Search results for "Cinder cone"
showing 9 items of 9 documents
Maars of the Westeifel, Germany
2008
Within the Westeifel Volcanic Field 27% of the 250 Quaternary eruptive centers are maars. Maars form as a result of a highly explosive interactive process between rising melt and groundwater. In the Westeifel, probably thermal water plays an important role for the productive phreatomagmatic interaction process and, con-sequently, the high number of maars. The Westeifel maars show all transitions to scoria cones. Only the youngest maars are filled by a maar lake or a raised bog, and are well preserved. The older maars show a low diameter to depth ratio. Nearly one third of the Westeifel maars were formed during the Weichselian glaciation period. The isostatic movements during the increasing …
The Quaternary Eifel Volcanic Fields
1983
The Quaternary (ca. 0.7 Ma) volcanic fields in the western central part of the Rhenish Massif (West Eifel and East Eifel) have formed roughly synchronously with the main Quaternary phase of uplift The fields are 50 and 30 km long, elongated in NW-SE direction, contain ca. 240 and 90 volcanoes and are dominantly made of K-rich nephelinitic-leucititic-basanitic scoria cones. The larger West Eifel differs from the East Eifel field by more mafic and silica-undersaturated magmas, greater abundance and larger size of peridotite xenoliths and near absence of highly differentiated magmas contrasted with the occurrence of four highly differentiated phonolite volcanoes in the smaller East Eifel field…
Geodynamic setting of Upper Miocene to Quaternary alkaline basalts from Harrat al ‘Uwayrid (NW Saudi Arabia): Constraints from K Ar dating, chemical …
2019
Highlights • Volcanic activity of Harrat Uwayrid (NW Arabia) lasted from 8.2 to 0.3 Ma. • Alkali olivine basalts are followed by basanites, tephrites and tephriphonolites. • Sr-Nd-Pb isotopic ratios of all volcanic rocks suggest a PREMA source. • Different degrees of partial melting of amphibole-garnet-spinel lherzolite • Lithospheric mantle source rather than asthenosphere or plume-type mantle Abstract The volcanic field of Harrat ar Rahah-’Uwayrid (NW Saudi Arabia) consists of an older plateau basalt sequence that overlies Cambrian sandstone and younger cinder cones with smaller flows that are concentrated in the central part of this field. Petrographic and whole rock geochemical data ind…
Tertiary maars of the Hocheifel Volcanic Field, Germany
2008
In the Hocheifel only three maars are known. The Eckfeld Maar, filled with Eocene lacustrine sediments, is located at the southern boundary of the volcanic field, where the Tertiary peneplain has been eroded only slightly. The ages of the Jungferweiher Maar in the southeast and the Dottingen Maar in the northeast of the Tertiary Hocheifel Volcanic Field (THVF) are unknown and their timing within the THVF is uncertain. In contrast to the surrounding area, the central part of the THVF is deeply eroded. Here, six large diatremes (>600 m) were identified in the area of Kelberg with one exception. So far, no relics of crater sediments have been found within the large diatremes. They probably rep…
On the Volcanology of the West Eifel Maars
1987
The Quaternary alkali-basaltic volcanic field of the West Eifel is the classic maar region of the world. Related to the formation of the continental rift zone which extends through Central Europe, ultrabasic magmas rose from the upper mantle through the continental crust and fed 240 small volcanoes. Next to scoria cones with their lava flows, maars are most frequent and represent 25% of the volcanoes. Since 1820 and until 1970 their origin was mostly believed to be related to explosive exsolution of juvenile volatile phases. Since 1970, however, several authors have suggested that the West Eifel maars are phreatomagmatic in origin, i.e. rising magma contacted groundwater in near-surface lev…
On the growth of maars and diatremes and its relevance to the formation of tuff rings
1986
Small and large maars exist associated with small and large diatremes, respectively, their subsurface feeder structures. The problem of size and growth of maar-diatreme volcanoes is discussed from a phreatomagmatic point of view from field data, some geophysical data, and short-lived historic maar eruptions. A hydrostatic pressure barrier of usually about 20–30 bars is assumed to control the maximum depth level of explosive magma/groundwater interactions. Similar to the situation in submarine and subglacial volcanism, initial maar-forming water vapour explosions are therefore assumed to occur at shallow depth and to produce a small maar with a shallow diatreme. Because of limited availabili…
Geochemistry and origin of ultramafic enclaves and their basanitic host rock from Kula Volcano, Turkey
2013
Abstract The Quaternary Kula Volcanic Province is located in western Anatolia, Turkey. This Na-alkaline anorogenic volcanism includes exposures of around 80 cinder cones, lava flows, and tuffs, representing one of the youngest volcanic activities in this region (1.9–0.026 Ma). The magmatism is related to an extensional regime and is interpreted as being derived predominantly from the asthenospheric mantle. The lava flows are mostly of a basanitic composition and host rare comagmatic enclaves. The enclaves are composed of two dominant lithologies: amphibolites and clinopyroxenites with and without olivine. Amphibole is usually resorbed and replaced by a rhoenite-rich breakdown corona. The mi…
Syn- and post-eruptive mechanism of the Alaskan Ukinrek Maars in 1977
2008
The two alkali olivine basaltic Ukinrek Maars (East Maar and West Maar) and one scoria cone within East Maar erupted within eleven days (March 30–April 9, 1977) on the Alaskan Peninsula, 13 km north of Mt. Peulik, an andesite volcano of the Aleutian Range. The East Maar, with a diameter of 300 m, is located within a small graben system striking N 1100 E, oblique to the Aleutian trench in a distance of 350 km. On these tensional faults two eruption centres occur: The East Maar and a scoria cone on the southeastern margin of its crater bottom. The scoria cone was active more or less during the whole eruption activity of East Maar. The West Maar, with a diameter of 140 m, is located just west …
Precise chronology of Polynesian temple construction and use for southeastern Maui, Hawaiian Islands determined by 230Th dating of corals
2015
International audience; Emergent archaic states in pre-contact Hawai'i used a ritual control hierarchy implemented through a system of temples to manage production, extract tribute, and reinforce the legitimacy of the ruling elites. Based on a limited sample of precise 230Th dates from coral offerings on Maui Island temples it had been hypothesized that this temple system rapidly expanded during the period from A.D. 1580–1640. We tested this hypothesis by obtaining an expanded sample of 39 new 230Th coral dates from temples in Kahikinui District, and one sample from the summit of a cinder cone that likely had ritual significance. Combined with seven coral dates previously obtained, this yie…