New light on caldera evolution - Askja, Iceland

Journal Article · Mon Apr 01 00:00:00 EST 1991 · Geology; (USA)

DOI:https://doi.org/10.1130/0091-7613(1991)019<0352:NLOCEA>2.3.CO;2· OSTI ID:5611189

Brown, G C; Everett, S P; Rymer, H; McGarvie, D W; Foster, I ^[1]

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1. The Open University, Milton Keynes (England)

The large multiple-caldera volcanic system of Askja, central Iceland, is composed principally of subglacial basaltic hyaloclastite-pillow-lava formations and postglacial basaltic scoria and flows. Traditionally, such calderas are believed to be formed by downfaulting and ring-fracture collapse. Whereas this certainly applies to the smaller A.D. 1875 caldera, the older main caldera may have developed positive relief during subglacial construction of laterally confined hyaloclastite ridges above erupting fractures. This is supported by the evidence of a large negative gravity anomaly that reaches minima over the marginal low-density ridges but which is less negative within the caldera, where relatively dense postglacial lavas are believed to cover a more limited hyaloclastite succession beneath the caldera floor.

• OSTI ID: 5611189
• Journal Information: Geology; (USA), Vol. 19:4; ISSN 0091-7613
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CALDERAS
GEOLOGIC HISTORY
ICELAND
DENSITY
GEOLOGIC FRACTURES
GEOLOGY
GLACIERS
GRAVITY SURVEYS
LAVA
ORIGIN
VOLCANIC REGIONS
VOLCANISM
DEVELOPING COUNTRIES
EUROPE
GEOLOGIC STRUCTURES
GEOPHYSICAL SURVEYS
ISLANDS
PHYSICAL PROPERTIES
SURVEYS
580000* - Geosciences