Abstract: Methane clumped-isotope compositions provide a new approach to understanding the formational conditions of methane from both biogenic and thermogenic sources. Under some conditions, these compositions can be used to reconstruct the formational temperatures of the gas, and this capability can be applied to common subsets of both biogenic and thermogenic systems. Additionally, there are examples in which clumped-isotope compositions do not reflect gas-formation temperatures but instead mixing effects and kinetic phenomena; such kinetic effects also occur in common and recognizable subtypes of biogenic and thermogenic gases. Here we review the use of methane clumped-isotope measurements for understanding the origin of methane in the subsurface. We review methane clumped-isotope measurements from numerous biogenic and thermogenic natural gas reservoirs. We then place these measurements in the context of common frameworks for identifying the formational conditions of methane including the use of methane δ 13 C and δD values and C 1 /C 2–3 ratios. Finally, we propose a framework for how methane clumped isotopes can be used to identify the origin of methane accumulations.

Abstract: While coalbed methane (CBM) is a significant source of natural gas production globally, uncertainties regarding the proportions of biogenic and thermogenic natural gas in CBM reservoirs still remain. We integrate major gases, hydrocarbon composition, hydrocarbon stable isotopes and noble gases in fluids from 20 producing CBM wells to more accurately constrain the genetic source of natural gases in the eastern Illinois Basin, USA. Previous studies have indicated primarily biogenic production of methane (>99.6%) with negligible contributions from thermogenic natural gases. However, by integrating noble gases, we identify quantifiable (up to 19.2%) contributions of exogenous thermogenic gas in produced gases from the Seelyville and Springfield coal seams. Thermogenic gases are distinguished by a positive relationship between methane, ethane and helium-4, lower C 1 /C 2 +, heavier δ 13 C-CH 4 , more radiogenic noble gases ( 4 He, 21 Ne*, 40 Ar*), and lower abundances of atmospherically derived gases ( 20 Ne, 36 Ar). Biogenic gases displayed lighter δ 13 C-CH 4 , higher C 1 /C 2 +, higher levels of atmospheric gases and lower abundances of radiogenic noble gases. Our data suggest that natural gases from a deeper, exogenous thermogenic source likely migrated to the Pennsylvanian-aged coals at an unknown time and later mixed with biogenic methane diluting the geochemical signature of the thermogenic methane within the Springfield and Seelyville coal seams.

Abstract Timely detection and quantification of lava effusion rates are crucial for volcanic hazard mitigation during effusive eruptions. Satellite-based detection methods typically exploit the exceptional radiant heat fluxes associated with lava effusion, but effusive eruptions can also emit prodigious amounts of sulphur dioxide (SO 2 ). Measuring the magnitude and temporal evolution of SO 2 emissions provides an additional means for monitoring effusive eruptions, complementing thermal monitoring. Examples of effusive eruptions detected since 1978 using ultraviolet (UV) satellite measurements of SO 2 emissions by the Total Ozone Mapping Spectrometer (TOMS), Ozone Monitoring Instrument (OMI) and Ozone Mapping and Profiler Suite (OMPS) are reviewed. During many effusive eruptions, trends in SO 2 production mimic the classic waxing–waning pattern characteristic of such events that is also seen in thermal infrared (TIR) hotspot data, suggesting a qualitative link between SO 2 emissions and lava effusion rates. An example of lava effusion rate calculation based on TOMS SO 2 measurements is presented for the 1998 eruption of Cerro Azul (Galápagos Islands), for which detailed eruption observations and independent estimates of effusion rates are available. Combining TOMS-derived SO 2 emission rates with estimates of sulphur content in Cerro Azul lavas yields lava effusion rates almost identical to independently derived values, demonstrating the utility of the technique.

Abstract Burning and evolving for over 50 years, the anthracite coal fire in Centralia, Pennsylvania, has provided researchers with an ideal environment to study how shallow coal fires affect surface vegetation, nutrients and soil, landscape subsidence, organisms, fire migration, as well as human health. Ten years ago, surface temperatures from some gas exhaust vents were measured to be between 456° and 540 °C, and the fire was recorded to be moving rapidly at a rate of 20–22 m/yr. However, the fire has changed considerably since that time. Today, the average annual temperature of surface exhaust vents is ~65 °C, and its rate of movement is nearly unperceivable. In light of the changing parameters of the fire, Centralia continues to provide an interesting environment in which to study the effects of a subsurface anthracite coal fire on the landscape. This field trip will examine the geologic structure of the region, the Buck Mountain coal succession, the geomorphic features produced by the fire, the environmental consequences related to the removal of natural resources like coal, how a government responds to regional environmental disasters like coal fires, and the legacy of a coal fire on a region. Over the past decade, this fire and its influence on the landscape have changed considerably. However, there are still many interesting things to learn from this fire and the surrounding region.

