910 resultados para Gold deposits


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Diseñado para proporcionar un fácil apoyo para los alumnos que necesitan para ganar la confianza y la motivación en su lectura. La historia trata de un grupo de amigos que viven y asisten a la escuela en una zona llamada Wolf Hill. Además de las divertidas aventuras, la historia también se ocupa de cuestiones sobre la amistad, la escuela y la vida en un moderno entorno urbano. Diseñada en capítulos, para que parezca novela popular para niños mayores, y así aumentar la confianza y el interés de aquellos que pueden gustarles la lectura de historias destinadas a los niños más pequeños. Loz y sus amigos encuentran algunas monedas antiguas en un escondite secreto y quieren saber si tienen valor.

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Destinado a los alumnos, tiene como objetivo estimularlos y motivarlos mediante la vinculación de la ciencia a la vida real. Cada capítulo abarca una serie de características:una actividad de iniciación al comienzo de cada capítulo, que permite a los profesores evaluar el nivel de comprensión del tema por el alumno antes de seguir avanzando; preguntas para garantizar que los alumnos han comprendido el trabajo; palabras clave para ampliar el vocabulario y fomentar el uso exacto de los términos científicos; recuerdo para resumir las conceptos; lista de los sitios web pertinentes para ayudar a ilustrar los temas tratados y estimular la investigación individual.

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Es el primero de una serie de tres volúmenes, uno por cada año de estudio, de la etapa clave tres (Key Stage 3). Escrito en colaboración con la Agencia de Destrezas Básicas (The Basic Skills Agency) asegura a los estudiantes de los niveles 2-4 una cobertura total del currículo nacional inglés. Las unidades están diseñadas para complementar los esquemas de trabajo del año escolar y promueven un acercamiento interactivo a la enseñanza. Los textos literarios y no literarios proporcionan la base para las tareas que se centran en el desarrollo de habilidades específicas incluida la expresión oral.

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Es el segundo de una serie de tres volúmenes, uno por cada año de estudio, de la etapa clave tres (Key Stage 3). Escrito en colaboración con la Agencia de Destrezas Básicas (The Basic Skills Agency) asegura a los estudiantes de los niveles 2-4 una cobertura total del currículo nacional inglés. Las unidades están diseñadas para complementar los esquemas de trabajo del año escolar y promueven un acercamiento interactivo a la enseñanza. Los textos literarios y no literarios proporcionan la base para las tareas que se centran en el desarrollo de habilidades específicas incluida la expresión oral.

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Destinado a los alumnos, tiene como objetivo estimularlos y motivarlos mediante la vinculación de la ciencia a la vida real. Cada capítulo abarca una serie de características:una actividad de iniciación al comienzo de cada capítulo, que permite a los profesores evaluar el nivel de comprensión del tema por el alumno antes de seguir avanzando; preguntas para garantizar que los alumnos han comprendido el trabajo; palabras clave para ampliar el vocabulario y fomentar el uso exacto de los términos científicos; recuerdo para resumir las conceptos; lista de los sitios web pertinentes para ayudar a ilustrar los temas tratados y estimular la investigación individual.

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Este recurso, diseñado para ser utilizado junto con los libros del alumno, tiene por objeto apoyar a los profesores proporcionando actividades, en hojas fotocopiables, para los alumnos que necesiten mejorar sus conocimientos, mediante la vinculación de la ciencia con la vida real y motivar y estimular así su aprendizaje . Prevee actividades para que los estudiantes que necesiten mejorar sus conocimientos, alcancen el nivel adecuado. Tiene CD-ROM.

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Disequilibria between Pb-210 and Ra-226 can be used to trace magma degassing, because the intermediate nuclides, particularly Rn-222, are volatile. Products of the 1980-1986 eruptions of Mount St. Helens have been analysed for (Pb-210/Ra-226). Both excesses and deficits of Pb-210 are encountered suggesting rapid gas transfer. The time scale of diffuse, non-eruptive gas escape prior to 1980 as documented by Pb-210 deficits is on the order of a decade using the model developed by Gauthier and Condomines (Earth Planet. Sci. Lett. 172 (1999) 111-126) for a non-renewed magma chamber and efficient Rn removal. The time required to build-up Pb-210 excess is much shorter (months) as can be observed from steady increases of (Pb-210/Ra-226) with time during 1980-1982. The formation of Pb-210 excess requires both rapid gas transport through the magma and periodic blocking of gas escape routes. Superposed on this time trend is the natural variability of (Pb-210/Ra-226) in a single eruption caused by tapping magma from various depths. The two time scales of gas transport, to create both Pb-210 deficits and Pb-210 excesses, cannot be reconciled in a single event. Rather Pb-210 deficits are associated with pre-eruptive diffuse degassing, while Pb-210 excesses document the more vigorous degassing associated with eruption and recharge of the system. (c) 2006 Elsevier B.V. All rights reserved.

