A report on the macroinvertebrates of the Columbia River estuary found in deposits of volcanic ash from the May 18, 1980 eruption of mount St. Helens

Following the May 18, 1980 eruption of Mount St. Helens, up to 11.5 cm of volcanic ash was deposited in sections of the upper Columbia River estuary. A survey of the benthic infauna of this area indicates that most taxa were able to inhabit the ash, suggesting that the material is nontoxic to most groups. However, the abundance of the taxa examined was dependent on the distribution of the ash within the sediment column. Except for the oligochaetes, animal densites were reduced in areas where volcanic ash lay atop the sediment surface as compared to areas where the ash layer had been buried beneath, or mixed with sands and/or muds. The ash apparently affects the infauna through some physical means, possibly related to its fine grain size.     

Soil parent materials and soil properties in two separate catchment areas on the Jos Plateau, Nigeria

On the Jos Plateau, soils derived from basalt and volcanic ash are much more intensively and extensively utilized for agricultural purposes than the granite soils. This study was carried out to determine the differences that may have contributed to this discrimination. Twenty four soil profiles were dug and described in two separate catchment areas that really portray the variance. Soil samples were analysed using standard procedures. The results show that basalt and volcanic ash-derived soils have relatively deeper profiles, lower bulk density, higher contents of clay, organic matter, exchangeable bases, micro-nutrients (Cu & Zn) and weatherable minerals. They are also higher in their CEC and base saturation percentage while available water capacity, hydraulic conductivity and natural water content are more adequate in them. Hence, the basalt and volcanic ash soils are more favourable for crop growth while the deficiencies in granite soils present more constraints to agricultural land use. Consequently, there are differences between the soil types in their crop-yielding capacities. These differences constitute a reflection of soil parent material influence. Agriculture in the area is mainly low-input. There is the need for improved management practices for the enhancement of soil conditions of granite areas in particular and the whole area in general. This revised version was published online in July 2006 with corrections to the Cover Date.     

海拉尔—塔木察格盆地中部富油凹陷高含凝灰质碎屑岩储层成因及油气勘探意义

海拉尔—塔木察格盆地中部富油凹陷下白垩统铜钵庙组和南屯组广泛发育高含凝灰质碎屑岩储层,并已于其中获得了工业突破,但对其成因机制认识不清。在岩心、薄片、录井和测井等资料综合研究的基础上,结合大量海拉尔—塔木察格盆地及周边地区的火山事件分析,认为中部富油凹陷发育的高含凝灰质碎屑岩的岩石类型主要包括凝灰质砂岩、凝灰质泥岩、凝灰岩和沉凝灰岩。不同时期、不同凹陷高含凝灰质碎屑岩储层发育特点各异,整体来看从铜钵庙组到南屯组储层中的凝灰质含量越来越低,高含凝灰质碎屑岩储层主要发育在铜钵庙组和南一段沉积时期。高含凝灰质碎屑岩储层中的火山物质并非来源于自身断陷期发生的基性火山活动,而是来自于大兴安岭地区大规模的酸性火山喷发事件。海拉尔—塔木察格盆地高含凝灰质碎屑岩储层的成因机制包括两种类型：一种是同沉积期火山灰直接空降入湖型;另一种是同沉积期火山灰先沉降至陆上经河流搬运后再沉积的水携型。高含凝灰质碎屑岩储层中的火山碎屑物质受有机酸作用易于溶蚀,次生孔隙发育,为深部油气成藏提供了有效储层空间,并且火山喷发活动对优质烃源岩的形成具有促进作用,对于油气勘探具有重要意义。     

