Helens Eruption Research Articles

Mapping the tephra fallout risk: an example from Vesuvius, Italy

THE goal of evaluating the risks related to the reactivation of a quiescent volcano requires the reconstructions of the eruptive history of the volcano, the construction therefrom of a behavioural model of the volcano so as to define the 'maximum expected event9 and the subsequent quantitative models allowing reliable simulation of such an event to be set up and hazard and risk maps to be developed. We have followed this approach to infer the size and character of the explosive eruption of Vesuvius to be expected after a 45-year rest period1,2, and we used a numerical model, tested on the recent Mount St Helens eruption and the Vesuvius eruption in AD 79 3,4, to simulate tephra transport and fallout. By combining the fallout model with a statistical analysis of the wind regime and with the density of urban settlement, we were able to assess quantitatively the tephra fallout risk.

Effects of tephra addition on soil processes in Spodosols in the Cascade Range, Washington, U.S.A.

A study was conducted in the Cascade Range of Washington State, U.S.A., to examine the effects of tephra additions on soil processes occurring in Spodosols. Unleached tephra from the 18 May 1980 Mt. St. Helens eruption was applied in 5 or 15 cm depths to soils that had escaped airfall tephra deposition in 1980 but had received periodic additions of tephra during the Holocene. Soil solutions were collected from the major genetic horizons of tephra-treated and non-treated profiles. Interpretation of soil solution composition provided an instantaneous record of the response of soil processes to the added tephra. Soluble salts, composed of basic cations (Ca 2+ = Na + > Mg 2+ > K +) and SO 4 2−, were initially leached from the tephra. Basic cations in the leachate displaced H + and Al 3+ from the exchange sites in the original upper horizons. The soluble salts and Al 3+ migrated through the soil profile where their concentrations were greatly attenuated by interaction with the solid phase. Calcium, K +, Al 3+ and SO 4 2− were strongly retained in the B horizons whereas Na +, Mg 2+ and Cl − showed little affinity for the solid phase. Biological uptake, anion adsorption, exchange reactions and neoformation of minerals may all be responsible for the differential movement of solutes through the soil profile. No enhancement of elemental leaching was measured from the C horizon during the first four months of monitoring. Podzolization, the prevailing process in these mountains, was relatively unaffected by the addition of tephra.

Network Television News Coverage of Environmental Risks

Despite the criticisms that surround television coverage of environmental risk, there have been relatively few attempts to measure what and whom television shows. Most research has focused analysis on a few weeks of coverage of major stories like the gas leak at Bhopal, the Three Mile Island nuclear accident, or the Mount St. Helen's eruption. To advance the research into television coverage of environmental risk, an analysis has been made of all environmental risk coverage by the network nightly news broadcasts for a period of more than two years. Researchers have analyzed all environmental risk coverage-564 stories in 26 months-presented on ABC, CBS, and NBC's evening news broadcasts from January 1984 through February 1986. The quantitative information from the 564 stories was balanced by a more qualitative analysis of the television coverage of two case studies-the dioxin contamination in Times Beach, Missouri, and the suspected methyl isocyanate emissions from the Union Carbide plant in Institute, West Virginia. Both qualitative and quantitative data contributed to the analysis of the role played by experts and environmental advocacy sources in coverage of environmental risk and to the suggestions for increasing that role.

A numerical model for simulation of tephra transport and deposition: Applications to May 18, 1980, Mount St. Helens eruption

A numerical model for the computation of tephra fall accumulation resulting from Plinian or sub‐Plinian eruptions is presented. Mass accumulation at the ground level is found by solving a continuity equation which describes the transport of tephra in the atmosphere. The treatment incorporates horizontal advection due to wind, vertical gravitational settling, and dispersion due to atmospheric turbulence. Aspects of the parameters which enter the model, such as settling velocity, diffusion coefficients, deposition velocity, and source shape, are considered and discussed. Particular attention is devoted to settling velocity dependence on particle size and density, to deposition velocity behavior in weak and strong wind fields, and to eddy diffusion coefficient dependence on atmospheric conditions, particle size, and density. The results for some theoretical cases are presented to illustrate the behavior of the model. The validity of the model is tested by comparing observed and calculated deposits for the May 1980 Mount St. Helens eruption. The model predicts a double thickness maximum, the first near the volcano, the second at a distance of about 300 km, as was observed in the actual deposit.

