Understanding faults and volcanics, plus life inside a rock

Orange-like rocks in Utah with iron-oxide rinds and fossilized bacteria inside that are believed to have eaten the interior rock material, plus noted similarities to “bacterial meal” ingredients and rock types on Mars; fine-tuning the prediction of volcanic hazards and warning systems for both high population zones and at Tristan da Cunha, home to the most remote population on Earth; news from SAFOD; and discovery in Germany of the world’s oldest known mosses.


Biosignatures link microorganisms to iron mineralization in a paleoaquifer

Karrie A. Weber et al., School of Biological Sciences, University of Nebraska, Lincoln, Nebraska 68588, USA. Posted online 15 June 2012; doi: 10.1130/G33062.1.

Iron oxide rocks in an ancient aquifer give scientists clues about where to look for past life on Mars and other planets, including Earth. Scientists at the University of Nebraska-Lincoln and University of Western Australia have been studying rocks in Utah that resemble an orange with an iron cemented rind and an interior that consists of glued sand. These rocks formed millions of years ago in an ancient aquifer. Using microscopic methods, Karrie Weber and colleagues found tiny fossilized bacteria inside of these rocks, along with evidence corroborating that the bacteria were once alive inside the rock. Weber and colleagues think that these bacteria “ate” the iron in the rock to form the iron oxide mineral-rich rind. All of the ingredients for a bacterial meal exist on Mars and other areas on Earth. This has led the Weber and colleagues to theorize that similar iron-rich rocks could have been formed by bacteria and could still be forming today. The scientists are continuing to study how bacteria form rocks below Earth’s surface so to better understand the conditions that support life and the signatures that life leaves behind. This research is supported by the University of Nebraska Research Office and Nebraska Tobacco Settlement Fund.


Relationship between dike and volcanic conduit distribution in a highly eroded monogenetic volcanic field: San Rafael, Utah, USA

Koji Kiyosugi et al., Dept. of Geology, University of South Florida, 4202 East Fowler Avenue, Tampa, Florida 33620, USA. Posted online 15 June 2012; doi: 10.1130/G33074.1.

Cities like Auckland (NZ) and Mexico City are located within active volcanic fields, where new volcanoes will likely form in the future, creating a wide range of hazards. Where will these volcanoes form and what warning will residents have of impending eruptions? The geologic record preserved in old volcanic fields helps address this question. Koji Kiyosugi and colleagues studied magmatic system below an extinct volcanic field: the San Rafael subvolcanic field in Utah, USA. Below volcanoes, intrusive magma bodies formed before and during volcanic eruptions create vertical pipes (conduits) and vertical and horizontal sheets (dikes and sills, respectively). It is possible to observe these features of the magmatic system in great detail in this eroded volcanic field. Kiyosugi and colleagues mapped 63 conduits, ~2000 dike segments, and 12 sill complexes in the San Rafael. They find that the distribution of volcano conduits matches the major features of dike distribution, including development of clusters and distribution of outliers. These statistical models are then applied to the distributions of volcanoes in several recently active volcanic fields, where the distribution of intrusive magma bodies must be inferred from very sparse data. This comparison supports the use of statistical models in probabilistic hazard assessment for distributed volcanism.


Tristan da Cunha: Constraining eruptive behavior using the 40Ar/39Ar dating technique

Anna Hicks et al., Dept. of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, Norfolk NR4 7TJ, UK. Posted online 15 June 2012; doi: 10.1130/G33059.1.

Tristan da Cunha (South Atlantic) is an active volcano and home to the most remote population in the world. The volcano last erupted in 1961, forcing the temporary evacuation of all 261 islanders. In an attempt to constrain eruptive behavior and better anticipate likely future activity, new 40Ar/39Ar ages were measured on 15 rock samples, carefully selected to reflect possible temporal correlations between eruptive style, composition, or vent location. All sample sites were precisely dated, including a very young deposit (3,000 plus or minus 1,000 years old). Results revealed no spatio-temporal pattern to activity at parasitic cones and recent volcanism from these eruptive centers varies in style, volume, and composition with time. Timing of a large-scale sector collapse was constrained to a 14,000-year window, and ages showed that the northern sector of the edifice was built very rapidly. It seems likely that the entire edifice was constructed piecemeal and has a far more complex evolution that previously assumed. Of particular significance to hazard assessment is the discovery that the summit was contemporaneously active with recent activity on the flanks and inhabited low lying coastal strips. The results present significant uncertainty in terms of anticipating future eruptive scenarios, and reflect the necessity for effective risk reduction measures on Tristan.


Bubble geobarometry: A record of pressure changes, degassing, and regassing at Mono Craters, California

James M. Watkins et al., Dept. of Earth and Planetary Science, University of California, Berkeley, California 94720-4767, USA. Posted online 15 June 2012; doi: 10.1130/G33027.1.

Obsidian, natural volcanic glass, is one of the most recognizable rocks on Earth’s surface. Obsidian exhibits a wide range in textures that record volcanic processes. For example, flow bands in obsidian and healed fractures provide field evidence that lava can break and then heal (like silly putty) in volcanic feeder systems. The orientation of bubbles and microscopic crystals can be used to infer obsidian flow dynamics and the timing and rates of crystallization. In this study, James M. Watkins and colleagues use new measurements on bubbles in obsidian to infer the pressure history of rising magma. Unlike bubbles that grow in an open can of soda, bubbles in magma can both grow and shrink as they rise toward Earth’s surface. The study shows, for the first time, that the glass around bubbles preserves a record of physical changes in the magma feeder system prior to eruption. The measurements thus offer a new probe for inferring volcanic processes that are inaccessible to direct observation


Frictional properties and sliding stability of the San Andreas fault from deep drill core

B.M. Carpenter et al., Dept. of Geosciences and Energy Institute Center for Geomechanics, Geofluids, and Geohazards, Pennsylvania State University, University Park, Pennsylvania 16802, USA. Posted online 15 June 2012; doi: 10.1130/G33007.1.

Experimental studies on samples collected from the actively slipping San Andreas Fault, as part of San Andreas Fault Observatory at Depth (SAFOD) drilling in central California, USA, have provided important new insights into the mechanics and slip behavior of the fault at depth. B.M. Carpenter and colleagues report, for the first time, on the frictional properties of intact fault rock samples recovered from seismogenic depths. Their results explain several fundamental and longstanding observations along the San Andreas fault, including (1) the inferred extreme mechanical weakness and creeping behavior of the active fault in central California; (2) the occurrence and observed stress drop of repeating micro-earthquakes on faults to the northeast of the actively creeping fault strand; and (3) highly localized fault weakness, as documented by an extraordinarily sharp transition from frictionally weak fault rock within the main creeping strand of the San Andreas fault to stronger wall rock more than a mile away.


Subsidence of the West Siberian Basin: Effects of a mantle plume impact

Peter J. Holt et al., Geospatial Research Ltd., Durham University, Durham DH1 3LE, UK. Posted online 15 June 2012; doi: 10.1130/G32885.1.