火山灰沉积与页岩有机质富集关系探讨——以五峰组—龙马溪组含气页岩为例

现代火山活动喷发形成的火山灰沉降到海水中能够提高海洋表层生产力、促进浮游生物繁盛,有利于有机质形成与富集沉积。而地质历史时期火山灰（斑脱岩）沉积与有机质富集关系研究相对较少,且存在着争议。以我国华南地区奥陶纪-志留纪转折期五峰组-龙马溪组页岩为例,开展含火山灰页岩层段与正常沉积的页岩层段的TOC含量、古生产力、氧化还原条件等对比分析,以探讨两者之间关系。研究结果初步表明:火山灰对高生产力背景的海洋区域影响相对较弱,对其有机质富集的促进作用不明显,而沉积水体氧化还原条件（富氧-贫氧-缺氧变化）与有机质含量关系密切,是这一时期有机质富集的主控因素。由于火山活动对沉积环境影响是十分复杂的过程,未来需要利用地质、地球化学等多种测试手段,开展更高分辨率（如厘米级、毫米级尺度）综合对比研究,精细解剖火山活动对有机质形成及富集作用的影响。火山活动相关的沉积事件是非常规油气沉积学重要研究内容之一,厘定它与页岩有机质富集关系,对我国页岩油气等非常规油气勘探开发具有重要意义。     

Geochemical and mineralogical anomalies of the late Permian coal in the Zhijin coalfield of southwest China and their volcanic origin

This paper describes the influence of volcanic ash on the concentrations and occurrences of associated elements in coal in the Zhijin Coalfield in western Guizhou Province, China. Our studies reveal that the No. 9 coal seam in the Zhijin Coalfield has very high content of Fe (4.34%), Cu (369.90 μg/g), U (49.6 μg/g), Mo (63.10 μg/g), Zn (33.97 μg/g), and Zr (841.80 μg/g). The studies have also found that elements, such as Fe and Cu, do not occur as sulfides in this coal seam, in sharp contrast to many other coal seams in China. The geochemical and mineralogical anomalies of the coal seam are attributed to synsedimentary volcanic ash. In addition to normal macerals and minerals in coal, a volcanic-influenced material (VIM) derived from volcanic ash, detrital material of terrigenous origin and organic matter was identified under polarized-light reflectance microscopy and scanning electron microscopy equipped with energy-dispersive X-ray (EDX) analyzer. The volcanic-influenced material is the main carrier of the above elements in this coal. Six types of the volcanic-influenced material (VIM-1, VIM-2, VIM-3, VIM-4, VIM-5, and VIM-6) are further distinguished on the basis of their structures and compositions. To the best of our knowledge, this is the first report that presents a detailed classification of coal components with a high content of volcanic ash.     

Properties of dust source material and volcanic ash in Iceland

The volcanic origin, primarily basaltic, of most of the surface material in Iceland influences its physical properties and appearance. Size distributions, shape analyses and melting experiments were made for surface material collected in high-erosion dust source areas and fresh volcanic ash deposits to determine whether they differ from one another and from dust from other major dust sources. The major differences found between Icelandic dust and dust from other major dust sources in the world, such as the Sahara, are in the particle shapes, lower density and darker colour. Icelandic dust particles greater than 20 μm retain volcanic morphological properties that are also found in fresh volcanic ash. Dust and fresh volcanic ash particles less than 20 μm are crystalline and blocky in nature, similar to the dust from other global source regions. The finer grained (<20 μm) Icelandic particles will have similar suspension and transport behaviours and be similarly hazardous to health and infrastructure as non-Icelandic dust. The coarser particles (>20 μm) will have different suspension and transport behaviours than other dusts due to the volcanic morphology. Icelandic surface material has between 5% and 30% glassy particles compared to fresh volcanic ash which has more than 50% glassy particles. Glassy particles were observed to melt at a lower temperature than the mineral grains; and, as a result, volcanic ash is found to be more threatening to aircraft engines than the typical dust from Iceland. Icelandic dust was observed to be blocky, or plate-like in the respirable size fraction, suggesting similar health hazards as dust from other regions.     

