Implicit in the goals of eruption forecasting is the assumption that improved forecasts will help to mitigate the immediate impacts of volcanic eruptions see Chapter 3. Volcanoes affect a host of Earth systems and vice versa. Thus, two central questions about the spatial and temporal impacts of large volcanic eruptions are 1 How do landscapes, the hydrosphere, and the atmosphere respond to volcanic eruptions? The products of volcanic eruptions change landscapes and introduce particles and gases into the atmosphere and oceans.
However, the impacts of larger eruptions, such as the last super-eruption 26, years ago Oruanui, New Zealand , are less well understood. Important unanswered questions are whether the impacts of very large eruptions can be anticipated by scaling up the impacts of smaller eruptions e. That is, will very large eruptions have unanticipated consequences for the environment and hence for human populations? Volcanic eruptions can profoundly change the landscape, initially through both destructive flank failure and caldera formation and constructive lava flows, domes, and pyroclastic deposits processes, which destroy vegetation and change the physical nature of the surface e.
After explosive activity ends, secondary hazards may continue to affect local and global environments for months, years, or decades. These hazards include explosions within pyroclastic flows that occur within a few months of pyroclastic density current emplacement Torres et al. Volcanic dust, in particular, is easily remobilized from the surface of pyroclastic deposits, as illustrated by frequent dust storms downwind of historically active volcanic regions e.
Studies on the adverse effects of remobilized ash on ecosystems are few, but are increasingly recognized as an important component of ecosystem response and recovery.
- Undersea Volcanoes Erupt with Gravity, Shifting Earth's Climate.
- Volcano eruptions have deep origins - BBC News.
- Jahrgang Crochet Patterns für Hüte (German Edition).
On even longer time scales, the landscape continues to respond by erosion and redeposition of loose surface material, rearrangement of drainage systems, regrowth of often different vegetation, and reintroduction of fauna. There are no comprehensive studies of the nature and time scales of landscape and ecosystem response, although detailed studies have traced recovery after individual volcanic eruptions e.
The effects of eruptions on Earth surface processes are easy to observe and thus are fairly well quantified. Less apparent are the effects of reawakening magmatic systems on subsurface processes, particularly hydrothermal systems important for generation of energy and, over longer time spans, formation of ore deposits. Observable interactions of magmatic and groundwater systems include geophysical and geochemical signals that can be difficult to distinguish from signals of magmatic unrest. Although volcanic eruptions are commonly preceded and followed by phreatic eruptions from hydrothermal systems e.
Similarly, magmatic CO 2 leaked slowly into volcanic lakes can suddenly destabilize and release lethal dense gas plumes e. Beneath the surface, magmatic—geothermal systems can generate geothermal energy and create ore deposits. It had generally been assumed that voluminous explosive volcanism is incompatible with porphyry formation. Active magmatic systems, however, are able to provide the requisite metal-bearing brines e. This newly emerging understanding posits an active role for magmatism, and raises new questions about the timing of magmatism and ore formation.
Although CO 2 emitted from erupting and passively degassing volcanoes is the major pathway for mantle-derived CO 2 to enter the atmosphere Kelemen and Manning, , it is a minor component of the global mass of atmospheric CO 2 Burton et al. For this reason, CO 2 release from all but the very largest eruptions is unlikely to change climate significantly Self et al.
Emissions of SO 2 from human activities and volcanoes, including diffuse emissions from nonerupting volcanoes, are shown in Figure 4. Volcano location plays an important role, with tropical eruptions being more capable of producing global impacts because seasonal variations in the Intertropical Convergence Zone facilitate transfer of aerosols between hemispheres e.
Less well understood are the impacts of major volcanic injections of halogen gases Cl, Br into the stratosphere, which could cause significant ozone depletion and generate localized ozone holes e. The best documented global climate impact of large explosive eruptions is cooling, typically followed by winter warming of Northern Hemisphere continents, as illustrated by the eruption of Pinatubo McCormick et al.
The negative radiative forcing caused largely by stratospheric sulfate aerosols resulted in a global tropospheric cooling of 0. This temperature decrease is similar to those estimated for other sulfur-rich eruptions, such as Krakatau and Tambora in Indonesia and El Chichon in Mexico. Such temperature anomalies are short lived, so that by the tem-. The relationship between cooling and large explosive eruptions is complex and includes not only the effect of SO 2 gas but also the effects of other emitted material particularly H 2 O, halogens, and ash , as well as the details of atmospheric chemistry that control the production and size of volcanic aerosols e.
