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At least 91 records · Page 5

The Model Intercomparison Project on the Climatic Response to Volcanic Forcing (VolMIP): Experimental Design and Forcing Input Data for CMIP6

The enhancement of the stratospheric aerosol layer by volcanic eruptions induces a complex set of responses causing global and regional climate effects on a broad range of timescales. Uncertainties exist regarding the climatic response to strong volcanic forcing identified in coupled climate simulations that contributed to the fifth phase of the Coupled Model Intercomparison Project (CMIP5). In order to better understand the sources of these model diversities, the Model Intercomparison Project on the climatic response to Volcanic forcing (VolMIP) has defined a coordinated set of idealized volcanic perturbation experiments to be carried out in alignment with the CMIP6 protocol. VolMIP provides a common stratospheric aerosol data set for each experiment to minimize differences in the applied volcanic forcing. It defines a set of initial conditions to assess how internal climate variability contributes to determining the response. VolMIP will assess to what extent volcanically forced responses of the coupled ocean-atmosphere system are robustly simulated by state-of-the-art coupled climate models and identify the causes that limit robust simulated behavior, especially differences in the treatment of physical processes. This paper illustrates the design of the idealized volcanic perturbation experiments in the VolMIP protocol and describes the common aerosol forcing input data sets to be used.

Volcanoes↗

Assessing the Impact of Large Volcanic Eruptions of the Last Millennium (850-1850 CE) on Australian Rainfall Regimes

Explosive volcanism is an important natural climate forcing, impacting global surface temperatures and regional precipitation. Although previous studies have investigated aspects of the impact of tropical volcanism on various ocean–atmosphere systems and regional climate regimes, volcanic eruptions remain a poorly understood climate forcing and climatic responses are not well constrained. In this study, volcanic eruptions are explored in particular reference to Australian precipitation, and both the Indian Ocean Dipole (IOD) and El Niño–Southern Oscillation (ENSO). Using nine realizations of the last millennium (LM) (850–1850CE) with different time-evolving forcing combinations, from the NASA GISS ModelE2-R, the impact of the six largest tropical volcanic eruptions of this period are investigated. Overall, we find that volcanic aerosol forcing increased the likelihood of El Niño and positive IOD conditions for up to four years following an eruption, and resulted in positive precipitation anomalies over north-west (NW) and south-east (SE) Australia. Larger atmospheric sulfate loading during larger volcanic eruptions coincided with more persistent positive IOD and El Niño conditions, enhanced positive precipitation anomalies over NW Australia, and dampened precipitation anomalies over SE Australia.

Blake, Stephanie A. P.↗

Forecasting Rates of Volcanic Activity on Terrestrial Exoplanets and Implications for Cryovolcanic Activity on Extrasolar Ocean Worlds

Like the planets and moons in our solar system, the surfaces of terrestrial exoplanets may be shaped by volcanic activity. The magnitudes and rates of volcanic activity on terrestrial exoplanets will be intimately linked to their sizes and internal heating rates and can either facilitate or preclude the existence of habitable environments. In order to place bounds on the potential for such activity, we estimate total internal heating rates for 53 exoplanets with masses and radii up to∼8M⊕and 2R⊕, respectively, assuming that internal heating is drawn from both radiogenic and tidal sources. We then compare these internal heating rates to those of the planets and moons in our solar system in an attempt to constrain the expected rates of volcanic activity on these extrasolar worlds. We find that all 53 of the exoplanets surveyed are likely to have volcanic activity at their surfaces, and that at least 26% of these planets may be extrasolar ocean worlds. The majority of these ocean worlds may be similar in structure to the icy moons of the giant planets, having internal oceans beneath layers of surface ice. If so, these planets may exhibit cryovolcanism (i.e., icy volcanism)at their surfaces. Recent studies have shown that extrasolar volcanism could be detected by high-resolution spectrographs on existing ground-based telescopes. In the case of planets with densities and/or effective temperatures that are consistent with H2O-rich compositions, spectral identification of excess water vapor and other molecules that are explosively vented into space during cryovolcanic eruptions could serve as a way to infer the presence of subsurface oceans, and therefore indirectly assess their habitability. Considering the implications for habitability, our results suggest that continued characterization of terrestrial exoplanets in terms of their potential for volcanic activity should be a priority in the coming years.

