Search results for "Geology"

Non-explosive, dome-forming eruptions at Mt. Taranaki, New Zealand

2012

Abstract Volcanic domes may be emplaced rapidly and with few hazardous consequences, even at the summit of large stratovolcanoes. In this study the most recent activity of Mt. Taranaki in New Zealand is shown to have been a passive effusion of a c. 5.9 million m3 lava dome with minor associated explosions and little syn-eruptive hazard. This event, the Sisters eruption, appears to have been unrecorded by local indigenous populations but likely occurred between A.D. 1785 and 1820. The magma erupted is chemically distinct from the preceding A.D. 1755 Tahurangi eruption. Based on breakdown of hornblende crystal rims, the Sisters magma was probably only four days outside the hornblende stabilit…

Assessing dye-tracer technique for rill flow velocity measurements

2018

Abstract Rill erosion is considered one of the most important processes affecting soil because of the large amount of soil loss. The rill network acts as sediment source and is able to transport both rill flow-detached particles and those delivered from the interrill areas. Small flow depth in a rill and steep slope values of its bed affect significantly flow hydraulics. When rill flow velocity is measured using a dye-tracing method, the mean velocity is calculated by multiplying the measured surface velocity of the leading edge of the tracer plume by a correction factor. The main uncertainty of the dye-tracing technique stands in the relationship between mean and surface flow velocity. In …

Using LIDAR topography data for determination of morphology and terrace levels of the River Ogre Valley in Middle Latvia Lowland [abstract].

2016

Intrusion within a transtensional tectonic domain: the Čistá granodiorite (Bohemian Massif)—structure and rheological modelling

2000

Abstract The Cista granodiorite stock, which intrudes the Tis granite laccolith, and their Neoproterozoic country rocks of the Tepla–Barrandian zone were studied by means of structural analysis and anisotropy of magnetic susceptibility. The rocks were dated by the Pb–Pb evaporation on zircons, determining the age of the Cista granodiorite and Tis granite at 373 Ma and 504 Ma, respectively. The structures in the country rocks are characterised by an axial cleavage dipping to the northwest and overprinting the folded bedding. S1 cleavage bears NE–SW-trending mineral lineations, which plunge to the northeast or southwest at shallow angles. The cleavage is deformed by D2 kink-bands, which indic…

Study of the morphological affinity between two species of benthic foraminifera from restricted environments: Rosalina douvillei (Cushman, 1928) and …

2020

A biometric comparison is carried out on selected tests of the foraminiferal species Rosalina douvillei (Cushman, 1928) and Trichohyalus aguayoi (Bermudez, 1935). The Rosalina douvillei specimens were recovered from the marginal marine Oligocene/Miocene site of Russingen (Mainz Basin, Germany), the lacustrine beds of the lower Miocene site of Bunol (Valencian Community, Spain) and the middle/ upper Miocene site of Fuendetodos (Aragon, Spain). The Trichohyalus aguayoi tests were collected in the current coastal lagoon of Torreblanca and recovered from Holocene cores sampled in the Peniscola marsh and in the coastal lagoon of l’Albufera de Valencia, all them in the Valencian Community (Spain)…

Sedimentary model and high-frequency cyclicity in a Mediterranean, shallow-shelf, temperate-carbonate environment (uppermost Miocene, Agua Amarga Bas…

1996

Uppermost Tortonian to lower Messinian temperate carbonates crop out in the Agua Amarga Basin (SE Spain). They consist of four units. The lower three units can be tentatively assigned to the lowstand systems tract of a fourth-order sequence, constituting in turn the lowstand (‘megatrough unit’), transgressive (‘breccia unit’) and highstand (‘bedded unit’) stages of a higher-order cycle. All these materials were deposited in a small pull-apart basin related to the sinistral Carboneras strike-slip fault system. The best represented is the bedded unit (up to 25 m thick), which consists of bioclastic, bryozoan/bivalve-dominated calcarenites/calcirudites with abundant fragments of echinoids, bar…

Single zircon evaporation ages from Obudu Plateau: First evidence of archaean components in the schists of south-eastern Nigeria

1998

Exceptional mobility of an advancing rhyolitic obsidian flow at Cordón Caulle volcano in Chile

2013

The emplacement mechanisms of rhyolitic lava flows are enigmatic and, despite high lava viscosities and low inferred effusion rates, can result in remarkably, laterally extensive (30 km) flow fields. Here we present the first observations of an active, extensive rhyolitic lava flow field from the 2011-2012 eruption at Cordón Caulle, Chile. We combine high-resolution four-dimensional flow front models, created using automated photo reconstruction techniques, with sequential satellite imagery. Late-stage evolution greatly extended the compound lava flow field, with localized extrusion from stalled, ~35 m-thick flow margins creating80 breakout lobes. In January 2013, flow front advance continu…

The emissions of CO2 and other volatiles from the world’s subaerial volcanoes

2019

AbstractVolcanoes are the main pathway to the surface for volatiles that are stored within the Earth. Carbon dioxide (CO2) is of particular interest because of its potential for climate forcing. Understanding the balance of CO2 that is transferred from the Earth’s surface to the Earth’s interior, hinges on accurate quantification of the long-term emissions of volcanic CO2 to the atmosphere. Here we present an updated evaluation of the world’s volcanic CO2 emissions that takes advantage of recent improvements in satellite-based monitoring of sulfur dioxide, the establishment of ground-based networks for semi-continuous CO2-SO2 gas sensing and a new approach to estimate key volcanic gas param…

Tropical Atlantic temperature seasonality at the end of the last interglacial

2015

The end of the last interglacial period, ~118 kyr ago, was characterized by substantial ocean circulation and climate perturbations resulting from instabilities of polar ice sheets. These perturbations are crucial for a better understanding of future climate change. The seasonal temperature changes of the tropical ocean, however, which play an important role in seasonal climate extremes such as hurricanes, floods and droughts at the present day, are not well known for this period that led into the last glacial. Here we present a monthly resolved snapshot of reconstructed sea surface temperature in the tropical North Atlantic Ocean for 117.7±0.8 kyr ago, using coral Sr/Ca and δ18O records. W…