Geyser Vent Research Articles

The Relation Between Decadal Droughts and Eruptions of Steamboat Geyser in Yellowstone National Park, USA

AbstractIn the past century, most eruptions of Steamboat Geyser in Yellowstone National Park's Norris Geyser Basin were mainly clustered in three episodes: 1961–1969, 1982–1984, and ongoing since 2018. These eruptive episodes resulted in extensive disturbance to surrounding trees. To characterize tree response over time as an indicator of geyser activity adjustments to climate variability, aerial and ground images were analyzed to document changes in tree coverage around the geyser since 1954. Radiocarbon dating of silicified tree remnants from within 14 m of the geyser vent was used to examine geyser response to possible variations in decadal to centennial precipitation patterns. We searched for atypical or absent growth rings in cores from live trees in years associated with large geyser eruptions. Photographs indicate that active eruptive phases have adversely affected trees up to 30 m from the vent, primarily in the dominant downwind direction. Radiocarbon dates indicate that the geyser formed before 1878, in contrast to the birthdate reported in historical documents. Further, the ages of the silicified trees cluster within three episodes that are temporally correlated with periods of relative drought in the Yellowstone region during the 15th–17th centuries. The discontinuous growth of trees around the geyser suggests that changes in eruptive patterns occur in response to decadal to multidecadal droughts. This inference is supported by the lack of silicified specimens with more than 20 annual rings and by the existence of atypical or missing rings in live trees during periods of extended geyser activity.

Imaging the Subsurface Plumbing Complex of Steamboat Geyser and Cistern Spring With Hydrothermal Tremor Migration Using Seismic Interferometry

AbstractSteamboat Geyser in Yellowstone National Park is the tallest active geyser on Earth and is believed to have hydrologic connection to Cistern Spring, a hydrothermal pool ∼100 m southwest from the geyser vent. Despite broad scientific interest, rare episodic Steamboat eruptions have made it difficult to study its eruption dynamics and underground plumbing architecture. In response to the recent reactivation of Steamboat, which has produced more than 130 eruptions since March 2018, we deployed a dense seismic nodal array surrounding the enigmatic geyser in the summer of 2019. The array recorded abundant 1–5 Hz hydrothermal tremor originating from phase‐transition events within both Steamboat Geyser and Cistern Spring. To constrain the spatiotemporal distribution of the tremor sources, an interferometric‐based polarization analysis was developed. The observed tremor locations indicate that the conduit beneath Steamboat is vertical and extends down to ∼120 m depth and the plumbing of Cistern includes a shallow vertical conduit connecting with a deep, large, and laterally offset reservoir ∼60 m southeast of the surface pool. No direct connection between Steamboat and Cistern plumbing structures is found. The temporal variation of tremor combined with in situ temperature and water depth measurements of Cistern reveals interaction between Steamboat and Cistern throughout the eruption/recharge cycles. The observed delayed responses of Cistern Spring in reaction to Steamboat eruptions and recharge suggest that the two plumbing structures may be connected through a fractured/porous medium instead of a direct open channel, consistent with our inferred plumbing structure.

Plume Source Localization on Enceladus by Sequential Monte Carlo Method

Water vapor plumes emanating from the geyser vents at Enceladus’s south pole area invite the possibility of direct access to the subsurface liquid reservoir to acquire pristine biological material if it exists. Any descending lander adapted for plume localization is required to not only explore the icy plume environment during its descent, but it must also infer the location of the landing target—the plume source—autonomously. Compared with existing scenarios of terrestrial plume source localization methods, the source likelihood map (SLIM) method for an Enceladus mission offers a more extensive search area, a higher maneuver velocity, and a shorter search time. This paper investigates a particle-based odor source localization (pOSL) approach that offers the prospect of targeting one of the plume sources by autonomously measuring the concentration field. Reasons for the negative likelihood and overfitting issues associated with Bayesian SLIM are analyzed to build a novel probabilistic model. By implementing this model, the proposed pOSL algorithm evaluates the observation likelihood via posterior maximization method and estimates the source location via the sequential Monte Carlo method. The pOSL algorithm resolves difficulties associated with other methods while reducing the time complexity from to . The numerical simulations illustrate that the proposed approach is feasible and permits accurate targeting of Enceladus’s geyser vents.

