The Lost World: Environmental Effects During the Formation of a Giant Volcanic Province
Coffin, MF and Frey, FA and Wallace, P, The Lost World: Environmental Effects During the Formation of a Giant Volcanic Province, ODP Highlights: International Scientific Contributions from the Ocean Drilling Program, Joint Oceanographic Institutions, USA, 1, 1, p. 20. (2003) [Internal Newsletter]
Large igneous provinces (LIPs) form when extraordinary amountsof mantle-derived magma enter regions of the Earths crust. Theintense igneous activity during their creation temporarily increasesthe flux of mass and energy from the mantle to the crust, hydro-sphere, biosphere, and atmosphere, with many possible globalenvironmental effects. During Mesozoic and Cenozoic time, LIPs have typicallyformed in geologically brief (1-10 million year) episodes. Theyoungest LIP formed ~15 million years ago. On continentallithosphere, LIPs are also known as continental flood basalts,which are relatively well studied. Several are associated with massextinctions and environmental changes, although causal relation-ships and feedback loops are not well understood. On transition-al and oceanic lithosphere, respectively, divergent volcanicmargins and oceanic plateaus are relatively understudied, withdrilling being the primary means of sampling. Ocean drilling at the two most voluminous LIPs on Earth, the KerguelenPlateau/Broken Ridge in the southern Indian Ocean and theThe Lost World: Environmental Effects Duringthe Formation of a Giant Volcanic ProvinceOntong Java Plateau in the western Pacific, has providedinformation on the processes that form LIPs and their potentialenvironmental consequences. The uppermost crust of both the Kerguelen Plateau and BrokenRidge is dominated by the products of massive magmatism. Physicalcharacteristics of the LIP lava flows together with wood fragments,charcoal, pollen, spores and seeds in the shallow water sedimentsoverlying igneous basement, show that large portions of theKerguelen Plateau and Broken Ridge formed islands. After theirformation, the islands gradually subsided by as much as severalthousand meters to their present water depths.The large volume and long duration of subaerial basalticvolcanism on the Kerguelen Plateau and Broken Ridge, combinedwith the high latitude of the plateau, would all have contributed to potential global environmental changes involving climate, sealevel, oceanic anoxia, seawater composition, biological radiations,and extinctions. The eruption of enormous volumes of basalticmagma during their formation released volatiles such as carbondioxide (CO2), sulfur (S), chlorine (Cl), and fluorine (F). Because theLIP formed at high latitudes, where the tropopause is relatively low,the effects of these eruptions could have been intensified becauselarge basaltic eruption plumes can transport SO2and other volatilesinto the stratosphere. Sulfuric acid aerosol particles that form in thestratosphere after such erup-tions have a longer residencetime and greater global disper-sal than if the SO2remains inthe troposphere; therefore theyhave greater effects on climateand atmospheric chemistry.During the final stages ofplateau construction, highlyexplosive felsic eruptions likelyinjected both particulate materi-al and volatiles (SO2,CO2)directly into the stratosphere.Significant volume of explosive,subaerial felsic volcanism,undiscovered until 1999, wouldhave further contributed to theeffects of this plume volcanismon the global environment.