Магматизм океанов

Лекция №9. Примеры: Гавайи, Исландия


Schematic representation of possible aspects of a plume beneath the Hawaiian hotspot and its interaction with the lithosphere and asthenosphere beneath the Hawaiian Swell.

SWELL (Seismic Wave Exploration in the Lower Lithosphere)











Извержение 1783. Трещина Лаки.

Длина разлома 25 км.
площадь покрытая лавой 600 км2.
объем магмы 11 км3.
максимальная длина потока 56 км.

The Gjalp vent 1998, ERZ, which occurs in a chain including Grimsvotn and Bardabunga centres. The ice of the Vatnajokull can be see fracturing as it flows inwards towards the melt zone round the vent. The ice is covered in a layer of ash.
Photo: Scientific Inst., Uni. of Iceland
Mt Hekla in recent eruption, view north along the rift.
Note the two fresh black lava flows to the right. Elongate mountain ridges in distance are apparently due to subglacial lava emerging along rifts in the Pleistocene glacial time and being confined by ice and prevented from spreading laterally.
Photo: Thor Thordarson, Volcanic Institute of Iceland, 16-Feb-1991


вулкан Эльдфель (Eldfell). 1973

The small island of Heimaey, off the south coast of Iceland was involved in an eruption in 1973. The town of Vestmannaeyjar and its 5,000 inhabitants was evacuated. Over the course of almost 5 months of continuous volcanic activity, the islanders watched as the eastern part of their town was engulfed in thick ash and lava deposits. This photograph was taken in April of 1973 and it shows one of the houses in the eastern suburbs completely covered in ash. Icelandic geologists kept a careful watch on this small volcano, monitoring the gases emitted and the ejecta produced to try to predict the outcome of the eruption. The volcano (Eldfell), finally stopped in May, 1973, and in the subsequent 20 plus years the island has more or less returned to normal.



Variation diagram for all Icelandic rocks, (N = 3722). These range from depleted high degree melt magnesian basalts to rhyolites and alkali basalts to trachytes.
Note wide range in K especially. Rocks with high alumina (20 - 30% are mainly from gabbroic intrusions, eg the Krisuvik gabbro in the Reykjanes Peninsula.
Note distinctive ferro-basalts with high TiO2 (5%)




Аномалии по S-волнам под Исландией.
Combined interpretation based on data from seismic, controlled-source electromagnetic, and magnetotelluric experiments.
Seafloor bathymetry and seismic layer boundaries are quantitatively accurate based on swath bathymetry measurements and seismic
modelling. Similarly, estimates of electrical resistivity, porosity, melt content, and temperature are quantitative estimates based on
modelling and interpretation. Note the 10:1 break in scale at 10 km depth

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