Potential cauchy-poisson waves generated by submarine eruptions of kick 'em Jenny volcano

Kick 'em Jenny is the only known currently active submarine volcano in the Lesser Antilles. The volcano has erupted at least 10 times since first being discovered in 1939 and the summit has shoaled from a depth of 232 m in 1962 to its present-day depth of 150 m. Kick 'em Jenny is located in a province of explosive volcanism, has a known history of explosive eruptions and erupts magma of an explosive type. Future eruptions are likely to become increasingly more violent as the effect of the overlying water pressure becomes less. A preliminary study (Smith and Shepherd, 1993) suggests that Kick 'em Jenny is a prime candidate for tsunamigenic eruptions on a potentially hazardous scale, possibly affecting the whole of the eastern Caribbean region.The classic approach to problems of water waves generated by sudden disturbances of the free surface makes use of the Cauchy-Poisson-Lamb theory. A large number of theoretical developments to this theory have been made for specific forms of surface disturbance. A development by Unoki and Nakano (1953a, b) considers both two- and three-dimensional Cauchy-Poisson waves generated by finite initial elevations and impulses applied to a free surface of infinitely deep water. Unoki and Nakano's results compared well to the wave systems recorded following submarine eruptions of the Myojinsho Reef volcano in 1952–53.Given the similarity of the two situations, Unoki and Nakano's theory is applied to Kick 'em Jenny to provide estimates of potential Cauchy-Poisson wave heights throughout the eastern Caribbean for a range of eruption magnitudes. The results show that, although the waves generated are unlikely to pose much of a threat to the eastern Caribbean as a whole, they should be considered a hazard to the islands immediately adjacent to the volcano including Grenada, the Grenadines, and St Vincent.     

Phanerozoic equal-area maps

This paper outlines a method used to make paleocontinental maps and outlines its limitations. 15 pairs of new Lambert equal-area paleocontinental maps are presented, drawn at 40 Ma intervals from the present-day back to 560 Ma (early Cambrian time).

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Zusammenfassung 15 Paare von paläoglobalen Karten werden hier nach einer Lambertschen flächengetreuen Projektion mit Hilfe eines Rechnerprogrammes dargestellt. Der Zeitabschnitt umfaßt in 40 Mill. Jahres-Schritten die letzten 560 Mill. Jahre seit dem Kambrium.

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Résumé Ce travail définit la méthode utilisée pour dresser des cartes paléocontinentales, ainsi que ses limitations. — 15 paires de cartes paléocontinentales sont présentées, dessinées à des intervalles de 40 M. a. depuis l'époque actuelle jusqu'à 560 M. a. (début du Cambrien).

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, , . 15 , , .. 560 , 40 .

     

Zeitfragen der Orogenese

Ohne ZusammenfassungKurzfassung. Die ausführliche Arbeit erscheint in einem der folgenden Bände dieser Zeitschrift.     

Controls on the chemistry of springs at Teels Marsh,Mineral County,Nevada

Evaporative process plays a dominant role in determining the water chemistry of the springs at Teels Marsh, a closed basin in western Nevada. Analysis of the spring waters indicates that calcium, magnesium, sulfate, and silica are removed from solution during dry periods, even though groundwater is undersaturated with respect to gypsum, amorphous silica, and sepiolite. The removal mechanism is precipitation of authigenic phases such as gypsum above the water table, in the vadose zone.In episodes of rain and snowfall in which none of the waters enters the phreatic zone, ions in the rain and snow accumulate near the ground surface. This accumulation of material, together with the sparse rain and snowfall, inhibits chemical weathering of silicate minerals. Only at high elevations in the basin is there sufficient fluxing of water through the alluvium for silicate weathering to make a significant contribution to the sodium content of the springs. When a sufficiently heavy rainfall occurs, salts are partially dissolved and the ions transported to the permanent groundwater. The kinetics of dissolution of secondary phases in the vadose zone exert an important control on the composition of the springs.     

Plesiosaurs

Plesiosaurs are an unusual and intriguing group of extinct aquatic reptiles ( Fig. 1 ). They are sauropterygians, a group known from an array of semi‐aquatic forms during the Triassic period: placodonts, pachypleurosaurs and nothosaurs. The first plesiosaurs are known from the very latest Triassic, but by the Early Jurassic plesiosaurs were cosmopolitan in distribution and lasted successfully to the latest Cretaceous, when they became victims of the K‐T extinction event. Plesiosaurs were predominantly marine organisms, although their fossils are not uncommon in brackish or even fresh water deposits. We know that all plesiosaurs were carnivorous; many of them were top predators in their respective ecosystems. But with no living descendants (or analogues) plesiosaurs are mysterious fossil organisms—as we will see, many questions regarding their biology remain unanswered or contentious. However, plesiosaurs are currently undergoing renewed scientific attention.

Figure 1 Open in figure viewer PowerPoint The beautifully preserved skeleton of the plesiosaur Rhomaleosaurus victor seen in ventral view, from the Lower Jurassic (Toarcian) of Holzmaden, Germany (total length 3.44 m). Redrawn from Fraas (1910).     

