What is a volcano?

Water vapour plays a key role in the Earth's energy balance. Almost 50% of the absorbed solar radiation at the surface is used to cool the surface, through evaporation, and warm the atmosphere, through release of latent heat. Latent heat is the single largest factor in warming the atmosphere and in transporting heat from low to high latitudes. Water vapour is also the dominant greenhouse gas and contributes to a warming of the climate system by some 24°C (Kondratev 1972). However, water vapour is a passive component in the troposphere as it is uniquely determined by temperature and should therefore be seen as a part of the climate feedback system. In this short overview, we will first describe the water on planet Earth and the role of the hydrological cycle: the way water vapour is transported between oceans and continents and the return of water via rivers to the oceans. Generally water vapour is well observed and analysed; however, there are considerable obstacles to observing precipitation, in particular over the oceans. The response of the hydrological cycle to global warming is far reaching. Because different physical processes control the change in water vapour and evaporation/precipitation, this leads to a more extreme distribution of precipitation making, in general, wet areas wetter and dry areas dryer. Another consequence is a transition towards more intense precipitation. It is to be expected that the changes in the hydrological cycle as a consequence of climate warming may be more severe that the temperature changes.

The Cenozoic alkali basalt centres in north-eastern Brazil are believed to represent the surface track of the passage of the craton over the Fernando de Noronha plume (O’Connor and Duncan, 1990). This hypothesis is at present largely unconstrained because the only one previously studied xenolith occurrence, Pico Cabuji, showed large isotopic differences with xenoliths from the Fernando de Noronha island (Rivalenti et al., 2000). We revisit this hypothesis on the basis of a larger geochemical and isotope data set on the xenoliths of unstudied Brazilian localities (Fig. 1). Texturally, the xenoliths define three group: 1) porphyroclastic (lherzolites, harzburgites and one wehrlite); 2) protogranular (lherzolites and harzburgites); 3) transitional between groups 1 and 2 (lherzolites and harzburgites). Equilibrium temperature and pressure ranges 950 – 1280°C, 1.9 – 2.5 GPa in group 1, 830 – 990°C, 1.3 – 1.8 GPa in group 2, 890 – 980°C, 1.5 – 2 GPa in group 3. . The three textural groups have a similar mg# range in clinopyroxene, but the porphyroclastic clinopyroxenes have, at any given mg# value, lower Ti, Al, Ca and Na and higher Fe concentrations (a.f.u.), with respect to the protogranular ones, and the cpx of the transitional xenoliths define an array intermediate between the others. Orthopyroxenes have opposite characteristics with respect to cpx, so that the porphyroclastic ones are the richest in Ti, Al, Ca, Na and the lowest in Fe. In group 1 the REE patterns of clinopyroxenes vary from convex upward, typical of phases in equilibrium with alkaline melts, to spoon shaped, to steadily LREE-enriched in wehrlite (Fig. 2). Group 2 clinopyroxene are predominately LREE – depleted and enriched only in Th and U and group 3 clinopyroxenes are similar to those of group 2, but have higher LREE concentrations and in some cases spoon-shaped profiles. Sr and Nd isotopes of the group 1 clinopyroxenes form an array between DM and an EMI-like component, present also in the host basalts, whereas the protogranular xenoliths exhibit large spreading of the Sr-isotopic values (Fig. 3). The samples with higher 87Sr/86Sr trend towards EMII. Potential melts in equilibrium with the group 1 clinopyroxenes are similar to the alkali basalts hosting the xenoliths and those estimated from protogranular clinopyroxenes are similar, except for a higher concentration of the highly incompatible elements Th and U, to Mesozoic tholeiitic basalts of north-eastern Brazil. These results are consistent with the following conclusions: a) the xenoliths sampled a mantle section whose deepest and shallowest regions are represented by the group 1 and 2 xenoliths, respectively, being those of group 3 derived from an intermediate region; b) the geothermal gradient of the section was as high as 15°C/Km; c) geochemical modelling supports that the deepest region underwent reactive porous flow of alkali basalt, isotopically closer to EMI, whereas metasomatism was controlled by percolation and crystallisation under decreasing melt mass in the regions represented by the group 3 and 2 xenoliths; d) lithosphere predating metasomatism is largely represented by the group 2 xenoliths, which isotopically plot in between DM and an EMII component, thus considered as lithospheric. Similarity with Mesozoic basalts of the group 2 and 3 potential melts calculated from clinopyroxene and high 87Sr/86Sr in clinopyroxene suggests that these xenoliths predominately record mantle processes predating the Cenozoic event. A comparison of the characteristics of north-eastern Brazil and Fernando de Noronha shows that the respective lithospheres record similar stratigraphy, interaction with an asthenospheric EMI component and also similar heterogeneity in the cooler lithosphere section documented by the protogranular xenoliths. This similarity lends support to the notion that the lithosphere beneath Fernando de Noronha is a detached piece of the continental one. None of the characteristics of north-eastern Brazil xenolith suite provides unquestionable evidence of plume interference. For example, the mantle stratigraphy documented by the textural, geochemical, isotopic and thermal variations and its high geothermal gradient, often considered a typical result of plume impingement on the lithosphere are also found in other mantle sections where processes are not controlled by plume. If the existence of the Fernando de Noronha plume is given as granted, the only evidence of its interaction with the north-eastern Brazil lithosphere is the similarity of isotope compositions and processes of the lithosphere of the two localities. The isotopic arrays of the porphyroclastic xenoliths in both cases indicate that a lithosphere having DM characteristics was enriched by an asthenospheric basaltic melt having EMI-like characteristics. If asthenosphere melting was triggered by the addition of plume material, then the enriched component may represent a plume characteristic.