Targeting the geysers on Enceladus by viffing descent through the icy plumes

The ice plumes emanating from the geyser vents at Enceladus’ south pole offer an enticing route for direct access to acquire pristine astrobiological samples. Unlike traditional landing scenarios where the location of the landing target is known a priori, we propose that one or more penetrators explore the plume environment via lateral maneuvers during the descent to Enceladus’ surface to infer the location of promising landing sites by autonomously measuring the plume ice/vapour concentration at multiple locations within the plume. This offers the prospect of targeting the vent sources of the plumes for direct access to subsurface material prior to its ejection. We examine four types of “viffing” (vector-in-forward flight) descent profiles and the impulsive velocity increment (ΔV) required for the lateral maneuvers: (i) a ballistic descent trajectory with a minimal ΔV cost represents the reference trajectory that implements no lateral search maneuvers; (ii) a planar descent with a decaying lateral oscillation which has an intermediate ΔV cost and a small search area; (iii) a nested series of decreasing sized box trajectories offering intermediate ΔV costs of varying degrees depending on the specific parameters; and, (iv) a quasi-spiral trajectory of decreasing radius which imposes the highest ΔV cost but with the largest lateral search area. Computations and simulations determined that the proposed viffing maneuvers are feasible and permit accurate targeting of Enceladian geyser vents at modest cost in ΔV. We also briefly assessed the problem of mapping the Enceladian plume during the descent, which will ultimately be necessary for viffing.

Geometry of Geyser Plumbing Inferred From Ground Deformation

AbstractBroadband seismic data were recorded on the ground surface around an exceptionally regular eruptive system, geyser El Jefe, in the El Tatio geyser field, Chile. We identify two stages in the eruption, recharge and discharge, characterized by a radial expansion and contraction, respectively, of the surface around the geyser. We model the deformation with spherical sources that vary in size, location, and pressure, constrained by pressure observations inside the conduit that are highly correlated with deformation signals. We find that in order to fit the data, the subsurface pressure sources must be laterally offset from the geyser vent during the recharge phase and that they must migrate upward toward the vent during the eruption phase. This pattern is consistent with models in which ascending fluids accumulate and then are released from a bubble trap that is horizontally offset from the shallow conduit of the geyser.

The Miocene Atastra Creek sinter (Bodie Hills volcanic field, California and Nevada): 4D evolution of a geomorphically intact siliceous hot spring deposit

The Atastra Creek siliceous hot spring deposit, or sinter, occurs in the Paramount-Bald Peak alteration zone, due north of the Bodie precious metals mining district in the Miocene Bodie Hills volcanic field, California and Nevada, U.S.A. Distinctive features include its geomorphically intact geyser vent mounds, the presence of growth-fault-stepped sinter terraces that developed westward along a NNW trending fault, and atypical Hg, Sb and As concentrations. High-temperature (>75 °C), subaerial, proximal apron sinter occurs in two settings – (1) radiating botryoidal geyserite in vent mounds and (2) bedded geyserite (columnar, nodular, size-sorted geyser eggs) intercalated with mid- to low-temperature (<60 °C), middle to distal apron terrace sinter. The active geyser vent mounds migrated from south to north across the apron terrace through time. A newly recognized, visually striking type of sinter – termed silica infiltrate herein – formed directly beneath the subaerial geyserite deposits. It is characterized by mainly parallel, thin, irregular beds of white silica with narrow borders of dark blue-gray silica, as well as swirly to globular white silica, all chaotically linked together by silica ‘necks’ and ‘bridges’. The silica infiltrate permeates the pre-existing sinter, and is interpreted to represent super-heated fluid injections into the immediately overlying geyser vent mounds and pools. The adjacent sinter sheets preserve fluid-flow directions of warm-water channels that traversed the discharge apron, including microbial streamer fabric and wavy laminated sinter with flattened bubbles. More distal sinter textures are recorded by rimmed terracettes with mammillated and palisade microbial fabrics and rare, warm pool-related stromatolites. However, plants are absent, probably due to the high metalloids, in particular As. Post-depositional events include an inferred hydrothermal eruption breccia and an interpreted drop in the water table accompanied by incursion of steam acid condensate, as evidenced by pervasive hydrothermal alteration of the Atastra Creek deposits. Hence, the well-exposed sedimentary facies distributions, well-preserved geomorphology, and stratigraphic and structural relationships together allow an unusually complete, paleoenvironmental reconstruction of the Atastra Creek paleohydrothermal deposit.