For example, SO 2 is a greenhouse gas that could counteract the cooling effect of sulfate aerosols Schmidt et al. Thus, the balance between SO 2 and aerosols in different parts of the atmosphere is complicated, as is the resulting climate response. Large explosive eruptions can also affect global circulation patterns such as the North Atlantic Oscillation and ENSO Robock, , although the mechanism s by which this happens are not well understood LeGrande et al.
Finally, eruptions have been linked to substantial but temporary decreases. Documentation of the atmospheric impact of recent explosive eruptions provides important constraints for testing short-term climate model predictions and for exploring the effects of proposed geoengineering solutions to global warming e. Large effusive eruptions have a somewhat different effect on the atmosphere because of their long durations e. Basaltic eruptions, in particular, can be both voluminous and long lived, and can therefore affect local, regional, and possibly global climate.
The former had a regional Northern Hemisphere impact in the form of dry fogs of sulfuric acid H 2 SO 4 , while the latter produced dangerously high local levels of SO 2. The difference reflects not only the larger volume of the Laki eruption, but also the season summer versus winter because sunlight plays an important role in the oxidation of SO 2 to H 2 SO 4 Gislason et al.
In the extreme, the large volume and long duration of ancient flood basalts may have perturbed the atmosphere over time scales of decades to centuries to even millennia Figure 4. The effects of injecting large amounts of water by volcanic eruptions into the dry stratosphere could affect climate by accelerating the formation of sulfate aerosol by OH radicals or by decreasing the ozone formation potential of the system Glaze et al.
These examples emphasize the need to better characterize plume gas and aerosol chemistry as well as coupling of gas-phase chemistry with aerosol microphysics in climate models. Because satellite-based remote sensing observations of volcanic gases are heavily biased toward SO 2 e.
Volcanic ash may be a key source of nutrients such as iron and thus capable of stimulating biogeochemical responses Duggen et al. During the week following the VEI 4 eruption of Anatahan, Northern Mariana Islands, for example, satellite-based remote sensing detected a 2—5-fold increase in biological productivity in the ocean area affected by the volcanic ash plume Lin et al. These impacts can be particularly pronounced in low-nutrient regions of the oceans. A more indirect and longer-term impact of very large volcanic eruptions is caused by the rapid addition of CO 2 and SO 2 to the atmosphere, which affects seawater pH and carbonate saturation.
Carbon-cycle model calculations Berner and Beerling, have shown that CO 2 and SO 2 degassed from the million-year-old basalt eruptions of the Central Atlantic Magmatic Province could have affected the surface ocean for 20,—40, years if total degassing took place in less than 50,—, years.
Ocean acidification from the increased atmospheric CO 2 may have caused near-total collapse of coral reefs Rampino and Self, Rapid injection of large amounts of CO 2 into the atmosphere by volcanic eruptions also provides the best analog for studying the long-term effects of 20th-century CO 2 increases on ocean chemistry. Into these depths, Tolstoy, a marine geophysicist with the Lamont-Doherty Earth Observatory of Columbia University, dropped 12 seismographs. They would help her track volcanism at the seabed.
Her quest was driven by an attempt to measure the contribution such underwater volcanoes make to the global climate over thousands of years. They spew lava, carbon dioxide and other elements into the deep oceans. The carbon gets trapped in circulating water, cycled to different regions of the ocean, where it gets caught up in upwelling currents and emitted to the atmosphere. The process can take up to 2, years and adds a fraction of the 88 million metric tons of carbon belched out by the volcanoes to the atmosphere.
Tolstoy wanted to figure out how often these volcanoes erupt and what causes their eruption. In it, she finds that the Earth's volcanism is tied to minute shifts in motion of the Earth around the sun, as well as to sea levels, in a chain of events that scientists have never before envisioned. The cusp of Tolstoy's work depended on real-time monitoring of underwater volcanoes that lie along the 37, miles of ocean ridges on this planet. She had data from 10 volcanoes, from the East Pacific as well as historical information collected from a few other ridges.
Filtered and unfiltered fluids were sampled at the vent after finding a steady temperature on the intake probe and pumping fluid at a known rate using the hydrothermal fluid and particle sampler HFPS. Temperature and volume of fluid collected were monitored throughout the 10—min sampling time required to obtain approximately 1 l of fluid. Chemical analyses, such as sulfide, magnesium, and silica, as well as epifluorescent counts and culturing were performed on unfiltered and filtered fluid samples. Because the HFPS records temperature throughout the sampling procedure, the average temperature of the water collected can be calculated and compared with the average temperature of the water passed through the filters used for DNA analysis.