The preservation potential of ash layers in the deep‐sea: the example of the 1991‐Pinatubo ash in the South China Sea

Following the eruption of Mount Pinatubo on 15 June 1991, volcanic ash was transported westward to the South China Sea in an atmospheric plume, falling out and settling to the sea floor within days and forming an up to 10 cm thick layer on an area >400 000 km². Immediately after deposition, surviving deep‐burrowing animals re‐opened their connection to the sea floor to obtain water for respiration and/or food take‐up. Later, small‐sized meiofauna and then macrofauna re‐colonized the sea floor, mixing newly deposited organic fluff with the underlying ash. Consequently, ash deposits thinner than 1 mm have not often been observed as a continuous layer when cored six years after the eruption, while ash about 2 mm thick is now patchily bioturbated. In areas covered by ash thicker than 5 mm, mixing by benthic animals is controlled mainly by the adaptation of the burrowing fauna to variations in grain‐size, the rate of background sedimentation, the availability of benthic food on and within the sediment and pore water oxygen levels. With respect to these factors, four provinces can be distinguished: (i) Along the Philippines margin run‐off from land fuels primary production that, in turn, leads to a high benthic food content. The benthic fauna is adapted to a variable grain‐size and rapid sedimentation. Therefore, mixing is intense and the preservation potential of the ash layer is low. (ii) In areas affected by deposition of hyperpycnites and turbidites, i.e. in canyons in front of river mouths and in the Manila Trench, the ash layer is preserved due to rapid burial. (iii) The area to the west to about 116° E receives low amounts of benthic food, benthic mixing is less intense and the preservation potential of the ash is high. (iv) The central South China Sea, where the ash is thinner than 3 cm, is affected by intense wind mixing and upwelling and the benthic food content is high; thus, the chance that the ash will be preserved as a sharp‐based layer is low. Consequently, the style of ash preservation has palaeo‐environmental significance. Older buried and burrowed event layers provide further information to elucidate the fate of the 1991 Pinatubo ash layer; in general their appearance fits with observations in the Recent.     

Physical character of archean felsic volcanism in the vicinity of the Helen iron Mine,Wawa, Ontario,Canada

Archean felsic volcanic rocks form a 2000 m thick succession stratigraphically below the Helen Iron Formation in the vicinity of the Helen Mine, Wawa, Ontario. Based on relict textures and structures, lateral and vertical facies changes, and fragment type, size and distribution, the felsic volcanic rocks have been subdivided into (a) lava flows and domes (b) hyalotuffs, (c) bedded pyroclastic flows, (d) massive pyroclastic flows, and (e) block and ash flows.Lava flows and domes are flow-banded, massive, and/or brecciated and occur throughout the stratigraphic succession. Dome/flow complexes are believed to mark the end of explosive eruptive cycles. Deposits interpreted as hyalotuffs are finely bedded and composed dominantly of ash-size material and accretionary lapilli. These deposits are interlayered with bedded pyroclastic flow deposits and probably formed from phreatomagmatic eruptions in a shallow subaqueous environment. Such eruptions led to the formation of tuff cones or rings. If these structures emerged they may have restricted the access of seawater to the eruptive vent(s), thus causing a change in eruptive style from short, explosive pulses to the establishment of an eruption column. Collapse of this column would lead to the accumulation of pyroclastic material within and on the flanks of the cone/ring structure, and to flows which move down the structure and into the sea. Bedded pyroclastic deposits in the Wawa area are thought to have formed in this manner, and are now composed of a thicker, more massive basal unit which is overlain by one or more finely bedded ash units. Based on bed thickness, fragment and crystal size, type and abundance, these deposits are further subdivided into central, proximal and distal facies.Central facies units consist of poorly graded, thick (30–80 m) basal beds composed of 23–60% lithic and 1–8% juvenile fragments. These are overlain by 1–4 thinner ash beds (2–25 cm). Proximal facies basal beds range from 2–35 m in thickness and are composed of 15–35% lithic and 4–16% juvenile fragments. Typically, lithic components are normally graded, whereas juvenile fragments are inversely graded. These basal beds are overlain by ash beds (2–14 in number) which range from 12 cm to 6 m in thickness. Distal basal beds, where present, are thin (1–2 m), and composed of 2–8% lithic and 6–21% juvenile fragments. Overlying ash beds range up to 40 in number.The climax of pyroclastic activity is represented by a thick (1000 m) sequence of massive, poorly sorted, pyroclastic flow deposits which are composed of 5–15% lithic fragments and abundant pumice. These deposits are similar to subaerial ash flows and appear to mark the rapid eruption of large volumes of material. They are overlain by felsic lavas and/or domes. Periodic collapse of the growing domes produced abundant coarse volcanic breccia. The overall volcanic environment is suggestive of caldera formation and late stage dome extrusion.     