Measuring pressure in the source region for geysers, Geyser Valley, Kamchatka

Liquid water and steam that erupt at geysers are provided from deeper reservoirs, whose location, geometry and pressure are in general poorly known. Here we report measurements at two geysers from a field experiment in Geyser Valley, Kamchatka, designed to measure pressure in the reservoir providing water to the geysers. Water level in the geyser conduit was controlled, and the recharge to the geyser conduit was measured by monitoring the discharge needed to maintain the controlled water level. Recharge is not constant, but depends on water level in the geyser. From the relationship between water level in the conduit and recharge to the conduit, we can estimate the hydraulic head in the reservoir that supplies water to the geyser. Hydraulic head in the two studied reservoirs is within a couple of meters of the elevation of the geyser vents and the adjacent rivers. Pressures in the reservoirs are low enough that the reservoirs should not be prone to hydrothermal explosions, and explain why flooding of geysers in Geyser Valley terminated their eruptions.

Locating hydrothermal acoustic sources at Old Faithful Geyser using Matched Field Processing

In 1992, a large and dense array of geophones was placed around the geyser vent of Old Faithful, in the Yellowstone National Park, to determine the origin of the seismic hydrothermal noise recorded at the surface of the geyser and to understand its dynamics. Old Faithful Geyser (OFG) is a small-scale hydrothermal system where a two-phase flow mixture erupts every 40 to 100 min in a high continuous vertical jet. Using Matched Field Processing (MFP) techniques on 10-min-long signal, we localize the source of the seismic pulses recorded at the surface of the geyser. Several MFP approaches are compared in this study, the frequency-incoherent and frequency-coherent approach, as well as the linear Bartlett processing and the non-linear Minimum Variance Distorsionless Response (MVDR) processing. The different MFP techniques used give the same source position with better focalization in the case of the MVDR processing. The retrieved source position corresponds to the geyser conduit at a depth of 12 m and the localization is in good agreement with in situ measurements made at Old Faithful in past studies.

Formation of multilayered photosynthetic biofilms in an alkaline thermal spring in Yellowstone National Park, Wyoming.

In this study, glass rods suspended at the air-water interface in the runoff channel of Fairy Geyser, Yellowstone National Park, WY, were used as a substratum to promote the development of biofilms that resembled multilayered mat communities in the splash zone at the geyser's source. This approach enabled the establishment of the temporal relationship between the appearance of Cyanobacteria, which ultimately formed the outer green layer, and the development of a red underlayer containing Roseiflexus-like Chloroflexi. This is the first study to define time-dependent successional events involved in the development of differently colored layers within microbial mats associated with many thermal features in Yellowstone National Park. Initial (1-month) biofilms were localized below the air-water interface (60 to 70 degrees C), and the majority of retrieved bacterial sequence types were similar to Synechococcus and Thermus isolates. Biofilms then shifted, becoming established at and above the air-water interface after 3 months. During winter sampling (6 to 8 months), distinct reddish orange microcolonies were observed, consistent with the appearance of Roseiflexus-like sequences and bacteriochlorophyll a pigment signatures. Additionally, populations of Cyanobacteria diversified to include both unicellular and filamentous cell and sequence types. Distinct green and red layers were observed at 13 months. Planctomycetes-like sequences were also retrieved in high abundance from final biofilm layers and winter samples. Finally, biomass associated with geyser vent water contained Roseiflexus-like sequence types, in addition to other high-abundance sequence types retrieved from biofilm samples, supporting the idea that geothermal water serves as an inoculum for these habitats.