Environmental changes linked to Deccan volcanism are still poorly known. A major limitation resides in the paucity of direct Deccan volcanism markers and in the geologically short interval where both impact and volcanism occurred, making it hard to evaluate their contributions to the mass extinction. We investigated the low-magnetic-susceptibility interval just below the iridium-rich layer of the Bidart (France) section, which was recently hypothesized to be the result of paleoenvironmental perturbations linked to paroxysmal Deccan phase 2. Results show a drastic decrease of detrital magnetite and presence of scarce akaganeite, a hypothesized reaction product formed in the aerosols derived from reaction of a volcanic plume with water and oxygen in the high atmosphere. A weathering model of the consequences of acidic rains on a continental regolith reveals nearly complete magnetite dissolution after ~31,000 yr, which is consistent with our magnetic data and falls within the duration of the Deccan phase 2. These results highlight the nature and importance of the Deccan-related environmental changes leading up to the end- Cretaceous mass extinction.

This review summarizes and assesses a series of papers presented at the Geological Society of America Annual Meeting in 2011 on the changing composition of Earth's early atmosphere. This is a developing field, with differing views, due largely to the facts of an incomplete rock record and negligible preservation of the gaseous components of the atmosphere. Nevertheless, there are constraints, available through geological proxies in the form of chemical sedimentary rocks that reflect the composition of the hydrosphere, and because the two are directly linked, the atmosphere. A review of the geological constraints on atmospheric conditions is presented for early Earth, from its formation at 4.56 Ga up to 1.8 Ga, followed by a developing model that links changing atmosphere/hydrosphere conditions and biosphere evolution to changes in planetary tectonics, including the evolving supercontinent cycle.

Volcanic features are common on geologically active earthlike planets. Megascale or “super” eruptions involving >1000 Gt of magma have occurred on both Earth and Mars in the geologically recent past, introducing prodigious volumes of ash and volcanic gases into the atmosphere. Here we discuss felsic (explosive) and mafic (flood lava) supereruptions and their potential atmospheric and environmental effects on both planets. On Earth, felsic supereruptions recur on average about every 100–200,000 years and our present knowledge of the 73.5 ka Toba eruption implies that such events can have the potential to be catastrophic to human civilization. A future eruption of this type may require an unprecedented response from humankind to assure the continuation of civilization as we know it. Mafic supereruptions have resulted in atmospheric injection of volcanic gases (especially SO 2 ) and may have played a part in punctuating the history of life on Earth. The contrast between the more sustained effects of flood basalt eruptions (decades to centuries) and the near-instantaneous effects of large impacts (months to years) is worthy of more detailed study than has been completed to date. Products of mafic supereruptions, significantly larger than known from the geologic record on Earth, are well preserved on Mars. The volatile emissions from these eruptions most likely had global dispersal, but the effects may not have been outside what Mars endures even in the absence of volcanic eruptions. This is testament to the extreme variability of the current Martian atmosphere: situations that would be considered catastrophic on Earth are the norm on Mars.

Abstract Volcanoes are not randomly distributed over the Earth's surface. Most are concentrated on the edges of continents, along island chains, or beneath the sea where they form long mountain ranges. More than half of the world's active volcanoes above sea level encircle the Pacific Ocean (see Fig. 1 ). The concept of plate tectonics explains the locations of volcanoes and their relationship to other large-scale geologic features. The Earth's surface is made up of a patchwork of about a dozen large plates and a number of smaller ones that move relative to one another at <1 cm to ~10 cm/yr (about the speed at which fingernails grow). These rigid plates, with average thickness of ~80 km, are separating, sliding past each other, or colliding on top of the Earth's hot, viscous interior. Volcanoes tend to form where plates collide or spread apart ( Fig. 2 ) but can also grow in the middle of a plate, like the Hawaiian volcanoes ( Fig. 3 ). Of the more than 1,500 volcanoes worldwide believed to have been active in the past 10,000 years, 169 are in the United States and its territories ( Ewert et al., 2005 ) (see Fig. 4 ). As of spring 2007, two of these volcanoes, Kilauea and Mount St. Helens, are erupting, while several others, including Mauna Loa, Fourpeaked, Korovin, Veniaminof, and Anatahan, exhibit one or more signs of restlessness, such as anomalous earthquakes, deformation of the volcano's surface, or changes in volume and composition