Lynnae C Quick↗

Chapter 3: Petrologic Evolution of Martian Volcanism and Clues from Meteorites

The formation and evolution of the Martian surface, and ultimately the fate of its various volcanic regions, are revealed in the chemistry of Martian meteorites, and the mineralogy of the crust. The interpretation of the chemistry from remote sensing instrumentation from orbiters and landers/rovers has been strongly influenced by our knowledge of geochemical processes on Earth, the Moon, and other asteroidal, rocky bodies [1]. The composition, and thus evolution, of the Martian crust has been resultant from SNC (shergottite –nakhlite –chassignite) meteorites, which are the igneous counterpart of rocks of Martian origin [2, 3, 4]. These meteorites are chemically similar to terrestrial basalts and cumulates, with the exception of higher concentrations of iron and other volatile elements (i.e., phosphorous, chlorine, chalcophile) [5]. From Tuff et al. [2], most Martian meteorites have relatively young crystallization ages ranging from 1.4 billion years to 180 million years ago [6]. These are considered to be derived from young, usually lightly-cratered volcanic regions, such as the Tharsis volcanic region [6, 7]. Though mainly basaltic in composition, surface rocks are richer in nickel and sulfur with lower manganese/iron ratios than Martian meteorites [2], which can be explained by the differences in oxygen fugacity during melting of the sulfur-rich mantle [2, 8]. From this difference, Martian meteorites are tied to surface rocks through an early (3.7 billion years ago) oxidation of the uppermost mantle, producing the more recent volcanic rocks [2]. The variety of compositions from basaltic, olivine volcanic rocks through pyroxene-cumulate nakhlites and peridotite chassignites, enable the hypothetical reconstructions of the silicic evolution of Mars similar to techniques used on Earth [2, 5, 9]. In this chapter, we will explore the basic Martian composition of the crust and mantle in regards to volcanic regions, the crustal components of the North-South dichotomy, and more detail of the SNC meteorites in relation to the evolution of the mantle for volcanism.

C Ahrens↗

Volcanic Field Sites for Artemis Testing and Training

The Artemis Program will reestablish human presence on the Moon and lead to a new era of scientific discovery and exploration. Led by the National Aeronautics and Space Administration (NASA), the Artemis Program is a collaboration of space agencies and companies around the world. An integrated effort between various disciplines of science, engineering, and mission operations is currently developing methods, facilities, and analog field locations to train astronauts and test hardware and concepts of operations. These efforts aim to best prepare for the next steps of human exploration on the lunar surface and beyond. Numerous terrestrial volcanic field sites were evaluated and selected for their unique roles in helping to prepare for the lunar surface mission phases. This effort heavily leveraged the comprehensive academic research conducted at these field sites, as well as the tremendous Apollo heritage. The currently selected volcanic field sites include the San Francisco Volcanic Field in Northern Arizona, the Potrillo Volcanic Field in southern New Mexico, the highlands of Iceland, and the Southwestern Nevada Volcanic Field. Within each of these volcanic field sites numerous specific testing and training locations are being further developed utilizing the analogous terrain and unique features in these regions. Recent Artemis testing and training events have been conducted at a number of these volcanic field sites by both a dedicated Artemis Geology Training Team and a Joint Extra Vehicular Activity (EVA) Testing Team. This presentation will highlight the selected sites as well as the objectives and accomplishments of some of the recent field-testing events and training courses. Additionally, we continually strive to pursue additional sites, locations, data sets, collaborations, and partnerships in this endeavor and welcome knowledge transfer and community input.

Trevor Graff↗

Observing Ocean Ecosystem Responses to Volcanic Ash

Volcanic eruptions can be catastrophic events, particularly when they occur in inhabited coastal environments. They also play important roles in climate and biogeochemical cycles, including through nutrient deposition in the ocean. Volcanic ash studies in the ocean have focused on the phytoplankton response, generally quantifying changes in chlorophyll-a concentration. Many gaps remain in addressing fundamental questions regarding why volcanic ash deposition may enhance or limit both phytoplankton growth and/or drive community composition shifts. Here we outline a wide, multidisciplinary vision for monitoring volcanic eruptions near ocean ecosystems from satellites, including considerations for characteristics of airborne volcanic ash and ash geochemistry in seawater. Ultimately, observations beyond chlorophyll-a are needed to quantify phytoplankton communities (including harmful algal blooms) and possible impacts across higher trophic levels. We synthesize relevant research from volcanic studies as well as atmospheric and ocean sciences to identify the ‘known unknowns’ in ash-ecosystem studies. Our goal is to move toward an improved understanding of how real-time and near-real-time monitoring of volcanic eruptions can help address societally relevant questions.

volcano↗

Mount Etna as A Terrestrial Laboratory to Investigate Recent Volcanic Activity on Venus By Future Missions: A Comparison With Idunn Mons, Venus