Comparison of computer modeling results with the observed subsidence patterns from the West Siberian Basin provides new insight into the origin of the Siberian Traps flood basalts and constrains the temperature, size, and depth of an impacting mantle plume head during and after the eruption of the Siberian Traps at the Permian-Triassic boundary (250 million years ago). Peter J. Holt and colleagues compare subsidence patterns from a one-dimensional model of conductive heat flow to observed subsidence calculated from studies of the sediments in the basin. This results in a best-fit scenario with a 50-km-thick initial plume head with a temperature of 1500 degrees Celsius situated 50 km below the surface, and an initial regional crustal thickness of 34 km, which is in agreement with published values. The observed subsidence and modeling results agree very well, including a 60-90-million-year delay between the eruption of the flood basalts and the first regional sedimentation. These results reemphasize the viability of a mantle plume origin for the Siberian Traps, provide important constraints on the dynamics of mantle plume heads, and suggest a thermal control for the subsidence of the West Siberian Basin.


The relationship between surface kinematics and deformation of the whole lithosphere

L. Flesch and R. Bendick, Dept. of Earth and Atmospheric Sciences, Purdue University, 550 Stadium Mall Drive, West Lafayette, Indiana 47907-2051, USA. Posted online 15 June 2012; doi: 10.1130/G33269.1.

There has been a proliferation of geoscience research efforts over the past decade because of the new understanding of how the surface of the continents are moving using GPS surface observations. This data has been used either to asses forward numerical models of lithospheric or constrain inversions for the dynamics of continents to identify the forces driving the observed deformation. Such efforts inherently assume that information about dynamics is efficiently transferred from lithospheric depths to the surface. This is indisputably the case for oceanic lithosphere, but L. Flesch and R. Bendick show that it applies only in a limited subset of the plausible mechanical strength configurations for continents. Making such an assumption in other cases results in unreasonable conclusions about either the mechanical properties of the lithosphere or incorrectly complicated heterogeneous balance of forces.



Variability in the length of the sea ice season in the Middle Eocene Arctic

Catherine E. Stickley et al., Dept. of Geology, University of Tromsø, N-9037 Tromsø, Norway. Posted online 15 June 2012; doi: 10.1130/G32976.1.

Finely laminated marine sediments of middle Eocene age (about 45 million years old) are preserved along the Lomonosov Ridge in the central Arctic. These sediments comprise two main components: (1) those indicative of sea ice (fossil species of the delicate, sea ice-dwelling diatom Synedropsis spp.[siliceous microfossils]) and sea ice-rafted debris (sea ice-IRD); and (2) those indicative of open marine conditions (e.g., other diatom taxa and siliceous microfossil types). Their coexistence strongly implies seasonality, but to know with certainty, the annual flux cycle must be reconstructed. For the first time, Catherine E. Stickley and colleagues use a non-destructive technique to resolve and reconstruct seasonal-scale flux events from these sediments. They reveal discrete productivity-flux events at ultra-high (e.g., about 30 microns) resolution and show that seasonality is expressed at the submillimeter scale by successions of discrete mono-specific laminae and micro-lenses of Synedropsis species, of sea ice-IRD, and of open-water taxa. These findings indicate that first-year winter sea ice existed in the Arctic during the middle Eocene. A preliminary assessment of annual cycles shows that suborbital variability existed on the order of multi-decadal to centennial duration. Stickley and colleagues argue that this reflects variations in the sea ice season length. Past records at such time scales are especially important because they may reveal patterns of Earth system behavior of direct relevance to modern observations of Arctic change.


Oldest known mosses discovered in Mississippian (late Visean) strata of Germany

Maren Hübers and Hans Kerp, Forschungsstelle für Paläobotanik, Institut für Geologie und Paläontologie, Westfälische Wilhelms-Universität Münster, Schlossplatz 9,48143 Münster, Germany. Posted online 15 June 2012; doi: 10.1130/G33122.1.

Today bryophytes, with about 20,000 species of hornworts, liverworts, and mosses, are the most diverse group of non-vascular land plants. Mosses are important constituents of terrestrial ecosystems, from the tropics to the high latitudes. In many modern wetland ecosystems, mosses play a major role in nutrient cycling and water storage. Molecular clock data indicate that mosses appeared before the first vascular land plants, but their fossil record is extremely poor. Carboniferous wetland environments, with their unequaled accumulation of plant biomass, likely provided ideal habitats for mosses. Coal floras have been studied in great detail, but the fossil record of Carboniferous mosses is remarkably meager, though it should be noted that mosses are often difficult to recognize. Three types of mosses showing cellular preservation have now been identified from approx. 330 million-year-old rocks from eastern Germany. These are the oldest unequivocal mosses known to date, and even though the remains are small, they demonstrate that mosses formed part of Carboniferous ecosystems. The moss fossils were obtained from organic residues after whole-rock samples had been dissolved. This method, which is now rarely used for studying Carboniferous flora, may reveal that mosses were more widespread than commonly thought.


A detailed record of shallow hydrothermal fluid flow in the Sierra Nevada magmatic arc from low-delta-18O skarn garnets

Megan E. D’Errico et al., Dept. of Geology, Trinity University, San Antonio, Texas 78212, USA. Posted online 15 June 2012; doi: 10.1130/G33008.1.

Garnet from skarns exposed at Empire Mountain, Sierra Nevada (California, USA) batholith have variable delta-18O values, including the lowest known delta-18O values of skarn garnet in North America. Such values indicate that surface-derived meteoric water was a significant component of the fluid budget of the skarn-forming hydrothermal system, which developed in response to shallow emplacement (~3.3 km) of the 109 million year old quartz diorite of Empire Mountain. Brecciation in the skarns and alteration of the Empire Mountain pluton suggests that fracture-enhanced permeability was a critical control on the depth to which surface waters penetrated to form skarns and later alter the pluton. Compared to other Sierran systems, much greater volumes of skarn rock suggest an exceptionally vigorous hydrothermal system that saw unusually high levels of decarbonation reaction progress, likely a consequence of the magma intruding relatively cold wall rocks inboard of the main locus of magmatism in the Sierran arc at that time.


The influence of a mantle plume head on the dynamics of a retreating subduction zone

Peter G. Betts et al., School of Geosciences, Monash University, Clayton, VIC 3800, Australia. Posted online 15 June 2012; doi: 10.1130/G32909.1.

Earth subduction zones are where two geological plates of the outer Earth converge and the dense ocean crust sinks into the mantle. Subduction zones form an important component of mantle convection. Mantle plumes are hot buoyant material that rises from deep in the interior of the Earth and interact with the Earth’s crust. When plumes interact with ocean crust they can form large areas of buoyant ocean floor topography. Subduction zones can migrate backward and interact with mantle plumes, causing the subduction zone to change behavior. Peter G. Betts and colleagues modeled this geological situation and have discovered that subduction zone/plume interactions can cause massive geological damage at the edges of plates. The buoyant plume head hinders subduction and causes the subduction zone to migrate forward causing intense deformation in the adjacent geological plate. The subducting oceanic plate is also damaged and large tears can form allowing the plume to migrate across plate boundaries. The Yellowstone hotspot may be an ancient example of this process.

