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Disruption of Tephra Fall Deposits Caused by Lava Flows during Basaltic Eruptions

Brown, R.J.; Thordarson, T.; Self, S.; Blake, S.

Disruption of Tephra Fall Deposits Caused by Lava Flows during Basaltic Eruptions Thumbnail


T. Thordarson

S. Self

S. Blake


Observations in the USA, Iceland and Tenerife, Canary Islands reveal how processes occurring during basaltic eruptions can result in complex physical and stratigraphic relationships between lava and proximal tephra fall deposits around vents. Observations illustrate how basaltic lavas can disrupt, dissect (spatially and temporally) and alter sheet-form fall deposits. Complexity arises through synchronous and alternating effusive and explosive activity that results in intercalated lavas and tephra deposits. Tephra deposits can become disrupted into mounds and ridges by lateral and vertical displacement caused by movement (including inflation) of underlying pāhoehoe lavas and clastogenic lavas. Mounds of tephra can be rafted away over distances of 100 s to 1,000 s m from proximal pyroclastic constructs on top of lava flows. Draping of irregular topography by fall deposits and subsequent partial burial of topographic depressions by later lavas can result in apparent complexity of tephra layers. These processes, deduced from field relationships, have resulted in considerable stratigraphic complexity in the studied proximal regions where fallout was synchronous or alternated with inflation of subjacent lava sheets. These mechanisms may lead to diachronous contact relationships between fall deposits and lava flows. Such complexities may remain cryptic due to textural and geochemical quasi-homogeneity within sequences of interbedded basaltic fall deposits and lavas. The net effect of these processes may be to reduce the usefulness of data collected from proximal fall deposits for reconstructing basaltic eruption dynamics.


Brown, R., Thordarson, T., Self, S., & Blake, S. (2015). Disruption of Tephra Fall Deposits Caused by Lava Flows during Basaltic Eruptions. Bulletin of Volcanology, 77(10), Article 90.

Journal Article Type Article
Acceptance Date Sep 10, 2015
Online Publication Date Sep 18, 2015
Publication Date Oct 1, 2015
Deposit Date Sep 8, 2015
Publicly Available Date Sep 18, 2016
Journal Bulletin of Volcanology
Print ISSN 0258-8900
Electronic ISSN 1432-0819
Publisher Springer
Peer Reviewed Peer Reviewed
Volume 77
Issue 10
Article Number 90
Keywords Pāhoehoe, Lava, Tephra fall deposit, Basaltic eruption.


Accepted Journal Article (2.5 Mb)

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