The recently selected missions to Venus have opened a new era for the exploration of this planet. These missions will provide information about the chemistry of the atmosphere, the geomorphology, local-to-regional surface composition, and the rheology of the interior. One key scientific question to be addressed by these future missions is whether Venus remains volcanically active, and if so, how its volcanism is currently evolving. Hence, it is fundamental to analyze appropriate terrestrial analog sites for the study of possibly active volcanism on Venus. To this regard, we propose Mount Etna - one of the most active and monitored volcanoes on Earth - as a suitable terrestrial laboratory for remote and in-situ investigations to be performed by future missions to Venus. Being characterized by both effusive and explosive volcanic products, Mount Etna offers the opportunity to analyze multiple eruptive styles, both monitoring active volcanism and identifying the possible occurrence of pyroclastic activity on Venus. We directly compare Mount Etna with Idunn Mons, one of the most promising potentially active volcanoes of Venus. Despite the two structures show a different topography, they also show some interesting points of comparison, and in particular: a) comparable morpho-structural setting, since both volcanoes interact with a rift zone, and b) morphologically similar volcanic fields around both Mount Etna and Idunn Mons. Given its ease of access, we also propose Mount Etna as an analog site for laboratory spectroscopic studies to identify the signatures of unaltered volcanic deposits on Venus.

P D DIncecco↗

Sampling the ENSO response to tropical volcanic eruptions in the GISS-E2-1 model: physical & biogeochemical ocean effects

Despite observational evidence that an El-Niño is likely to follow tropical volcanic eruptions (Predybaylo et al, 2017), modelling studies have so far reached no consensus on either the sign or physical mechanism of El Niño response to volcanism (Khodri et al, 2017) . A previous modelling study found that following the Pinatubo eruption, the tropical Pacific developed El Niño-like conditions that triggered a decrease in the upwelling of DIC and increased carbon uptake (Eddebbar et al., 2019). However, the carbon cycle response to volcanisms as it depends on ENSO phase remains unclear. Here we perform thirty ensemble control simulations using the GISS-E2-1-G model to sample the pre-industrial control ENSO cycle and thirty more to superimpose a Pinatubo-like volcanic eruption. We find that the model tends to favor the development of a weak El-Niño following the volcanic eruption only in the case of a volcano that erupts at the start of a neutral ENSO phase. In response to the weak El-Niño, some anomalies have the same sign as those that develop from a strong El-Niño, such as weaker winds, shallower mixed layer depths, less direct but more diffuse radiation at the surface of the ocean, less nitrate, and lower primary productivity. However, other anomalies show the opposite sign as those from a strong El-Niño, such as more precipitation, less surface DIC, and less surface ocean pCO 2 . In contrast to the neutral phase, the volcanic response during positive ENSO and negative ENSO phases are swamped by the model’s internal variability.

ENSO↗

Hemispherically Asymmetric Volcanic Forcing of Tropical Hydroclimate During the Last Millennium

Volcanic aerosols exert the most important natural radiative forcing of the last millennium. State-of-the-art paleoclimate simulations of this interval are typically forced with diverse spatial patterns of volcanic forcing, leading to different responses in tropical hydroclimate. Recently, theoretical considerations relating the intertropical convergence zone (ITCZ) position to the demands of global energy balance have emerged in the literature, allowing for a connection to be made between the paleoclimate simulations and recent developments in the understanding of ITCZ dynamics. These energetic considerations aid in explaining the well-known historical, paleoclimatic, and modeling evidence that the ITCZ migrates away from the hemisphere that is energetically deficient in response to asymmetric forcing. Here we use two separate general circulation model (GCM) suites of experiments for the last millennium to relate the ITCZ position to asymmetries in prescribed volcanic sulfate aerosols in the stratosphere and related asymmetric radiative forcing. We discuss the ITCZ shift in the context of atmospheric energetics and discuss the ramifications of transient ITCZ migrations for other sensitive indicators of changes in the tropical hydrologic cycle, including global streamflow. For the first time, we also offer insight into the large-scale fingerprint of water isotopologues in precipitation (delta sup 18 Op) in response to asymmetries in radiative forcing. The ITCZ shifts away from the hemisphere with greater volcanic forcing. Since the isotopic composition of precipitation in the ITCZ is relatively depleted compared to areas outside this zone, this meridional precipitation migration results in a large-scale enrichment (depletion) in the isotopic composition of tropical precipitation in regions the ITCZ moves away from (toward). Our results highlight the need for careful consideration of the spatial structure of volcanic forcing for interpreting volcanic signals in proxy records and therefore in evaluating the skill of Common Era climate model output.

