bluuebunny/crossref_metadata_2025 huggingface dataset:
Testing the interbasin flow hypothesis at Death Valley, California
Authors: Nelson Stephen T. , Anderson Katherine , Mayo Alan L.
Published: October 2006

Interbasin flow is a process by which groundwater moves from one topographic basin to another through an intervening structural or topographic barrier. For decades, interbasin flow has been the prevailing conceptual paradigm for groundwater movement in the arid southwestern United States wherever carbonate rocks are thought to be in continuous contact [e.g., Anderson, 2002]. This conceptual model of groundwater flow is especially relevant in the Death Valley region where water resources are scarce and where the U.S. government has conducted underground nuclear tests and has planned for the storage of spent nuclear fuel at Yucca Mountain, Nevada. Recent studies of large flux springs (∼10,000 L/min) in the Furnace Creek area of Death Valley, California (Figure 1), however, indicate that the concept of interbasin flow may be fundamentally flawed, or at least not as universally applicable as previously thought. Rather, it appears that aquifers supplying Furnace Creek springs were replenished locally during episodes of wet climate more than 9500 yr ago, a contention supported by extensive regional fossil spring deposits [Quade et al., 2003].
Thermogenic gas hydrates in the northern Cascadia margin
Authors: Chapman Ross , Pohlman John , Coffin Rick , Chanton Jeff , Lapham Laura
Published: October 2006

Gas hydrates are ice‐like solids that form in rigid cage structures under specific conditions of pressure, temperature, and gas and water concentration. Marine gas hydrates are stable in pore spaces of sediments in water depths greater than ∼300 m beneath the slopes of active and passive continental margins [Kvenvolden, 1988]. The lower limit of hydrate occurrence in marine sediments is determined by the geothermal gradient, so that the zone of hydrate stability is generally contained within the first few hundred meters of sediment. Continental hydrates occur in polar permafrost regions in the Arctic and Siberia. Most of the hydrates that have been discovered contain methane derived from microbial processes.

Other hydrocarbons can also form hydrates, but in different structures of the surrounding water cages. Structure I, the most prevalent form, contains mostly (>99%) microbial methane, a small amount of ethane, and traces of C2+ hydrocarbons [Sassen et al, 2001]. Structure II and structure H hydrates contain significant quantities of thermogenic methane and larger, more complex hydrocarbons formed at high temperatures from fossil organic matter (i.e.,kerogen) or oil [Sassen and MacDonald, 1994].The gas origin is inferred from measurements of the carbon‐13 isotopic ratio (δ13); microbial methane is depleted in 13C (δ13 <−60‰) relative to thermogenic methane (δ13 from −20‰ to −50‰).
The end of the rainbow? Color schemes for improved data graphics
Authors: Light Adam , Bartlein Patrick J.
Published: October 2006

Modern computer displays and printers enable the widespread use of color in scientific communication, but the expertise for designing effective graphics has not kept pace with the technology for producing them. Historically even the most prestigious publications have tolerated high defect rates in figures and illustrations [Cleveland, 1984],and technological advances that make creating and reproducing graphics easier do not appear to have decreased the frequency of errors. Flawed graphics consequently beget more flawed graphics as authors emulate published examples. Color has the potential to enhance communication, but design mistakes can result in color figures that are less effective than grayscale displays of the same data.
New insights into the origin and evolution of the Hikurangi oceanic plateau
Authors: Hoernle Kaj , Hauff Folkmar , Werner Reinhard , Mortimer Nicholas
Published: October 2006

Oceanic plateaus and continental flood basalts, collectively referred to as large igneous provinces (LIPs), represent the most voluminous volcanic events on Earth. In contrast to continental LIPs, relatively little is known about the surface and internal structure, range in age and chemical composition, origin, and evolution of oceanic plateaus, which occur throughout the worlds oceans [e.g., Mahoney and Coffin, 1997].

One of the major goals of the R/V Sonne SO168 ZEALANDIA expedition (depart Wellington, 3 December 2002, return Christchurch, 15 January 2003) was to investigate the Hikurangi oceanic plateau off the east coast of New Zealand.
New integrated data management system for Ridge2000 and MARGINS research
Authors: Carbotte S. M. , Arko R. , Chayes D. N. , Haxby W. , Lehnert K. , O'Hara S. , Ryan W. B. F. , Weissel R. A. , Shipley T. , Gahagan L. , Johnson K. , Shank T.
Published: October 2006

The initiation of dedicated databases for the U.S. National Science Foundation (NSF)‐supported Ridge2000 and MARGINS programs provides the opportunity to develop a data management system capable of handling the primary data types of marine geoscience research.

Ridge2000 and MARGINS are broad initiatives focused on fundamental problems of crustal creation, evolution, and destruction along the world's tectonic plate boundaries. These programs involve the collection of a wide range of geophysical data types, as well as rock, fluid, and biological samples, and time series data.
Multidisciplinary impact of the deep mantle phase transition in perovskite structure
Authors: Lay Thorne , Heinz Dion , Ishii Miaki , Shim Sang‐Heon , Tsuchiya Jun , Tsuchiya Taku , Wentzcovich Renata , Yuen David
Published: October 2006

A phase transition in (Mg, Fe) SiO3 (magnesium silicate‐perovskite) for pressure‐temperature conditions near the base of Earth's mantle, first reported in May 2004, is stimulating strong multidisciplinary excitement and interactions. Experimentally and theoretically determined characteristics of this phase transition indicate that it may hold the key to understanding enigmatic seismological structures in the D” region of the lowermost mantle, with important implications for heat transport, thermal instabilities, and chemical properties of the lower mantle.

