Antarctic Glaciovolcanism

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Subglacially erupted volcanoes in Antarctica

[Read about some of Antarctica's erupting volcanoes:

http://www2.le.ac.uk/departments/geology/geoblog/penguin-rookery-at-risk-from-volcanic-eruption

http://www2.le.ac.uk/departments/geology/geoblog/bristol-blows-its-top

[see also http://blogs.agu.org/georneys/2013/02/05/fire-and-ice-antarctic-glaciovolcanism-provides-clues-to-past-climate/ ]

 

[Note: no images to be used away from this site without permission of the author (contact jls55@le.ac.uk)]

Introduction

In common with other environments, volcanoes also erupt beneath ice sheets and glaciers. Examples are well known from currently and formerly glaciated regions of the world, particularly Iceland, British Columbia and Antarctica. The volcanism is distinctive and has been given its own title: “glaciovolcanism”. Glaciovolcanism is defined as “the interactions of magma with ice in all its

Antarctic volcano distribution

Distribution of volcanoes in Antarctica. Only a few are active.

forms, including snow, firn and any meltwater” [1,2]. It is a very young science with a history of sporadic research extending back less than a century but interest in the topic has expanded dramatically since about 2000. As well as providing invaluable information on the construction of volcanoes in a uniquely hostile and inaccessible environment, important when predicting the consequences of modern glaciovolcanic eruptions (e.g. Eyjafjallajokull in Iceland, 2010), glaciovolcanic studies have also been developed into what is probably now the most powerful methodology for deriving multiple critical parameters of past ice sheets, mainly the Antarctic Ice Sheet [e.g. 3,4,5].

Subglacially erupted volcanoes as an ice sheet proxy

Studies of past ice sheets using glaciovolcanic outcrops are still in their infancy. They are best developed for examples in Antarctica, where the two largest investigations have now been completed. Because ice is not preserved in the geological record (it melts), it is not intuitively obvious how volcanic sequences can preserve a detailed record of that ice. However, the following information can be derived routinely from glaciovolcanic sequences [1,3,4]:
i.    Was ice formerly present?
ii.   Ice thickness.
iii.  Ice basal thermal regime.
iv.  Ice surface elevation.
v.   Ice sheet structure.
Because the volcanic sequences are typically quite thick (hundreds of metres) and contain resistant rocks such as lavas, they are able to persist through multiple overriding events by ice, unlike many much thinner (typically just

Tuya cartoon

Cartoon perspective view of a typical basaltic glacivolcanic edifice known as a tuya, dominated by encircling pahoehoe lava-fed deltas.

metres) glacial sedimentary sequences. However, volcanic eruptions commonly occur at intervals of several tens to hundreds of thousands of years. Thus, the volcanic record is coarse in resolution, comparable with terrestrial glacial sediments but generally worse than in marine sediments.

Glaciovolcanism in Antarctica

Antarctica is the largest glaciovolcanic province in the world. There are many volcanoes and they occur all the way from the sub-Antarctic South Sandwich Islands, through the Antarctic Peninsula and Marie Byrd Land, and into East Antarctica, a distance of about 5000 km. Eruptions coincided with the development of the Antarctic Ice Sheet. The volcanoes are overwhelmingly

Mt Melbourne

Mt Melbourne, active volcano in northern Victoria Land

basaltic and there are few examples of more evolved magmatic compositions [6,7]. They range from very large stratovolcanoes with summit elevations up to 4 km a.s.l. and basal diameters of 40-60 km, to volcanic fields composed multiple small centres [6,9]. The individual volcanoes are often extremely beautiful but the extensive cover of snow and ice and the remote locations can make accessing them quite challenging. However, unlike lower-latitude volcanoes which are typically obscured extensively by vegetation, volcanic outcrops in Antarctica are

Mt Erebus, image by Tim Burton

Mt Erebus, active Antarctic volcano. Image courtesy of Tim Burton.