Understanding faults and volcanics, plus life inside a rock

Orange-like rocks in Utah with iron-oxide rinds and fossilized bacteria inside that are believed to have eaten the interior rock material, plus noted similarities to “bacterial meal” ingredients and rock types on Mars; fine-tuning the prediction of volcanic hazards and warning systems for both high population zones and at Tristan da Cunha, home to the most remote population on Earth; news from SAFOD; and discovery in Germany of the world’s oldest known mosses.


Biosignatures link microorganisms to iron mineralization in a paleoaquifer

Karrie A. Weber et al., School of Biological Sciences, University of Nebraska, Lincoln, Nebraska 68588, USA. Posted online 15 June 2012; doi: 10.1130/G33062.1.

Iron oxide rocks in an ancient aquifer give scientists clues about where to look for past life on Mars and other planets, including Earth. Scientists at the University of Nebraska-Lincoln and University of Western Australia have been studying rocks in Utah that resemble an orange with an iron cemented rind and an interior that consists of glued sand. These rocks formed millions of years ago in an ancient aquifer. Using microscopic methods, Karrie Weber and colleagues found tiny fossilized bacteria inside of these rocks, along with evidence corroborating that the bacteria were once alive inside the rock. Weber and colleagues think that these bacteria “ate” the iron in the rock to form the iron oxide mineral-rich rind. All of the ingredients for a bacterial meal exist on Mars and other areas on Earth. This has led the Weber and colleagues to theorize that similar iron-rich rocks could have been formed by bacteria and could still be forming today. The scientists are continuing to study how bacteria form rocks below Earth’s surface so to better understand the conditions that support life and the signatures that life leaves behind. This research is supported by the University of Nebraska Research Office and Nebraska Tobacco Settlement Fund.


Relationship between dike and volcanic conduit distribution in a highly eroded monogenetic volcanic field: San Rafael, Utah, USA

Koji Kiyosugi et al., Dept. of Geology, University of South Florida, 4202 East Fowler Avenue, Tampa, Florida 33620, USA. Posted online 15 June 2012; doi: 10.1130/G33074.1.

Cities like Auckland (NZ) and Mexico City are located within active volcanic fields, where new volcanoes will likely form in the future, creating a wide range of hazards. Where will these volcanoes form and what warning will residents have of impending eruptions? The geologic record preserved in old volcanic fields helps address this question. Koji Kiyosugi and colleagues studied magmatic system below an extinct volcanic field: the San Rafael subvolcanic field in Utah, USA. Below volcanoes, intrusive magma bodies formed before and during volcanic eruptions create vertical pipes (conduits) and vertical and horizontal sheets (dikes and sills, respectively). It is possible to observe these features of the magmatic system in great detail in this eroded volcanic field. Kiyosugi and colleagues mapped 63 conduits, ~2000 dike segments, and 12 sill complexes in the San Rafael. They find that the distribution of volcano conduits matches the major features of dike distribution, including development of clusters and distribution of outliers. These statistical models are then applied to the distributions of volcanoes in several recently active volcanic fields, where the distribution of intrusive magma bodies must be inferred from very sparse data. This comparison supports the use of statistical models in probabilistic hazard assessment for distributed volcanism.


Tristan da Cunha: Constraining eruptive behavior using the 40Ar/39Ar dating technique

Anna Hicks et al., Dept. of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, Norfolk NR4 7TJ, UK. Posted online 15 June 2012; doi: 10.1130/G33059.1.

Tristan da Cunha (South Atlantic) is an active volcano and home to the most remote population in the world. The volcano last erupted in 1961, forcing the temporary evacuation of all 261 islanders. In an attempt to constrain eruptive behavior and better anticipate likely future activity, new 40Ar/39Ar ages were measured on 15 rock samples, carefully selected to reflect possible temporal correlations between eruptive style, composition, or vent location. All sample sites were precisely dated, including a very young deposit (3,000 plus or minus 1,000 years old). Results revealed no spatio-temporal pattern to activity at parasitic cones and recent volcanism from these eruptive centers varies in style, volume, and composition with time. Timing of a large-scale sector collapse was constrained to a 14,000-year window, and ages showed that the northern sector of the edifice was built very rapidly. It seems likely that the entire edifice was constructed piecemeal and has a far more complex evolution that previously assumed. Of particular significance to hazard assessment is the discovery that the summit was contemporaneously active with recent activity on the flanks and inhabited low lying coastal strips. The results present significant uncertainty in terms of anticipating future eruptive scenarios, and reflect the necessity for effective risk reduction measures on Tristan.


Bubble geobarometry: A record of pressure changes, degassing, and regassing at Mono Craters, California

James M. Watkins et al., Dept. of Earth and Planetary Science, University of California, Berkeley, California 94720-4767, USA. Posted online 15 June 2012; doi: 10.1130/G33027.1.

Obsidian, natural volcanic glass, is one of the most recognizable rocks on Earth’s surface. Obsidian exhibits a wide range in textures that record volcanic processes. For example, flow bands in obsidian and healed fractures provide field evidence that lava can break and then heal (like silly putty) in volcanic feeder systems. The orientation of bubbles and microscopic crystals can be used to infer obsidian flow dynamics and the timing and rates of crystallization. In this study, James M. Watkins and colleagues use new measurements on bubbles in obsidian to infer the pressure history of rising magma. Unlike bubbles that grow in an open can of soda, bubbles in magma can both grow and shrink as they rise toward Earth’s surface. The study shows, for the first time, that the glass around bubbles preserves a record of physical changes in the magma feeder system prior to eruption. The measurements thus offer a new probe for inferring volcanic processes that are inaccessible to direct observation


Frictional properties and sliding stability of the San Andreas fault from deep drill core

B.M. Carpenter et al., Dept. of Geosciences and Energy Institute Center for Geomechanics, Geofluids, and Geohazards, Pennsylvania State University, University Park, Pennsylvania 16802, USA. Posted online 15 June 2012; doi: 10.1130/G33007.1.

Experimental studies on samples collected from the actively slipping San Andreas Fault, as part of San Andreas Fault Observatory at Depth (SAFOD) drilling in central California, USA, have provided important new insights into the mechanics and slip behavior of the fault at depth. B.M. Carpenter and colleagues report, for the first time, on the frictional properties of intact fault rock samples recovered from seismogenic depths. Their results explain several fundamental and longstanding observations along the San Andreas fault, including (1) the inferred extreme mechanical weakness and creeping behavior of the active fault in central California; (2) the occurrence and observed stress drop of repeating micro-earthquakes on faults to the northeast of the actively creeping fault strand; and (3) highly localized fault weakness, as documented by an extraordinarily sharp transition from frictionally weak fault rock within the main creeping strand of the San Andreas fault to stronger wall rock more than a mile away.


Subsidence of the West Siberian Basin: Effects of a mantle plume impact

Peter J. Holt et al., Geospatial Research Ltd., Durham University, Durham DH1 3LE, UK. Posted online 15 June 2012; doi: 10.1130/G32885.1.

