Widespread uplift and ‘trapdoor’ faulting on Galápagos volcanoes observed with radar interferometry


Volcanic uplift, caused by the accumulation of magma in subsurface reservoirs, is a common precursor to eruptions1,2. But, for some volcanoes, uplift of metres or more has not yet led to an eruption3. Here we present displacement maps of volcanoes in the Galápagos Islands, constructed using satellite radar interferometry, that might help explain this dichotomy. We show that all but one of the seven volcanoes on the islands of Isabela and Fernandina deformed during 1992–99. Cerro Azul and Fernandina erupted4,5,6 during the observation period and show evidence of inflation, co-eruptive deflation and shallow dyke intrusion. In contrast, the largest volcano, Sierra Negra, has not erupted, yet exhibits spatially and temporally variable deformation, with a maximum uplift of 2.7 m between 1992 and 1999, which can be modelled by a shallow inflating sill. Inflation during 1997–98, however, was accompanied by ‘trapdoor’ faulting on a steeply dipping fracture system within the caldera. Repeated trapdoor faulting over geological time has formed an arcuate intra-caldera ridge within Sierra Negra and may have acted to relax stresses above the magma chamber, inhibiting summit eruptions. Similar processes may help explain large uplift unaccompanied by eruptive activity at other volcanoes.

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Figure 1: Observed deformation at Isabela and Fernandina (main image), the westernmost islands in the Galápagos archipelago (inset).
Figure 2: Radar interferograms of Sierra Negra volcano showing uplift during three time periods.
Figure 3: Deformation at Darwin volcano during 1992–98.
Figure 4: Two models for the Sierra Negra deformation during 1998–99.
Figure 5: Model for the observed deformation on Sierra Negra during 1997–98.


  1. 1

    Dvorak, J. J. & Dzurisin, D. Volcano geodesy: the search for magma reservoirs and the formation of eruptive vents. Rev. Geophys. 35, 343–384 ( 1997).

  2. 2

    Lipman, P. W., Moore, J. G. & Swanson, D. A. Bulging of the north flank before the May 18 eruption–geodetic data. USGS Prof. Pap. 1250, 143– 155 (1981).

  3. 3

    Newhall, C. G. & Dzurisin, D. Historical unrest at large calderas of the world. USGS Bull. 1855, 509– 520 (1988).

  4. 4

    Naumann, T. & Geist, D. Physical volcanology and structural development of Cerro Azul Volcano, Isabela Island, Galápagos: Implication for the development of Galápagos-type shield volcanoes. Bull. Volcanol. 61, 497–514 (2000).

  5. 5

    Mouginis-Mark, P. J., Snell, H. & Ellisor, R. GOES satellite observations of the 1998 eruption of Volcan Cerro Azul, Galápagos Islands. Bull. Volcanol. 62, 188–198 (2000).

  6. 6

    Jónsson, S. et al. A shallow-dipping dike fed the 1995 flank eruption at Fernandina volcano, Galápagos, observed by satellite radar interferometry. Geophys. Res. Lett. 26, 1077–1080 (1999).

  7. 7

    Geist, D., Howard, K. A., Jellinek, A. M. & Rayder, S. The volcanic history of Volcán Alcedo, Galápagos Archipelago: A case study of rhyolitic oceanic volcanism. Bull. Volcanol. 56, 243–260 (1994).

  8. 8

    Simkin, T. & Siebert, L. Volcanoes of the World 2nd edn (Geoscience, Tucson, 1994).

  9. 9

    Bonafede, M. & Mazzanti, M. Modelling gravity variations consistent with ground deformation in the Campi Flegrei caldera (Italy). J. Volcanol. Geotherm. Res. 81, 137– 157 (1998).

  10. 10

    Wicks, C. Jr, Thatcher, W. & Dzurisin, D. Migration of fluids beneath Yellowstone caldera inferred from satellite radar interferometry. Science 282, 458–462 (1998).