All minerals undergo phase transitions with increasing depth into the Earth, reorganizing their crystal structures into denser‐packed forms stable over a finite range of pressures and temperatures. The changes in material properties across such transitions often give rise to detectable contrasts in seismic velocities and density.
Mount St. Helens reawakens
Authors: Dzurisin Daniel , Vallance James W. , Gerlach Terrance M. , Moran Seth C. , Malone Stephen D.
Published: October 2006

Following 18 years of relative quiescence, Mount St. Helens volcano (MSH) became restless and began erupting again during September–December 2004.

On 23 September, the U.S. Geological Survey's (USGS) David A. Johnston Cascades Volcano Observatory (CVO) and the Pacific Northwest Seismograph Network (PNSN) at the University of Washington detected the onset of a shallow earthquake swarm beneath the 1980–1986 lava dome. The Mount St. Helens Emergency Response Plan defines three alert levels that differ from normal background activity: Level 1, Notice of Volcanic Unrest (unusual activity detected); Level 2, Volcano Advisory (eruption likely but not imminent); and Level 3, Volcano Alert (eruption imminent or in progress).
Jason 1 detects the 26 December 2004 tsunami
Authors: Gower Jim
Published: October 2006

Satellite altimeters have detected mid‐ocean tsunami waves only once in the past, with relatively small amplitude [Okal et al., 1999], according to published reports. The 26 December 2004 tsunami changes this picture dramatically. This event was the strongest to have occurred since satellite altimetry started in the 1970s. Instruments now in orbit can measure sea surface height with sufficient resolution (a few centimeters for the average of a 5‐km circle of ocean), but measure only along their tracks, and cannot provide a full picture of an event. Also, they are unlikely to be optimally placed for early detection near the source earthquake. By chance, however, Jason 1 was in the right place at the right time.
Community InSAR Workshop calls for robust program and dedicated satellite mission
Authors: Donnellan Andrea , Glasscoe Margaret , Zebker Howard
Published: October 2006

A recent workshop to guide U.S. efforts in interferometric synthetic aperture radar (InSAR) was supported by an overwhelming community response. Workshop participants called for a robust InSAR program that includes improved access to InSAR data and a dedicated U.S.‐led InSAR mission.

Held last fall, the workshop brought together researchers in the fields of crustal deformation, cryospheric studies, hydrology land cover, oceanography, and planetary sciences with specialists in information technology and education and outreach. The workshop's purpose was to inform the community of the state of the art in satellite radar, to describe mission opportunities, and to receive community recommendations for needed InSAR measurements of Earth and planetary processes. Over 350 people registered their interest in the workshop, and 220 participants from 116 institutions and a variety of disciplines attended.
Integrating climate‐hydrology forecasts and multi‐objective reservoir management for northern California
Authors: Georgakakos K. P. , Graham N. E. , Carpenter T. M. , Yao H.
Published: October 2006

The Integrated Forecast and Reservoir Management (INFORM) Project was conceived to demonstrate increased water‐use efficiency in Northern California water resources operations through (1) the innovative application of climate, hydrologic, and decision science, and (2) reciprocal technology transfer activities between the INFORM scientists and the staff of federal and state agencies with an operational forecast and management mandate in Northern California.

Toward achieving this goal, INFORM objectives include implementing a prototype integrated forecast‐management system for primary Northern California reservoirs, for individual reservoirs as well as system‐wise. Project objectives also include demonstrating the utility of climate and hydrologic forecasts through near‐real‐time tests of the integrated system with actual data and management input.
Could the Mw = 9.3 Sumatra earthquake trigger a geomagnetic jerk?
Authors: Florindo Fabio , De Michelis Paola , Piersanti Antonio , Boschi Enzo
Published: October 2006

The magnetic field observed at the Earth's surface is not a stationary feature. It is characterized by time variations ranging from milliseconds (micropulsations) to millions of years (the time interval between field reversals). Time variations with periods of a year or longer are related to Earth's outer core sources, whereas for shorter timescales an external origin is invoked (i.e.,solar activity).

One of the most interesting time variations of the geomagnetic field is represented by the “geomagnetic jerk.” It is idealized as a rapid change in the slope of the secular variation, defined as the first derivative of the geomagnetic field. This means that the secular variation roughly appears as a series of straightline segments separated by geomagnetic jerks.
Evaluating landslide damage during the 2004 Chuetsu earthquake, Niigata Japan
Authors: Sidle Roy C. , Kamai Toshitaka , Trandafir Aurelian C.
Published: October 2006

A series of earthquakes, the strongest with a magnitude of 6.6 on the Richter scale (6.8 on the Japan Meteorological Agency (JMA) scale), jolted Niigata Prefecture, Japan, late in the afternoon of 23 October 2004, killing about 40 people and injuring about 3000, largely as the result of building collapse. More than 100,000 residents were forced to evacuate their homes, and 2200 residents of Yamakoshi village and other areas have not yet returned.