Comparison of computer modeling results with the observed subsidence patterns from the West Siberian Basin provides new insight into the origin of the Siberian Traps flood basalts and constrains the temperature, size, and depth of an impacting mantle plume head during and after the eruption of the Siberian Traps at the Permian-Triassic boundary (250 million years ago). Peter J. Holt and colleagues compare subsidence patterns from a one-dimensional model of conductive heat flow to observed subsidence calculated from studies of the sediments in the basin. This results in a best-fit scenario with a 50-km-thick initial plume head with a temperature of 1500 degrees Celsius situated 50 km below the surface, and an initial regional crustal thickness of 34 km, which is in agreement with published values. The observed subsidence and modeling results agree very well, including a 60-90-million-year delay between the eruption of the flood basalts and the first regional sedimentation. These results reemphasize the viability of a mantle plume origin for the Siberian Traps, provide important constraints on the dynamics of mantle plume heads, and suggest a thermal control for the subsidence of the West Siberian Basin.


The relationship between surface kinematics and deformation of the whole lithosphere

L. Flesch and R. Bendick, Dept. of Earth and Atmospheric Sciences, Purdue University, 550 Stadium Mall Drive, West Lafayette, Indiana 47907-2051, USA. Posted online 15 June 2012; doi: 10.1130/G33269.1.

There has been a proliferation of geoscience research efforts over the past decade because of the new understanding of how the surface of the continents are moving using GPS surface observations. This data has been used either to asses forward numerical models of lithospheric or constrain inversions for the dynamics of continents to identify the forces driving the observed deformation. Such efforts inherently assume that information about dynamics is efficiently transferred from lithospheric depths to the surface. This is indisputably the case for oceanic lithosphere, but L. Flesch and R. Bendick show that it applies only in a limited subset of the plausible mechanical strength configurations for continents. Making such an assumption in other cases results in unreasonable conclusions about either the mechanical properties of the lithosphere or incorrectly complicated heterogeneous balance of forces.



Variability in the length of the sea ice season in the Middle Eocene Arctic

Catherine E. Stickley et al., Dept. of Geology, University of Tromsø, N-9037 Tromsø, Norway. Posted online 15 June 2012; doi: 10.1130/G32976.1.

Finely laminated marine sediments of middle Eocene age (about 45 million years old) are preserved along the Lomonosov Ridge in the central Arctic. These sediments comprise two main components: (1) those indicative of sea ice (fossil species of the delicate, sea ice-dwelling diatom Synedropsis spp.[siliceous microfossils]) and sea ice-rafted debris (sea ice-IRD); and (2) those indicative of open marine conditions (e.g., other diatom taxa and siliceous microfossil types). Their coexistence strongly implies seasonality, but to know with certainty, the annual flux cycle must be reconstructed. For the first time, Catherine E. Stickley and colleagues use a non-destructive technique to resolve and reconstruct seasonal-scale flux events from these sediments. They reveal discrete productivity-flux events at ultra-high (e.g., about 30 microns) resolution and show that seasonality is expressed at the submillimeter scale by successions of discrete mono-specific laminae and micro-lenses of Synedropsis species, of sea ice-IRD, and of open-water taxa. These findings indicate that first-year winter sea ice existed in the Arctic during the middle Eocene. A preliminary assessment of annual cycles shows that suborbital variability existed on the order of multi-decadal to centennial duration. Stickley and colleagues argue that this reflects variations in the sea ice season length. Past records at such time scales are especially important because they may reveal patterns of Earth system behavior of direct relevance to modern observations of Arctic change.


Oldest known mosses discovered in Mississippian (late Visean) strata of Germany

Maren Hübers and Hans Kerp, Forschungsstelle für Paläobotanik, Institut für Geologie und Paläontologie, Westfälische Wilhelms-Universität Münster, Schlossplatz 9,48143 Münster, Germany. Posted online 15 June 2012; doi: 10.1130/G33122.1.

Today bryophytes, with about 20,000 species of hornworts, liverworts, and mosses, are the most diverse group of non-vascular land plants. Mosses are important constituents of terrestrial ecosystems, from the tropics to the high latitudes. In many modern wetland ecosystems, mosses play a major role in nutrient cycling and water storage. Molecular clock data indicate that mosses appeared before the first vascular land plants, but their fossil record is extremely poor. Carboniferous wetland environments, with their unequaled accumulation of plant biomass, likely provided ideal habitats for mosses. Coal floras have been studied in great detail, but the fossil record of Carboniferous mosses is remarkably meager, though it should be noted that mosses are often difficult to recognize. Three types of mosses showing cellular preservation have now been identified from approx. 330 million-year-old rocks from eastern Germany. These are the oldest unequivocal mosses known to date, and even though the remains are small, they demonstrate that mosses formed part of Carboniferous ecosystems. The moss fossils were obtained from organic residues after whole-rock samples had been dissolved. This method, which is now rarely used for studying Carboniferous flora, may reveal that mosses were more widespread than commonly thought.


A detailed record of shallow hydrothermal fluid flow in the Sierra Nevada magmatic arc from low-delta-18O skarn garnets

Megan E. D’Errico et al., Dept. of Geology, Trinity University, San Antonio, Texas 78212, USA. Posted online 15 June 2012; doi: 10.1130/G33008.1.

Garnet from skarns exposed at Empire Mountain, Sierra Nevada (California, USA) batholith have variable delta-18O values, including the lowest known delta-18O values of skarn garnet in North America. Such values indicate that surface-derived meteoric water was a significant component of the fluid budget of the skarn-forming hydrothermal system, which developed in response to shallow emplacement (~3.3 km) of the 109 million year old quartz diorite of Empire Mountain. Brecciation in the skarns and alteration of the Empire Mountain pluton suggests that fracture-enhanced permeability was a critical control on the depth to which surface waters penetrated to form skarns and later alter the pluton. Compared to other Sierran systems, much greater volumes of skarn rock suggest an exceptionally vigorous hydrothermal system that saw unusually high levels of decarbonation reaction progress, likely a consequence of the magma intruding relatively cold wall rocks inboard of the main locus of magmatism in the Sierran arc at that time.


The influence of a mantle plume head on the dynamics of a retreating subduction zone

Peter G. Betts et al., School of Geosciences, Monash University, Clayton, VIC 3800, Australia. Posted online 15 June 2012; doi: 10.1130/G32909.1.

Earth subduction zones are where two geological plates of the outer Earth converge and the dense ocean crust sinks into the mantle. Subduction zones form an important component of mantle convection. Mantle plumes are hot buoyant material that rises from deep in the interior of the Earth and interact with the Earth’s crust. When plumes interact with ocean crust they can form large areas of buoyant ocean floor topography. Subduction zones can migrate backward and interact with mantle plumes, causing the subduction zone to change behavior. Peter G. Betts and colleagues modeled this geological situation and have discovered that subduction zone/plume interactions can cause massive geological damage at the edges of plates. The buoyant plume head hinders subduction and causes the subduction zone to migrate forward causing intense deformation in the adjacent geological plate. The subducting oceanic plate is also damaged and large tears can form allowing the plume to migrate across plate boundaries. The Yellowstone hotspot may be an ancient example of this process.

