Click on the above image to see a full-size version of the color-shaded relief map, with caption, from Pardee et al. (1999).
Click on the above image to see a full-size version of various models of propagating rift geometry, with caption.
Pito Deep detailed bathymetry, with locations of submersible magnetometer experiments. Click on the above image to see a full-size version.
We have surveyed this anomalous area along the
superfast spreading East Pacific Rise with SeaBeam (1983), SeaMARC II (1987),
GLORIA (1989), and NAUTILE (1993). Our results defined the present plate
boundaries, structural geometry, origin, and tectonic evolution of this young
oceanic microplate. The east and west boundaries are accretional, with
multiple ridge segments propagating north and south respectively, so the
geometry of these boundaries is constantly changing. The north and south
boundaries are complex transform boundaries, but with areas of compression
and extension caused by the rapid clockwise rotation of the microplate about
a pole near the center of the microplate. The microplate geometry resembles
the broad transform zone geometry of model C at lower right, but on a scale so
large (~ 400 x 400 km) that the overlap zone can no longer be deformed by
pervasive shearing, but instead begins to rotate as an independent
microplate, driven by the right-lateral shear couple on the northern and
southern boundaries of this giant left-stepping ridge offset, as described
quantitatively by Hans Schouten‘s edge-driven microplate model. We interpret
this area as a modern analog of past large-scale rift jumps.
Several of our investigations in this area have
focused on Pito Deep in the NE corner of the microplate. Pito Deep, Earth‘s
deepest (6,000 m) axial valley, is the latest in a series of rifts that have
propagated north into this area as the Easter Microplate developed. The trace
of the initial propagator tip can be seen at the right edge of the detailed
bathymetry map, and followed back to Easter Island, showing that Easter
Island formed at this propagator tip ~5 Ma, and suggesting that these
propagators (and equivalent southward propagators mapped by Hey et al. (1995,
Nature) were driven by Easter hotspot pulses. Our current work in this area
involves analysis of data from a 2005 multidisciplinary ALVIN, Jason II, and
DSL-120A expedition led by Jeff Karson of Duke, and details are available
from the Pito Deep website.
- Hey, R.N., D.F. Naar, M.C. Kleinrock, W.J. Phipps Morgan, E. Morales, and J.G. Schilling, Microplate tectonics along a superfast seafloor spreading system near Easter Island, Nature, 317, 320-325, 1985.
- Schilling, J.G., H. Sigurdsson, A. Davis, and R.N. Hey, Easter microplate evolution, Nature, 317, 325-331, 1985.
- Naar, D.F. and R.N. Hey, Fast rift propagation along the East Pacific Rise near Easter Island, J. Geophys. Res., 91, 3425-3438, 1986.
- Naar, D.F. and R.N. Hey, Speed limit for oceanic transform faults, Geology, 17, 420-422, 1989.
- Searle, R.C., R.I. Rusby, J. Engeln, R.N. Hey, J. Zukin, P.M. Hunter, T.P. LeBas, H.-J. Hoffman, and R. Livermore, Comprehensive sonar imaging of the Easter microplate, Nature, 341, 701-705, 1989.
- Naar, D.F. and R.N. Hey, Recent Pacific-Easter-Nazca plate motions, in Evolution of Mid-Oceanic Ridges, Geophysical Monograph Series, AGU, 9-30, 1989.
- Sempere, J.-C., J. Gee, D.F. Naar, and R.N. Hey, Three-dimensional inversion of the magnetic field over the Easter-Nazca propagating rift near 25° S, 112° 25' W, J. Geophys. Res., 94, 17409-17420, 1989.
- Hagen, R.A., N.A. Baker, D.F. Naar, and R.N. Hey, Bathymetry and submarine geology in the vicinity of Easter Island, Marine Geophys. Res., 12, 297-315, 1990.
- Naar, D.F. and R.N. Hey, Tectonic evolution of the Easter microplate, J. Geophys. Res., 96, 7961-7993, 1991.
- Martinez, F., D.F. Naar, T.B. Reed (IV), and R.N. Hey, Three-dimensional SeaMARC II, gravity, and magnetics study of large-offset rift propagation at the Pito rift, Easter microplate, Marine Geophys. Res., 13, 255-285, 1991.
- Naar, D.F., F. Martinez, R.N. Hey, T.B. Reed(IV), and S. Stein, Pito rift: How a large-offset rift propagates, Marine Geophys. Res., 13, 287-309, 1991.
- Hey, R.N., P.D. Johnson, F. Martinez, J. Korenaga, M.L. Somers, Q.J. Huggett, T.P. LeBas, R.I. Rusby, and D.F. Naar, Plate boundary reorganization at a large-offset, rapidly propagating rift, Nature, 378, 167-170, 1995.
- Cogne, J.P., J. Francheteau, V. Courtillot, and Pito93 Scientific Team (including R.N. Hey), Large rotation of the Easter microplate as evidenced by oriented paleomagnetic samples from the ocean floor, Earth and Planet. Sci. Lett., 136, 213-222, 1995.
- Hekinian, R., J. Francheteau, R. Armijo, J.P. Cogne, M. Constantin, J. Girardeau, R. Hey, D.F. Naar, and R. Searle, Petrology of the Easter microplate region in the South Pacific, J. Volcanology & Geothermal Res., 72, 259-289, 1996.
- Korenaga, J. and R.N. Hey, Recent dueling propagation history at the fastest spreading center, the East Pacific Rise, 26° -32°S, J. Geophys. Res., 101, 18023-18041, 1996.
