquake activity surrounding the Pacific Ocean. It exists where Earth’s tectonic plates collide – specifically, plates that make up the seafloor converge with plates that carry continents.

From Cape Mendocino in northern California and north past Oregon, Washington state and into British Columbia, an oceanic plate is being pushed eastward and downward – a process called subduction – beneath the North American plate. This relatively small Juan de Fuca plate is located between the huge Pacific plate and the Pacific Northwest.

New seafloor rock – rich with water in cracks and minerals – emerges from an undersea volcanic ridge some 250 miles off the coast, from northern California into British Columbia. That seafloor adds to the western edge of the Juan de Fuca plate and pushes it east-northeast under the Pacific Northwest, as far as Idaho.

The part of the plate diving eastward and downward is called the slab, which ranges from 30 to 60 miles thick as it is jammed under the North American plate. The part of the North American plate above the diving slab is shaped like a wedge.

When the leading, eastern edge of the diving slab descends deep enough, where pressures and temperatures are high, water-bearing minerals such as chlorite and amphibole release water from the slab, and the slab and surrounding mantle rock begin to melt. That is why the Cascade Range of active volcanoes extends north-to-south – above the slab and parallel but about 120 miles inland from the coast – from British Columbia south to Mount Shasta and Lassen Peak in northern California.

In the new image, yellow-orange-red areas correspond to higher electrical conductivity (or lower resistivity) in places where fluids and melts are located.

The underground image produced by the new study shows where water and molten rock accumulate atop the descending slab, and the route they take to the magma chamber that feeds eruptions of Mount Rainier:

– The rock begins to melt atop the slab about 50 miles beneath Mount Rainier. Wannamaker says it is best described as partly molten rock that contains about 2 percent water and “is a mush of crystals within an interlacing a network of molten rock.”

– Some water and partly molten rock actually gets dragged downward atop the descending slab, to depths of 70 miles or more.

– Other partly molten rock rises up through the upper mantle wedge, crosses into the crust at a depth of about 25 miles, and then rises into Rainier’s magma chamber – or at least the lobe of the chamber that crosses under the line of sensors used in the study. Evidence suggests the magma moves upward at least 0.4 inches per year.

– The new magnetotelluric image also shows a shallower zone of fluid perhaps 60 miles west of Rainier and 25 miles deep at the crust-mantle boundary. Wannamaker says it is largely water released from minerals as the slab is squeezed and heated as it dives.

The seismic data were collected during 2008-2009 for other studies. The magnetotelluric data were gathered during 2009-2010 by authors of the new study.

Wannamaker and colleagues placed an east-west line of magnetotelluric sensors: 60 that made one-day measurements and looked as deep as 30 miles into the Earth, and 20 that made measurements for a month and looked at even greater depths.

Scientists discover evidence of super-fast deep earthquake

As scientists learn more about earthquakes that rupture at fault zones near the planet’s surface-and the mechanisms that trigger them-an even more intriguing earthquake mystery lies deeper in the planet.

Scientists at Scripps Institution of Oceanography at UC San Diego have discovered the first evidence that deep earthquakes, those breaking at more than 400 kilometers (250 miles) below Earth’s surface, can rupture much faster than ordinary earthquakes. The finding gives seismologists new clues about the forces behind deep earthquakes as well as fast-breaking earthquakes that strike near the surface.

Seismologists have documented a handful of these events, in which an earthquake’s rupture travels faster than the shear waves of seismic energy that it radiates. These “supershear” earthquakes have rupture speeds of four kilometers per second (an astonishing 9,000 miles per hour) or more.

In a National Science Foundation-funded study reported in the June 11, 2014, issue of the journal Science, Scripps geophysicists Zhongwen Zhan and Peter Shearer of Scripps, along with their colleagues at Caltech, discovered the first deep supershear earthquake while examining the aftershocks of a magnitude 8.3 earthquake on May 24, 2013, in the Sea of Okhotsk off the Russian mainland.