characteristically very clean and beautifully exposed. In places such as northern Victoria Land, cliff sections up to 2 km high extend 10 or 20 km laterally [8]. However, many volcanoes have minimal exposure or have been extensively removed by multiple overriding ice sheets, particularly in the Antarctic Peninsula. A curiosity of subglacially erupted volcanoes is that, because they are formed of alternating thick sections of lavas and fragmental rocks and are

Mt Hampton

Mt Hampton: well preserved 11 m.yr.-old extinct Antarctic volcano.

therefore technically stratovolcanoes, the frequent development of lava-fed deltas (see below) has resulted in volcano profiles with slopes less than 15° that are normally associated with (lava-dominated) shield volcanoes. Both terms have been used to describe Antarctic volcanoes.

The Pliocene Antarctic Peninsula Ice Sheet

The Antarctic Peninsula hosts numerous mainly small volcanic edifices with ages extending between 7.5 Ma and present [6,9]. Conversely, several much larger stratovolcanoes are present in the northern part of the region [10,11]. Of the latter, the longest-lived and most important by far is the James Ross Island Volcanic Group (JRIVG) which is dominated by the Mt Haddington volcano. In situ outcrops in the JRIVG extend back to 6.25 Ma but eruptions probably commenced at least 10 m.y. ago. Several of the volcanic outcrops in the Antarctic Peninsula were important for defining features of glaciovolcanism that resulted in fundamental advances for understanding volcano construction as well as for palaeoenvironmental investigations [e.g. 12-15]. The morphology and other important characteristics of the Antarctic Peninsula Ice Sheet are extremely poorly known for periods prior to the LGM. Two generic types of glaciovolcanic sequences are present in the Peninsula, known as sheet-like

Antarctic Peninsula generic sequence types

Cartoons showing two typical generic types of glaciovolcanic sequences that crop out in the Antarctic Peninsula (taken from ref. 4).

sequences (a sequence type defined in Antarctica; 12,16] and sequences dominated by multiple lava-fed deltas (a lava-fed delta is analogous to a sedimentary delta but formed entirely by volcanic rocks, i.e. subaerial capping lavas (“topsets”) overlying subaqueous foreset hyaloclastite breccias (2,15). Characteristics of the sequences enabled a detailed history of ice sheet thicknesses to be deduced, which showed that the Antarctic Peninsula Ice Sheet has varied in thickness up to c. 850 m but was typically much less (< 400 m) for the period 6.25 Ma to present [3,4]. It thus simply draped rather than drowned

APIS ice thicknesses based on glaciovolc sequences

Thickness of the Antarctic Peninsula Ice Sheet calculated from multiple glaciovolcanic sequences (taken from ref. 4).

the landscape although it was probably persistent even through ice-poor periods corresponding to interglacials [17]. The basal thermal regime was overwhelmingly polythermal (sub-polar) [2,18,19].

The Mio-Pliocene East Antarctic Ice Sheet

Glaciovolcanic sequences are also widespread in northern Victoria Land, mainly as overlapping very large stratovolcanoes or volcanic shields. They are scattered along c. 800 km of the periphery of the present East Antarctic Ice Sheet that faces the Ross Sea [8]. The sequences are mainly Late Miocene in age (c. 12-5 Ma) and consist of several main types:  lava-fed deltas, volcanic sheet-like sequences, a glacial-lacustrine

Hallett Coast volcanoes map

Satellite image of the Hallett Coast with three large overlapping Late Miocene volcanoes distinguished (taken from ref. 5).

sequence and pyroclastic cones [7]. They were formed in association with a glacial cover that was typically only a few hundred metres thick (< 300 m). There is also no evidence ice-free conditions, which therefore either did not occur or else left no record. These observations suggest the presence of a thin persistent Late Miocene ice dome

Hallett Coast generic glaciovolc sequences

Cartoons showing generic glaciovolcanic sequence types found in northern Victoria Land, Antarctica (taken from ref. 5).