Radiative forcing↗

Lunar volcanism in space and time

The role of lunar volcanism in the history of the moon is documented using lunar-orbit and earth-based data along with characterizations derived from Apollo and Luna sample-return missions. Characteristics of mare and highland volcanic features are described, Apollo and Luna results are discussed, and the characteristics of other mare deposits and of other highland features of possible volcanic origin are summarized. Major conclusions are that: (1) there is little unequivocal morphologic evidence for highland volcanism, (2) lunar mare lavas appear to have originated from depths of 100 to 500 km, (3) impact melting does not appear to have been a factor in the generation of mare lavas, (4) mare volcanism was characterized by massive outpourings of very fluid volatile-poor lava analogous to terrestrial flood basalts, (5) mare volcanism took place from 3.83 to about 2.5 billion years ago, (6) the preferential occurrence of mare deposits in large impact basins appears to be generically unrelated to basin formation, and (7) a thicker farside crust may be responsible for the distinctive nearside-farside asymmetry of mare deposits.

Head, J. W., III↗

Similarity laws of lunar and terrestrial volcanic flows

A mathematical model for the terrestrial and lunar volcanic flows is proposed. This mathematical model, which is one-dimensional, steady duct flow of a mixture of a gas and small solid particles (rock), has been analyzed in detail. The similarities and the differences of the essential features of lunar and terrestrial volcanic flows are determined. Numerical results for the equilibrium two-phase flows of lunar and terrestrial volcanics under similar conditions are presented. The main results of the theoretical model are: the lunar crater is much larger than the corresponding terrestrial crater; the exit velocity from the lunar volcanic flow may be higher than the lunar escape velocity but the exit velocity of terrestrial volcanic flow is much less than that of the linear case (this result confirms the hypothesis that Australian tektites came from the moon, as a stream of rock and gas of extremely high speed), and the thermal effects on the lunar volcanic flow are much larger than those in the terrestrial case.

Pai, S. I.↗

Volcanism in the Noachis-Hellas region of Mars, 2

Mariner 9 and Viking Orbiter imagery has been examined to investigate volcanism in the Noachis-Hellas region of Mars. A wide variety of probable and possible volcanic features, including cinder cones, flood lavas, wrinkel ridges, cratered domes on the floors of impact craters, shield volcanoes, and possible stratovolcanoes has been observed. The flood lavas of ridged plains and broad, low shield volcanoes are indicative of very fluid lavas of ultrabasic or very basic basaltic composition. Evidence for relatively recent pyroclastic volcanism is present in numerous probable cinder cones and some isolated cratered mountains tentatively identified as stratovolcanoes. The volcanic complex and ridged plains at 68 deg S, 323 deg W appear to be relatively young. The occurrence of the five major volcanic centers of the Noachis-Hellas region at the intersections of ancient Hellas impact basin rings with a postulated northeast-trending fracture system suggests that large-scale volcanic activity may have begun soon after formation of the basin.

Peterson, J. E.↗

Volcanic features of Io

The various volcanic landforms observed on Io by Voyager 1 are described and compared with similar features on earth. Ionian calderas, observed to cover 5% of the surface, are generally found to be of low relief, similar to certain terrestrial calderas. Flow patterns observed include dark, linear markings with lobate margins resembling terrestrial lava flows, bright lobate markings originating at calderas, and a bright flow feature surrounding the calderas. Positive relief features associated with volcanic structures include pancake-like constructions similar to low volcanic cones, sheet-like structures, rugged mountains, and a type of surface upheaval. Bright and dark diffuse markings have also been found. The implications of the high rates of volcanic activity and the apparent abundance of sulfur on Io for the type of volcanism observed are discussed, and it is concluded that while there are strong arguments for sulfur flows on the surface of Io, silicate volcanism of the type observed on earth may also occur.

Carr, M. H.↗

Geochemistry of volcanic rocks from the Wawa greenstone belt

The Wawa greenstone belt is located in the District of Algoma and extends east-northeast from Lake Superior to the western part of the Sudbury District in Ontario, Canada. Recent mapping by Attoh has shown that an unconformity at the base of the Dore' Formation and equivalent sedimentary rocks marks a significant stratigraphic break which can be traced throughout the volcanic belt. This break has been used to subdivide the volcanic-sedimentary into pre- and post-Dore' sequences. The pre-Dore' sequence includes at least two cycles of mafic-to-felsic volcanism, each capped by an iron-formation unit. The post-Dore' sequence includes an older mafic-to-felsic unit, which directly overlies sedimentary rocks correlated with the Dore' Formation, and a younger felsic breccia unit interpreted to have formed as debris flows from a felsic volcanic center. In the present study, samples of both the pre-and post-Dore' volcanic sequences were analyzed for major and trace elements, incuding rare earths (REE). This preliminary study is part of an ongoing program to assess the petrogenesis of the volcanic rocks of the Wawa greenstone belt.

