Abstract Two volcanoes in Marie Byrd Land, Mount Berlin and Mount Takahe, can be considered active, and a third, Mount Waesche, may be as well; although the chronology of activity is less well constrained. The records of explosive activity of these three volcanoes is well represented through deposits on the volcano flanks and tephra layers found in blue ice areas, as well as by the presence of cryptotephra layers found in West and East Antarctic ice cores. Records of effusive volcanism are found on the volcano flanks but some deposits may be obscured by pervasive glacerization of the edifices. Based on a compilation of tephra depths–ages in ice cores, the activity patterns of Mount Takahe and Mount Berlin are dramatically different. Mount Takahe has erupted infrequently over the past 100 kyr. Mount Berlin, by contrast, has erupted episodically during this time interval, with the number of eruptions being dramatically higher in the time interval between c. 32 and 18 ka. Integration of the Mount Berlin tephra record from ice cores and blue ice areas over a 500 kyr time span reveals a pattern of geochemical evolution related to small batches of partial melt being progressively removed from a single source underlying Mount Berlin.

Abstract In the last two centuries, demographic expansion and extensive urbanization of volcanic areas have increased the exposure of our society to volcanic hazards. Antarctica is no exception. During the last decades, the permanent settlement and seasonal presence of scientists, technicians, tourists and logistical personnel close to active volcanoes in the south polar region have increased notably. This has led to an escalation in the number of people and the amount of infrastructure exposed to potential eruptions. This requires advancement of our knowledge of the volcanic and magmatic history of Antarctic active volcanoes, significant improvement of the monitoring networks, and development of long-term hazard assessments and vulnerability analyses to carry out the required mitigation actions, and to elaborate on the most appropriate response plans to reduce loss of life and infrastructure during a future volcanic crisis. This chapter provides a brief summary of the active volcanic systems in Antarctica, highlighting their main volcanological features, which monitoring systems are deployed (if any), and recent (i.e. Holocene and/or historical) eruptive activity or unrest episodes. To conclude, some notes about the volcanic hazard assessments carried out so far on south polar volcanoes are also included, along with recommendations for specific actions and ongoing research on active Antarctic volcanism.

Abstract In Marie Byrd Land and Ellsworth Land 19 large polygenetic volcanoes and numerous smaller centres are exposed above the West Antarctic Ice Sheet along the northern flank of the West Antarctic Rift System. The Cenozoic (36.7 Ma to active) volcanism of the Marie Byrd Land Volcanic Group (MBLVG) encompasses the full spectrum of alkaline series compositions ranging from basalt to intermediate (e.g. mugearite, benmoreite) to phonolite, peralkaline trachyte, rhyolite and rare pantellerite. Differentiation from basalt is described by progressive fractional crystallization; however, to produce silica-oversaturated compositions two mechanisms are proposed: (1) polybaric fractionation with early-stage removal of amphibole at high pressures; and (2) assimilation–fractional crystallization to explain elevated 87 Sr/ 86 Sr i ratios. Most basalts are silica-undersaturated and enriched in incompatible trace elements (e.g. La/Yb N >10), indicating small degrees of partial melting of a garnet-bearing mantle. Mildly silica-undersaturated and rare silica-saturated basalts, including tholeiites, are less enriched (La/Yb N <10), a result of higher degrees of melting. Trace elements and isotopes (Sr, Nd, Pb) reveal a regional gradient explained by mixing between two mantle components, subduction-modified lithosphere and HIMU-like plume ( 206 Pb/ 204 Pb >20) materials. Geophysical studies indicate a deep thermal anomaly beneath central Marie Byrd Land, suggesting a plume influence on volcanism and tectonism.

Abstract Nineteen large (2348–4285 m above sea level) central polygenetic alkaline shield-like composite volcanoes and numerous smaller volcanoes in Marie Byrd Land (MBL) and western Ellsworth Land rise above the West Antarctic Ice Sheet (WAIS) and comprise the MBL Volcanic Group (MBLVG). Earliest MBLVG volcanism dates to the latest Eocene (36.6 Ma). Polygenetic volcanism began by the middle Miocene (13.4 Ma) and has continued into the Holocene without major interruptions, producing the central volcanoes with 24 large (2–10 km-diameter) summit calderas and abundant evidence for explosive eruptions in caldera-rim deposits. Rock lithofacies are dominated by basanite and trachyte/phonolite lava and breccia, deposited in both subaerial and ice-contact environments. The chronology of MBLVG volcanism is well constrained by 330 age analyses, including 52 new 40 Ar/ 39 Ar ages. A volcanic lithofacies record of glaciation provides evidence of local ice-cap glaciation at 29–27 Ma and of widespread WAIS glaciation by 9 Ma. Late Quaternary glaciovolcanic records document WAIS expansions that correlate to eustatic sea-level lowstands (MIS 16, 4 and 2): the WAIS was +500 m at 609 ka at coastal Mount Murphy, and +400 m at 64.7 ka, +400 m at 21.2 ka and +575 m at 17.5 ka at inland Mount Takahe.