Abstract Minerals derived from coal-fire gas and found encrusting vents and ground fissures form by isochemical or mass-transfer processes. Isochemical processes include sublimation and gas-liquid–solidification (GLS). Evidence for sublimation includes elements found in both the gas and minerals as well as the occurrence of euhedral crystals. Textural evidence for GLS includes drip and flow condensates. Mass-transfer processes are more complex and include gas-altered substrate (GAS), gas-liquid–altered substrate (GLAS), gas-liquid–precipitation (GLP), and gas reaction ± liquid-solidification (GRLS) processes. During GAS, the depositional substrate is altered by reaction with one or more components of coal-fire gas, whereas during GLAS, the substrate is altered by reaction with a liquid solution. Evidence for GLAS includes vesicles and minerals with ions acquired from the underlying substrate. GRLS is characterized by reaction among select-gas components, ultimately responsible for mineralization. Differentiating GAS, GLAS, and GRLS from one another is difficult if the mineralized by-products of combustion are dissolved by water or windswept from an altered substrate. Amorphous bulb-like masses at the end of elongated crystals are evidence for GLP. Minerals reported to be coal-fire sublimates on the basis of textural evidence may actually be the reaction products of select-gas components exhaled from a vent or fissure. Reactions involving coal-fire gas components have never been identified. Additional mineral forming reactions based on isochemical and mass-transfer processes are possible. Some coal-fires minerals may be vectors for the transmission of toxins to humans by inhaled dust particles or by food grown in soils that contain these minerals.

Abstract Unusual dike-like bodies and lenses of paralava, up to 1–5 m long and 10 cm thick, are found in the “olive” unit of the combustion metamorphic complex in the Hatrurim Basin, Israel. High-temperature rocks of the “olive” unit are composed of anorthite and clinopyroxene (diopside-hedenbergite-esseneite) and are connected with pipe-like explosion structures. The paralavas are cryptocrystalline rocks that exhibit vesicular and fluidal textures. The main mineral assemblage in these rocks, identified by electron-microprobe analysis and X-ray diffraction, consists of basic plagioclase + Fe-Ti oxides + clinopyroxene + K-feldspar + tridymite ± apatite. The silica content of the paralavas is similar to that of basalt, whereas the high calcium content suggests similarity to anorthosite. The occurrence of glass in the paralava is evidence for melting. The glasses are compositionally similar to rhyolites and more acidic melts. Melting temperatures were at least 1100 °C. The presence of pipe-like explosion structures, the occurrence of melted rocks, and various geological relationships throughout the Hatrurim Basin provide evidence for a new hypothesis about the genesis of this pyrometamorphic complex. The combustion metamorphic rocks in the Hatrurim Basin in Israel formed as a result of repeated ignition of hydrocarbon gases. The setting we envisage has many geological features typical of mud-volcano provinces. The occurrence of paralavas is restricted to the areas of gas ignition.

Abstract Considerable natural remanent magnetization of the calcareous rocks in the Mottled Zone, Israel, is commonly related to surface combustion metamorphism. The vector sum of inductive and remanent magnetization (effective magnetization) was determined based on a study of the magnetic properties of rocks and interpretation of T (the modulus of geomagnetic field vector) and ▵ Z (the increment of vertical component of geomagnetic field) anomalies. Ground multiscale magnetic measurements indicate that the high-grade metamorphic rocks of the Mottled Zone, which have a spotty distribution, are characterized by extensive variations in magnetic fields and susceptibility, with a median value of ∼200 × 10 −5 SI. This magnetic pattern is similar to other areas of combustion metamorphism. Low-temperature hydrothermal rocks have a relatively homogeneous magnetic susceptibility with the same median value. Relatively homogeneous and moderate magnetization also was observed in some outcrops of the Mishash formation, which underlies the Mottled Zone rocks. High-grade metamorphism and locally varying magnetization may be due to the burning of gases. The local aeromagnetic maxima observed within the Hatrurim Basin and quantitative interpretation of some magnetic anomalies suggest magnetic sources with relatively homogeneous and stable magnetization and greater area and depth. The formation of such bodies requires a regional source for magnetization processes (e.g., gas flow from depth along faults). A more detailed study, including a helicopter survey and special ground and laboratory analyses, must be performed for a complete characterization of the complex magnetic system.