Late Pleistocene and Early Holocene lake‐level fluctuations in the Lahontan Basin,Nevada: Implications for the distribution of archaeological sites

The Great Basin of the western U.S. contains a rich record of Late Pleistocene and Holocene lake‐level fluctuations as well as an extensive record of human occupation during the same time frame. We compare spatial‐temporal relationships between these records in the Lahontan basin to consider whether lake‐level fluctuations across the Pleistocene‐Holocene transition controlled distribution of archaeological sites. We use the reasonably well‐dated archaeological record from caves and rockshelters as well as results from new pedestrian surveys to investigate this problem. Although lake levels probably reached maximum elevations of about 1230–1235 m in the different subbasins of Lahontan during the Younger Dryas (YD) period, the duration that the lakes occupied the highest levels was brief. Paleoindian and Early Archaic archaeological sites are concentrated on somewhat lower and slightly younger shorelines (_1220–1225 m) that also date from the Younger Dryas period. This study suggests that Paleoindians often concentrated their activities adjacent to large lakes and wetland resources soon after they first entered the Great Basin. © 2008 Wiley Periodicals, Inc.     

Upper Jurassic record of Polyphylloseris (Egypt, Northern Sinai)

Genus Polyphylloseris is a scleractinian colonial coral that has been established by d’Orbigny (1849) from the Neocomian of Yonne, France. The genus is characterized by having elevated domal calices that are mammillar or craterlike in shape and with porous confluent septa. Columella is absent or rudimentary, and the lower surface of the corallum is covered with a thick and wrinkled holotheca. Specimens having the above-mentioned characteristics have been collected from the Upper Jurassic Arousiah Member of the Masajid Formation (Callovian–Oxfordian) of Gebel Maghara, Northern Sinai, Egypt. They are characterized by having a cupolate colonial form and porous pennulate septa which reach 40–50 in number. Based on these characters and other characters such as density of septa, height, and width of mammillar calices, the studied material is attributed to a new species named Polyphylloseris magharensis. The new species is a first undoubted record of Polyphylloseris in the Jurassic. Previously recorded undoubted ages of the genus are Early and Late Cretaceous. The fewer number of septa and the smaller-sized and closer mammillar calices allow differentiation of the species from other species such as Polyphylloseris icaunensis d’Orbigny and Polyphylloseris convexa d’Orbigny.     

Mineralogical and Geochemical Constraints on the Sediment Sources of Late Stone Age Pottery from the Birimi Site,Northern Ghana

The mineralogy and bulk chemical compositions of 15 Kintampo (Late Stone Age) potsherds from the Birimi site on the Gambaga Escarpment and eight samples of local sediment were determined with the intent of characterizing these wares and identifying the material used in their manufacture. Sediment from clay pits still used by potters north of the escarpment contains iron‐rich laterite clasts (100 × XFeO_t = 100 × FeO_t/[FeO_t + Al₂O₃ + SiO₂] ≥10). Sedimentary clasts in stream sediments are relatively siliceous and iron‐poor (100 × XFeO_t < 10). Bulk geochemical data together with the compositions of lithic clasts (laterite, siltstone/sandstone) link the pottery to sediment sources, including escarpment sediments not presently used by Ghanaian potters. Fresh granite clasts found in some of the sherds were not found in the analyzed sediment samples, although some of their distinctive mineralogical constituents (e.g., variably barian alkali feldspar) are present. The analytical data suggest that pots found at Birimi were made locally by mixing escarpment sediment with clay and stream sediment brought in from below the escarpment. This contrasts with present‐day practice, whereby the pots themselves are imported. The place where Birimi pottery was made and the outcrop source of aluminous sediment (mudstone with an “escarpment” trace element signature) used in these wares, however, remain unidentified. © 2013 Wiley Periodicals, Inc.     

Kinematic interpretation of remnant en-echelon rift segments of the southwestern Japan Sea

The southwestern Japan Sea and the margin of southwestern Japan feature parallel elongate extensional sub-basins and grabens. These structures are oblique to the trend of southwestern Japan and are interpreted as the remnant of an en-echelon array. Such a right-stepping remnant en-echelon pattern indicates sinistral rifting of the southwestern Japan block from Asia. The major extensional fault trends are parallel over a distance of 600 km. Infinitesimal kinematic relations show that it is unlikely that these faults initiated in response to rotation about the nearby pole determined from paleomagnetic studies. Rather, an earlier stage of rifting about a distant pole is indicated. The rotational pole of this early rifting was probably located at least 6000 km away from the rift and the pole of rotation was offset from the rift trend by a similar distance. Rifting about this distant rotational pole loosened the southwestern Japan continental block from the Asian mainland making it susceptible to a large rotation about a nearby pole.     

A revised estimate of the life span for Lake Nasser

A number of estimates of the potential life span of Lake Nasser located in Egypt and Sudan have been made in the past several years. Published estimates range from as little as 20 years (Sterling 1970) to over 1500 years (Makary 1982). The wide range of differing values is a function of many variables, including computation method, input data, and theoretical assumptions underlying the mathematical approach taken. Such a broad range of values is typical of sedimentation studies performed for areas that lack an adequate historic data base.One of the chief constraints to development of a reliable estimate the Lake Nasser's case has been lack of sufficient historical data on which to construct a useful data base. Enough information of this type has been collected since the reservoir's formation in 1964 to permit a realistic assessment of its life span. Granted the obvious need to determine the useful lifetime of this or any other reservoir, it is now possible to assess the reliability of the current official estimate for Lake Nasser. By applying appropriate modifications and additional data to the official estimate, an improved estimate was made.The time forecasted for filling of the reservoir by the official estimate is 362 years, somewhat less than the original design life of 500 years. By taking into account changes in the hydrological regime of the Nile after 1964 and another compaction factor, an estimate of 535 years was made. The additional time before filling estimated in the revision is significant for decision rules governing operation of the Aswan High Dam.