Soil moisture climate data record observed from space

This shows dry areas and moist areas - a map created from satellite data. -  ESA / Vienna University of Technology / Free University Amsterdam
This shows dry areas and moist areas – a map created from satellite data. – ESA / Vienna University of Technology / Free University Amsterdam

The future of the world’s climate is determined by various parameters, such as the density of clouds or the mass of the Antarctic ice sheet. One of these crucial climate parameters is soil moisture, which is hard to measure on a global scale. Now, the European Space Agency (ESA), in cooperation with the Vienna University of Technology (Institute of Photogrammetry and Remote Sensing) and the Free University of Amsterdam, is presenting a data set, containing global soil moisture data from 1978 to 2010. This was possible by extensive mathematical analysis of satellite data.

Watch a video of the data here:

Warmer Climate Changes Soil Moisture

Even though soil moisture makes up only about 0.001 % of the total water found on earth, it plays a crucial rule in the climate system. “The link between climate and soil moisture is still not well understood, because so far reliable long-term data has not been available”, says professor Wolfgang Wagner (Vienna University of Technology). One of the predicted consequences of global warming is that warming will lead to higher evaporation rates and hence soil drying in some regions. But drier soils themselves will heat up the air near the land surface. This positive feedback mechanism may thus act to increase the number of extreme heat waves similar to those experienced in Western Europe in 2003 and Russia in 2010. On the other hand, hot air can hold more water and lead to increased precipitation in some regions. “The effects of climate change vary from region to region”, says Wolfgang Werner, “this makes it all the more important to have reliable long-term data for the whole globe.”

Microwaves from Space

Soil moisture can be measured with satellites using microwave radiation. Unlike visible light, microwaves can penetrate clouds. Satellites can either measure the earths natural microwave radiation to calculate the local soil moisture (passive measurement) or the satellite sends out microwave pulses and measures how strongly the pulse is reflected by the surface (active measurement). Over the years, various satellites with different measurement methods have been used. “It is a great challenge to extract reliable soil moisture data from these very different datasets, spanning several decades”, says Wolfgang Wagner.

To address the current lack of long-term soil moisture data the European Space Agency (ESA) has been supporting the development of a global soil moisture data record derived by merging measurements acquired by a series of European and American satellites. ESA is now happy to announce that the release of the first soil moisture data record spanning the period 1978 to 2010. The soil moisture data record was generated by merging two soil moisture data sets, one derived from active microwave observations and the other from passive microwave observations. The active data set was generated by the Vienna University of Vienna (TU Wien) based on observations from the C-band scatterometers on board of ERS-1, ERS-2 and METOP-A; the passive data set was generated by the VU University Amsterdam in collaboration with NASA based on passive microwave observations.

Technological Challenges

The harmonization of these datasets aimed to take advantage of both microwave techniques, but still the challenges were significant. Amongst other issues, the potential influences of mission specifications, sensor degradation, drifts in calibration, and algorithmic changes had to be accounted for as accurately as possible. Also, it had to be guaranteed that the soil moisture data retrieved from the different active and passive microwave instruments are physically consistent. As this is the first release of such a product, not all caveats and limitations of the data are yet fully understood. It will therefore require the active cooperation of the remote sensing and climate modeling communities to jointly validate the satellite and model data, and advance the science in both fields along the way.

Soil moisture climate data record observed from space

This shows dry areas and moist areas - a map created from satellite data. -  ESA / Vienna University of Technology / Free University Amsterdam
This shows dry areas and moist areas – a map created from satellite data. – ESA / Vienna University of Technology / Free University Amsterdam

The future of the world’s climate is determined by various parameters, such as the density of clouds or the mass of the Antarctic ice sheet. One of these crucial climate parameters is soil moisture, which is hard to measure on a global scale. Now, the European Space Agency (ESA), in cooperation with the Vienna University of Technology (Institute of Photogrammetry and Remote Sensing) and the Free University of Amsterdam, is presenting a data set, containing global soil moisture data from 1978 to 2010. This was possible by extensive mathematical analysis of satellite data.

Watch a video of the data here:

Warmer Climate Changes Soil Moisture

Even though soil moisture makes up only about 0.001 % of the total water found on earth, it plays a crucial rule in the climate system. “The link between climate and soil moisture is still not well understood, because so far reliable long-term data has not been available”, says professor Wolfgang Wagner (Vienna University of Technology). One of the predicted consequences of global warming is that warming will lead to higher evaporation rates and hence soil drying in some regions. But drier soils themselves will heat up the air near the land surface. This positive feedback mechanism may thus act to increase the number of extreme heat waves similar to those experienced in Western Europe in 2003 and Russia in 2010. On the other hand, hot air can hold more water and lead to increased precipitation in some regions. “The effects of climate change vary from region to region”, says Wolfgang Werner, “this makes it all the more important to have reliable long-term data for the whole globe.”

Microwaves from Space

Soil moisture can be measured with satellites using microwave radiation. Unlike visible light, microwaves can penetrate clouds. Satellites can either measure the earths natural microwave radiation to calculate the local soil moisture (passive measurement) or the satellite sends out microwave pulses and measures how strongly the pulse is reflected by the surface (active measurement). Over the years, various satellites with different measurement methods have been used. “It is a great challenge to extract reliable soil moisture data from these very different datasets, spanning several decades”, says Wolfgang Wagner.

To address the current lack of long-term soil moisture data the European Space Agency (ESA) has been supporting the development of a global soil moisture data record derived by merging measurements acquired by a series of European and American satellites. ESA is now happy to announce that the release of the first soil moisture data record spanning the period 1978 to 2010. The soil moisture data record was generated by merging two soil moisture data sets, one derived from active microwave observations and the other from passive microwave observations. The active data set was generated by the Vienna University of Vienna (TU Wien) based on observations from the C-band scatterometers on board of ERS-1, ERS-2 and METOP-A; the passive data set was generated by the VU University Amsterdam in collaboration with NASA based on passive microwave observations.

Technological Challenges

The harmonization of these datasets aimed to take advantage of both microwave techniques, but still the challenges were significant. Amongst other issues, the potential influences of mission specifications, sensor degradation, drifts in calibration, and algorithmic changes had to be accounted for as accurately as possible. Also, it had to be guaranteed that the soil moisture data retrieved from the different active and passive microwave instruments are physically consistent. As this is the first release of such a product, not all caveats and limitations of the data are yet fully understood. It will therefore require the active cooperation of the remote sensing and climate modeling communities to jointly validate the satellite and model data, and advance the science in both fields along the way.

Studying soil to predict the future of earth’s atmosphere

BYU soil scientist Richard Gill studies the effects rising levels of CO2 have on soils. -  Jaren Wilkey/BYU
BYU soil scientist Richard Gill studies the effects rising levels of CO2 have on soils. – Jaren Wilkey/BYU

When it comes to understanding climate change, it’s all about the dirt.

A new study by researchers at BYU, Duke and the USDA finds that soil plays an important role in controlling the planet’s atmospheric future.

The researchers set out to find how intact ecosystems are responding to increased levels of carbon dioxide in the atmosphere. The earth’s current atmospheric carbon dioxide is 390 parts per million, up from 260 parts per million at the start of the industrial revolution, and will likely rise to more than 500 parts per million in the coming decades.