Using Microcomputer Game-Simulation Experiments to Study Family Response to the Mt. St. Helens Eruptions

Computerized game-simulation experiments were conducted as part of a larger study of response to the 1980 eruptions of Mt. St. Helens. Sixty 3-person families from three Washington state communities (experimental group) and 10 families from Minnesota (control group) were studied. Results of the game-simulation indicate that different aspects of individual preferences and family decisions with respect to relocation were (1) highly consistent in the game-simulation, (2) responsive to the simulated threat, and (3) compatible with response data from studies of other actual natural hazards. Family behavior in the game-simulation was strongly related to actual family behavior when the volcano erupted as reported by wives but weakly related to the family behavior as reported by husbands and teenagers. If the wives' reports of family responses to the actual threat of the volcano are more accurate than the husbands' or teenagers', then the data suggest close agreement between the game-simulation behaviors and how the same families responded to the real hazard. The control families showed behavior predictably different from that of the experimental sample in response to the game-simulation. Thus, to the extent that game-simulation experiments tap actual participant experiences, they generate realistic or externally valid responses. Keywords: game-simulation, experiment, decision making, family, disasters, computer.

Air pressure waves from Mount St. Helens eruptions

Weather station barograph records as well as infrasonic recordings of the pressure wave from the Mount St. Helens eruption of May 18, 1980, have been used to estimate an equivalent explosion airblast yield for this event. Pressure amplitude versus distance patterns in various directions compared with patterns from other large explosions, such as atmospheric nuclear tests, the Krakatoa eruption, and the Tunguska comet impact, indicate that the wave came from an explosion equivalent of a few megatons of TNT. The extent of tree blowdown is considerably greater than could be expected from such an explosion, and the observed forest damage is attributed to outflow of volcanic material. The pressure‐time signature obtained at Toledo, Washington, showed a long, 13‐min duration negative phase as well as a second, hour‐long compression phase, both probably caused by ejecta dynamics rather than standard explosion wave phenomenology. The peculiar audibility pattern, with the blast being heard only at ranges beyond about 100 km, is explicable by finite amplitude propagation effects. Near the source, compression was slow, taking more than a second but probably less than 5 s, so that it went unnoticed by human ears and susceptible buildings were not damaged. There was no damage at Toledo (54 km), where the recorded amplitude would have broken windows with a fast compression. An explanation is that wave emissions at high elevation angles traveled to the upper stratosphere, where low ambient air pressures caused this energetic pressure oscillation to form a shock wave with rapid, nearly instantaneous compression. Atmospheric refraction then returned part of this wave to ground level at long ranges, where the fast compressions were clearly audible.

Geothermal exploration of Roccamonfina volcano, Italy

The Quaternary volcano of Roccamonfina, located within the Roman high-potassic province, developed in the time interval 1.5-0.25 Ma, initially as a stratocone which later was partially destroyed by phreatomagmatic explosions. The last evolutionary stage is represented by intra-crater latite domes and trachybasalt flows ( ca. 15 Ma). Geophysical data, primarily from gravity and MT/EM surveys, demonstrate that the volcano formed at a complex structural intersection above a NE-trending Pliocene graben. The same data, confirmed by the result of an 887 m test well, indicate that the volcano has not undergone caldera subsidence of the type exemplified by the Valles Caldera of New Mexico, but more probably had a series of post-stratocone lateral blasts akin to the 1980 Mount St. Helens eruptions. Hot springs near the western foot of the volcano, and the presence of young highly-evolved rocks suggested that the area could have geothermal potential. However, geochemical and isotopic data provide no indication of the present existence of a hydrothermal system, whilst the lack of alteration (both at the surface and in the test well) suggest that no such system existed in the past. Geophysical data show no anomalous features which might be associated with a geothermal reservoir or with hydrothermal alteration. These negative conclusions, strongly supported by the low temperature of the test well (35°C at 886 m), demonstrate fairly conclusively that Roccamonfina is non-prospective for high-enthalpy geothermal resources.