Abstract Coal fires are one of the most common geohazards in most coal-producing countries, such as india and China. Combustion can occur spontaneously or due to anthropogenic causes, either within underground coal seams or in exposed layers of coal on Earth’s surface. Once started, coal fires are difficult to extinguish and sometimes cannot be controlled. In addition to burning millions of tons of coal, the fires have an enormous negative impact on the local and global environments. Coal fires produce large quantities of greenhouse gases, such as CO, CO 2 , CH 4 , SO x , and NO x , which have a direct impact on the local and global atmospheric composition. Since the preindustrial era, the concentration of CO 2 , a major greenhouse gas that contributes to global warming, has increased from 280 ppm to 375 ppm. Land subsidence is an associated problem in areas that are affected by coal fires. Coal fires also create operational difficulties in existing mines and endanger human safety. After the first use of remote sensing to study a coal fire in the early 1960s, this technology became a useful and convenient tool for the detection and monitoring of additional coal fires. Several air- and spaceborne thermal remote sensors are available for studying coal fires. Coal-fire–related emissions have not been studied extensively; ground-based methods mainly use CO 2 detection instruments or other indirect calculations (e.g., amount of coal burnt). Few attempts are being made to estimate coal-fire emission using remote sensing.

A coupled ocean-atmosphere general circulation model was used to perform multi-centennial climate simulations of the Eemian interglacial and the subsequent glacial inception. The simulations were performed as equilibrium experiments with orbital parameters and greenhouse gas concentrations set to values of 125,000 and 115,000 yr before present (B.P.). These dates represent periods with enhanced and weakened seasonal cycles of insolation in the Northern Hemisphere. A consistent reaction of seasonal temperatures is simulated for most continental regions. Comparisons with pollen-based reconstructions of European temperatures show that the model simulates realistic spatial temperature patterns for the warm phase of the Eemian. In the case of the simulation for 115,000 yr B.P., the model reacts with a long-term cooling trend. This trend is associated with a continuous increase in Northern Hemisphere sea-ice volume and an expansion of the permanently snow-covered areas over North America. Although summer precipitation is reduced in this region, the changes in seasonality of temperature lead to significant higher amounts of summer snowfall. The strengthened North Atlantic circulation does not compensate the cooling of the Northern Hemisphere. The snow accumulation starts in northeastern Canada where southward winds transport cold Arctic air into the continent. The accumulated snow volume on the North American continent is equivalent to a reduction of sea level at a rate of ∼10 cm per century at the end of the simulation.

Springs encircling Santa María volcano in Guatemala generally contain bicarbonate waters. Bicarbonate waters southwest of the persistently active Santiaguito lava dome are characterized by high Mg/Ca. Other springs contain acid sulfate or chloride waters. Most acid sulfate and chloride waters are spatially confined to springs, wells, and streams of the Zunil and Zunil-II (Sulfur Mountain) geothermal fields on the flanks of the Cerro Quemado dome complex, 5 km to the east-northeast of Santa María. Some acid sulfate waters have unusually high S/Cl ratios (20–70). Chloride waters are dilute versions of typical geothermal brines. The δ 13 C ratios of all waters fall in a very narrow range (−11.5‰ to −8.5‰). The nonreactive gas compositions from fumaroles encircling Santa María are typical of those sampled at other subduction zone volcanoes. Most fumarolic gases from Santa María have notably lighter δ 13 C ratios compared to gases sampled from elsewhere on the Central American volcanic front. The He and C isotopic values of fumarolic gas samples from the Santa María region indicate significant mantle input. Estimated magmatic δ 13 C ratios for Zunil and Zunil-II, however, are lighter than accepted mantle values (−11‰ to −14‰). This is most likely caused by shallow crustal contamination. All of the spring waters from the Santa María region represent variable interactions between magmatic/hydrothermal fluids and meteoric waters. There is, however, only limited mixing between bicarbonate, acid sulfate, and chloride waters. Surface discharges of chloride waters are inhibited by high precipitation rates. The high S/Cl ratios of some of the acid sulfate waters from Zunil/Zunil-II reflect extensive scrubbing by the underlying hydrothermal system. High Mg/Ca bicarbonate waters from springs south-southwest of the Santiaguito dome complex have experienced enhanced water-rock interaction, and their slightly heavier δ 13 C ratios (−9.5‰ to −8‰) hint at a small distinction between magmatic δ 13 C at Zunil/Zunil-II and Santa María. This supports previous suggestions that the hydrothermal system beneath the Zunil area is independent of Santa María. Gas samples from Zunil/Zunil-II and Cerro Quemado, on the other hand, do share similar δ 13 C ratios, strengthening the notion that magmatism at the latter is propelling the hydrothermal system northeast of Santa María. Hence, monitoring of the springs and fumaroles at Zunil/Zunil-II could prove useful in forecasting of future activity at Cerro Quemado.