Details of a magnitude 6.7 aftershock of the event captured Zhan’s attention. Analyzing data from the IRIS (Incorporated Research Institutions for Seismology) consortium, which coordinates a global network of seismological instruments, Zhan noted that most seismometers around the world yielded similar records, all suggesting an anomalously short duration for a magnitude 6.7 earthquake.

Data from one seismometer, however, stationed closest to the event in Russia’s Kamchatka Peninsula, told a different story with intriguing details.

After closely analyzing the data, Zhan not only found that the aftershock ruptured extremely deeply at 640 kilometers (400 miles) below the earth’s surface, but its rupture velocity was extraordinary-about eight kilometers per second (five miles per second), nearly 50 percent faster than the shear wave velocity at that depth.

“For a 6.7 earthquake you would expect a duration of seven to eight seconds, but this one lasted just two seconds,” said Shearer, a geophysics professor in the Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics (IGPP) at Scripps. “This is the first definitive example of supershear rupture for a deep earthquake since previously supershear ruptures have been documented only for shallow earthquakes.”

“This finding will help us understand why deep earthquakes happen,” said Zhan. “One quarter of earthquakes occur at large depths, and some of these can be pretty big, but we still don’t understand why they happen. So this earthquake provides a new observation for deep earthquakes and high-rupture speeds.”

Zhan also believes the new information will be useful in examining ultra-fast earthquakes and their potential for impacting fault zones near the earth’s surface. Although not of supershear caliber, California’s destructive 1994 Northridge earthquake had a comparable size and geometry to that of the 6.7 Sea of Okhotsk aftershock.

“If a shallow earthquake such as Northridge goes supershear, it could cause even more shaking and possibly more damage,” said Zhan.

Earthquakes explained? New research shows friction and fracture are closely related

Professor Jay Fineberg at the Hebrew University of Jerusalem's Racah Institute of Physics (shown here) and his graduate student Ilya Svetlizky have demonstrated that the seemingly disparate processes of fracture and friction are actually intimately intertwined. Their research has implications for describing the mechanics deep beneath the earth's surface that drive earthquakes. -  (Photo: Hebrew University)
Professor Jay Fineberg at the Hebrew University of Jerusalem’s Racah Institute of Physics (shown here) and his graduate student Ilya Svetlizky have demonstrated that the seemingly disparate processes of fracture and friction are actually intimately intertwined. Their research has implications for describing the mechanics deep beneath the earth’s surface that drive earthquakes. – (Photo: Hebrew University)

Overturning conventional wisdom stretching all the way to Leonardo da Vinci, new Hebrew University of Jerusalem research shows that how things break (fracture) and how things slide (friction) are closely interrelated. The breakthrough study marks an important advance in understanding friction and fracture, with implications for describing the mechanics that drive earthquakes.

Over 500 years ago, da Vinci described how rough blocks slide over one another, providing the basis for our understanding of friction to this day. The phenomenon of fracture was always considered to be something totally different.

But new research by Prof. Jay Fineberg and his graduate student Ilya Svetlizky, at the Hebrew University’s Racah Institute of Physics, has demonstrated that these two seemingly disparate processes of fracture and friction are actually intimately intertwined.

Appearing in the journal Nature, their findings create a new paradigm that’s very different from the da Vinci version, and, according to the researchers, give us a new understanding of how earthquakes actually occur.

Fineberg and Svetlizky produced “laboratory earthquakes” showing that the friction caused by the sliding of two contacting blocks can only occur when the connections between the surfaces are first ruptured (that is, fractured or broken) in an orderly, “organized” process that takes place at nearly the speed of sound.

How does this happen? Before any motion can occur, the blocks are connected by interlocking rough contacts that define their interface. In order for motion to occur, these connections have to be broken. This physical process of breaking is called a fracture process. This process is described by the theory of crack propagation, say the researchers, meaning that the stresses (or forces) that exist at the front edge of a crack become highly magnified, even if the overall forces being applied are initially quite small.