Book reviews : Saarinen, T.F. and Sell, J.L. 1985: Warning and response to the Mount St Helens eruption. Albany: State University of New York Press. 240 pp. US$36.50 cloth, US$12.95 paper

Book reviews : Saarinen, T.F. and Sell, J.L. 1985: Warning and response to the Mount St Helens eruption. Albany: State University of New York Press. 240 pp. US$36.50 cloth, US$12.95 paper

The development of a multidisciplinary plan for evaluation of the long-term health effects of the Mount St. Helens eruptions.

The emphasis of this article is on the approach that was taken to evaluating the chronic or delayed effects of the volcanic eruptions of Mount St. Helens in 1980. This strategy has been very successful and may be useful as a model for addressing the possible health effects of other environmental hazards. The steps in this process were: 1) identification of the physical and physicochemical characteristics of the hazard; 2) formation of hypotheses about biologically plausible effects of the hazard on human health; and 3) development of a plan for evaluating the health effects and, were possible, for controlling or minimizing adverse health effects. The third step involved a multidisciplinary group that included public health officials, medical specialists, and research scientists, including a geologist.

Immediate public health concerns and actions in volcanic eruptions: lessons from the Mount St. Helens eruptions, May 18-October 18, 1980.

A comprehensive epidemiological evaluation of mortality and short-term morbidity associated with explosive volcanic activity was carried out by the Centers for Disease Control in collaboration with affected state and local health departments, clinicians, and private institutions. Following the May 18, 1980 eruption of Mount St. Helens, a series of public health actions were rapidly instituted to develop accurate information about volcanic hazards and to recommend methods for prevention or control of adverse effects on safety and health. These public health actions included: establishing a system of active surveillance of cause-specific emergency room (ER) visits and hospital admissions in affected and unaffected communities for comparison; assessing the causes of death and factors associated with survival or death among persons located near the crater; analyzing the mineralogy and toxicology of sedimented ash and the airborne concentration of resuspended dusts; investigating reported excesses of ash-related adverse respiratory effects by epidemiological methods such as cross-sectional and case-control studies; and controlling rumors and disseminating accurate, timely information about volcanic hazards and recommended preventive or control measures by means of press briefings and health bulletins. Surveillance and observational studies indicated that: excess in morbidity were limited to transient increases in ER visits and hospital admissions for traumatic injuries and respiratory problems (but not for communicable disease or mental health problems) which were associated in time, place, and person with exposures to volcanic ash; excessive mortality due to suffocation (76 per cent), thermal injuries (12 per cent), or trauma (12 per cent) by ash and other volcanic hazards was directly proportional to the degree of environmental damage--that is, it was more pronounced among those persons (48/65, or about 74 per cent) who, at the time of the eruption, were residing, camping, or sightseeing (despite restrictions) or working (with permission) closer to the crater in areas affected by the explosive blast, pyroclastic and mud flows, and heavy ashfall; and de novo appearance of ash-related asthma was not observed, but transient excesses in adverse respiratory effects occurred in two high-risk groups--hypersusceptibles (with preexisting asthma or chronic bronchitis) and heavily exposed workers. Laboratory and field studies indicated that: volcanic ash had mild to moderate fibrogenic potential, consisting of greater than 90 per cent (by count) respirable size particles which contained 4-7 per cent (by weight) crystalline free silica (SiO2).(ABSTRACT TRUNCATED AT 400 WORDS)