The three strongest earthquakes (M>6.2 on the JMA scale) occurred within less than 40 min with epicenters spread across Ojiya city and Hirokami and Yamakoshi villages in Niigata Prefecture. These earthquakes were characterized by shallow focal depths (9–14 km) that generated strong levels of ground motion, resulting in extensive damage throughout the region.
A splash in Earth gravity from the 2004 Sumatra Earthquake
Authors: Sabadini Roberto , Dalla Via Giorgio , Hoogland Masja , Aoudia Abdelkrim
Published: October 2006

The 26 December 2004 Sumatra earthquake displaced a large amount of material in the radial direction with respect to the Earth's center, and the earthquake is thus expected to have permanently changed the gravity in a broad region surrounding its causative fault.

This article examines gravity changes, which are here quantified by geoid anomaly patterns depicting the displacement of the sea surface's hydrostatic component after the earthquake. The article focuses on the feasibility of the detection of these patterns by gravity space missions. Models of changes in the rotation and oblateness of the Earth due to global gravitational effects of the earthquake have already been reported [Chao and Gross, 2005].
Advances in controlled‐source seismic imaging
Authors: Hole J. A. , Zelt C. A. , Pratt R. G.
Published: October 2006

The current rapid growth in the number of seismometers available to the research community, combined with increasing computer power, will allow improvement in the type and quality of seismic images of the crust and lithosphere. An example of improved imaging capability is the inversion of the full seismic waveform, rather than solely travel times, in controlled‐source surveys (seismic refraction or reflection using human‐induced ground shaking).

At the 12th Deep Seismic Methods workshop in 2003, sponsored by the International Association of Seismology and Physics of the Earth's Interior (IASPEI), an analysis of computer‐generated data exemplified the potential of increased source and station density. The synthetic seismic data set was generated from a geologic model that includes large‐, medium‐, and small‐scale stochastic variation. The source and seismometer spacing mimic imminent community capabilities. The Earth model was kept secret, and the data were made available for analysis (http://crust. geol.vt.edu/hole/ccss/). Figure 1 illustrates the results of blind travel time and waveform tomography applied to the data.The images, described in more detail below, illustrate an excellent match to the true Earth model.
Keeping pseudoscience out of AGU meetings
Authors: Craddock Robert A.
Published: October 2006

I found the editorial, “Speaking Up For Science” (Eos, 86,(24), 14 June 2005, p. 225) disturbing, but not for the reasons you intended. The Smithsonian made a mistake, but nowhere do you discuss its efforts to correct that.

More troublesome to me as a member of AGU is the blatant hypocrisy contained in the editorial. How many posters or presentations have been made at AGU meetings in the last 10–20 years that support creationism, intelligent design, or other forms of pseudo‐science, such as the so‐called “face” on Mars?
Second phase of paleoclimate modelling intercomparison project
Authors: Crucifix M. , Braconnot P. , Harrison S. P. , Otto‐Bliesner B.
Published: October 2006

By devoting an entire chapter of the fourth assessment report (AR4) to paleoclimates, the Intergovernmental Panel on Climate Change (IPCC) has recognized that studying past climates is essential for comprehending the climate system, and hence for predicting its future evolution.

In particular, numerical simulations of past climates, different from today constitute an independent test of the performance and reliability of the general circulation models commonly used for climate predictions. This idea is the motivation for the Paleoclimate Modelling Intercomparison Project (PMIP), a long‐standing initiative endorsed by the World Climate Research Programme and the International Geosphere and Biosphere Programme. The focus has so far been on two reference periods, chosen as being the most representative of cold and warm climate intervals in the recent past: the Last Glacial Maximum (LGM, 21,000 years ago) and the mid‐Holocene (6000 years ago).
Chicxulub Crater Seismic Survey prepares way for future drilling
Authors: Morgan Jo , Urrutia‐Fucugauchi Jaime , Gulick Sean , Christeson Gail , Barton Penny , Rebolledo‐Vieyra Mario , Melosh Jay
Published: October 2006

Sixty‐five million years ago, a large meteorite hit the Earth and formed the ∼200‐km‐wide Chicxulub crater in Yucatán, Mexico. The well‐known, massive extinction event at the Cretaceous‐Tertiary (K‐T) boundary appears to have been caused, at least in part, by this impact. In the first few seconds after impact the surface of the Earth was pushed down to form a cavity ∼35 km deep, and in the next few hundred seconds this cavity collapsed to form a multi‐ring basin with an inner peak ring.

To examine the rings and subsurface structure of this superbly preserved impact crater, a seismic experiment was shot across the crater in January and February 2005 by a team of scientists from Mexico, the United States, and the United Kingdom (Figure 1).
Modeling past atmospheric CO2: Results of a challenge
Authors: Wolff Eric , Kull Christoph , Chappellaz Jerome , Fischer Hubertus , Miller Heinz , Stocker Thomas F. , Watson Andrew J. , Flower Benjamin , Joos Fortunat , Köhler Peter , Matsumoto Katsumi , Monnin Eric , Mudelsee Manfred , Paillard Didier , Shackleton Nick
Published: October 2006

The models and concepts used to predict future climate are based on physical laws and information obtained from observations of the past. New paleoclimate records are crucial for a test of our current understanding.