湖北黄石、浙江长兴煤山二叠-三叠系界线处火山物质及粘土岩成因探讨

本文对湖北黄石、浙江长兴煤山剖面二叠-三叠系界线附近粘土岩层作了碎屑物的分析和测试,并计算了它们的百分含量。与火山活动有关的碎屑主要有石英(其中含六方双锥状的β石英)、锆石、磷灰石、玻璃圆球、铁质圆球及火山灰等。有些样品中还有电气石、石榴石及锐钛矿等。笔者认为粘土岩层的成因是火山物质在海水中沉积蚀变而成。火山喷出口不在工作区内,生物绝灭的主要原因不是火山活动引起的。     

中上扬子地区奥陶纪-志留纪之交火山作用对有机质富集的影响

为了研究火山作用对黑色泥岩有机质富集机制的影响,以重庆市武隆区焦页143-5井岩心为研究对象,借助汞元素含量、总硫、总有机碳和钡元素含量等手段,分析上扬子地区奥陶系与志留系之交(五峰组-龙马溪组)火山活动和有机质富集的耦合关系.结果表明,汞元素富集层位(龙马溪组底部)对应着海洋生产力指标(总有机碳和生源钡)的高值,同时,上扬子地区多个剖面的火山凝灰岩的厚度分布与有机碳含量空间分布有很好的对应关系,亦表明火山作用与有机质富集具有紧密联系.因此,认为多期次的、广泛的火山喷发可能是奥陶纪与志留纪之交中上扬子地区有机质富集的重要原因.      

Archaeological evidence for dating the Loma Caldera eruption,Ceren, El Salvador

A Classic Period agricultural village in El Salvador was partially destroyed and encased in pyroclastic debris during the eruption of Loma Caldera about A.D. 590. The eruption was phreatomagmatic in nature, depositing alternating units of “muddy” pyroclastic surge beds and units of air fall lapilli, pumice, and volcanic bombs. This ephemeral eruptive left only a partially eroded collapsed tephra ring. The eruption began with earth tremors and possible steam explosions, giving enough warning to allow the inhabitants of the nearby village to flee, but violent enough that they left behind many of their most valuable personal items. The low temperature of wet ash surge units, which were likely emplaced as “ash hurricanes,” preserved much of the vegetation and other botanical remains surrounding the village. Analysis of the maturity of maize preserved in agricultural fields, and the presence or absence of blossoming and fruiting plants indicates that the eruption occurred in the mid-rainy season, probably late August or September. The placement of artifacts within buildings indicate that the eruption occurred in the early evening, after the inhabitants had returned from their agricultural fields and eaten an evening meal, but before retiring for the night. Although the exact year of the eruption can only be estimated within the uncertainty of radiocarbon dating, the season of the year and the time of day can be identified with unusual precision. © 1996 John Wiley & Sons, Inc.     