Abstract Since Jurassic time ( c. 200 Ma), Antarctica has had a greater diversity of volcanism than other southern continents. It includes: (1) voluminous mafic and felsic volcanism associated with the break-up of Gondwana; (2) a long-lived continental margin volcanic arc, including back-arc alkaline volcanism linked to slab rollback; (3) small-volume mafic alkaline volcanism associated with slab-window formation; and (4) one of Earth's major continental rift zones, the West Antarctic Rift System (WARS), with its numerous large alkaline central volcanoes. Several of Antarctica's volcanoes are still active. This chapter is a review of the major volcanic episodes and their principal characteristics, in their tectonic, volcanological and palaeoenvironmental contexts. Jurassic Gondwana break-up was associated with large-scale volcanism that caused global environmental changes and associated mass extinctions. The volcanic arc was a major extensional arc characterized by alternating volcanic flare-ups and lulls. The Neogene rift-related alkaline volcanism is dominated by effusive glaciovolcanic eruptions, overwhelmingly as both pāhoehoe- and ‘a‘ā-sourced lava-fed deltas. The rift is conspicuously poor in pyroclastic rocks due to the advection and removal of tephra erupted during glacial intervals. Volcanological investigations of the Neogene volcanism have also significantly increased our knowledge of the critical parameters and development of the Antarctic Ice Sheet.

Abstract A combination of aerogeophysics, seismic observations and direct observation from ice cores, and subglacial sampling, has revealed at least 21 sites under the West Antarctic Ice Sheet consistent with active volcanism (where active is defined as volcanism that has interacted with the current manifestation of the West Antarctic Ice Sheet). Coverage of these datasets is heterogeneous, potentially biasing the apparent distribution of these features. Also, the products of volcanic activity under thinner ice characterized by relatively fast flow are more prone to erosion and removal by the ice sheet, and therefore potentially under-represented. Unsurprisingly, the sites of active subglacial volcanism that we have identified often overlap with areas of relatively thick ice and slow ice surface flow, both of which are critical conditions for the preservation of volcanic records. Overall, we find the majority of active subglacial volcanic sites in West Antarctica concentrate strongly along the crustal-thickness gradients bounding the central West Antarctic Rift System, complemented by intra-rift sites associated with the Amundsen Sea–Siple Coast lithospheric transition.

Abstract Petrological investigations over the past 30 years have significantly advanced our knowledge of the origin and evolution of magmas emplaced within and erupted on top of the Antarctic Plate. Over the last 200 myr Antarctica has experienced: (1) several episodes of rifting, leading to the fragmentation of Gondwana and the formation by c. 83 Ma of the current Antarctica Plate; (2) long-lived subduction that shut down progressively eastwards along the Gondwana margin in the Late Cretaceous and is still active at the northernmost tip of the Antarctic Peninsula; and (3) broad extension across West Antarctica that produced one of the Earth's major continental rift systems. The dynamic tectonic history of Antarctica since the Triassic has led to a diversity of volcano types and igneous rock compositions with correspondingly diverse origins. Many intriguing questions remain about the petrology of mantle sources and the mechanisms for melting during each tectonomagmatic phase. For intraplate magmatism, the upwelling of deep mantle plumes is often evoked. Alternatively, subduction-related metasomatized mantle sources and melting by more passive means (e.g. edge-driven flow, translithospheric faulting, slab windows) are proposed. A brief review of these often competing models is provided in this chapter along with recommendations for ongoing petrological research in Antarctica.

Abstract The Marie Byrd Land volcanic province is a late Cenozoic alkaline basalt-trachyte volcanic field on the Pacific coast of West Antarctica. Most of these volcanoes are partially buried beneath the West Antarctic ice sheet, but in some, a combination of tectonic uplift and lowering of ice level has exposed basal hydrovolcanic sections produced by eruptions in an englacial environment. Some of the largest and best preserved hydrovolcanic structures are delta-like in form, with gentle distal slopes, and foreset bedded deposits composed of hyaloclastites, pillow breccias, pillow lavas, subaerial flows and air fall tephras. Three broad categories of processes related to delta evolution are described here; (1) flow of lava from a subaerial to an englacial environment; (2) intrusion of dykes and sills; and (3) edifice settling, which includes a variety of down-slope movement phenomena. This paper focuses on documenting post-depositional structures that are superbly exposed in these deltas. It describes the apparently province-wide lack of pillow lava cores in Marie Byrd Land englacial volcanoes, and factors that may be related to this anomaly, and it describes characteristics of hyaloclastites that are relevant to future glaciological, sedimentological and geophysical studies of the West Antarctic ice sheet.

Abstract Knowledge of variations in the extent and thickness of the Antarctic Ice Sheet is key for understanding the behaviour of Southern Hemisphere glaciers during the last ice age and for addressing issues involving global sea level, ocean circulation and climate change. Insight into past ice-sheet behaviour also will aid predictions of future ice-sheet stability. Here, we review terrestrial evidence for changes in ice geometry that occurred in the Ross Sea sector of Antarctica at the Last Glacial Maximum (LGM) and during subsequent deglaciation. During the LGM, a thick grounded ice sheet extended close to the continental shelf edge in the Ross Embayment. This ice reached surface elevations of more than 1000 m along the coast of the central and southern Transantarctic Mountains and Marie Byrd Land. The local LGM occurred by 18 ka on the coast, but as late as 7–10 ka inland. The first significant thinning took place at roughly 13 ka, with most ice loss happening in the Holocene. This history makes it unlikely that the Ross Sea sector was a major contributor to meltwater pulse 1A (MWP 1A). Resolution of a possible Antarctic origin for MWP 1A awaits detailed reconstructions from all sectors of the ice sheet.