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Iceland, the Farallon Slab, and dynamic topography of the North Atlantic

Clinton P. Conrad, Carolina Lithgow-Bertelloni and Keith E. Louden
Iceland, the Farallon Slab, and dynamic topography of the North Atlantic
Geology (Boulder) (March 2004) 32 (3): 177-180


Upwelling or downwelling flow in Earth's mantle is thought to elevate or depress Earth's surface on a continental scale. Direct observation of this "dynamic topography" on the seafloor, however, has remained elusive because it is obscured by isostatically supported topography caused by near-surface density variations. We calculate the nonisostatic topography of the North Atlantic by correcting seafloor depths for lithospheric cooling and sediment loading, and find that seafloor west of the Mid-Atlantic Ridge is an average of 0.5 km deeper than it is to the east. We are able to reproduce this basic observation in a model of mantle flow driven by tomographically inferred mantle densities. This model shows that the Farallon slab, currently in the lower mantle beneath the east coast of North America, induces downwelling flow that deepens the western North Atlantic relative to the east. Our model also predicts dynamic support of observed topographic highs near Iceland and the Azores, but suggests that the Icelandic high is due to local upper-mantle upwelling, while the Azores high is part of a plate-scale lower-mantle upwelling to the south. An anomalously deep area off the coast of Nova Scotia may be associated with the downwelling component of edge-driven convection at the continental boundary. Thus, several of the seafloor's topographic features can only be understood in terms of dynamic support from flow in Earth's mantle.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 32
Serial Issue: 3
Title: Iceland, the Farallon Slab, and dynamic topography of the North Atlantic
Affiliation: University of Michigan, Department of Geological Sciences, Ann Arbor, MI, United States
Pages: 177-180
Published: 200403
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 27
Accession Number: 2004-028831
Categories: OceanographySolid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch maps
N37°00'00" - N40°00'00", W31°00'00" - W25°00'00"
N63°40'00" - N66°30'00", W24°45'00" - W13°30'00"
S57°00'00" - N60°00'00", W62°00'00" - E03°00'00"
N00°00'00" - N75°00'00", W80°00'00" - E20°00'00"
Secondary Affiliation: Dalhousie University, CAN, Canada
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200409
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