(1958). Measuring Reading Comprehension. The Clearing House: A Journal of Educational Strategies, Issues and Ideas: Vol. 32, No. 6, pp. 343-345.

The discovery of large amounts of soot in clays deposited at the Cretaceous‐Paleogene (K‐Pg) boundary and linked to the ~65 Ma Chicxulub impact crater led to the hypothesis that major wildfires were a consequence of the asteroid impact. Subsequently, several lines of evidence, including the lack of charcoal in North American sites, were used to argue against global wildfires. Close to the impact site fires are likely to be directly ignited by the impact fireball, whereas globally they could be ignited by radiation from the reentry of hypervelocity ejecta. To‐date, models of the latter have yet to take into account that ejection—and thus the emission of thermal radiation—is asymmetric and dependent on impact angle. Here, we model: (1) the impact and ejection of material, (2) the ballistic continuation of ejecta around a spherical Earth, and (3) the thermal pulse delivered to the Earth's surface when ejecta reenters the atmosphere. We find that thermal pulses in the downrange direction are sufficient to ignite flora several thousand kilometers from Chicxulub, whereas pulses at most sites in the uprange direction are too low to ignite even the most susceptible plant matter. Our analyses and models suggest some fires were ignited by the impact fireball and ejecta reentry, but that the nonuniform distribution of thermal radiation across the surface of the Earth is inconsistent with the ignition of fires globally as a direct and immediate result of the Chicxulub impact. Instead, we propose that the desiccation of flora by ejecta reentry, as well as the effects of postimpact global cooling/darkness, left much of the terrestrial flora prone to fires, and that the volume of soot in the global K‐Pg layer is explained by a combination of syn‐ and postimpact wildfires.

The Advanced Research Projects Agency (ARPA) has initiated the Synthetic Theater of War (STOW) program to expand the current distributed interactive simulation (DIS) capability to handle larger exercises. Characterizations of the unclassified network traffic from the Synthetic Theater of War-Europe (STOW-E) demonstration are assessed in the context of self-similarity. At small time scales, the LAN traffic oscillates between burstiness and smoothness, whereas the WAN traffic exhibits smoothness. However, both the LAN and the WAN traffic exhibit high burstiness on larger time scales. Therefore, the traffic shows characteristics that would be produced by Poisson-type and self-similar processes. Additionally, in comparing the STOW-E traffic with an asymptotically self-similar process, we find that it has an unusually high Hurst parameter (i.e., H/spl sim/1). A simple mathematical model for the traffic is an uncorrelated process whose parameters vary according to another asymptotically self similar process of high burstiness. Since a combination of self-similar processes results in an asymptotically self-similar process, we conjecture that future STOW traffic should behave as asymptotically modulated self-similar processes.

In supernova (SN), the ejected material drives powerful shock fronts into the stellar winds of progenitor stars at speeds of tens of thousand kilometers per second. A layer of shocked circumstellar material (CSM) and ejected material develops that can be observed in X‐ray emission due to the high associated temperatures (106–109 K). Analysis of the interaction between the ejected material and CSM leads to information on the temperature and density structure as well as the mass loss rate of the progenitor star As the SN blast wave moves to ever increasing radii, it offers an opportunity to study older and older stellar winds over periods of tens of thousands of years in the history of the progenitors. To date there have been 32 SN detected in X‐rays in the past ≈30 years, and a detailed study offers interesting new insights into the stellar wind history of the progenitor stars. The analysis shows that all young (<40 years) X‐ray emitting SN detected have strikingly similar CSM density profiles, ranging more than 9 orders of magnitude (0.1–108 cm−3) over a distance range of 7 orders of magnitude from the sites of the explosions.