The Vostok ice core record [Petit et al., 1999] showed that over the past 420 kyr (1 kyr = 1000 years), Antarctic climate and concentrations of the greenhouse gases carbon dioxide (CO2) and methane (CH4,) were tightly coupled. In particular, CO2 seemed to be confined between bounds of about 180 ppmv (parts per million by volume) in glacial periods and 280 ppmv in interglacials; both gases rose and fell with climate as the Earth passed through four glacial/interglacial cycles.
Sumatra tsunami affects observations by GRACE satellites
Authors: Bao L. F. , Piatanesi Alessio , Lu Y. , Hsu H. T. , Zhou X. H.
Published: October 2006

Changes in the Earth's gravity field are caused by the redistribution of mass within the Earth and on or above its surface. While previous studies [Tapley, 2004; Wahr, 2004] showed that the Gravity Recovery and Climate Experiment (GRACE) satellite mission, executed by NASA, had successfully determined oceanic mass redistribution, the relative motions between two GRACE satellites caused by the 2004 Sumatra tsunami is still uncertain.

This present study combines a numerical model of the tsunami and GRACE orbit data to estimate the realistic effect of oceanic mass redistribution on the inter‐satellite range‐rate change between two GRACE satellites. The GRACE mission is designed to map out the Earth's gravity field to high accuracy. Instead of measuring the Earth gravity field or mass variations directly GRACE estimates a set of spherical harmonic coefficients denoting the Earth gravity field each month by measuring range changes between two spacecrafts [Chambers et al., 2004].
Count‐a‐thon of airplane contrails
Authors: Chambers L. H. , Duda D. P.
Published: October 2006

The third Contrail Count‐a‐Thon of the GLOBE (Global Learning and Observations to Benefit the Environment) project is being held during Earth Science Week 2005 in October. Reports of sky observations—including those of contrail‐free skies—taken between 11:00 A.M. and 1:00 P.M. local time on 13 October 2005 are welcome from any interested observers (including Eos readers), whether or not they are associated with local schools, clubs, parks, or other groups. The Web site with instructions and the report form is available at http://www.globe.gov/earthsciweek2005.

Clouds remain one of the main sources of uncertainty in efforts to understand and predict the Earth's global climate [Cess et al., 1990]. Although satellite instruments and techniques to study clouds continue to improve, contrails are a cloud type of significant interest that remains a challenge to study.
Chapopote Asphalt Volcano may have been generated by supercritical water
Authors: Hovland M. , MacDonald I. R. , Rueslåtten H. , Johnsen H. K. , Naehr T. , Bohrmann G.
Published: October 2006

Asphalt volcanoes and lava‐like flows of solidified asphalt on the seafloor (Figure 1) were first discovered and described by MacDonald et al. [2004]. The flows covered more than one square kilometer of a dissected salt dome at abyssal depths (∼3000 m) in the southern Gulf of Mexico. “Chapopote” (93°26′W, 21°54′N) was one of two asphalt volcanoes they discovered. MacDonald et al. determined that the apparently fresh asphalt must initially have flowed in a hot state, and subsequently chilled, contracted, and solidified, much in the same way as normal lava does on the surface of the Earth.

The two asphalt‐volcanoes discovered occur at the apex of salt domes that pierce through the seafloor. These “piercement salt domes,” known as the Campeche Knolls, are pertinent features of the deep Campeche Sedimentary Basin, which has a sediment thickness of about 10 km. According to conventional theory [Vendeville and Jackson, 1992], piercement salt domes represent “salt diapirs” that have risen up, due partly to density contrasts between salt and clay/sand from the “mother salt” located between 7 and 10 km below seafloor. A salt diapir is a vertical body of sub‐surface salt, which is most often circular in cross section, is one to several kilometers in diameter, and can be 8–10 km high.
Repeat hydrography cruises reveal chemical changes in the North Atlantic
Authors: Feely Richard A. , Talley Lynne D. , Johnson Gergory C. , Sabine Christopher L. , Wanninkhof Rik
Published: October 2006

The U.S. contribution to a large international effort to document long‐term trends in carbon storage and transport in the global oceans by reoccupying selected hydrographic sections on decadal timescales began with three North Atlantic cruises in 2003. The initial results from these reoccupation cruises have shown significant long‐term changes in oxygen, carbon dioxide (CO2), and several other measurable parameters since the last global survey, which occurred in 1993.

The ocean has a memory of the climate system and is second only to the Sun in affecting variability in the seasons and longterm climate change. The ocean stores an estimated 1000 times more heat than the atmosphere, and 50 times more carbon. Additionally the key to possible abrupt climate change may lie in deep‐ocean circulation.
U.S. Earth observation programs may still be at risk
Authors: Zielinski Sarah
Published: October 2006

A recent interim report from a committee of the National Research Council (NRC) of the U.S. National Academies warned that the U.S. system of environmental satellites was “at risk of collapse” (see Eos, 10 May 2005, p. 186). Nearly six months later, despite assurances from NASA that the agency would work to address in its fiscal year (FY) 2007 budget some of the imbalances that have led to mission delays and cancellations, these satellite programs may still be at risk.

NASA funding for Earth science has suffered in recent years due to several pressures on the budget: deficit reduction, efforts to restore the space shuttle program, and plans for missions to the Moon and Mars. The NRC report, which was released as a draft in April and in its final form on 8 September, noted that six planned missions with implications for Earth science research were delayed, descoped, or canceled in the proposed FY2006 NASA budget.
Bed load sediment transport in ephemeral and perennial gravel bed streams
Authors: Almedeij Jaber , Diplas Panayiotis
Published: October 2006

Perennial gravel streams are usually dominated by a bed material stratified in terms of grain size, with a coarse surface layer overlying a finer subsurface (Figure 1a). However, field observations from some ephemeral gravel streams in the Middle East and other locations exhibit the opposite stratification (Figure 1b).