Petrography and genesis of spicular and columnar geyserite from the Whakarewarewa and Orakeikorako geothermal areas, North Island, New Zealand

Domal masses of geyserite, which surround many geyser vents in the Whakarewarewa geothermal area, are formed largely of spicules, spicule columns, and shrub columns. The non-branching spicules and the branches of branching spicules, individually up to 3 cm high and 1 mm diameter, have a laminated core encased by siliceous cortex. Silicified microbes are rare in the core but common in the cortex. Silicified microbial mats and pseudodendrites are found in the crevices between neighbouring spicules. Shrub columns, up to 5 cm high and 1.5 cm in diameter, are formed of opal-A that was precipitated around a three-dimensional, branching, shrub-like microbial (?) structure. The shrub branches, which are hollow with scalloped walls, do not contain any evidence of the original microbes or minerals that formed them. Silicified microbial mats are present between the columns. Microbial boring and etching by acidic steam led to local diagenetic degradation of these columns. In the geyserite mounds at Whakarewarewa, spicules and spicule columns are common, whereas shrub columns are rare. Interbedding and intercalation of spicular geyserite with shrub columnar geyserite indicate, however, that these different morphologic entities probably formed under similar environmental conditions on the mounds around the geyser vents. Petrographic evidence shows that the spicules, spicule columns, and shrub columns grew through a combination of biotic and abiotic processes.

Silicified Microbes in a Geyser Mound: The Enigma of Low-Temperature Cyanobacteria in a High-Temperature Setting

A geyser mound, which has formed around the vent of an abandoned well-bore in the Tokaanu geothermal area (North Island, New Zealand) over the last 50 years, is formed primarily of white opal-A along with lesser amounts of black opal-A, reticulate, amorphous or poorly crystalline clay, halite, and scattered detrital quartz grains. Despite the boiling water ejected from the vent, at least 19 taxa of silicified microbes are present in the geyserite. Calothrix , Phormidium , and Synechococcus dominate. Other microbes, including local concentrations of diatoms, are widely scattered. The dominance of cyanobacteria is enigmatic given that these microbes typically are found in cooler water environments (< 60°C) on the medial to distal parts of geyser and hot-spring discharge aprons. The proximal zone around a geyser vent is environmentally unstable because it oscillates between periodic eruptions of boiling water and cooler phases in accord with the eruptive cycle of the geyser. Thus, the environmental niches on a geyser mound are temporally and spatially variable. The periodicity, duration, and magnitude of the eruptions, and the dispersal patterns of boiling water during eruptions control the distribution of the microenvironmental niches and their temporal changes. Dispersal and cooling of the ejected water will, for example, be controlled by factors such as height of the erupted water, ambient air temperature, and prevailing wind direction. Biotas compatible with relatively cool waters may thrive on geyser mounds because they inhabit areas that are not inundated constantly by boiling water. Their development and the sinter fabrics that they generate in the proximal zone of a geyser vent means that ancient deposits must be interpreted with caution.

Thermodynamics of Geysers: Application to Titan

General constraints on geyser phenomena are developed and applied to speculative methane geysers on Titan. Variation of boiling point with depth of ethane–methane–nitrogen fluids is found to be of order 0.3 K m −1, in contrast with around 2 K m −1 for water on Earth. It is found that geysers are possible on Titan but require enhancements of ∼100 above global-average geothermal heat flux, a factor similar to that required on Earth. Eruption velocities of order 25 m s −1 appear to be typical for 10-m-deep geyser vents on both Earth and Titan. While eruption velocities on Earth are usually limited by the low sound speed in water–steam mixtures, sound speeds in Titan fluids are higher and the Titan limit is imposed by the available energy in the boiling fluid. Eruption intervals should be nearly the same for geysers with equivalent plumbing. There is an interesting symmetry between geysers on Titan and those on Earth: The volatility of the relevant fluid scales with the available heat flow.

Relationship between Spring and Geyser Activity and the Deposition and Morphology of High Temperature (&gt; 73 C) Siliceous Sinter, Yellowstone National Park, Wyoming, U.S.A.