Although fluorescence microscopy provides a crucial window into the physiology of living specimens, many biological processes are too fragile, are too small, or occur too rapidly to see clearly with existing tools. We crafted ultrathin light sheets from two-dimensional optical lattices that allowed us to image three-dimensional (3D) dynamics for hundreds of volumes, often at subsecond intervals, at the diffraction limit and beyond. We applied this to systems spanning four orders of magnitude in space and time, including the diffusion of single transcription factor molecules in stem cell spheroids, the dynamic instability of mitotic microtubules, the immunological synapse, neutrophil motility in a 3D matrix, and embryogenesis in Caenorhabditis elegans and Drosophila melanogaster. The results provide a visceral reminder of the beauty and the complexity of living systems.

The formation of stars is a key process in astrophysics. Detailed knowledge of the physical mechanisms that govern stellar birth is a prerequisite for understanding the formation and evolution of our galactic home, the Milky Way. A theory of star formation is an essential part of any model for the origin of our solar system and of planets around other stars. Despite this pivotal importance, and despite many decades of research, our understanding of the processes that initiate and regulate star formation is still limited. Stars are born in cold interstellar clouds of molecular hydrogen gas. Star formation in these clouds is governed by the complex interplay between the gravitational attraction in the gas and agents such as turbulence, magnetic fields, radiation and thermal pressure that resist compression. The competition between these processes determines both the locations at which young stars form and how much mass they ultimately accrete. It plays out over many orders of magnitude in space and time, ranging from galactic to stellar scales. In addition, star formation is a highly stochastic process in which rare and hard-to-predict events, such as the formation of very massive stars and the resulting feedback, can play a dominant role in determining the evolution of a star-forming cloud. As a consequence of the wide range of scales and processes that control star formation, analytic models are usually restricted to highly idealized cases. These can yield insight, but the complexity of the problem means that they must be used in concert with large-scale numerical simulations. Here we summarize the state of modern star formation theory and review the recent advances in numerical simulation techniques.

Transfer microbiological studies under the surface of the Earth to exploration of deep intraterrestrial microbial life is important to allows exceeding the current framework of science. Microbial life is determined by physical, geochemical, and biological factors such as the availability of liquid water, energy, nutrients, and trace elements. Additionally, conditions including ambient temperature, pH, salinity, and pressure interact with biological systems to define the space for life. Recent studies have shown the presence and activity of cells in deep marine sediments and in the continental deep biosphere. Characterizing the bacterial community composition and recognition of diversity of microorganisms may play an important role in biogeochemical carbon cycling and potential biotechnological application of these microorganisms.

Community ecology and ecosystem ecology seem to have existed in different worlds. Levin (1989) suggests that the gulf between the two is the consequence of the different historical traditions in each. Community ecology, for example, emerged from basic studies, where generalized patterns were sought in the natural interactions among the biota. From the outset, the goal has been to deduce general and simple theory. On the other hand, many of the modelling approaches developed to understand ecosystem dynamics emerged from specific applied problems, where not only biotic but abiotic and human disturbances transformed ecosystem function. That tradition, therefore, is often more complete, but at the price of producing a collection of complex specific examples from which generalization is difficult.

Study of large project management basing on the research of time and space scales is the at the forefront of the trend.But for now, it is still resting on the basic work stage for large projects based on the time space multi-dimensional definition. A large project construction and operation is bound to place on the space area and near projects of social and economic impact, in addition to the internal effects and characteristics. What is more, it will reflect the index at different stages of dynamic change in the time series. This article will make an analysis of large-scale spatial spillover effects of the project and have the selection of large projects indicators which can reflect on regional economic and social impact. Besides this article is from the perspective of time and space, applying the spatial econometrics, it dynamic traces of index in time scale, analysis, reflects the characteristics of a large project for large projects.

