Galapagos rift at 86 /sup 0/W 5. Variations in volcanism, structure, and hydrothermal activity along a 30-kilometer segment of the rift valley

Journal Article · Wed Feb 10 04:00:00 EST 1982 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB087iB02p01149· OSTI ID:5545756

Ballard, R D; van Andel, T H; Holcomb, R T

A 30-km segment of the Galapagos Rift near 86 /sup 0/W has been mapped in detail using the Angus towed camera system, the submersible Alvin, and multi-narrowbeam sonar data. Recent volcanic activity and active hydrothermal circulation are evident along the entire length of the segment mapped. There are, however, clear along-strike variations in these processes which render previous two-dimensional models obsolete. Although alternate explanations are possible, eruptive sequences appear to begin with the outpouring of surface-fed sheet flows and end with more channelized pillow flows. In the western portion of the rift studied, sheet flows dominate with the entire valley floor covered by recent flows associated with a broad shield volcano. The eastern portion, on the other hand, is narrower; consisting primarily of less voluminous pillow flows of apparently the same youthful age. Three possible models for the volcanic evolution of this rift segment are presented. According to the first model, the extrusive portion of the crust is formed by a distinct volcanic episode, followed by a long period of volcanic quiescence. The volcanic phase begins with voluminous sheet flows emerging from numerous eruptive fissures, which in time evolve into a narrow pillow ridge. Farther along-strike, where the flows are smaller and the extrusive zone narrow, the marginal portions undergo continued fissuring and subsequent uplift to form marginal highs and lows. This deformational activity also affects the extrusive zone once volcanic activity ends, converting the distinctly lobate topography of the active period into highly lineated fault-controlled terrain. According to the second model, extension and volcanism can be viewed as a continuous process without major periods of volcanic quiescence. The initial lava flows of a new eruptive sequence fill low areas, frequently spilling over local sills and flooding much of the rift valley.

• Research Organization: Department of Ocean Engineering, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543
• OSTI ID: 5545756
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 87:B2; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580500* -- Oceanography-- (1980-1989)
EARTH CRUST
GEOLOGIC MODELS
GEOLOGIC STRUCTURES
GROUND UPLIFT
LAVA
OCEANIC CRUST
PACIFIC OCEAN
PLATE TECTONICS
RIFT ZONES
SEA-FLOOR SPREADING
SEAS
SEDIMENTS
SURFACE WATERS
TECTONICS
VOLCANISM
VOLCANOES