ABSTRACT Six classes of alkaline hot springs and geysers are here distinguished in Yellowstone National Park based on activity and eruptive style: (1) non-surging, non-boiling springs, (2) gently surging, non-boiling springs, (3) non-surging to gently surging, boiling springs; (4) strongly surging springs, (5) fountain geysers, and (6) cone geysers. Each displays morphologically distinctive siliceous sinter deposits in the high-temperature (> 73°C) parts of the vent and outflow systems. Non-surging and gently surging, non-boiling springs that do not overflow their rims develop thin digitate to lilypad-like sinter rims that grow horizontally over the pool surfaces. Similar springs with rim overflow have rims that accrete vertically. Boiling springs often have nearly circular, steep-sided pools and rims dominated by splash and rim-overflow and composed mainly of spicular and columnar sinter. Fountain geysers, characterized by broad fountain-like eruption bursts, have a central vent surrounded by a zone of spicular sinter beyond which is a broad, flat-bottomed moat, but lack steep sinter cones. Cone geysers have narrow vents, jet-like discharges that cool rapidly and fall close to the vent, and steep-sided spicule-dominated sinter cones. Sinter deposition takes place within three main zones: (1) fully subaqueous sides and bottoms of vent pools, outflow basins, and outflow channels; (2) periodically wetted splash zones surrounding hot springs and geysers; and (3) largely subaerial parts of the rim and outflow areas wetted mainly by overflow and surging and that dry quickly. Fully subaqueous surfaces are covered by fine earthy particulate siliceous sediment (PSS) composed largely of amorphous silica spherules and spherule aggregates that appear to have precipitated around heterogeneous nuclei, including microbes. Splash zones of hot springs and geysers are characterized by spicular sinter. Largely subaerial zones, wetted mainly by rim overflow and surging with little or no splash, show complex varieties of terraced, columnar, and knobby sinter. The highest silica deposition rates occur where surfaces are wetted frequently and evaporate to dryness, such as the tops of spicules, columns, and knobs. Associated lower areas and crevices that remain wet or moist show slow accumulation of PSS. Most continuously wet surfaces in high-temperature (> 73°C) hot spring and geyser vent and outflow systems are probably covered by microbial biofilms. Although microbes may locally influence rates of silica deposition and sinter microstructure, the results of this study suggest that the depositional sites, morphology, and macrostructuring of high-temperature sinter are controlled largely by the processes of surface wetting, evaporation, and drying.

Microbial Construction of Siliceous Stalactites at Geysers and Hot Springs: Examples from the Whakarewarewa Geothermal Area, North Island, New Zealand

Abstract Siliceous stalactites, formed of opal-A laminae that are concentrically arranged around a hollow soda-straw, are common features structures in some of the geyser and hot spring deposits at Whakarewarewa and other geothermal areas of New Zealand. These siliceous stalactites contain diverse biota of bacteria (including cyanobacteria), fungi, and diatoms that lived on the stalactite surfaces, with locally abundant pollen grains, and springtails. The microbes are the templates for much of the opaline silica precipitation and thereby controlled most of the fabrics that form the stalactite laminae. Siliceous stalactites form at sites of dripping water below the overhanging edges of geyserite rims that surround geyser vents, and along the steep margins of sinter terraces on discharge aprons. Stalactites may hang as isolated individuals or may coalesce to form dripstone draperies along terrace or rim margins. Stalactite growth is controlled by the volume, temperature, and the silica concentration of the ...

Microbial Construction of Siliceous Stalactites at Geysers and Hot Springs: Examples from the Whakarewarewa Geothermal Area, North Island, New Zealand