Recent studies have found that under the same range of flow strengths, such an ephemeral stream has a much higher transport efficiency of bed load sediment (the movement of particles by rolling and sliding on the bed, or by making short hops of a few grain diameters in distance), which suggests a completely different behavior from perennial streams [e.g., Laronne and Reid, 1993; Reid and Laronne, 1995].
Putting the geology back into Earth models
Authors: McCaffrey Kenneth , Holdsworth Robert , Imber Jonathan , Clegg Phillip , De Paola Nicola , Jones Richard , Hobbs Richard , Holliman Nick , Trinks Immo
Published: October 2006

New digital methods for data capture can now provide photorealistic, spatially precise, and geometrically accurate three‐dimensional (3‐D) models of rocks exposed at the Earth's surface [Xu et al., 2000; Pringle et al., 2001; Clegg et al., 2005]. These “virtual outcrops” have the potential to create a new form of laboratory‐based teaching aids for geoscience students, to help address accessibility issues in fieldwork, and generally to improve public awareness of the spectacular nature of geologic exposures from remote locations worldwide.

This article addresses how virtual outcrops can provide calibration, or a quantitative “reality check,” for a new generation of high‐resolution predictive models for the Earth's subsurface.
Island arc debris avalanches and tsunami generation
Authors: Silver Eli , Day Simon , Ward Steve , Hoffmann Gary , Llanes Pilar , Lyons Amelia , Driscoll Neal , Perembo Russ , John Susan , Saunders Steve , Taranu Felix , Anton Lawrence , Abiari Isabela , Applegate Bruce , Engels Jenny , Smith Jamie , Tagliodes Jones
Published: October 2006

On the early morning of 13 March 1888, roughly five cubic kilometers of the Ritter Island volcano fell violently into the sea northeast of Papua New Guinea (Figure 1). This event, the largest lateral collapse of a volcanic island in historical time, flung devastating tsunamis tens of meters high onto adjacent shores [Cooke, 1981].

Calamitous as they might be, natural disasters like these must be viewed in perspective. One should ask, “Were the events of that March day unique, or are they common geological occurrences?” Partly to address this question, a seafloor imaging and sampling program was conducted around Ritter Island and elsewhere along the Bismarck volcanic arc during November–December 2004 on the research vessel Kilo Moana.
Hurricane Ivan's Impact along the northern Gulf Of Mexico
Authors: Stone Gregory W. , Walker Nan D. , Hsu A. , Babin Adele , Liu Baozhu , Keim Barry D. , Teague William , Mitchell Douglas , Leben Robert
Published: October 2006

Just over a year after the landfall of Hurricane Ivan, scientists have now had an opportunity to evaluate a variety of oceanographic and geologic responses to this storm. Hurricanes Ivan, Katrina,and Rita are among the most powerful hurricanes recently to enter the Gulf of Mexico.

Although it weakened from a very powerful Category 5 hurricane to a Category 3 before making landfall along the Alabama coast, Hurricane Ivan devastated the coasts of northwestern Florida and Alabama on 16 September 2004. This article summarizes what researchers have learned about Hurricane Ivan as it moved into the Gulf and made landfall along the northeastern Gulf of Mexico coast. The article focuses on storm meteorology, sea state,shelf circulation, and sediment transport on the shelf and along the coast.
Monitoring volcano eruptions and lava domes with Doppler radar
Authors: Voege Malte , Hort Matthias , Seyfried Ralf
Published: October 2006

About 10 percent of the world's population lives in the vicinity of one of the planet's approximately 1500 active volcanoes. These volcanoes represent a large threat to human lives and regional economies, especially in highly‐populated areas. This makes effective and reliable volcanic hazard mitigation absolutely mandatory.

Because volcanoes are complex systems, hazard mitigation can be achieved only by applying numerous techniques, such as geophysical monitoring, thorough mapping of previous activity and numerical simulations of different eruption scenarios.
Formation of channelized lava flows on an unconfined slope
Authors: Kerr R. C. , Griffiths R. W. , Cashman K. V.
Published: October 2006

The formation of channelized lava flows on a wide uniform slope is investigated both theoretically and experimentally. When a lava is released at a constant flow rate from a point source, we predict that it flows both down and across the slope at the same rate in a early time regime before undergoing a transition to a long‐time regime where down‐slope flow is faster than lateral flow. Eventually, the lateral flow is stopped by the strength of the growing surface crust, and the flow then travels down slope in a channel of constant width. Using scaling analysis, we derive expressions for the final channel width in both flow regimes, as a function of the flow rate, the slope, the density difference driving the flow, the lava viscosity, the thermal diffusivity, and the yield strength of the crust. We also find a dimensionless flow morphology parameter that controls whether the subsequent channel flow occurs in a “mobile crust” regime or in a “tube” regime. These theoretical predictions are in good agreement with laboratory experiments in which polyethylene glycol wax flows down a wide uniform slope under cold water. The theory is also applied to the understanding of the formation of a basaltic sheet flow lobe in Hawaii, which had an estimated crust yield strength of order 6 × 104 Pa.
Two‐hundred‐fifty years of reconstructed and modeled tropical temperatures
Authors: Wilson Rob , Tudhope Alexander , Brohan Philip , Briffa Keith , Osborn Timothy , Tett Simon
Published: October 2006

