Article Figures & Data
Figures
- Fig. 1.
(a) Location of the main components of the West Antarctic Rift System and confirmed volcanoes (red circles: after LeMasurier et al. 1990; Smellie & Edwards 2016). (b) Location of Holocene volcanoes (red circles) in the Ethiopia/Kenya branch of the East African Rift (red shaded area). The majority of this activity is aligned along the rift axis with occasional flank volcanism. Data from Siebert & Simkin (2002) and Global Volcanism Program (2013).
- Fig. 2.
Location map of conical edifices (circles) identified from Bedmap2 (greyscale background) across the West Antarctic Rift System. The data are tabulated in Table 2. The circle colour represents the confidence factor used to assess the likelihood of cones being subglacial volcanoes, and the circle size is proportional to the cone's basal diameter. Circles with black rims represent volcanoes that have been confirmed in other studies (LeMasurier et al. 1990; Smellie & Edwards 2016), generally those that have tips which protrude above the ice surface.
- Fig. 3.
The upper panel shows an echogram from NASA's Icebridge mission (NSIDC 2014) that shows generally good agreement between a cone on the echogram and on the Bedmap2 data. The lower panel shows an echogram from Corr & Vaughan (2008) with basal topography picking out two cones; the dark layer above the bed is tephra believed to have erupted around 2000 years ago.
- Fig. 4.
Cross-sections of three cones from this study (numbers 21, 60 and 91: see Fig. 2 and Table 2 for more details and locations) and three prominent shield volcanoes, namely Mauna Kea (Hawaii), Erta Ale and Marsabit (East African Rift).
- Fig. 5.
Volume/height chart of the cones from this study (crosses) superimposed over data from volcanoes worldwide (Grosse et al. 2014). The cones closely fit the morphology data for shield volcanoes, as would be expected for basalt-dominated rift volcanism.
Tables
- Table 1.
Classification scheme used in assessing confidence that a cone extracted from Bedmap2 (Fretwell et al. 2013) can be interpreted as a volcano
Confidence assessment criterion Dataset/source Confidence score 0 0.5 1 (1) Distance to nearest raw ice-thickness measurement Figure 3 in Fretwell et al. (2013) >15 km 5–15 km <5 km (2) Expression in ice-surface DEM overlying identified subglacial cone Bedmap2 ice-surface DEM: Fretwell et al. (2013) No expression Associated but off-centre anomaly Direct overlying anomaly (3) Expression in MODIS imagery of the ice surface overlying the identified subglacial cone MODIS Mosaic of Antarctica: Scambos et al. (2007) No expression Weak expression Clear expression (4) Magnetic anomaly data ADMAP: Kim et al. (2007) No anomaly Weak anomaly Clear anomaly (5) Gravity anomaly data Studinger et al. (2002); Damiani et al. (2014); Scheinert et al. (2016) No anomaly Weak anomaly Clear anomaly Full scores are given in Table 2.
- Table 2.
Tabulation of subglacial cone coordinates, dimensions and volcanic-interpretation confidence factors (see Table 1)