Pseudo-oolites in rocks of the Ulundi Formation, lower part of the Archaean Fig Tree Group (South Africa)

The Ulundi Formation of the lowermost Fig Tree Group in the type area in the Barberton Mountain Land consists of a sequence of quartz—sericite schists, banded cherts and tuffaceous rocks up to 40 m thick. It overlies talc—carbonate schists assigned to the upper part of the Onverwacht Group. In the cherts, which in parts represent the sulfide facies of a banded-iron formation, silicified spheroids have been observed which appear to be diagenetically altered, locally zeolitized accretionary lapilli. Portions of the cherts formed through silicification of fine-grained felsic tuffs and contain abundant stylolite seams along which 4% of the rock thickness has been removed by intrastratal solution during deformation.A supposedly organogenic spheroidal structure, Ramsaysphera, has been previously described from the upper part of the Ulundi Formation. The spheroids, with diameters of up to 8 mm, occur in a distinct bed of up to at least 1.6 m thickness and can be traced in outcrop over an area which originally covered 17 × 30 km. The bed was deposited in fairly still water of several 100 m depth. The spheroids accumulated with only little finer-grained detrital material, the interstices between them being filled by cherty silica and minor amounts of dolomite. Up to 65% of the spheroids consist of tectonically elongated, originally round fragments of a micro-felsitic groundmass with remnants of phenocrysts. The majority of the remaining spheroids consists of concentrically banded bodies of siliceous material with minor amounts of chlorite and sericite, as well as small dolomite crystals. These spheroids represent highly altered granules of volcanic glass deposited from volcanic ash clouds through a body of water. The prototype of Ramsay-sphera also belongs to this group of spheroids, and there is little microscopic or macroscopic evidence for its explanation as an organic structure.     

Minerals formed and mineral formation from volcanic ash by weathering

Weathering of volcanic ash and pumice is unique regarding minerals formed and mineral formation. These minerals include allophane, imogolite, opaline silica and some halloysites, and have distinctive structures and properties. Studies on the surface and subsurface weathering of various volcanic ashes in different settings are reviewed. This review illustrates that relatively rapid weathering of finely comminuted volcanic ash well reflects the effects of climate, vegetation and time, and produces various combinations of weathering products. The moisture regime, the nature and amount of organic matter incorporated, the deposition of volcanic ash as overburden, and the chemical and mineralogical composition of parent ash are important in controlling the mineral formation in weathered volcanic ash.     

Potential impact on water resources from future volcanic eruptions at Long Valley,Mono County,California, U.S.A.

Earthquakes, ground deformation, and increased geothermal activity at Long Valley caldera after mid-1980 suggest the possibility of a volcanic eruption in the near future. An eruption there could have serious consequences for the City of Los Angeles, depending on the magnitude and volume of material ejected because surface water in Mono Basin plus surface and groundwater in Owens Valley accounts for about 80 percent of its water supply. Eruptions of moderate to very large magnitude could impede the supply of water from this area for several days, weeks, or even years by discharging small to large volumes of volcanic ash and causing lahars. Soon after an eruption, water quality would likely be affected by the accumulation of organic debris and microorganisms in surface waters.     

长白山火山活动发展阶段及火山灾害评价

长白山地区火山活动划分二个发展阶段：以点一线形式喷发形成的广阔玄武岩台地阶段一焊缝构造发展阶段;中心式大规模喷发形成的锥状火山机构一焊点构造发展阶段,长白山地区乃至吉林东部地区中一新生代以来抬升平均速率81m／Ma及白头山一泉阳一露水河一带中生代以来存在一个火山坳陷盆地。     

Volcanic Eruption Induced Floods. A Rainfall-Runoff Model Applied to the Vesuvian Region (Italy)

Explosive events are commonly accompanied or followed byheavy rains. These eruption-induced storms together with thedeposition of large amounts of ash contribute to destabilise thehydrological cycle in the areas affected by volcanic eruptions.Flooding of the region surrounding the active volcano can easilyfollow, increasing the complexity of the volcanic crisis and itsmanagement. This is particularly true in the case of Vesuvius,that is not only characterized by a dramatic volcanic hazard, butit is also located within an area that is normally prone to flood hazard. A complete assessment of the impact associated with explosive volcaniceruptions should involve a flood hazard assessment for the region.This work represents a first attempt to address the problem: atopographically based rainfall-runoff model was here applied to theVesuvian area where two main sub-basins were analysed. The modelwas applied to evaluate the role of selected parameters on the totaldischarge at the basins' outlet. These parameters were chosen amongthose likely to be affected by an explosive event and were variedthrough a reasonable range. Results confirm that the deposition oflarge amounts of ash can affect the temporal evolution of the dischargeand its maximum value, for a given precipitation event. The simulationspresented outline the need for a detailed flood forecasting study for theVesuvian area, that should be included within the hazard mitigation strategies.     