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Banded sediments outcrop widely in the intertidal zone of the Severn Estuary and have been suggested, on the basis of textural analysis, to have formed in response to seasonal variations in sea temperature and windiness (Holocene, 14 (2004) 536). Here palynological and sedimentological analyses of banded sediments of mid-Holocene date from Gold Cliff, on the Welsh side of the Severn Estuary, are combined to test and further develop the hypothesis of seasonal deposition. Pollen percentage and concentration data are presented from a short sequence of bands to establish whether textural variations in the bands coincide with variations in pollen content reflecting seasonal flowering patterns. It is shown that fine-grained band parts contain higher total pollen concentrations, and a higher proportion of pollen from late spring- to summer-flowering plants, than coarse-grained band parts. Pollen in the coarser deposits appears primarily to reflect deposition from the buffering `reservoir' of suspended pollen in the estuarine water-body and from rivers, when there is little pollen in the air in winter, while the finer sediments contain pollen deposited from the atmosphere during the flowering season, superimposed on these `background' sources. The potential of such deposits for refining chronologies and identifying seasonality of coastal processes is noted, and the results of charcoal particle analysis of the bands presented as an example of how they have the potential to shed light on seasonal and annual patterns of human activity. (C) 2004 Elsevier Ltd. All rights reserved.

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Deposits of coral-bearing, marine shell conglomerate exposed at elevations higher than 20 m above present-day mean sea level (MSL) in Bermuda and the Bahamas have previously been interpreted as relict intertidal deposits formed during marine isotope stage (MIS) I I, ca. 360-420 ka before present. On the strength of this evidence, a sea level highstand more than 20 m higher than present-day MSL was inferred for the MIS I I interglacial, despite a lack of clear supporting evidence in the oxygen-isotope records of deep-sea sediment cores. We have critically re-examined the elevated marine deposits in Bermuda, and find their geological setting, sedimentary relations, and microfaunal assemblages to be inconsistent with intertidal deposition over an extended period. Rather, these deposits, which comprise a poorly sorted mixture of reef, lagoon and shoreline sediments, appear to have been carried tens of meters inside karst caves, presumably by large waves, at some time earlier than ca. 310-360 ka before present (MIS 9-11). We hypothesize that these deposits are the result of a large tsunami during the mid-Pleistocene, in which Bermuda was impacted by a wave set that carried sediments from the surrounding reef platform and nearshore waters over the eolianite atoll. Likely causes for such a megatsunami are the flank collapse of an Atlantic island volcano, such as the roughly synchronous Julan or Orotava submarine landslides in the Canary Islands, or a giant submarine landslide on the Atlantic continental margin. (c) 2006 Elsevier B.V. All rights reserved.

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Our recent paper [McMurtry, G.M., Tappin, D.R., Sedwick, P.N., Wilkinson, I., Fietzkc, J. and Sellwood, B., 2007a. Elevated marine deposits in Bermuda record a late Quaternary megatsunami. Sedimentary Geol. 200, 155-165.] critically re-examined elevated marine deposits in Bermuda, and concluded that their geological setting, sedimentary relations, micropetrography and microfaunal assemblages were inconsistent with sustained intertidal deposition. Instead, we hypothesized that these deposits were the result of a large tsunami that impacted the Bermuda island platform during the mid-Pleistocene. Hearty and Olson [Hearty, P.J., and Olson, S.L., in press. Mega-highstand or megatsunami? Discussion of McMurtry et al. "Elevated marine deposits in Bermuda record a late Quaternary megatsunami": Sedimentary Geology, 200, 155-165, 2007 (Aug. 07). Sedimentary Geol. 200, 155-165.] in their response, attempt to refute our conclusions and claim the deposits to be the result of a +21 m eustatic sea level highstand during marine isotope stage (MIS) 11. In our reply we answer the issues raised by Hearty and Olson [Hearty, P.J., and Olson, S.L., in press. Mega-highstand or megatsunami? Discussion of McMurtry et al. "Elevated marine deposits in Bermuda record a late Quaternary megatsunami": Sedimentary Geology, 200, 155-165, 2007 (Aug. 07). Sedimentary Geol. 200,155-165.] and conclude that the Bermuda deposits do not provide unequivocal evidence of a prolonged +21 m eustatic sea level highstand. Rather, the sediments are more likely the result of a past megatsunami in the North Atlantic basin. (c) 2008 Elsevier B.V. All rights reserved.