  11. 11

    Reynolds, R. W., Geist, D. & Kurz, M. D. Physical volcanology and structural development of Sierra Negra volcano, Isabela island, Galápagos archipelago. Geol. Soc. Am. Bull. 107, 1398–1410 (1995).

  12. 12

    Murray, J. B. The influence of loading by lavas on the siting of volcanic eruption vents on Mt Etna. J. Volcanol. Geotherm. Res. 35, 121–139 (1988).

  13. 13

    Briole, P., Massonnet, D. & Delacourt, C. Post-eruptive deformation associated with the 1986–87 and 1989 lava flows on Etna detected by radar interferometry. Geophys. Res. Lett. 24, 37–40 (1997).

  14. 14

    Stevens, N. F. Surface movements of emplaced lava flows measured by SAR interferometry. J. Geophys. Res. (in the press).

  15. 15

    Cervelli, P., Murray, M. H., Segall, P., Aoki, Y. & Kato, T. Estimating source parameters from deformation data, with an application to the March 1997 earthquake swarm off the Izu Peninsula, Japan. J. Geophys. Res. (in the press).

  16. 16

    Mogi, K. Relations between the eruptions of various volcanoes and the deformation of the ground surface around them. Bull. Earth. Res. Inst. Univ. Tokyo 36, 99–134 ( 1958).

  17. 17

    Geist, D., Naumann, T. & Larson, P. Evolution of Galápagos magmas: Mantle and crustal level fractionation without assimilation. J. Petrol. 39, 953–971 (1998).

  18. 18

    Allen, J. F. & Simkin, T. Fernandina Volcano's evolved, well-mixed basalts: Mineralogical and petrological constraints on the nature of the Galápagos plume. J. Geophys. Res. 105, 6017– 6041 (2000).

  19. 19

    Lawson, C. L. & Hanson, R. J. Solving Least Squares Problems (Prentice-Hall, Englewood Cliffs, New Jersey, 1974).

  20. 20

    Kanamori, H. & Anderson, D. L. Theoretical basis of some empirical relations in seismology. Bull. Seismol. Soc. Am. 65 , 1073–1095 (1975).

  21. 21

    Rowland, S., Munro, D. C. & Perez-Oviedo, V. Volcán Ecuador, Galápagos islands: erosion as a possible mechanism for the generation of steep-sided basaltic volcanoes. Bull. Volcanol. 56, 271– 283 (1994).

  22. 22

    Massonnet, D. et al. The displacement field of the Landers earthquake mapped by radar interferometry. Nature 364, 138– 142 (1993).

  23. 23

    Zebker, H., Rosen, P., Goldstein, R., Gabriel, A. & Werner, C. On the derivation of coseismic displacement fields using differential radar interferometry: The Landers earthquake. J. Geophys. Res. 99, 19617–19643 ( 1994).

  24. 24

    Massonnet, D. & Feigl, K. Radar interferometry and its application to changes in the Earth's surface. Rev. Geophys. 36 , 441–500 (1998).

  25. 25

    Mouginis-Mark, P. J., Rowland, S. K. & Garbeil, H. Slopes of western Galápagos volcanoes from airborne interferometric radar. Geophys. Res. Lett. 23, 3767–3770 (1996).

  26. 26

    Goldstein, R. M., Zebker, H. A. & Werner, C. L. Satellite radar interferometry: Two-dimensional unwrapping. Radio Sci. 23, 713–720 (1988).

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We thank the European Space Agency for providing the SAR data and for supporting F.A. with a post-doctoral fellowship. This study was also supported by NASA. We thank D. Geist and P. Lundgren for comments.

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Stanford University, Department of Geophysics, Mitchell Building, Stanford, California94305-2215, USA

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Amelung, F., Jónsson, S., Zebker, H. et al. Widespread uplift and ‘trapdoor’ faulting on Galápagos volcanoes observed with radar interferometry. Nature 407, 993–996 (2000). https://doi.org/10.1038/35039604

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