Recent large‐scale palaeoclimate reconstructions of past temperature have been essentially biased to the extratropics owing to a paucity of proxy data in tropical regions. Herein we describe the first coral‐based reconstruction of sea surface temperatures (SSTs) for the whole of the tropics (30°N–30°S). It was developed from 14 disparate coral records located in the Indian and Pacific oceans. Over the most replicated period, the reconstruction explains 57% of the tropical SST variance. However, the strength of this signal weakens markedly as the number of coral records decreases. The reconstruction is robust between 1850 and 1993, but some fidelity is indicated back as far as the mid 18th century. These results suggest that ambiguities in the low frequency domain of δ18O measurements can be partially overcome by pooling together multiple time series from different locations around the tropics. Agreement with simulations from two general circulation models indicates that the late 20th century is likely the warmest period in the tropics for the last 250 years, and that this recent warming can only be explained by anthropogenic forcing. The high frequency variability is dominated by the El Niño–Southern Oscillation. The reconstruction, owing to the small number of coral records, is unfortunately restricted both in time and space. Therefore we hope that this study will spur the palaeoclimate community to develop new and longer proxy series to improve the current meager data‐base of temperature sensitive series in the tropics.
The “African humid period” and the record of marine upwelling from excess 230Th in Ocean Drilling Program Hole 658C
Authors: Adkins Jess , deMenocal Peter , Eshel Gidon
Published: October 2006

Using a high‐resolution 230Th normalized record of sediment flux, we document the deglacial and Holocene history of North African aridity and coastal upwelling at Ocean Drilling Program Hole 658C. At both the end of the Younger Dryas and after the 8.2 ka event, there are significant drops in terrigenous accumulation at our site, indicating an increase in the monsoon moisture flux over Africa at this time. At 5.5 ka, there is an abrupt end to the “African humid period” and a return to stronger upwelling conditions. For carbonate and opal fluxes the 230Th normalization completely changes the shape of each record based on percentage variations alone. This site is a clear example of how variations in one sediment component can obscure changes in the others, and it demonstrates the need for radionuclide measurements more generally in paleoceanography. By taking our new records and a large amount of previous data from this site we conclude that increases in African moisture are tightly coupled to decreases in coastal upwelling intensity.
Properties and geoeffectiveness of halo coronal mass ejections
Authors: Michalek G. , Gopalswamy N. , Lara A. , Yashiro S.
Published: October 2006

Halo coronal mass ejections (HCMEs) originating from regions close to the center of the Sun are likely to be geoeffective. Assuming that the shape of HCMEs is a cone and that the HCMEs propagate with constant angular widths and velocities, at least in their early phase, we have developed a technique which allowed us to obtain the space speed, width, and source location. We apply this technique to obtain the parameters of all full HCMEs observed by the Solar and Heliospheric Observatory (SOHO) mission's Large Angle and Spectrometric Coronagraph (LASCO) experiment until the end of 2002. Using this data, we examine which parameters determine the geoeffectiveness of HCMEs. We show that in the considered period of time, only fast halo CMEs (with space velocities higher than ∼1000 km/s) and originating from the Western Hemisphere close to the solar center could cause intense geomagnetic storms. We illustrate how the HCME parameters can be used for space weather forecast. It is also demonstrated that the strength of a geomagnetic storm does not depend on the determined width of HCMEs. This means that HCMEs do not have to be very large to cause major geomagnetic storms.
Fluvial suspended sediment dynamics: Implications for particulate organic carbon transport modeling
Authors: Bungartz Heinz , Krüger Angela , Engelhardt Christof
Published: October 2006

The effect of fluvial suspended sediment aggregation on the hydrodynamic transport properties of particulate organic carbon (POC) was investigated using a combination of field measurement and numerical modeling. Field‐based settling tube experiments were conducted to obtain particle settling velocity frequency distributions of a 4‐km‐long section of a lake outlet river at two distinct discharge levels (6.8 and 29.7 m3 s−1). Results of field studies conducted in April 2001 and April 2002 showed that the lacustrine settling velocity frequency distributions of suspended particulate matter (SPM) and POC were altered owing to the formation of riverine aggregates having comparatively higher settling velocities. Data suggest that aggregation promoted deposition fluxes of POC; these fluxes were in turn closely tied to the processes that controlled deposition of SPM. Data interpretation was aided by the employment of a hydrodynamic sediment transport model. The approach used to integrate aggregation in the sediment transport simulations represents the interaction of multiple settling velocity mass fractions. Both field data and modeling demonstrated the effect of aggregation on the increase in deposition fluxes of POC.
The great plume debate
Authors: Foulger Gillian R. , Fitton J. Godfrey , Presnall Dean C. , Morgan W. Jason
Published: October 2006

It has been 40 years since Wilson [1963] first suggested that the Hawaiian Islands were produced by the oceanic lithosphere moving over a stationary ‘hot spot’ in the mantle, and 30 years since Morgan [1971] suggested that plumes exist in the Earth's mantle and play an important role in convection. Subsequently, large igneous provinces (LIPs), volcanic continental margins, and large oceanic plateaus, along with smaller‐volume seamounts and ocean‐island chains, have all been attributed to mantle plumes.