- Rappaport, Y., D.F. Naar, C.C. Barton, Z.J. Liu, and R.N. Hey, Morphology and distribution of seamounts surrounding Easter Island, J. Geophys. Res., 102, 24713-24728, 1997. Hey, R.N., Subtle error on sea floor, Nature, 396, 210, 1998.
- Pardee, D.R., R.N. Hey, and F. Martinez, Cross-sectional areas of mid-ocean ridge axes bounding the Easter and Juan Fernandez microplates, Mar. Geophys. Res., 20, (1999), 517-531, 2000.
- Hey, R.N., Propagating Rifts and Microplates, in Encyclopedia of Ocean Sciences, eds. J.H. Steele, S.A.Thorpe, and K.K. Turekian, Academic Press, London, Volume 4, 2300-2308, 2001.
- Hey, R.N., F. Martinez, S. Diniega, D.F. Naar, J. Francheteau, and the Pito93 Scientific Team (R. Armijo, M. Constantin, J.P. Cogne, J. Girardeau, R. Hekinian, and R. Searle), Preliminary attempt to characterize the rotation of seafloor in the Pito Deep area of the Easter Microplate using a submersible magnetometer, Mar. Geophys. Res., 23, 1-12, 2002.
- Naar, D.F., R. Hekinian, M. Segonzac, J. Francheteau, and the Pito Dive Team (R. Armijo, J.-P. Cogne, M. Constatin, J. Girardeau, R. Hey, and R. Searle), Vigorous venting and biology at Pito Seamount, Easter Island, Mid-Ocean Ridges: Hydrothermal Interactions Between the Lithosphere and Oceans, Geophysical Monograph Series 148, American Geophysical Union, 10.1029/148GM13, 305-318, 2004.
- Hey, R.N., Propagating Rifts and Microplates at Mid-Ocean Ridges, in Encyclopedia of Geology, eds. R.C. Selley, R. Cocks and I. Plimer, Academic Press, London, 396-405, 2004.
- Karson, J.A., J. Francheteau, J.S. Gee, K.M. Gillis, N.W. Hayman, R. Hekinian, R.N. Hey, S.D. Hurst, E.M. Klein, D.F. Naar, R.J. Varga and Pito Deep 2005 Scientific Party, Nested-scale investigation of tectonic windows into super-fast spread crust exposed at the Pito Deep rift, Easter Microplate, SE Pacific, InterRidge News v. 14, 5-8, 2005.
- Hey, R.N., J.S. Gee, and the Pito Deep 2005 Science Party, ALVIN Magnetometer Investigations of Pito Deep, Easter Microplate, Eos Trans. AGU, 86(52), Fall Meet. Suppl., Abstract T33D-0592, 2005.
- Hey, R., Seafloor Spreading, in Encyclopedia of Solid Earth Geophysics, ed. H. Gupta, Springer, Dordrecht, ISBN 978-90-481-8701-0, 1055-1059, 2011.
- Hey, R.N., Propagating Rifts and Microplates at Mid-Ocean Ridges, in Elsevier’s Science Direct online reference program, Earth Systems and Environmental Sciences, ed. S. Elias, in press, 2013.
- Hey, R.N., Propagating Rifts and Microplates at Mid-Ocean Ridges, www.sciencedirect.com/science/article/pii/B978012409548903027X, in Elsevier’s Science Direct online Reference Module in Earth Systems and Environmental Sciences, ed. S. Elias, ISBN: 978-0-12-409548-9, 2013.
- Hey, R.N., Tectonics: Propagating Rifts and Microplates at Mid-Ocean Ridges, www.sciencedirect.com/science/article/pii/B978012409548903027X, in Elsevier’s Science Direct online Reference Module in Earth Systems and Environmental Sciences, ed. S. Elias, ISBN: 978-0-12-409548-9, 2015.
- ** 1983 April: Sea Beam investigation of the Easter Microplate, Easter Island-Callao, Scripps Institution of Oceanography, chief scientist R.N. Hey, R/V THOMAS WASHINGTON.
- ** 1987 October–November: SeaMARC II investigation of the Easter Microplate, Easter Island-Easter Island, Hawaii Institute of Geophysics, chief scientist R.N. Hey, R/V MOANA WAVE.
- * 1988 October–November: GLORIA survey of the Easter Microplate, Papeete-Valparaiso, British Institute of Oceanographic Sciences, chief scientist R.C. Searle, RRS CHARLES DARWIN.
- * 1993 November: NAUTILE submersible investigation of the Easter microplate, Easter Island-Easter Island, Universite de Bretagne Occidentale, chief scientist J. Francheteau, R/V NADIR, DSRV NAUTILE.
- * 2005 January-March: DSL-120A, Jason and Alvin investigations of Pito Deep, Easter Microplate, Duke University/ University of South Florida/ University of Hawaii/Scripps Institution of Oceanography, chief scientist J. Karson, R/V ATLANTIS, DSV ALVIN.
- ** Chief Scientist
- * Co-Chief Scientist
Students involved in this research
- D. Naar
- M. Kleinrock
- J. Phipps Morgan
- J. Korenaga
- R. Rusby
- J. Zukin
- J. Gee
- R. Hagen
- N. Baker
- F. Martinez
- Y. Rappaport
- J. Liu
- D. Pardee
- A. Gascho
- P. Johnson
- S. Diniega
- J. Favia
- H. Ibarra
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