“The insights gained from our study provide a new paradigm for understanding friction and give us a new, fundamental description of the mechanics and behavior that drive earthquakes, the sliding of two tectonic blocks within natural faults,” says Fineberg. “In this way, we can now understand important processes that are generally hidden kilometers beneath the earth’s surface.”

New study of largely unstudied mesophotic coral reef geology

This is Platy coral representative of the US Virgin Islands mesophotic habitats. -  Photo by David Weinstein
This is Platy coral representative of the US Virgin Islands mesophotic habitats. – Photo by David Weinstein

A new study on biological erosion of mesophotic tropical coral reefs, which are low energy reef environments between 30-150 meters deep, provides new insights into processes that affect the overall structure of these important ecosystems. The purpose of the study was to better understand how bioerosion rates and distribution of bioeroding organisms, such as fish, mollusks and sponges, differ between mesophotic reefs and their shallow-water counterparts and the implications of those variations on the sustainability of the reef structure.

Due to major advancements in deeper underwater diving technology, a large renewal of interest in mesophotic reefs has pulsed through the scientific community because of their high biodiversity, vast extent, and potential refuge for shallower water reef species at risk from the impacts of climate change.

“Studying how mesophotic reefs function and thrive is especially critical now, when considering results from the new IPCC report reviewed by over 1700 expects said that coral reefs are the most vulnerable marine ecosystems on Earth to the adverse effects of climate change,” said David Weinstein, Rosenstiel School Ph.D. student and lead author of the study. “Developing effective environmental management strategies for these important reef systems requires a basic fundamental understanding of the underlining architecture that supports and creates diverse biological ecosystems.”

Weinstein and his research team used previously identified mesophotic reefs at 30-50 meters deep located in the U.S. Virgin Islands composed of a surprising number of coral growing on top different types of reef structures (patches, linear banks, basins) to better understand the role sedimentary processes have in creating and maintaining so many different structures that are critical for maximizing the biodiversity and health of the ecosystem. Researchers analyzed coral rubble and coral skeleton discs collected after one and two years of exposure to determine the sources and rates of bioerosion at these reefs.

Results of the study found that the architecturally unique structures in the study area experience significantly different bioerosion rates.

“This has very important implications when trying to predict how these reefs will grow over time and where preservation efforts might be most effective,” said Weinstein.

Although erosion of the coral skeleton disks at the very deepest sites was more uniform, the researchers suggest that this is likely because the substrates used in the study were all of uniform composition, unlike the diverse composition of the sites. These results imply that bioerosional processes at these depths still exaggerate differences in reef structure depending on the amount of living and dead coral at each reef, the amount of time that material is exposed on the surface, and different localized current flows experienced.

The study also confirmed important concepts in coral geology research that lacked proof from studies venturing deeper than 35 meters. Coral reef bioerosion in the U.S. Virgin Islands and potentially in most of the Caribbean does generally decreases with depth. This result stems from the finding that parrotfish are now the most significant bioeroding group from shallow reefs down to a mesophotic reef transition zone identified by Weinstein at 30-35 meters in depth. The study also was able to conclude bioeroding sponges are the primary organisms responsible for long-term structural modification of mesophotic reefs beyond the transitional zone.

“Coral reefs are essentially a thin benthos veneer draped upon a biologically produced inorganic three-dimensional foundation that creates habitats for many marine organisms,” said Weinstein. “Since mesophotic reefs grow so much slower than shallower reefs, identifying the sources and rate of erosion on mesophotic reefs is even more important to understand the long-term structural sustainability of these tropical reefs systems.”

However, Weinstein suggests that other processes, such as coral growth rates and cementation, must also be more fully studied before scientists have a complete understanding of mesophotic coral reefs.

The paper, currently available online and scheduled for print in a special coral reef edition of the journal Geomorphology later this summeris one of the first to address mesophotic reef sedimentology.