What they found, published in the current issue of Nature Climate Change, is that the interaction between plants and soils controls how ecosystems respond to rising levels of CO2 in the atmosphere.

“As we forecast what the future is going to look like, with the way we’ve changed the global atmosphere, often times we overlook soil,” said BYU biology professor Richard Gill, a coauthor on the study. “The soils matter enormously and the feedbacks that occur in the soil are ultimately going to control the atmosphere.”

The research shows that even in the absence of climate change, humans are impacting vital ecosystems as the composition of the earth’s atmosphere changes. They observed that changes in atmospheric CO2 caused changes in plant species composition and the availability of water and nitrogen.

Researchers worry that if the ability of plants and soils to absorb carbon becomes saturated over time then CO2 in the atmosphere will increase much more quickly than it has in the past.

“We don’t just have to be concerned about climate change, we have to be concerned about the other changes in atmospheric chemistry,” Gill said. “Globally we’re changing the earth’s atmosphere and we know that is going to influence the systems we depend on. To forecast those changes, you have to understand deeply what is happening in soils.”

The BYU-Duke team has been studying the effects of increased carbon dioxide in soils for the last 12 years.

Gill’s particular role in the ongoing research is to monitor and measure the changes in the nitrogen cycle and carbon dynamics due to atmospheric CO2. To do this, Gill brings soil samples from a Texas research site back to his BYU lab and does laboratory chemistry on the soil.

Naturally, when a plant dies the nitrogen in that plant is reabsorbed back into the soil. Gill is finding that increased CO2 may help plants grow well at first, but it causes the nitrogen to be tied up in “plant litter” and microbes that usually chew it up and release it back into the soil are struggling to do so.

“The big takeaway is that humanity is changing the earth’s atmosphere; we’ve increased atmospheric CO2 by almost 50 percent since the industrial revolution and these changes have cascading effects in both natural and managed systems,” Gill said. “Whether those are changes in how plants use water or changes in soil fertility, these are byproducts of the choices we make.”

Studying soil to predict the future of earth’s atmosphere

BYU soil scientist Richard Gill studies the effects rising levels of CO2 have on soils. -  Jaren Wilkey/BYU
BYU soil scientist Richard Gill studies the effects rising levels of CO2 have on soils. – Jaren Wilkey/BYU

When it comes to understanding climate change, it’s all about the dirt.

A new study by researchers at BYU, Duke and the USDA finds that soil plays an important role in controlling the planet’s atmospheric future.

The researchers set out to find how intact ecosystems are responding to increased levels of carbon dioxide in the atmosphere. The earth’s current atmospheric carbon dioxide is 390 parts per million, up from 260 parts per million at the start of the industrial revolution, and will likely rise to more than 500 parts per million in the coming decades.

What they found, published in the current issue of Nature Climate Change, is that the interaction between plants and soils controls how ecosystems respond to rising levels of CO2 in the atmosphere.

“As we forecast what the future is going to look like, with the way we’ve changed the global atmosphere, often times we overlook soil,” said BYU biology professor Richard Gill, a coauthor on the study. “The soils matter enormously and the feedbacks that occur in the soil are ultimately going to control the atmosphere.”

The research shows that even in the absence of climate change, humans are impacting vital ecosystems as the composition of the earth’s atmosphere changes. They observed that changes in atmospheric CO2 caused changes in plant species composition and the availability of water and nitrogen.

Researchers worry that if the ability of plants and soils to absorb carbon becomes saturated over time then CO2 in the atmosphere will increase much more quickly than it has in the past.

“We don’t just have to be concerned about climate change, we have to be concerned about the other changes in atmospheric chemistry,” Gill said. “Globally we’re changing the earth’s atmosphere and we know that is going to influence the systems we depend on. To forecast those changes, you have to understand deeply what is happening in soils.”

The BYU-Duke team has been studying the effects of increased carbon dioxide in soils for the last 12 years.

Gill’s particular role in the ongoing research is to monitor and measure the changes in the nitrogen cycle and carbon dynamics due to atmospheric CO2. To do this, Gill brings soil samples from a Texas research site back to his BYU lab and does laboratory chemistry on the soil.

Naturally, when a plant dies the nitrogen in that plant is reabsorbed back into the soil. Gill is finding that increased CO2 may help plants grow well at first, but it causes the nitrogen to be tied up in “plant litter” and microbes that usually chew it up and release it back into the soil are struggling to do so.

“The big takeaway is that humanity is changing the earth’s atmosphere; we’ve increased atmospheric CO2 by almost 50 percent since the industrial revolution and these changes have cascading effects in both natural and managed systems,” Gill said. “Whether those are changes in how plants use water or changes in soil fertility, these are byproducts of the choices we make.”

Volcanic gases could deplete ozone layer

Giant volcanic eruptions in Nicaragua over the past 70,000 years could have injected enough gases into the atmosphere to temporarily thin the ozone layer, according to new research. And, if it happened today, a similar explosive eruption could do the same, releasing more than twice the amount of ozone-depleting halogen gases currently in stratosphere due to manmade emissions.

Bromine and chlorine are gases that “love to react – especially with ozone,” said Kirstin Krüger, a meteorologist with GEOMAR in Kiel, Germany. “If they reach the upper levels of the atmosphere, they have a high potential of depleting the ozone layer.”

New research by Krüger and her colleagues, which she presented today at a scientific conference in Selfoss, Iceland, combined a mixture of field work, geochemistry and existing atmospheric models to look at the previous Nicaraguan eruptions. And the scientists found that the eruptions were explosive enough to reach the stratosphere, and spewed out enough bromine and chlorine in those eruptions, to have an effect on the protective ozone layer. Krüger’s talk was at the American Geophysical Union’s Chapman Conference on Volcanism and the Atmosphere.

Steffen Kutterolf, a chemical volcanologist with GEOMAR and one of Krüger’s colleagues, tackled the question of how much gas was released during the eruptions. He analyzed gases that were trapped by minerals crystallizing in the magma chambers, and applied a novel method that involves using the high-energy radiation from the German Electron Synchrotron in Hamburg to detect trace elements, including bromine. From that, Kutterolf estimated the amount of gas within magma before the eruptions, as well as the gas content in the lava rocks post-eruption. The difference, combined with existing field data about the size of the eruption, allowed the scientists to calculate how much bromine and chlorine are released.

Previous studies have estimated that in large, explosive eruptions – the type that sends mushroom clouds of ash kilometers high – up to 25 percent of the halogens ejected can make it to the stratosphere. For this study, the research team used a more conservative estimate of 10 percent reaching the stratosphere, to calculate the potential ozone layer depletion.

Taking an average from 14 Nicaraguan eruptions, the scientists found bromine and chlorine concentrations in the stratosphere jumped to levels that are equivalent to 200 percent to 300 percent of the 2011 concentrations of those gases. The Upper Apoyo eruption 24,500 years ago, for example, released 120 megatons of chlorine and 600 kilotons of bromine into the stratosphere.

