Comparison of conventional K-Ar and Ar40/Ar39 dating of young mafic volcanicrocks
Dating ; Geochronology ; K/Ar dating ; Methodology ; Pleistocene ; Quaternary ; United States of America ; Volcanicrock ; Western United States
The objective of this study was to compare the results using both Ar techniques on Quaternary volcanicrocks from 3 areas of the western United States : the Snake River Plain, Idaho, Mount Adams, Washington, and Crater Lake, Oregon. The samples
selected for comparison are representative of the rock types in the 3 areas.
Several occurrences of metamorphosed pre-Hercynian volcanicrocks crop out in the Paleozoic basement of Southern Sulcis (SW Sardinia), hosted in Cambrian-Early carboniferous sedimentary sequences belonging to two different structural units. - (NF)
This paper examines the geological and geomorphological conditions under wich the special riolith-tuff cliffs, the so-called « beehive rocks » south from the Bükk Mountains (NE-Hungary) were formed. - (JS)
A group of Ar-K dating data of volcanicrocks in Taiwan Island is listed in this paper, which clarifies the data of volcanic activity. This volcanic activity is closely related with plate movement since Mesozoic. Now there are still manifestations
of volcanic actions such as hot springs or fumaroles or solfataras.
The Tokaj Mountains differ from the other volcanic mountains of Hungary by strike, heavy dissection, (a younger) age of volcanism, a great diversity of volcanicrocks, paleogeographic circumstances (frequent marine transgressions). The paper deals
with the volcanic forms in detail, with their types, with erosional and derasional valleys and their development. - (ZK)
In-situ gamma-ray spectrometric study of weathered volcanicrocks in Hong Kong
Chemical erosion ; Geochemistry ; Geotechnics ; Hong Kong ; Volcanicrock ; Weathering
In this study, an integrated geochemical and in-situ GRS survey was conducted at 2 sites in Hong Kong where tuffs of varying weathering states were exposed. Field description of rock materials and sampling for elemental analyses were conducted at 57
Comparative geochemistry of volcanics from rift valleys, transform faults and aseismic ridges
It is suggested that transform faults have, by faulting, exposed more fractioned types of basaltic rocks (may be as intrusives) than the rift valley volcanics. While aseismic ridges have undergone a greater degree of differentiation than both
Chemical erosion ; Geochemistry ; Island ; Japan ; Microstructure ; Mineralogy ; Porosity ; Rock ; Rock mechanics ; Volcanicrock ; Weathering
To examine the mechanism of rock-strength reduction due to weathering, temporal changes in microstructure of 4 porous rhyolite were investigated at Kozu-shima Island in the western Pacific. With the results of mineralogical investigations
and laboratory tests of pore structure of the rocks, the AA. conclude that the microstructural changes due to chemical weathering strongly influence the reduction of rock strengths.
Formation of silica glaze rock coatings through water vapor interactions
Basalte ; Domaine aride ; Désert ; Enduit ; Géochimie ; Hawaii ; Humidité ; Mars ; Météorisation ; Silice ; Vapeur d'eau ; Vernis ; Volcan ; Zone subtropicale
Arid area ; Basalt ; Desert ; Geochemistry ; Hawaii ; Mars planet ; Moisture ; Rock coatings ; Rock varnish ; Silica ; Subtropical zone ; Volcano ; Water vapor ; Weathering
Basalto ; Campo árido ; Desierto ; Geoquímica ; Hawaii ; Humedad ; Meteorización ; Sílice ; Vapor de agua ; Volcán ; Zona subtropical
A two decade-long laboratory experiment tested importance of high water vapor content in silica glaze formation. Twenty years of exposing basalt rock chips to 80% and 90% levels of relative humidity revealed that water vapor alone can generate
silica glaze and may be an important factor in explaining why silica glaze is the dominant rock coating in humid warm drylands. In addition to adding a new dimension to the formation of terrestrial rock coatings, these findings may have importance
Paleomagnetism of the Flores volcanics, Vancouver Island, in place by Eocene time
The purpose of this paper is to describe paleomagnetic data from Eocene rocks of the Insular Belt, the westernmost element of the Canadian Cordillera. The possibility of using their paleomagnetism to reconstruct their attitude is considered
Geomorphological, hydrological and climatic significance of rock glaciers in the Andes of Central Chile (33-35°S)
Air temperature ; Andes ; Chile ; Hydrology ; Moisture ; Mountain ; Periglacial features ; Permafrost ; Rock glacier ; Spatial distribution ; Volcanism
of the mean annual air temperature of at least c. 5.5°C. South of Santiago, active rock glacier distribution ends at 35° 15'S due to lower topography, young volcanism and increased humidity.
