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| Titel |
The largest volcanic eruptions on Earth |
| VerfasserIn |
Scott Bryan, David Peate, Ingrid Ukstins Peate, Stephen Self, Michael Mawby, Dougal Jerram, Goonie Marsh |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250034824
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| Zusammenfassung |
| Large igneous provinces (LIPs) are sites of the most frequently recurring, largest volume
basaltic and silicic eruptions in Earth history. The magma volumes, eruptive mechanisms,
frequency and associated aerosol emissions of these eruptions are critical for understanding
any interpreted climate forcing and environmental change by LIPs. The largest volume
(>1000 km3 dense rock equivalent) and magnitude (>M8) eruptions produce areally
extensive (104-105 km2) basaltic lava flow fields and silicic ignimbrites and are the main
building blocks of LIPs. Available information on the largest eruptive units are
primarily from the Columbia River and Deccan provinces for the dimensions of flood
basalt eruptions, and the Paraná-Etendeka and Afro-Arabian provinces for the silicic
ignimbrite eruptions. In addition, three large-volume (675- 2,000 km3) silicic lava
flows have also been mapped out in the Mesoproterozoic Gawler Range province
(Australia), an interpreted LIP remnant. Magma volumes of >1000 km3 have also
been emplaced as high-level basaltic and rhyolitic sills in LIPs, and may contribute
substantial aerosol emissions through shallow degassing and crystallisation. The
data sets indicate comparable eruption magnitudes between the basaltic and silicic
eruptions, but due to considerable volumes residing as co-ignimbrite ash deposits, the
current volume constraints for the silicic ignimbrite eruptions may be considerably
underestimated. Magma composition thus appears to be no barrier to the volume of
magma emitted during an individual eruption. Despite this general similarity in
magnitude, flood basaltic and silicic eruptions are very different in terms of eruption
style, duration, intensity, vent configuration, and emplacement style. Flood basaltic
eruptions are dominantly effusive and Hawaiian-Strombolian in style, with magma
discharge rates of ~107-108 kg s-1 producing dominantly compound pahoehoe
lava flow fields. The major flood basalt eruption durations are most likely >10
yrs. Effusive and fissural eruptions have also emplaced some large-volume silicic
lavas, but discharge rates are unknown, and may be up to an order of magnitude
greater than those of flood basalt lava eruptions for emplacement to be on realistic
time scales (M8) basaltic eruptions have much shorter recurrence intervals of
103-104 years, whereas similar magnitude silicic eruptions have recurrence intervals
of up to 105 years. The huge volumes of basaltic and silicic magma erupted in
quick succession during LIP events raises several unresolved issues in terms of
locus of magma generation and storage (if any) in the crust prior to eruption, the
paths and rates of ascent from magma reservoirs to the surface, and relative aerosol
contributions to the stratosphere from the flood basaltic and rhyolitic eruptions. |
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