The dimensions and dynamics of volcanic eruption columns

Eruption columns can be divided into three regimes of physical behaviour. The basal gas thrust region is characterized by large velocities and decelerations and is dominated by momentum. This region is typically a few hundred metres in height and passes upwards into a much higher convective region where buoyancy is dominant. The top of the convective region is defined by the level of neutral density (heightHB) where the column has a bulk density equal to the surrounding atmosphere. Above this level the column continues to ascend to a heightHT due to its momentum. The column spreads horizontally and radially outwards between heightHT andHB to form an umbrella cloud. Numerical calculations are presented on the shape of eruption columns and on the relationships between the heightHB and the mass discharge rate of magma, magma temperature and atmospheric temperature gradients. Spreading rate of the column margins increases with height principally due to the decrease in the atmospheric pressure. The relationship between column height and mass discharge rate shows good agreement with observations. The temperature inversion above the tropopause is found to only have a small influence on column height and, eruptions with large discharge rates can inject material to substantially greater heights than the inversion level. Approximate calculations on the variation of convective velocities with height are consistent with field data and indicate that columns typically ascend at velocities from a few tens to over 200 m/s. In very large columns (greater than 30 km) the calculated convective velocities approach the speed of sound in air, suggesting that compressibility effects may become important in giant columns. Radial velocities in the umbrella region where the column is forced laterally into the atmosphere can be substantial and exceed 55 m/s in the case of the May 18th Mount St. Helens eruption. Calculations on motions in this region imply that it plays a major role in the transport of coarse pyroclastic fragments.

Warning and response to the mount St. Helen's eruption by Thomas F. Sarrinen and James L. Sell, State University of New York Press, 1985, No. of pages: 240 Price: $36.50 (hardback), $12.50 (soft covers)

Geological JournalVolume 21, Issue 1 p. 79-80 Book ReviewFree Access Warning and response to the mount St. Helen's eruption by Thomas F. Sarrinen and James L. Sell, State University of New York Press, 1985, No. of pages: 240 Price: $36.50 (hardback), $12.50 (soft covers) P. E. Baker, P. E. BakerSearch for more papers by this author P. E. Baker, P. E. BakerSearch for more papers by this author First published: January/March 1986 https://doi.org/10.1002/gj.3350210109AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume21, Issue1January/March 1986Pages 79-80 RelatedInformation

Warning and Response to the Mount St. Helen's Eruption

Warning and Response to the Mount St. Helen's Eruption

Mt. St. Helens volcanic ash: Effect of incorporated and unincorporated ash of two particle sizes on runoff and erosion

The effect of ash from the 1980 Mt. St. Helens eruption on runoff and rill erosion of cultivated land was studied in 1981 and 1982. Ash from the Pullman (fine particles) and Yakima, WA (coarse particles), areas was applied to a silt loam soil, and water was applied. Treatments were: bare soil (fine-silty, mixed, Mesic Pachic Ultic Haploxerolls); ash incorporated with soil; and unincorporated ash on the soil surface. Sediment concentration in runoff first increased with time to a maximum, then decreased to an approximate steady state. Sediment concentrations were higher for unincorporated ash as compared to ash incorporated with the underlying soil, and were even lower for bare soil. Sediment concentration was higher with Yakima ash as compared to Pullman ash or bare soil because of the less cohesive nature of Yakima ash. Rills became wide and shallow with Yakima ash, as compared to deeper and narrower rills for Pullman ash, because of the relatively more cohesive nature and finer particle size of Pullman ash. The finer Pullman ash caused formation of a surface seal, thus restricting the infiltration rate and producing a higher runoff rate than from rills with Yakima ash or bare soil.

The mechanism of the Mt. St. Helens eruption and speculations regarding Soret effects in planetary dynamics

Steady heat flux through a double diffusive layered convecting system demands each layer have the same Rayleigh number. If double diffusive convective layering occurs in a gaseous rotating proto-solar system nebula of uniform composition, this Rayleigh number criterion sets the distances from the centre of the nebula to each boundary layer of the convecting layers and these distances are given by the Titius-Bode law. In a layer of nebula convection, outgoing plumes will be retrograde, ingoing plumes prograde, such that where these plumes impinge on a boundary layer, vortices can be set up in the boundary layer with rotation along the same axis as the total cloud. Soret convection may serve to segregate the cloud isotopically, elementally and chemically.