Schulz, K. J.↗

Discrimination and supervised classification of volcanic flows of the Puna-Altiplano, Central Andes Mountains using Landsat TM data

Landsat Thematic Mapper (TM) images of portions of the Central Andean Puna-Altiplano volcanic belt have been tested for the feasibility of discriminating individual volcanic flows using supervised classifications. This technique distinguishes volcanic rock classes as well as individual phases (i.e., relative age groups) within each class. The spectral signature of a volcanic rock class appears to depend on original texture and composition and on the degree of erosion, weathering, and chemical alteration. Basalts and basaltic andesite stand out as a clearly distinguishable class. The age dependent degree of weathering of these generally dark volcanic rocks can be correlated with reflectance: older rocks have a higher reflectance. On the basis of this relationship, basaltaic lava flows can be separated into several subclasses. These individual subclasses would correspond to mappable geologic units on the ground at a reconnaissance scale. The supervised classification maps are therefore useful for establishing a general stratigraphic framework for later detailed surface mapping of volcanic sequences.

Mcbride, J. H.↗

Evidence for volcanism in NW Ishtar Terra, Venus

Venera 15/16 radar data for an area in NW Ishtar Terra, Venus, show an area with moderate radar return and a smooth textured surface which embays low lying areas of the surrounding mountainous terrain. Although this unit may be an extension of the lava plains of Lakshmi Planum to the southeast, detailed study suggests a separate volcanic center in NW Ishtar Terra. Lakshmi Planum, on the Ishtar Terra highland, exhibits major volcanic and tectonic features. On the Venera radar image radar brightness is influenced by slope and roughness; radar-facing slopes (east-facing) and rough surfaces (approx. 8 cm average relief) are bright, while west-facing slopes and smooth surfaces are dark. A series of semi-circular features, apparently topographic depressions, do not conform in orientation to major structural trends in this region of NW Ishtar Terra. The large depression in NW Ishtar Terra is similar to the calderas of Colette and Sacajawea Paterae, as all three structures are large irregular depressions. NW Ishtar Terra appears to be the site of a volcanic center with a complex caldera structure, possibly more than one eruptive vent, and associated lobed flows at lower elevations. The morphologic similarity between this volcanic center and those of Colette and Sacajawea suggests that centralized eruptions have been the dominant form of volcanism in Ishtar. The location of this volcanic center at the intersection of two major compressional mountain belts and the large size of the calders (with an inferred larg/deep magma source) support a crustal thickening/melting rather than a hot-spot origin for these magmas.

Gaddis, L.↗

Styles of volcanism on Venus - New Arecibo high resolution radar data

Arecibo high-resolution (1.5 to 2 km) radar data of Venus for the area extending from Beta Regio to western Eisila Regio provide strong evidence that the mountains in Beta and Eisila Regiones and plains in and adjacent to Guinevere Planitia are of volcanic origin. Recognized styles of volcanism include large volcanic edifices on the Beta and Eisila rises related to regional structural trends, plains with multiple source vents and a mottled appearance due to the ponding of volcanic flows, and plains with bright features surrounded by extensive quasi-circular radar-dark halos. The high density of volcanic vents in the plains suggests that heat loss by abundant and widely distributed plains volcanism may be more significant than previously recognized. The low density of impact craters greater than 15 km in diameter in this region compared to the average density for the higher northern latitudes suggests that the plains have a younger age.

Campbell, Donald B.↗

Composition of Syrtis Major volcanic plateau

Syrtis Major, a low-relief volcanic shield centered near 295 degrees 10 degrees N, is an old, well-preserved and exposed volcanic region on Mars which formed at the end of the heavy bombardment period. The composition of these volcanic materials has importance for understanding the thermal and chemical history of Mars. Imaging spectrometer data of the Syrtis Major volcanic plateau are used in this analysis to identify major compositional components. First and second order even channel reflectance spectra between 0.77 and 2.55 microns from four broad classes of materials on Syrtis Major are given. For the volcanic materials, there are three primary classes characterized by albedo, slope, and shape of the 10 micron band. To emphasize the latter, straight line continua were removed from each spectral segment and replotted in another figure. Each spectrum shows a band minima near 0.96 microns and 2.15 microns indicative of pyroxene mineral absorptions. Comparison of these band minima with studies of pyroxene reflectance spectra suggests that the pyroxenes in the volcanics of Syrtis Major are high calcium pyroxene with a Ca/(Mg+Fe+Ca) ratio of 0.2 to 0.3. The most likely pyroxene is an augite.

Mustard, John F.↗