or icefield draping the pre-Miocene topography in northern Victoria Land for the period, although it may have been confluent with the greater East Antarctic Ice Sheet similar to conditions present today [5]. The Late Miocene and Pliocene periods were much warmer than today but the Transantarctic Mountains hinterland was already uplifted to its current elevation prior to the volcanism and helped the ice sheet to establish and persist. The glacial thermal regime varied from wet-based and dynamic, to cold-based (frozen to its bed) and presumably relatively stable. The variations in glacial thermal regime indicate that the Mio-Pliocene East Antarctic Ice Sheet was polythermal and the previous paradigm of a single step-change from wet-based (sub-polar or temperate) more dynamic ice to a cold ice (frozen to its bed) regime, which has dominated geological thinking for > 30 yrs, is incorrect [20].

Antarctic Refugia & the survival of life through multiple glaciations

An important spin-off of the glaciovolcanic investigations in northern Victoria Land and the Antarctic Peninsula is the recognition that ice sheets persisting for millions of years were typically thin and were not the much thicker ice sheets most modelling studies had suggested. Evolutionary and biogeographical studies are now suggesting that contemporary Antarctic terrestrial and marine biotas had ancient origins and persisted through multiple glacial cycles extending back in time millions of years, but lacked a mechanism whereby this could occur. The new ice-thickness results, together with the likely long-term influence of volcanically heated geothermal areas, suggested a possible resolution of this issue, with the thin ice conditions potentially permitting the continuing existence of nunataks as ice-free refugia (e.g. 21). However, subsequent studies of potential inland sites showed that the nunatak's faunas are unique and depaperate compared with coastal sites and they cannot explain the persistence of species at those coastal sites. Conversely, geothermal areas associated with volcanoes may be a more plausible solution. Since the magma chambers of volcanoes cool down over long timescales (many tens of thousands of years, i.e. longer than a typical glacial), the associated areas of warm ground at the surface may also be very long-lasting. Antarctic volcanoes may thus potentially create viable conditions in which terrestrial life is able to persist through multiple glacials and be reseeded across Antarctica during the interglacial periods. Initial spatial modelling studies of Antarctic biodiversity support this hypothesis and have now demonstrated a clear relationship with the volcanic "hotspots" [22].