BOOK REVIEWS

Book reviewed in this article:Earthquake Mitigation Policy: The Experience of Two StatesShelter After DisasterAppropriate Technology for Water Supply and Sanitation: Meeting the Needs of the Poor for Water Supply and Waste Disposal1. Survival Strategies For and By Camp Refugees2. Sustaining Afghan Refugees in Pakistan3. Afghan Refugees in Pakistan: From Emergency Towards Self RelianceInternational Humanitarian Assistance ‐ Disaster Relief Actions in International Law and OrganizationWarning and Response to the Mount St. Helen's Eruption

Source mechanism of the May 18, 1980, Mount St. Helens eruption from regional surface waves

A reference source equalization method using regional surface waves from the Mount St. Helens eruption of May 18, 1980, and the Elk Lake event of February 14, 1981, was used to determine the St. Helens eruption source time history. The time domain deconvolution signals display a complex series of pulses lasting 250 s. An initial pulse was isolated and was found to have a smoothly varying two‐lobed radiation pattern for both Love and Rayleigh waves, suggesting a near‐horizontal point force directed south consistent with previous results. The initial southward force corresponds to the acceleration of the landslide in a northern direction about 5–10 s after the triggering earthquake. Lateral forces were isolated 70–140 s later, consistent with the occurrence of the large lateral blast and the slide changing its direction down the Toutle River Valley. There also appears to be significant source activity between 140 and 250 s after the initial pulse. This later activity exhibits forces in the northwest‐southeast azimuth and may correspond to the final deceleration of the landslide. Several vertical pulses were located between 10–60 and 100–120 s after the eruption began. Much of the vertical force represents the two sets of explosions which occurred during the eruption.

Excitation mechanism of atmospheric pressure waves from the 1980 Mount St Helens eruption

A new type of photodiode + scintillator (1 m2 x 1 cm) detector is developed to detect the large electro-magnetic burst under an EX-chamber. The threshold burst size is found to be 4.3 x 10 the 5 particles at the center of the scintillator. Therefore a gamma-ray family of 10 TeV is detectable by it, when it is set under 14 r.1. of iron. In addition, a very fast (2.4 nsec width) and very bright (correspond to 10 to the 6 particles) scintillation pulse has become avarable for this study.

The May 18, 1980 eruption of Mount St. Helens: 2. Modeling of dynamics of the Plinian Phase

The Plinian phase of the May 18, 1980, Mount St. Helens eruption is modeled as a steady state discharge of dacitic magma from a reservoir at 7–10 km depth at a rate of 1.94×107 kg/s. Properties of the magma, including preeruption volatile content (4.6% in the melt), temperature (920°–940° C), and confining pressure (190–250 MPa) are constrained by petrologic studies. Mass eruption rate, magma viscosity, and independent estimates of magma ascent velocity suggest a 95‐m‐diameter conduit at a depth below vapor saturation. Dispersal of pyroclasts indicate a minimum exit velocity of roughly 200 m/s during the Plinian phase. An upper limit of 330 m/s is obtained from the total amount of exsolved volatiles. Model‐derived vent diameters based on 0.1‐MPa exit pressure, petrologically inferred magma properties, and known mass eruption rate range from 105 to 135 m with a flared configuration. The calculated vent diameter, mass eruption rate, and exit velocity define conditions close to the transition between convective column rise and column collapse. These results are consistent with the sporadic generation of pyroclastic flows during a period characterized mainly by a sustained eruption column.

SAGE satellite observations of stratospheric aerosols from Mount St. Helens eruption: A two‐wavelength analysis

The Angström coefficient profiles deduced from 93 SAGE Satellite observations in July 1980 between 50°N and 70°N have been used to study the variation of the aerosol size distribution in the Mount St. Helens aerosol layer. In most cases a layer of large particles corresponding to the maximum extinction at 18–20 km is topped by a layer of small particles. The study of profiles averaged over 10° latitude bands for May to November 1980 have confirmed the extent of this situation, which contrasts with a rather constant size distribution within the unperturbed stratosphere in 1979. Assuming an equivalent log‐normal size distribution with an effective variance of 0.250, the logarithmic mode radius is found around 0.20 μm for the large‐particle layer and around 0.06 μm for the top layer. The inferred mass density profile is strongly influenced by this structure.