Other| February 01, 2001 Microbial Construction of Siliceous Stalactites at Geysers and Hot Springs: Examples from the Whakarewarewa Geothermal Area, North Island, New Zealand BRIAN JONES; BRIAN JONES 1Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada Search for other works by this author on: GSW Google Scholar ROBIN W. RENAUT; ROBIN W. RENAUT 2Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada Search for other works by this author on: GSW Google Scholar MICHAEL R. ROSEN MICHAEL R. ROSEN 3Wairakei Research Centre, Institute of Geological and Nuclear Sciences, Wairakei Research Centre, Private Bag 2000, Taupo, New Zealand Search for other works by this author on: GSW Google Scholar Author and Article Information BRIAN JONES 1Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada ROBIN W. RENAUT 2Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada MICHAEL R. ROSEN 3Wairakei Research Centre, Institute of Geological and Nuclear Sciences, Wairakei Research Centre, Private Bag 2000, Taupo, New Zealand Publisher: SEPM Society for Sedimentary Geology Accepted: 07 Oct 2000 First Online: 03 Mar 2017 Online Issn: 1938-5323 Print Issn: 0883-1351 Society for Sedimentary Geology PALAIOS (2001) 16 (1): 73–94. https://doi.org/10.1669/0883-1351(2001)016<0073:MCOSSA>2.0.CO;2 Article history Accepted: 07 Oct 2000 First Online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation BRIAN JONES, ROBIN W. RENAUT, MICHAEL R. ROSEN; Microbial Construction of Siliceous Stalactites at Geysers and Hot Springs: Examples from the Whakarewarewa Geothermal Area, North Island, New Zealand. PALAIOS 2001;; 16 (1): 73–94. doi: https://doi.org/10.1669/0883-1351(2001)016<0073:MCOSSA>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyPALAIOS Search Advanced Search Abstract Siliceous stalactites, formed of opal-A laminae that are concentrically arranged around a hollow soda-straw, are common features structures in some of the geyser and hot spring deposits at Whakarewarewa and other geothermal areas of New Zealand. These siliceous stalactites contain diverse biota of bacteria (including cyanobacteria), fungi, and diatoms that lived on the stalactite surfaces, with locally abundant pollen grains, and springtails. The microbes are the templates for much of the opaline silica precipitation and thereby controlled most of the fabrics that form the stalactite laminae.Siliceous stalactites form at sites of dripping water below the overhanging edges of geyserite rims that surround geyser vents, and along the steep margins of sinter terraces on discharge aprons. Stalactites may hang as isolated individuals or may coalesce to form dripstone draperies along terrace or rim margins. Stalactite growth is controlled by the volume, temperature, and the silica concentration of the water supplied to the growth site. These waters mainly originate from geyser or hot spring discharge. The microbes preserved in the stalactites, however, imply that silica precipitation took place after these waters had cooled.The growth and coalescence of geyser stalactites to form complex dripstone draperies plays an important role in the lateral accretion of sinter around the rims of many geysers and in progradation of sinter terraces. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Formation of silica oncoids around geysers and hot springs at El Tatio, northern Chile

ABSTRACTSiliceous oncoids, up to 4 cm in diameter, are common on the laterally extensive sinter aprons that surround the spectacular geysers and hot springs at El Tatio in northern Chile. Many of these complex oncoids developed close to geyser and spring vents that discharge boiling water. Internally the oncoids, which are composed of precipitated amorphous silica, are formed of complex arrays of spicules and concentric laminae as well as detrital volcanic grains. Spicular growth is dominant in most examples. The formation and growth of the spicules and concentric laminae were mediated by a microbial community which included filamentous microbes, mucus, and possibly bacteria. The microbes and mucus were silicified by replacement and encrustation. In some laminae the filamentous microbes lay parallel to the growth surface; in other laminae most filaments forming the thin mats were suberect. Amorphous silica precipitated between the filaments occluded porosity and commonly disguised the microbial fabric.The oncoids grew on the proximal sinter aprons around the geyser vents and hot spring pools. Most growth took place subaerially with the silica delivered to the precipitation sites by splashing water from the geysers and/or periodic shallow flooding of the discharge aprons. Unlike silica oncoids at other geothermal sites, vertical growth of oncoids that formed in some rimstone pools was not limited by water depth.

A mathematical model for pre-boiling convection in a geyser vent

A mathematical model for pre-boiling convection in a geyser vent

Pressure Waves from a Geyser

Abstract It seemed probable that as a geyser builds up toward eruption, it should send out detectable pressure waves, which might make it possible to predict the time of eruption. Waves produced by Old Faithful Geyser in Yellowstone National Park were detected by a sensitive microbarograph at various surface locations within a few hundred feet of the geyser vent. The waves occur in bursts, and tend to increase about 50 per cent in amplitude within five minutes prior to an eruption, and to decrease about 20 per cent in period within two minutes before an eruption. However, changes in amplitude and period within bursts of waves are great enough to obscure the longer-time variations, and to make it impossible to predict eruptions in the field by this method.