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Morphological Interpretation of Seamounts in American Samoa: Inferring Genesis Mechanisms through Shape and Distribution Analysis. Jed Roberts Master’s Candidate in Geography Department of Geosciences Oregon State University AAG San Francisco - April 19, 2007. Presentation Overview.

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Morphological Interpretation of Seamounts in American Samoa:

Inferring Genesis Mechanisms through Shape and Distribution Analysis

Jed Roberts

Master’s Candidate in Geography

Department of Geosciences

Oregon State University

AAG San Francisco - April 19, 2007



Study Area

Image produced by the U.S. National Park Service


Study Area

Eastern Volcanic Province

(American Samoa)

Western Volcanic Province

(Samoa)

Image produced by the U.S. National Park Service



Tectonic Setting

Image modified from Sandwell and Smith


Controversy

Artwork by Jayne Doucette, Woods Hole Oceanographic Institution

Artwork by Naoto Hirano, Scripps Institution of Oceanography




Multibeam Data

Merged with Sandwell and Smith 1km resolution predicted bathymetry

Image created using Fledermaus

Data source: The Seamount Catalog

www.earthref.org


Multibeam Data

With 210m resolution swaths isolated

Image created using Fledermaus

Data source: The Seamount Catalog

www.earthref.org



Methods | Identifying Seamounts

Slope Surface

Map created in Fledermaus

Data source: The Seamount Catalog

www.earthref.org


Methods | Identifying Seamounts

51 Seamounts Selected

Map created in Fledermaus

Data source: The Seamount Catalog

www.earthref.org



Methods | Characterizing Seamounts

Plan View

Cross-sectional View

Images created in Fledermaus


Methods | Characterizing Seamounts

Azimuth Angle

Summit Width

Slope Right

Slope Left

Height

Base Width

Base Depth

Images created in Fledermaus
















Methods | Distribution Analysis

Calculation of Area by -2640 m Cutoff

Total area before depth cutoff: 27,181 km2

Total area after depth cutoff: 22,745 km2

Map created in Fledermaus

Data source: The Seamount Catalog

www.earthref.org


Results | Distribution Analysis

ν0 = 2.6 ± 0.2 (per 1000 km2)

ß-1 = 138 m


Results | Distribution Analysis

ASSC is the American Samoa Seamount Chain, MAR is the Mid-Atlantic Ridge, ESC is the Easter Seamount Chain, EPR is the East Pacific Rise



Results | Interpretation

Directional Trends

Map created in Fledermaus

Data source: The Seamount Catalog

www.earthref.org





References

Abers, G. A., Parsons, B., and Weissel, J. K. 1988. Seamount abundances and distributions in

the southeast Pacific. Earth and Planetary Science Letters. 87: 137-51.

Bemis, K. G., and Smith, D. K. 1993. Production of small volcanoes in the Superswell region of

the South Pacific. Earth and Planetary Science Letters. 118: 251-62.

Hart, S. R., Staudigel, H., Koppers, A. A. P., Blusztajn, J., Baker, E. T., Workman, R., Jackson, M.,

Hauri, E., Kurz, M., Sims, K., Fornari, D., Saal, A., and Lyons, S. 2000. Vailulu'u undersea volcano: The New Samoa. Geochemistry Geophysics Geosystems. 1(12): 2000GC000108.

Hart, S. R., Coetzee, M., Workman, R. K., Blusztajn, J., Johnson, K. T. M., Sinton, J. M., Steinberger, B., and Hawkins, J. W. 2004. Genesis of the Western Samoa seamount province: age, geochemical fingerprint and tectonics. Earth and Planetary Science Letters. 227: 37-56.

Hirano, N., Takahashi, E., Yamamoto, J., Abe, N., Ingle, S.P., Kaneoka, I., Hirata, T., Kimura, J.,

Ishii, T., Ogawa, Y., Machida, S., and Suyehiro, K. 2006. Volcanism in Response to Plate Flexure. Science. 313: 1426-28.

Jaroslow, G. E., Smith, D. K., and Tucholke, B. E. 2000. Record of seamount production and

off-axis evolution in the western North Atlantic Ocean, 25º25'-27º10'N. Journal of Geophysical Research. 105(B2): 2721-36.

Kleinrock, M. C., and Brooks, B. A. 1994. Construction and destruction of volcanic knobs at

the Cocos-Nazca spreading system near 95ºW. Geophysical Research Letters. 21(21): 2307-10.

Magde, L. S., and Smith, D. K. 1995. Seamount volcanism at the Reykjanes Ridge:

Relationship to the Iceland hot spot. Journal of Geophyical Research. 100(B5): 8449-68.


References

Natland, J. H. 1980. The progression of volcanism in the Samoan linear volcanic chain. American Journal of Science. 280-A: 709-35.

Natland, J. H. 2004. The Samoan Chain: A Shallow Lithospheric Fracture System. www.mantleplumes.org (last accessed March 11, 2006).

Rappaport, Y., Naar, D. F., Barton, C. C., Liu, Z. J., and Hey, R. N. 1997. Mophology and

distrubution of seamounts surrounding Easter Island. Journal of Geophysical Research. 102(B11): 24,713-28.

Scheirer, D. S., and Macdonald, K. C. 1995. Near-axis seamounts on the flanks of the East

Pacific Rise, 8ºN to 17ºN. Journal of Geophysical Research. 100(B2): 2239-59.

Scheirer, D. S., MacDonald, K. C., Forsyth, D. W., and Shen, Y. 1996. Abundant Seamounts of

the Rano Rahi Seamount Field Near the Southern East Pacific Rise , 15º S to 19º S. Marine Geophysical Researches. 18: 13-52.

Smith, D. K. 1988. Shape analysis of Pacific seamounts. Earth and Planetary Science Letters.

90: 457-66.

Smith, D. K., and Jordan, T. H. 1988. Seamount Statistics in the Pacific Ocean. Journal of

Geophysical Research. 93(B4): 2899-918.

Smith, D. K., and Cann, J. R. 1990. Hundreds of small volcanoes on the median valley floor of

the Mid-Atlantic Ridge at 24º-30º N. Nature. 348: 152-5.

Smith, D. K., and Cann, J. R. 1992. The Role of Seamount Volcanism in Crustal Construction at

the Mid-Atlantic Ridge (24º-30ºN). Journal of Geophyical Research. 97(B2): 1645-58.


References

Walker, G. P. L., and Eyre, P. R. 1995. Dike complexes in American Samoa. Journal of Volcanology and Geothermal Research. 69: 241-54.

Workman, R. K., Hart, S. R., Jackson, M., Regelous, M., Farley, K. A., Blusztajn, J., Kurz, M., and Staudigel, H. 2004. Recycles metasomatized lithosphere as the origin of the Enriched Mantle II (EM2) end-member: Evidence from the Samoan Volcanic Chain. Geochemistry Geophysics Geosystems. 5(4): 2003GC000623.


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