Dense arrays of surface drifters are used to quantify the flow field on time and space scales over which high-frequency (HF) radar observations are measured. Up to 13 drifters were repetitively deployed off the Santa Barbara and San Diego coasts on 7 days during 18 months. Each day a regularly spaced grid overlaid on a 1-km2 (San Diego) or 4-km2 (Santa Barbara) square, located where HF radar radial data are nearly orthogonal, was seeded with drifters. As drifters moved from the square, they were retrieved and replaced to maintain a spatially uniform distribution of observations within the sampling area during the day. This sampling scheme resulted in up to 56 velocity observations distributed over the time (1 h) and space (1 and 4 km2) scales implicit in typical surface current maps from HF radar. Root-mean-square (RMS) differences between HF radar radial velocities obtained using measured antenna patterns, and average drifter velocities, are mostly 3–5 cm s−1. Smaller RMS differences compared with past validation studies that employ current meters are due to drifter resolution of subgrid-scale velocity variance included in time and space average HF radar fields. Roughly 5 cm s−1 can be attributed to sampling on disparate time and space scales. Despite generally good agreement, differences can change dramatically with time. In one instance, the difference increases from near zero to more than 20 cm s−1 within 2 h. The RMS difference and bias (mean absolute difference) for that day exceed 7 and 12 cm s−1, respectively.

The characteristics of submeso motions in the stable boundary layer are examined using observations from networks of sonic anemometers with network sizes ranging from a few hundred metres to 100 km. This study examines variations on time scales between 1 min and 1 h. The analysis focuses on the behaviour of the spectra of the horizontal kinetic energy, the ratios of the three velocity variances, their kurtosis, the dependence of horizontal variability on time scale, and the inter-relationship between vertical vorticity, horizontal divergence and deformation. Motions on larger time and space scales in the stable boundary layer are found to be nearly two-dimensional horizontal modes although the ratio of the vorticity to the divergence is generally on the order of one and independent of scale. One exception is a small network where stronger horizontal divergence is forced by a decrease in surface roughness. The horizontal variability, averaged over 1 h, appears to be strongly influenced by surface heterogeneity and increases with wind speed. In contrast, the time dependence of the horizontal structure on time scales less than one hour tends to be independent of wind speed for the present datasets. The spectra of the horizontal kinetic energy and the ratio of the crosswind velocity variance to the along-wind variance vary substantially between networks. This study was unable to isolate the cause of such differences. As a result, the basic behaviour of the submeso motions in the stable boundary layer cannot be generalized into a universal theory, at least not from existing data.

An experimental investigation was undertaken to examine the effect of a morphing surface on the flow over a sphere in the Reynolds number range of 5x10⁴ to 5x10⁵. Here, a morphing surface is defined as a continuous surface that undergoes small amplitude changes in order to excite flow instabilities, rather than utilizing large mechanical changes to the overall shape as with traditional aerodynamic control surfaces. The sphere was chosen as an ideal geometry for testing morphing surfaces, because of the well-known sensitivity of the flow to small asymmetries on the surface. In this study, an approximation of a morphing surface was made by dynamically moving a small isolated roughness element along the sphere, thus producing small amplitude time-dependent changes to the surface shape. An experimental apparatus was designed that produced the actuation with an internal motor, which moved the roughness element via magnetic interaction. A three-component piezoelectric force sensor placed inside the sphere allowed for accurate, instantaneous measurements of the global effect of the actuator on the flow. It was found that the moving roughness could produce an instantaneous lateral force as large as the drag. Simultaneous force and particle image velocimetry measurements in the subcritical regime were used to show that there is a relatively long timescale associated with the instability growth, entrainment of fluid, and local change of the position of separation. This allowed the roughness to trip an extended region of the flow at once. It is shown that the three-dimensionality of the disturbance leads to the production of two helical counter-rotating vortices in the wake. In addition, it is demonstrated that a mean side force can be obtained by oscillating the roughness element about a point, producing a lateral force an order of magnitude larger than the force caused by a stationary roughness element. Finally, the results from the dynamic roughness were used to help interpret the underlying physical mechanisms that govern the forcing on a smooth sphere.

This book presents the integrated contributions of hydrologists, meteorologists and ecologists to the first IHP/IAHS George Kovacs Colloquium in connection with the study of global hydrology and climate change. The atmospherical, hydrological and terrestrial components of the Earth's systems operate on different time and space scales. Resolving these scaling incongruities, as well as understanding and modelling the complex interaction of land surface processes at the different scales, represent a major challenge for hydrologists, ecologists and meteorological scientists alike. This book deals with time and space scale variations with reference to several topics including: soil water balance; ecosystems and interaction of flow systems; and macroscale hydrological modelling. This book will be of great use to researchers, engineers and forecasters with an interest in space and time scale variability.