For the last two to three decades, the tendency has been to focus research on those features of LIPs and hot spots that can be explained by the plume hypothesis and to neglect those that cannot. Many papers have treated the plume hypothesis as an a priori assumption, and there has been little questioning of the hypothesis.
NASA budget focuses on exploration
Authors: Zielinski Sarah
Published: October 2006

NASA has decided to rebalance its priorities following several years of healthy growth for science, turning its focus instead towards expanding support for manned space exploration, explained NASA Administrator Michael Griffin at a 16 February hearing before the U.S. House of Representatives Committee on Science.

The Bush Administration has requested $16.8 billion for NASA in Fiscal Year 2007, an increase of 3.2 percent over the previous year. Most of the benefit would go to the exploration program, which would get a 55 percent increase in funding—for a total of $3.9 billion—primarily for the development of the new Crew Exploration Vehicle and Crew Launch Vehicle. The science budget would grow by 1.5 percent in FY2007—to $5.3 billion—and then is projected to grow by just one percent per year in 2008–2011.
Database for Holocene geomagnetic intensity information
Authors: Donadini Fabio , Korhonen Kimmo , Riisager Peter , Pesonen Lauri J.
Published: October 2006

Over the past 40 years, paleomagnetists have continued to compile new data. A large part of these data are now archived in seven independent databases that are maintained by the International Association of Geomagnetism and Aeronomy (IAGA; (http://www.ngdc.noaa.gov/seg/geomag/paleo.shtml). Unfortunately, the IAGA paleointensity database [Perrin and Schnepp, 2004] does not contain data from archeological artifacts, which is a major part of available Holocene paleomagnetic intensity data. The more recent paleointensity compilation described by Korte et al. [2005], available at Earthref (http://earthref.org) as text files, covers only the past 7000 years. It also does not contain information on the paleointensity methods, materials used, or dating details needed to directly judge the quality of the intensity data contained in the database's files.
HiSeasNet: Oceanographic ships join the grid
Authors: Berger Jonathan , Orcutt John , Foley Steven , Bohlen Steven
Published: October 2006

HiSeasNet, the communications network providing full‐period Internet access for the U.S. academic ocean research fleet, is an enabling technology that is changing the way oceanography is done in the 21st century. With the installation in March 2006 of a system on the research vessel (R/V) Seward Johnson and the planned installation on the R/V Marcus Langseth later this year, all but two of the Universities National Oceanographic Laboratories System (UNOLS) fleet of large/global and intermediate/ocean vessels will be equipped with HiSeasNet capability.

HiSeasNet is a full‐service Internet Protocol (IP) satellite network utilizing Cisco technology. In addition to the familiar IP services—such as e‐mail, telnet, ssh, rlogin, Web traffic, and ftp—HiSeasNet can move real‐time audio and video traffic across the satellite links. Phone systems onboard research ships can be connected to their home institutions' phone exchanges. Video teleconferencing with the current 96 kilobits per second circuits supports compressed video frame rates at about 10 frames per second, allowing for effective conversations and demonstrations with ship‐to‐shore video.
Ocean surface drift revealed by synthetic aperture radar images
Authors: Liu Antony K. , Zhao Yunhe , Hsu Ming‐Kuang
Published: October 2006

Monitoring the world's oceans has proven to be challenging in the past because of their size, remoteness, and the lack of instrumentation capable of such observational coverage. Until now, ocean surface feature tracking analyses have been based on data from a lone, low‐Earth orbital satellite—images were collected from a single orbital sensor with repeat passes over the same ocean surface. This process was insufficient and incapable to track ocean features due to the satellite's long revisit interval that could not capture the daily complications of surface ocean circulation.

Today, ocean surface currents are being derived much more efficiently by performing ‘feature tracking,’ which uses data from the same types of sensors on different satellites to simultaneously monitor ocean surface phenomenon. In particular, tracking results indicate that multiple synthetic aperture radar (SAR) images overlapped in a short time can be used to derive ocean surface drift, and can help to identify oceanic processes.
Italy's investment in research
Authors: De Vivo Benedetto , Trigila Raffaello , Panza Giuliano , Peccerillo Angelo
Published: October 2006

The international scientific community should be made aware of the plight of the Earth sciences in Italy. The challenges facing the Italian research community recently have been addressed in various articles in Nature. We report here, for the sake of conciseness, on the work of King [2004], Brumfield [2006], and Abbott [2006].

Italy spends on scientific research a little over 1% of its gross domestic product (GDP), ranking twenty‐first out of 30 developed countries (Organization for Economic Development (OECD),Main Science and Technology Indicators, May 2005).This is a very low level for any industrialized country The average for the European Union (EU) is almost 2%, but according to the Lisbon agreement, signed in 2000 by the presidents of EU countries, the OECD countries should spend 3% of their GDP on research and development (R&D) by 2010.
Investigating subduction zone processes in Chile
Authors: Scherwath Martin , Flueh Ernst , Grevemeyer Ingo , Tillman Frederik , Contreras‐Reyes Eduardo , Weinrebe Wilhelm
Published: October 2006

The highly active subduction zone of southern Chile was the source region of the 1960 Valdivia megathrust earthquake (Mw= 9.5), the largest earthquake ever recorded.This region is currently under investigation by the multidisciplinary TIPTEQ (From the Incoming Plate to Mega‐Thrust Earthquake Processes) project, which is studying the structure, state, and deformation of the subduction zone lithosphere.