Absolute dating of the youngest sediments of the Swiss Molasse basin by apatite fission track analysis

A set of ash layer samples within the uppermost Upper Freshwater Molasse (OSM) sediments (N and E of Frauenfeld, Switzerland) was dated by apatite fission track (FT) means. The ages indicate an early Tortonian (perhaps latest Serravallian) eruption and sedimentation age of 11.5 ± 0.3 Ma. The age is in agreement with time constraints by Mammalian relicts which point to MN7-8. Due to the position of the ash layers close to the erosional gap and overlying Quaternary cover, the age represents a maximum age for the cessation of OSM sedimentation in the Swiss Molasse Basin. However, the end of Molasse sedimentation in this region had not stopped before the cover of OSM sediments by volcanic ash layers at the Höwenegg volcano (southern Germany), an event further constrained by an apatite FT age of 9.8 (?0.7/+0.8) Ma from a hornblende-bearing ash layer at Höwenegg. An isolated bentonitic ash layer occurring 25 km to the WSW of the main set of dated ashes (near Humlikon) has an age component identical to the OSM ash layers near Frauenfeld. The age suggests a source for this material within the Hegau, but is too young to be related to the volcanic activity at the Kaiserstuhl.The apatites from the ash layer samples show two distinct compositional populations, one very close to a Cl end member and one with apatites of equal proportions of Cl and OH end member. These populations are interpreted to have possibly originated from at least two distinct igneous sources for the ashes, separated by their eruption site or eruption time or both. The distinct compositional data on the volcanic apatites may provide a basis to clarify their origin in future work.     

Remains of trilobites and other species discovered in a volcanic ash bed of the end-Permian,Yangtze craton,South China

The remains of trilobites and other species were unexpectedly discovered in a volcanic ash layer beneath the Permian–Triassic Boundary (PTB). Based on a biostratigraphic investigation of the Zhongliangshan section in Chongqing, South China, the quantity of the species gradually decreased with subsequent volcanism. This finding provides an opportunity to further understand the disappearance of trilobites and the evolution of the mass extinction event. The temporal coincidence between the volcanic eruption event and the loss of trilobites and other species supports the idea of a cause-and-effect relationship. The species remains in the ash bed appeared before the disappearance of Clarkina yini and the climax of the negative carbon isotope excursion, which implies that the onset of the mass extinction occurred at the end-Permian. The explosive volcanic events caused massive releases of CO₂, toxic gases and volcanic ash and resulted in loss of habitat for certain species in the Tethys domain. This phenomenon may have led to the abrupt death of trilobites and the catastrophic collapse of biodiversity.     

河北省滦县李家屿灰场2#副坝区灰水运动的水文地质评价

韩家哨村位于河北滦县李家屿灰场北部谷地,地势低于灰场,距离约800m。灰场运行期间,该区地下水出现水位升高及水质变差等问题。本文从水文地质条件角度,详细研究灰水的运移途径及其对该区地下水的影响。韩家哨村区域地下水系统分为上层滞水和孔隙一裂隙（溶隙）潜水含水层系统。潜水含水层系统水力传导系数为172．6～203．4m^2／d。地下水补给主要来源于韩家哨村以南坝后地形较高区域及灰水。灰水渗漏优势区韩家哨村南部宽约200m的带状区域。灰场堆灰形成新的地下水分水岭致使灰水在20副坝坝前垂直下渗进入风化带,沿白云岩裂隙（溶隙）补给潜水含水层,并向韩家哨村区域流动补给孔隙含水层,改变后的潜水部分通过民井向外排泄。