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Book Chapter

Volcanic gaps and the consumption of aseismic ridges in South America

By
Amos Nur
Amos Nur
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Zvi Ben-Avraham
Zvi Ben-Avraham
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Published:
January 01, 1981

The gaps of volcanic activity and the associated shallow-dipping seismicity in South America can be explained by the consumption of the thick-rooted, buoyant, aseismic Nazca and Juan Fernandez Ridges and perhaps also the Cocos Ridge. The ridges erase the trench where they collide with the overriding continent. The point of collision migrates north or south along the plate boundary, depending on the orientation of the ridge relative to the direction of plate motion. This migration leaves behind a zone in which subduction is temporarily stopped; lack of subduction leads to the cessation of volcanism, perhaps owing to lack of water needed for partial melting.

Although the present aseismic ridges probably consist of basaltic cumulates, there is some indication that earlier-consumed parts of these ridges (or different, previously consumed ridges) contained continental fragments that are now embedded in the western coast of South America.

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Contents

GSA Memoirs

Nazca Plate: Crustal Formation and Andean Convergence

La Verne D. Kulm
La Verne D. Kulm
Editor
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Jack Dymond
Jack Dymond
Editor
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E. Julius Dasch
E. Julius Dasch
Editor
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Donald M. Hussong
Donald M. Hussong
Editor
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Roxanne Roderick
Roxanne Roderick
Associate Editor
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Geological Society of America
Volume
154
ISBN print:
9780813711546
Publication date:
January 01, 1981

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