484 SEAMOUNTS atolls highly desirable locations for settlement and vacation Glossary Abyssal hill A low-relief elongate hill formed by horst-and-graben style faulting around a mid-ocean ridge Alkali basalt A variety of basalt that has relatively high sodium and potassium contents Atoll A ring of carbonate reef islands enclosing a lagoon built atop a subsiding seamount in tropical latitudes Pillow lava A type of subaqueous lava flow consisting of spherical or elongate tubes formed by the rapid quenching of lava Tubes seen in cross-section often resemble pillows, with a flat base and a convex upper surface Scoria Glassy porous pyroclastic lava Surtseyan A type of volcanic eruption, based on observations at Surtsey in Iceland, which is the phreatomagmatic equivalent of a Hawaiian or quiescent lava flow eruption Tholeiitic basalt A variety of basalt characterized by the presence of orthopyroxene in addition to clinopyroxene and calcium-plagioclase See Also History of Geology Since 1962 Large Igneous Provinces Lava Mantle Plumes and Hot Spots Sedimentary Environments: Reefs (‘Build-Ups’) Sedimentary Processes: Particle-Driven Subaqueous Gravity Processes Tectonics: Hydrothermal Activity; Mid-Ocean Ridges Volcanoes Further Reading Barone AM and Ryan WBF (1990) Single plume model for asynchronous formation of Lamont Seamounts and adjacent Pacific Rise terrains Journal of Geophysical Research 95 N B7: 10801 10827 Batiza R (1989) Seamounts and seamount chains of the eastern Pacific In: Winterer EL, Hussong DM, and Decker RW (eds.) The Geology of North America, Volume N, The Eastern Pacific Ocean and Hawaii, pp 289 306 Boulder: Geological Society of America Batiza R and Vanko D (1984) Volcanic development of small oceanic central volcanoes on the flanks of the East Pacific Rise inferred from narrow beam echo sounder surveys Marine Geology 54: 53 90 Clague DA, Reynolds JR, and Davis AS (2000) Near ridge seamount chains in the north eastern Pacific Ocean Journal of Geophysical Research 105: 16 541 16 561 Davis EE (2000) Earth science: volcanic action at Axial Seamount Nature 403: 379 480 Johnson HP and Embley RW (eds.) (1990) Axial Seamount: an active ridge axis volcano on the central Juan de Fuca Ridge Journal of Geophysical Research 95: 12 689 12 966 Keating BH and McGuire WJ (2000) Island edifice failures and associated tsunami hazards Pure and Applied Geophysics 157: 899 955 Keating BH, Fryer P, Batiza R, and Boehlert W (eds.) (1987) Seamounts, Islands, and Atolls Geophyiscal Mono graph Series Volume 43 Washington DC: American Geophysical Union Mitchell NC (2001) Transition from circular to stellate forms of submarine volcanoes Journal of Geophysical Research 106: 1987 2004 Moore JG, Normark WR, and Holcomb RT (1994) Giant Hawaiian landslides Annual Review of Earth and Planetary Sciences 22: 119 144 Ranero CR and Von Huene R (2000) Subduction erosion along the Middle America convergent margin Nature 404: 748 752 Schmidt R and Schminke H U (2000) Seamounts and island building In: Sigurdsson H, Houghton B, McNutt SR, Rymer H, and Stix J (eds.) Encyclopedia of Volcanoes, pp 383 402 San Diego: Academic Press Takahashi E, Lipman PW, Garcia MO, Naka J, and Aramaki S (eds.) (2002) Hawaiian Volcanoes: Deep Un derwater Perspectives Geophysical Monograph Series Volume 128 Washington DC: American Geophysical Union Thorarinsson S (1967) Surtsey: The New Island in the North Atlantic New York: Viking Wessel P (2001) Global distribution of seamounts inferred from gridded Geosat/ERS altimetry Journal of Geophysical Research 106: 19 431 19 441