It is sometimes difficult to achieve a steady temperature during diffuse fluid sampling due to extreme micro-gradients in temperature and fluid flow, and repositioning the intake probe by 1 cm or less can result in significant changes in sampled fluid temperature. Whenever possible, we collected multiple fluid and particle samples without changing position. An ml aliquot of each fluid sample was preserved in formaldehyde 3. A background no detectable hydrothermal plume seawater sample from m depth and approximately m SE of the active vent site was collected using a l Niskin bottle mounted on a CTD conductivity, temperature, depth and filtered through a sterile mm 0.
Analytical methods are described in Butterfield et al. On shore, fluids were analyzed for major, minor, and trace elements. DNA was extracted exactly as described by Huber et al. A total of — white colonies for each library were selected and stored on agar plates. After sequencing 20 randomly chosen clones from each library, restriction fragment length polymorphism RFLP was then used to insure we had sequenced a representative community from each library. Different banding patterns were noted. Clones with unique RFLP patterns as well as the randomly selected clones were used in sequencing.
The PCR conditions were as follows: Sequences found to be non-chimeric were submitted for alignment to the RDP Sequence Alignment program, with common gaps conserved, and manually manipulated in the BioEdit v4. To find closely related sequences for phylogenetic analysis, sequences were submitted to the Advanced BLAST search program available through the National Center for Biotechnology Information.
Approximately nucleotide bases were used in phylogenetic analyses, with only homologous positions included in the comparisons. Negative branch lengths were prohibited. For each sample, 50 randomizations were performed; for ACE, S rare was set at 4 [ 31 ]. The GenBank nucleotide sequence accession numbers for the sequences determined in this study are as follows: Marker 33 is located on an eruptive fissure and is a long crack in basaltic sheet flows with a width of 30 cm and a length of several meters.
Some chemical characteristics of Marker 33 are shown in Fig. For a more detailed analysis and interpretation of the vent fluid geochemistry, as well as microscopic counts and culturing results, refer to Huber et al.enter site
Undersea Volcanoes Erupt with Gravity, Shifting Earth's Climate - Scientific American
Briefly, the ratio of hydrogen sulfide to other hydrothermal components decreased, while the end-member chloride concentration [ 1 , 21 , 33 ] increased, which is consistent with a decreasing vapor component over time in the hot source fluids [ 1 , 21 , 33 ]. Also important to consider is the degree of mixing between the end-member source fluid and crustal seawater that occurs below the point of venting, which is indicated by the temperature and simple chemical properties.
Six bacterial 16S rRNA gene clone libraries were prepared from fractionated filtered vent fluids, as well as a bacterial clone library from m, representing background deep-sea water. A negative control of sterile frozen filters was extracted and showed no bacterial amplification products. The first bp were sequenced in both directions from clones, and three were found to be chimeric and eliminated from subsequent analysis. A summary of the phylogenetic data for the three sampling years, divided into particle-attached and free-living fractions, based on the 17 taxonomic groups found in this study, is shown in Fig.
A sub-set of clones representing diverse bacterial phyla is presented on one of four phylogenetic trees, shown in Fig. Bacterial clones from each library listed with phylogenetic group, closest match, and percent similarity. The number is the last two digits of the year of sampling.
Composition of the Marker 33 particle-attached and free-living bacterial clone libraries in , , and based on taxonomic groupings of 16S rRNA sequences. The background sample is shown as well.
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Clones from this study are indicated in bold large font and labeled with PA particle-attached , FL free-living , CTD background seawater , and the appropriate year 98, 99, or Accession numbers for GenBank are provided for clones not from this study. The scale bar represents the expected number of changes per nucleotide position.
The majority of the clones were most closely related to uncultivated marine bacterioplankton, including the SAR11 cluster from coastal California waters [ 53 ], the Sargasso Sea [ 54 ], an ammonia biofilter [ 55 ], and the North Sea unpublished. Additionally, a number of clones from this study were closely related to the cultured marine bacterium Sphingomonas spp.
Clones belonging to the CFB group were found only in the particle-attached Marker 33 samples for all three years, as well as in the deep-sea background sample 12 clones, Fig. These clones were related to uncultivated marine CFB from a deep-sea cold seep [ 40 ], a mesoeutrophic reservoir [ 59 ], coastal waters off North Carolina [ 41 ], and the Sargasso Sea [ 54 ].