Over 90 days, from December 2004 to February 2005,TIPTEQ scientists on cruise S0181 of the German research vessel (R/V Sonne acquired a broad variety of geophysical and geological data in the research area offshore Chile between 35°S and 48°S (Figure 1).These data include active and passive source seismics, heat flow probing, magnetics, magnetotellurics for studying Earth conductivity, highresolution multibeam bathymetry, and sediment probes from gravity cores.
Probing electrical conductivity of the Trans‐European Suture Zone
Authors: Brasse Heinrich , Kreutzmann Anja , Cerv Vaclav , Ernst Tomasz , Jankowski Jerzy , Jozwiak Waldemar , Neska Anne , Pedersen Laust Börsting , Smirnov Maxim , Schwarz Gerhard , Sokolova Elena , Varentsov Ivan Mikhail , Hoffmann Norbert , Palshin Nikolay , Korja Toivo
Published: October 2006

The Trans‐European Suture Zone (TESZ) is the largest tectonic boundary in Europe, crossing northwest‐southeast through central Europe from the North Sea to the Black Sea. More than 2000 kilometers long, it constitutes a complex transition between the thick and cold East European Craton (EEQ/Baltic Shield, created more than 650 million years ago (Ma) during the Precambrian, and the warmer, younger Paleozoic (650 to 250 Ma) central European mobile belts.
Chesapeake Bay impact structure drilled
Authors: Gohn Gregory S. , Koeberl Christian , Miller Kenneth G. , Reimold Wolf Uwe , Cockell Charles S. , Horton J. Wright , Sanford Ward E. , Voytek Mary A.
Published: October 2006

The Chesapeake Bay impact structure was formed by a meteorite crashing to Earth during the late Eocene, about 35.5 million years ago (Ma). In May 2006, a scientific drilling project, sponsored by the International Continental Scientific Drilling Program (ICDP) and the U.S. Geological Survey (USGS), completed a deep coring program into the impact structure. The deep drilling produced one of the most complete geologic sections ever obtained in an impact structure, and studies of the core samples will allow scientists to understand a shallow‐marine impact event and its consequences at an unprecedented level.

This buried structure is the seventh largest, and one of the best preserved, of the known impact structures on Earth [Poag et al., 2004]. It consists of a 38‐kilometer‐wide, highly deformed central zone, which approximates the dimensions and location of the transient impact crater, surrounded by a shallower outer zone of sediment collapse known as the annular trough [Horton et al., 2005]. Together, these zones have a diameter of about 85 kilometers and a distinctive shape similar to an ‘inverted sombrero.’
Pluto loses its status as a planet
Authors: Zielinski Sarah , Kumar Mohi
Published: October 2006

Astronomers nave accepted a definition for ‘planet’ that excludes Pluto, instead relegating that object and at least two others to the status of ‘dwarf planet,’ in a series of votes taken on 24 August at the International Astronomical Union (IAU) 2006 General Assembly in Prague, Czech Republic.

Michael Brown, the California Institute of Technology astronomer who discovered the newly classified dwarf planet 2003 UB313, said, “If you started from scratch, and you looked at the solar system as you were flying in from outer space, you would very quickly realize that there are eight really large objects in the solar system and you would put those into one category and use one word to describe them…All of the other objects in the solar system are much smaller, and they belong to these vast populations of other objects.”
Ozone hole not yet recovering
Authors: Zielinski Sarah
Published: October 2006

The depletion of ozone in the stratosphere caused by chemicals such as chlorofluorocarbons (CFCs)—and the resulting annual hole in the ozone layer over Antarctica—is not getting any worse, although recovery has not yet begun, according to two of the scientists who discovered the cause of the ozone hole 20 years ago.

“If you look at the ozone records all over the world…the data indicates that the reduction in ozone has stopped,” said David Hofmann, director of the Global Monitoring Division of the U.S. National Oceanic and Atmospheric Administration's (NOAA) Earth System Research Laboratory (ESRL). He and ESRL senior scientist Susan Solomon spoke at a 22 August briefing in Washington, D.C.
Entrainment and bending in a major hydrothermal plume, Main Endeavour Field, Juan de Fuca Ridge
Authors: Rona Peter A. , Bemis Karen G. , Jones Christopher D. , Jackson Darrell R. , Mitsuzawa Kyohiko , Silver Deborah
Published: October 2006

We measure expansion rate and bending in a 23‐hour time series of acoustic images of the lower 25 m section of a buoyant hydrothermal plume rising from Grotto vent in the Main Endeavour Field, Juan de Fuca Ridge. We then calculate entrainment coefficient, the constant of proportionality relating mean inflow velocity at the plume edge to maximum mean upward velocity within the plume. The plume section alternately bends southwest at relatively high inclinations (37°) and northeast at lower inclinations at irregular intervals twice during this time period, apparently driven by current reversals in the mixed semi‐diurnal tidal cycle. The measured expansion rates (0.11–0.25 m/m) and calculated entrainment coefficients (0.07–0.18) are directly proportional to the degree of bending (R2 = 0.75). The loss of buoyancy flux related to enhanced mixing in a stratified environment during bending may contribute to reduction of potential rise height consistent with predicted (∼400 m) and measured (300–350 m) plume tops.