Volcanic sulfate aerosols alone can lead to an ozone increase – if chlorine levels are at low, pre-industrial levels, Krüger said. But bromine and chlorine are halogens, gases whose atoms have seven electrons in the outer ring. To reach a stable, eight-electron configuration, these atoms will rip electrons off of passing molecules, like ozone. So when an eruption also pumps bromine and chlorine levels into the stratosphere, the ozone-depleting properties of the gases together with aerosols is expected to thin the protective layer.

“As we have bromine and chlorine together, we believe that this can lead to substantial depletion,” she said. “And this is from one single eruption.”

Because the effects are in the stratosphere, where the volcanic gases can be carried across the globe, eruptions of tropical volcanoes could lead to ozone depletion over a large area, Krüger said, potentially even impacting the ozone over polar regions. However, that’s a question for future research to address. Some volcanic gases can last in the stratosphere up to six years, she added, although the most significant impacts from eruptions like Mount Pinatubo were within the first two years.

The next step in the research, Krüger said, is to investigate how much damage to the ozone layer the volcanic gases caused in the past – and what the damage could be from future volcanic eruptions in the active Central American region.

Volcanic gases could deplete ozone layer

Giant volcanic eruptions in Nicaragua over the past 70,000 years could have injected enough gases into the atmosphere to temporarily thin the ozone layer, according to new research. And, if it happened today, a similar explosive eruption could do the same, releasing more than twice the amount of ozone-depleting halogen gases currently in stratosphere due to manmade emissions.

Bromine and chlorine are gases that “love to react – especially with ozone,” said Kirstin Krüger, a meteorologist with GEOMAR in Kiel, Germany. “If they reach the upper levels of the atmosphere, they have a high potential of depleting the ozone layer.”

New research by Krüger and her colleagues, which she presented today at a scientific conference in Selfoss, Iceland, combined a mixture of field work, geochemistry and existing atmospheric models to look at the previous Nicaraguan eruptions. And the scientists found that the eruptions were explosive enough to reach the stratosphere, and spewed out enough bromine and chlorine in those eruptions, to have an effect on the protective ozone layer. Krüger’s talk was at the American Geophysical Union’s Chapman Conference on Volcanism and the Atmosphere.

Steffen Kutterolf, a chemical volcanologist with GEOMAR and one of Krüger’s colleagues, tackled the question of how much gas was released during the eruptions. He analyzed gases that were trapped by minerals crystallizing in the magma chambers, and applied a novel method that involves using the high-energy radiation from the German Electron Synchrotron in Hamburg to detect trace elements, including bromine. From that, Kutterolf estimated the amount of gas within magma before the eruptions, as well as the gas content in the lava rocks post-eruption. The difference, combined with existing field data about the size of the eruption, allowed the scientists to calculate how much bromine and chlorine are released.

Previous studies have estimated that in large, explosive eruptions – the type that sends mushroom clouds of ash kilometers high – up to 25 percent of the halogens ejected can make it to the stratosphere. For this study, the research team used a more conservative estimate of 10 percent reaching the stratosphere, to calculate the potential ozone layer depletion.

Taking an average from 14 Nicaraguan eruptions, the scientists found bromine and chlorine concentrations in the stratosphere jumped to levels that are equivalent to 200 percent to 300 percent of the 2011 concentrations of those gases. The Upper Apoyo eruption 24,500 years ago, for example, released 120 megatons of chlorine and 600 kilotons of bromine into the stratosphere.

Volcanic sulfate aerosols alone can lead to an ozone increase – if chlorine levels are at low, pre-industrial levels, Krüger said. But bromine and chlorine are halogens, gases whose atoms have seven electrons in the outer ring. To reach a stable, eight-electron configuration, these atoms will rip electrons off of passing molecules, like ozone. So when an eruption also pumps bromine and chlorine levels into the stratosphere, the ozone-depleting properties of the gases together with aerosols is expected to thin the protective layer.

“As we have bromine and chlorine together, we believe that this can lead to substantial depletion,” she said. “And this is from one single eruption.”

Because the effects are in the stratosphere, where the volcanic gases can be carried across the globe, eruptions of tropical volcanoes could lead to ozone depletion over a large area, Krüger said, potentially even impacting the ozone over polar regions. However, that’s a question for future research to address. Some volcanic gases can last in the stratosphere up to six years, she added, although the most significant impacts from eruptions like Mount Pinatubo were within the first two years.

The next step in the research, Krüger said, is to investigate how much damage to the ozone layer the volcanic gases caused in the past – and what the damage could be from future volcanic eruptions in the active Central American region.

Undersea volcano gave off signals before eruption in 2011

A team of scientists that last year created waves by correctly forecasting the 2011 eruption of Axial Seamount years in advance now says that the undersea volcano located some 250 miles off the Oregon coast gave off clear signals hours before its impending eruption.

The researchers’ documentation of inflation of the undersea volcano from gradual magma intrusion over a period of years led to the long-term eruption forecast. But new analyses using data from underwater hydrophones also show an abrupt spike in seismic energy about 2.6 hours before the eruption started, which the scientists say could lead to short-term forecasting of undersea volcanoes in the future.

They also say that Axial could erupt again – as soon as 2018 – based on the cyclic pattern of ground deformation measurements from bottom pressure recorders.

Results of the research, which was funded by the National Science Foundation, the National Oceanic and Atmospheric Administration, and the Monterey Bay Aquarium Research Institute (MBARI), are being published this week in three separate articles in the journal Nature Geoscience.

Bill Chadwick, an Oregon State University geologist and lead author on one of the papers, said the link between seismicity, seafloor deformation and the intrusion of magma has never been demonstrated at a submarine volcano, and the multiple methods of observation provide fascinating new insights.

“Axial Seamount is unique in that it is one of the few places in the world where a long-term monitoring record exists at an undersea volcano – and we can now make sense of its patterns,” said Chadwick, who works out of Oregon State’s Hatfield Marine Science Center in Newport, Ore. “We’ve been studying the site for years and the uplift of the seafloor has been gradual and steady beginning in about 2000, two years after it last erupted.

“But the rate of inflation from magma went from gradual to rapid about 4-5 months before the eruption,” added Chadwick. “It expanded at roughly triple the rate, giving a clue that the next eruption was coming.”

Bob Dziak, an Oregon State University marine geologist, had previously deployed hydrophones on Axial that monitor sound waves for seismic activity. During a four-year period prior to the 2011 eruption, there was a gradual buildup in the number of small earthquakes (roughly magnitude 2.0), but little increase in the overall “seismic energy” resulting from those earthquakes.

That began to change a few hours before the April 6, 2011, eruption, said Dziak, who also is lead author on one of the Nature Geoscience articles.

“The hydrophones picked up the signal of literally thousands of small earthquakes within a few minutes, which we traced to magma rising from within the volcano and breaking through the crust,” Dziak said. “As the magma ascends, it forces its way through cracks and creates a burst of earthquake activity that intensifies as it gets closer to the surface.

“Using seismic analysis, we were able to clearly see how the magma ascends within the volcano about two hours before the eruption,” Dziak said. “Whether the seismic energy signal preceding the eruption is unique to Axial or may be replicated at other volcanoes isn’t yet clear – but it gives scientists an excellent base from which to begin.”