References

1.    Smellie, 2000. Subglacial eruptions. In: Sigurdsson, H. (ed.) Encyclopaedia of Volcanoes.  Academic Press, San Diego, pp. 403-418.
2.    Smellie, 2006. The relative importance of supraglacial versus subglacial meltwater escape in basaltic subglacial tuya eruptions: an important unresolved conundrum. Earth-Science Reviews, 74, 241-268.
3.    Smellie, J.L., Johnson, J.S., McIntosh, W.C., Esser, R., Gudmundsson, M.T., Hambrey, M.J. and van Wyk de Vries, B. 2008. Six million years of glacial history recorded in the James Ross Island Volcanic Group, Antarctic Peninsula. Palaeogeography, Palaeoclimatology, Palaeoecology, 260, 122-148.
4.    Smellie, J.L., Haywood, A.M., Hillenbrand, C-D., Lunt, D.J. and Valdes, P.J. 2009. Nature of the Antarctic Peninsula Ice Sheet during the Pliocene: geological evidence & modelling results compared. Earth-Science Reviews, 94, 79-94.
5.    Smellie, J.L., Rocchi, S., Gemelli, M., Di Vincenzo, G. and Armienti, P. 2011. Late Miocene East Antarctic ice sheet characteristics deduced from terrestrial glaciovolcanic sequences in northern Victoria Land, Antarctica. Palaeogeography, Palaeoclimatology, Palaeoecology, 307, 129-149.
6.    LeMasurier, W. E. and J. W. Thomson (eds.) Volcanoes of the Antarctic plate and Southern Oceans.  American Geophysical Union, Antarctic Research Series, 48, 487 pp.
7.    Smellie, J.L., Rocchi, S. and Armienti, P. 2011. Late Miocene volcanic sequences in northern Victoria Land, Antarctica: products of glaciovolcanic eruptions under different thermal regimes. Bulletin of Volcanology, 73, 1-25.
8.    Hamilton, W., 1972. The Hallett Volcanic Province, Antarctica. United States Geological Survey Professional Papers, 456-C, 62 pp.
9.    Smellie, J.L.  1999. Lithostratigraphy of Miocene-Recent, alkaline volcanic fields in the Antarctic Peninsula and eastern Ellsworth Land.  Antarctic Science, 11, 362-378.
10.    Nelson, P. H. H., 1975. The James Ross Island Volcanic Group of north-east Graham Land. British Antarctic Survey Scientific Reports, 54, 1-62.
11.    Smellie, J.L., McIntosh, W.C. and Esser, R. 2006. Eruptive environment of volcanism on Brabant Island: evidence for thin wet-based ice in northern Antarctic Peninsula during the late Quaternary. Palaeogeography, Palaeoclimatology, Palaeoecology, 231, 233-252.
12.    Smellie, J.L., Hole, M.J. and Nell, P.A.R. 1993. Late Miocene valley-confined subglacial volcanism in northern Alexander Island, Antarctic Peninsula. Bulletin of Volcanology, 55, 273-288.
13.    Smellie, J.L. and Skilling, I.P. 1994. Products of subglacial eruptions under different ice thicknesses: two examples from Antarctica. Sedimentary Geology, 91, 115-129.
14.    Skilling, I. P., 1994. Evolution of an englacial volcano: Brown Bluff, Antarctica. Bulletin of Volcanology, 56, 573-591.
15.    Skilling, I. P. 2002. Basaltic pahoehoe lava-fed deltas: large-scale characteristics, clast generation, emplacement processes and environmental discrimination. In: Smellie, J.L., Chapman, M.G. (Eds.), Volcano–ice interaction on Earth and Mars. Geological Society, London, Special Publication, 202, 91-113.
16.    Smellie, J.L. 2008.  Basaltic subglacial sheet-like sequences: evidence for two types with different implications for the inferred thickness of associated ice. Earth-Science Reviews, 88, 60-88.
17.    Salzmann, U., Riding, J.B., Nelson, A.E. and Smellie, J.L. 2011. How likely was a green Antarctic Peninsula during warm Pliocene interglacials? A critical reassessment based on new palynofloras from James Ross Island. Palaeogeography, Palaeoclimatology, Palaeoecology, 309, 73-82.
18.    Hambrey, M.J., Smellie, J.L., Nelson, A.E. and Johnson, J.S. 2008. Late Cenozoic glacier—volcano interaction on James Ross Island and adjacent areas, Antarctic Peninsula region. Bulletin of the American Geological Society, 120, 709-731.

19.    Nelson, A.E., Smellie, J.L., Hambrey, M.J., Williams, M., Vautravers, M., Salzman, U., McArthur, J.M. and Regelous, M. 2009. Neogene glacigenic debris flows on James Ross Island, northern Antarctic Peninsula, and their implications for regional climate history. Quaternary Science Reviews, 28, 3138-3160.

20.    Smellie, J.L., Rochi, S. & 7 authors. 2014. Glaciovolcanic evidence for a polythermal Neogene East Antarctic Ice Sheet. Geology, 42, 39-41.

21.    Convey, P., Stevens, M.I., Hodgson, D.A., Smellie, J.L., Hillenbrand, C-D., Barnes, D.K.A., Clarke, A., Pugh, P.J.A., Linse, K. and Cary, S.C. 2009. Exploring biological constraints on the glacial history of Antarctica. Quaternary Science Reviews, 28, 3035-3048.

22. Fraser, C.I., Terauds, A., Smellie, J., Convey, P. and Chown, S.L. 2014. Geothermal activity helps life survive glacial cycles. Proceedings of the National Academy of Sciences, doi/10.1073/pnas.1321437111.

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