Rock glaciers in the Andes of Santiago de Chile occupy c. 10% of the total land surface between 3500 and 4250m ASL.. An estimated water equivalent of 0.3 km3 per 1000 km2 of mountain area is stored within them; this value is one order of magnitude
higher than in the Swiss Alps. Climate data indicate that the lowest occurences of active rock glaciers in the Andes of Santiago are not in equilibrium with modern climate. Relict features are found as low as at 2630 m ASL, implying a depression
The AA. applied the overcoring method to determine in-situ rock deformation by means of strain gage rosettes at 20 sites located within the area of active rifting. They determined numerous changes in the amount and the orientation of the maximum
and minimum horizontal crustal strain and consider these stress fluctuations to be caused by the pulsation of the Krafla volcanic centre.
Chemical erosion ; Erosion rate ; Field experiment ; Freeze-thaw cycle ; Island ; Japan ; Volcanicrock ; Weathering
To examine the rate of weathering, field experiments using microweight-loss techniques were carried out. Two kinds of porous rhyolite forming lava domes in Kozushima Island were selected : a younger rock and an older rock. Results show
that the younger rock has a lower weight loss, and the older rock a higher weight loss, and the rates of weight loss for both rocks on the ground surface is larger than that under the saturated grus layer. The first result shows that older rock has a higher rate
of chemical weathering than younger rock. The second result suggests that in addition to chemical weathering, physical weathering such as freeze-thaw weathering occurs on the ground surface.
Heretofore very little research has been done on a specific soil type in Hungary called „erubáz”, which develops on volcanicrocks. Its largest uniform and unbroken spot is located in the central part of Börzsöny Mountains (High Börzsöny
Geomorphogenesis ; Hungary ; Mountain ; Periglacial features ; Volcanism
The range of Tokaj Mountains is not only different from the rest of our volcanic mountains because of its N-S direction, but also the duration and extent of its volcanism, its volcanic material ; and the paleogeographical circumstances were
different too. As a result of all this, the mountain is very rich in morphological forms. In Hungary, these mountains are the richest in periglacial forms thanks to the varied collection of rocks and their settlement characteristics. - (ZK)
Soil-elevation relationships on a volcanic plateau in the Southern Cascade Range, northern California, USA
Altitude ; California ; Chronosequence ; Pedogenesis ; Precipitation ; Soil ; Soil properties ; Temperature ; United States ; Vegetation ; Volcanicrock
This paper presents the main features of an altitudinal sequence. They were determined from mapping soils on a late cenozoic volcanic plateau west-southwest of Lassen Peak, and from the analyses of 27 pedons sampled from 270 to 2 030 m above sea
Spatial variability of soils developing on basalt flows in the Potrillo volcanic field, southern New Mexico : prelude to a chronosequence study
Aquifer ; Arid area ; Basalt ; Chronosequence ; Natural recharge ; New Mexico ; Soil ; Soil properties ; Spatial variation ; United States of America ; Volcanicrock
This study seeks to improve the accuracy of a future soil chronosequence study in the Potrillo volcanic field by : further evaluating the evolution of basalt flow surface topography with time; identifying the systematic variability of soils