Clones were related to cultivated strains of Nitrospira spp. Five Gram-positive clones were found in the particle-attached Marker 33 populations, in both and Fig. Four clones belonging to the candidate division ABY1 were found in the and particle-attached Marker 33 populations, as well as the free-living Marker 33 population Fig. Three of these clones were most closely related to ABY1 environmental clones from Crater Lake [ 65 ], and the remaining clone to uncultivated bacteria from deep-sea sediments [ 45 ].
Volcano eruptions have deep origins
A single clone PAB98 belonging to the Thermodesulfobacterium was found in the particle-attached Marker 33 sample, and it was most closely related to an environmental clone from a hot spring sulfur mat in Iceland [ 67 ]. In the particle-attached Marker 33 sample, a single clone PA42B99 was found that fell into the Desulfurobacterium group and was most closely related to a clone from the in situ growth chamber in warm hydrothermal fluid [ 18 ].
Both groups are shown in Fig.
Among the seven bacterial clone libraries, representation of the taxonomic groups and phylotypes differed greatly. In each year, compared to the free-living Marker 33 populations, the particle-attached clone library from the same year always showed more species observed and a higher Shannon—Wiener index, ACE, and Chao1 estimator Table 3. Additionally, the particle-attached populations for all three years had greater diversity of taxonomic groups than the free-living populations Fig.
To compare the Marker 33 samples to the background sample, unique phylotypes in the particle-attached and free-living libraries for each year were consolidated to represent both fractions in one population, as they were in the background deep-sea sample. Based on species observed, the vent samples had more phylotypes than background seawater for all three years Table 3. Vent samples also had more taxonomic groups than the background sample.
The Shannon—Wiener index, though, is higher for the background sample compared to and ; the Marker 33 sample has the highest biodiversity index, with a value of 3. ACE estimates show the background sample having the lowest richness; Chao1 estimates a similar value for and the background sample, with and having higher values.
The Shannon—Wiener index, species observed, ACE and Chao1 estimators all increase over time at Marker 33 from to for the consolidated populations Table 3. Rarefaction analysis data not shown showed the same result. This study is part of an ongoing research program to describe the microbial diversity in the subseafloor at an active vent site Marker 33, Axial Seamount with the goals to identify microbial groups that are unique to these environments, gain an understanding of their physiology, and to determine if there is a correlation between species diversity and geochemical and physical characteristics of different subseafloor environments.
We have already reported on the archaeal diversity at Marker 33, which showed the indigenous subseafloor archaeal community consisted of clones related to both mesophilic and hyperthermophilic Methanococcales, as well as many uncultured Euryarchaeota [ 17 ].
It was also shown that the particle-attached fraction showed greater archaeal diversity than the free-living fraction indicating that the ability to attach to mineral surfaces and form biofilms may be a hallmark characteristic of subseafloor microbes. Most probable number MPN technique for estimating the number of viable organisms showed that Marker 33, like other subseafloor samples from new eruption sites, supports a hyperthermophilic community, despite a large seawater intrusion into these environments as indicated by the abundance of clones belonging to the putative seawater Marine Groups I and II archaea.
In this report we show a high diversity of bacteria in Marker 33 vent fluid samples analyzed in parallel for archaeal diversity. More than phylotypes from 17 different groups were identified over the sampling period. Like the results from the archaeal study, we found greater bacterial diversity associated with particles than in the free-living fraction and evidence for the presence of anaerobes and aerobes, and different thermal groups of bacteria.
This increase in diversity follows changes in the geochemical properties of the vent environment that is reflected mostly by the extent of seawater mixing with hydrothermal fluids and resulting temperature changes. These conditions could lead to an increase in habitat area for organisms having an oxidative metabolism that could also then lead to an increase in species diversity. Moreover, seawater microorganisms can serve as indicators of mixing to track this trend as well.
For example, in the Marine Group I archaea, a likely deep-sea water group, there were eight unique phylotypes detected in at Marker 33, only three in , and 10 in [ 17 ]. At Marker 33, variations in geochemical characteristics of the subsurface habitat due to dilution of seawater with hydrothermal fluid have the greatest influence on microbial community diversity. These include short-term small-scale variations, such as the amount of mixing with crustal seawater that occurs in the shallow subseafloor, as well as long-term larger-scale changes, including changes in the end-member hydrothermal fluid over time following the eruption [ 17 ].
Previous studies of animal diversity at hydrothermal vents show increasing diversity with increasing habitat area, heterogeneity, and age, as well as increasing diversity correlated with a disturbance until a plateau is reached [ 68 ].