The researchers also used a one-of-a-kind robotic submersible to bounce sound waves off the seafloor from an altitude of 50 meters, mapping the topography of Axial Seamount both before and after the 2011 eruption at a one-meter horizontal resolution. These before-and-after surveys allowed geologists to clearly distinguish the 2011 lava flows from the many previous flows in the area.

MBARI researchers used three kinds of sonar to map the seafloor around Axial, and the detailed images show lava flows as thin as eight inches, and as thick as 450 feet.

“These autonomous underwater vehicle-generated maps allowed us, for the first time, to comprehensively map the thickness and extent of lava flows from a deep-ocean submarine in high resolution,” said David Caress, an MBARI engineer and lead author on one of the Nature Geoscience articles. “These new observations allow us to unambiguously differentiate between old and new lava flows, locate fissures from which these flows emerged, and identify fine-scale features formed as the lava flowed and cooled.”

The researchers also used shipboard sonar data to map a second, thicker lava flow about 30 kilometers south of the main flow – also a likely result of the 2011 eruption.

Knowing the events leading up to the eruption – and the extent of the lava flows – is important because over the next few years researchers will be installing many new instruments and underwater cables around Axial Seamount as part of the Ocean Observatories Initiative. These new instruments will greatly increase scientists’ ability to monitor the ocean and seafloor off of the Pacific Northwest.

“Now that we know some of the long-term and short-term signals that precede eruptions at Axial, we can monitor the seamount for accelerated seismicity and inflation,” said OSU’s Dziak. “The entire suite of instruments will be deployed as part of the Ocean Observatories Initiative in the next few years – including new sensors, samplers and cameras – and next time they will be able to catch the volcano in the act.”

The scientists also observed and documented newly formed hydrothermal vents with associated biological activity, Chadwick said.

“We saw snowblower vents that were spewing out nutrients so fast that the microbes were going crazy,” he pointed out. “Combining these biological observations with our knowledge of the ground deformation, seismicity and lava distribution from the 2011 eruption will further help us connect underwater volcanic activity with the life it supports.”

Scientists from Columbia University, the University of Washington, North Carolina State University, and the University of California at Santa Cruz also participated in the project and were co-authors on the Nature Geoscience articles.

Undersea volcano gave off signals before eruption in 2011

A team of scientists that last year created waves by correctly forecasting the 2011 eruption of Axial Seamount years in advance now says that the undersea volcano located some 250 miles off the Oregon coast gave off clear signals hours before its impending eruption.

The researchers’ documentation of inflation of the undersea volcano from gradual magma intrusion over a period of years led to the long-term eruption forecast. But new analyses using data from underwater hydrophones also show an abrupt spike in seismic energy about 2.6 hours before the eruption started, which the scientists say could lead to short-term forecasting of undersea volcanoes in the future.

They also say that Axial could erupt again – as soon as 2018 – based on the cyclic pattern of ground deformation measurements from bottom pressure recorders.

Results of the research, which was funded by the National Science Foundation, the National Oceanic and Atmospheric Administration, and the Monterey Bay Aquarium Research Institute (MBARI), are being published this week in three separate articles in the journal Nature Geoscience.

Bill Chadwick, an Oregon State University geologist and lead author on one of the papers, said the link between seismicity, seafloor deformation and the intrusion of magma has never been demonstrated at a submarine volcano, and the multiple methods of observation provide fascinating new insights.

“Axial Seamount is unique in that it is one of the few places in the world where a long-term monitoring record exists at an undersea volcano – and we can now make sense of its patterns,” said Chadwick, who works out of Oregon State’s Hatfield Marine Science Center in Newport, Ore. “We’ve been studying the site for years and the uplift of the seafloor has been gradual and steady beginning in about 2000, two years after it last erupted.

“But the rate of inflation from magma went from gradual to rapid about 4-5 months before the eruption,” added Chadwick. “It expanded at roughly triple the rate, giving a clue that the next eruption was coming.”

Bob Dziak, an Oregon State University marine geologist, had previously deployed hydrophones on Axial that monitor sound waves for seismic activity. During a four-year period prior to the 2011 eruption, there was a gradual buildup in the number of small earthquakes (roughly magnitude 2.0), but little increase in the overall “seismic energy” resulting from those earthquakes.

That began to change a few hours before the April 6, 2011, eruption, said Dziak, who also is lead author on one of the Nature Geoscience articles.

“The hydrophones picked up the signal of literally thousands of small earthquakes within a few minutes, which we traced to magma rising from within the volcano and breaking through the crust,” Dziak said. “As the magma ascends, it forces its way through cracks and creates a burst of earthquake activity that intensifies as it gets closer to the surface.

“Using seismic analysis, we were able to clearly see how the magma ascends within the volcano about two hours before the eruption,” Dziak said. “Whether the seismic energy signal preceding the eruption is unique to Axial or may be replicated at other volcanoes isn’t yet clear – but it gives scientists an excellent base from which to begin.”

The researchers also used a one-of-a-kind robotic submersible to bounce sound waves off the seafloor from an altitude of 50 meters, mapping the topography of Axial Seamount both before and after the 2011 eruption at a one-meter horizontal resolution. These before-and-after surveys allowed geologists to clearly distinguish the 2011 lava flows from the many previous flows in the area.

MBARI researchers used three kinds of sonar to map the seafloor around Axial, and the detailed images show lava flows as thin as eight inches, and as thick as 450 feet.

“These autonomous underwater vehicle-generated maps allowed us, for the first time, to comprehensively map the thickness and extent of lava flows from a deep-ocean submarine in high resolution,” said David Caress, an MBARI engineer and lead author on one of the Nature Geoscience articles. “These new observations allow us to unambiguously differentiate between old and new lava flows, locate fissures from which these flows emerged, and identify fine-scale features formed as the lava flowed and cooled.”

The researchers also used shipboard sonar data to map a second, thicker lava flow about 30 kilometers south of the main flow – also a likely result of the 2011 eruption.

Knowing the events leading up to the eruption – and the extent of the lava flows – is important because over the next few years researchers will be installing many new instruments and underwater cables around Axial Seamount as part of the Ocean Observatories Initiative. These new instruments will greatly increase scientists’ ability to monitor the ocean and seafloor off of the Pacific Northwest.

“Now that we know some of the long-term and short-term signals that precede eruptions at Axial, we can monitor the seamount for accelerated seismicity and inflation,” said OSU’s Dziak. “The entire suite of instruments will be deployed as part of the Ocean Observatories Initiative in the next few years – including new sensors, samplers and cameras – and next time they will be able to catch the volcano in the act.”

The scientists also observed and documented newly formed hydrothermal vents with associated biological activity, Chadwick said.

“We saw snowblower vents that were spewing out nutrients so fast that the microbes were going crazy,” he pointed out. “Combining these biological observations with our knowledge of the ground deformation, seismicity and lava distribution from the 2011 eruption will further help us connect underwater volcanic activity with the life it supports.”

Scientists from Columbia University, the University of Washington, North Carolina State University, and the University of California at Santa Cruz also participated in the project and were co-authors on the Nature Geoscience articles.