Number Height (m) Average diameter (km) Elongation ratio Volume (km3) Latitude Longitude Volcano confidence factor Previously identified 1 2 3 4 5 Sum 1 800 26 1.08 106 −74.00 −80.38 0.5 1 1 0.5 0.5 3.5 Yes 2 600 14 1.15 23 −75.60 −81.60 1 1 0 1 0.5 3.5 No 3 300 7.5 1.14 3 −76.13 −83.53 1 0.5 0 1 0.5 3 No 4 300 18.5 1.18 20 −76.80 −85.27 1 0 0 1 0.5 2.5 No 5 650 24.5 1.04 77 −74.47 −86.40 0.5 0.5 0.5 0.5 0.5 2.5 No 6 350 17.5 1.19 21 −76.74 −87.50 1 0 0.5 1 0.5 3 No 7 250 17 1.27 14 −76.97 −87.89 1 0 0 1 0.5 2.5 No 8 950 29 1.07 157 −77.37 −88.10 1 0 1 0.5 0.5 3 No 9 300 19.5 1.05 22 −77.40 −89.38 1 0.5 1 0.5 0.5 3.5 No 10 350 15.5 1.07 17 −77.32 −90.34 1 0.5 1 0.5 0.5 3.5 No 11 600 32.5 1.17 124 −74.27 −89.58 0.5 0.5 0 0.5 0.5 2 No 12 550 36 1.06 140 −74.07 −91.18 0.5 0 1 0.5 0.5 2.5 No 13 450 27.5 1.20 67 −72.90 −91.30 0 1 0.5 0.5 0.5 2.5 No 14 500 22.5 1.25 50 −74.05 −92.90 1 1 0.5 1 0.5 4 No 15 1400 22.5 1.25 139 −73.73 −93.68 0.5 1 1 1 0.5 4 Yes 16 1450 19.5 1.29 108 −70.03 −125.97 1 1 1 1 0.5 4.5 Yes 17 1300 27 1.25 186 −73.89 −94.64 0.5 1 1 1 0.5 4 Yes 18 400 20 1.11 31 −78.03 −92.95 1 1 0 0.5 0.5 3 No 19 325 18.5 1.18 22 −78.21 −93.20 1 1 0 0.5 0.5 3 No 20 200 9.5 1.11 4 −78.20 −93.82 1 0.5 0 0.5 0.5 2.5 No 21 600 20.5 1.16 49 −78.15 −94.62 1 1 0 0.5 0.5 3 No 22 375 18.5 1.06 25 −78.68 −95.65 1 0 0.5 0.5 0.5 2.5 No 23 250 19 1.11 18 −78.52 −96.16 1 0.5 1 1 0.5 4 No 24 700 26.5 1.30 96 −78.13 −96.36 1 0.5 0 0.5 0.5 2.5 No 25 450 22.5 1.25 45 −78.00 −97.16 1 1 0 0.5 0.5 3 No 26 250 13.5 1.25 9 −78.67 −97.68 1 1 0 1 1 4 No 27 500 24.5 1.13 59 −74.97 −96.54 0.5 1 1 1 0.5 4 No 28 400 16.5 1.36 21 −74.86 −97.42 1 1 0 1 0.5 3.5 No 29 550 16 1.13 28 −75.07 −99.54 1 1 1 1 0.5 4.5 Yes 30 820 20.5 1.16 68 −74.73 −99.04 1 1 1 1 0.5 4.5 Yes 31 650 29 1.15 107 −75.07 −99.54 0.5 1 1 1 0.5 4 Yes 32 750 31 1.07 141 −74.03 −98.83 0.5 0 0 1 0.5 2 No 33 950 26 1.17 126 −74.21 −100.19 1 1 1 0.5 0.5 4 No 34 900 30 1.14 159 −74.51 −99.94 1 0 1 0.5 0.5 3 Yes 35 300 15.5 1.21 14 −74.72 −100.09 1 0 1 0.5 0.5 3 No 36 325 11.5 1.30 8 −75.24 −96.95 1 1 1 0.5 0.5 4 No 37 500 34 1.13 113 −72.19 −97.70 0 1 1 1 0.5 3.5 Yes 38 1025 40.5 1.19 330 −72.54 −97.61 0 0 0.5 1 0.5 2 Yes 39 400 20.5 1.16 33 −72.51 −98.38 0 1 1 1 0.5 3.5 Yes 40 525 28 1.15 81 −72.42 −99.23 0.5 1 1 1 0.5 4 Yes 41 325 20.5 1.16 27 −72.47 −99.94 0 1 1 1 0.5 3.5 Yes 42 550 33.5 1.16 121 −72.32 −101.07 0.5 1 1 0.5 0.5 3.5 Yes 43 225 11.5 1.30 6 −73.87 −103.30 0 0.5 1 1 0.5 3 No 44 675 26.5 1.12 93 −75.45 −103.29 1 1 1 0.5 1 4.5 No 45 350 9.5 1.38 6 −78.41 −101.96 1 0 0 0.5 0.5 2 No 46 575 23 1.19 60 −79.65 −101.80 1 0.5 0 1 0.5 3 No 47 275 12 1.18 8 −80.03 −101.60 1 0.5 0 0.5 0 2 No 48 250 13 1.17 8 −80.15 −101.46 1 0.5 0 0.5 0 2 No 49 175 21.5 1.15 16 −80.17 −103.39 0.5 0.5 0.5 0.5 2 No 50 325 22 1.20 31 −78.87 −102.91 1 0.5 0.5 0.5 0 2.5 No 51 225 27 1.16 32 −80.40 −105.61 0.5 1 0 1 0.5 3 No 52 1175 23 1.19 122 −78.74 −104.24 1 1 1 0.5 1 4.5 No 53 125 15 1.14 6 −77.61 −103.56 1 0.5 0.5 0.5 1 3.5 No 54 225 11.5 1.30 6 −82.05 −111.42 1 0.5 1 1 0.5 4 No 55 175 23 1.19 18 −77.43 −105.77 1 1 1 1 0.5 4.5 No 56 150 9 1.25 2 −77.70 −74.55 1 0.5 0 0.5 0 2 No 57 275 13.5 1.25 10 −78.46 −107.77 1 0.5 1 0.5 0 3 No 58 175 11 1.44 4 −76.72 −106.61 1 1 1 1 0.5 4.5 No 59 150 12.5 1.27 5 −76.87 −106.38 1 1 1 1 1 5 No 60 1200 33.5 1.16 264 −79.15 −111.05 1 0 1 1 1 4 No 61 450 14.5 1.23 19 −79.60 −111.45 1 0 0 1 0.5 2.5 No 62 200 6 1.40 1 −80.42 −114.00 1 0.5 0 1 0 2.5 No 63 425 10 1.22 8 −75.22 −106.92 0 0.5 0.5 0.5 0.5 2 No 64 450 18 1.12 29 −75.71 −108.40 1 0 1 0.5 1 3.5 No 65 375 14.5 1.23 15 −76.11 −107.68 1 0 1 0.5 1 3.5 No 66 400 17 1.27 23 −76.38 −109.78 1 0.5 1 1 1 4.5 No 67 325 10.5 1.33 7 −74.60 −110.62 0.5 1 1 0.5 0.5 3.5 No 68 400 19 1.24 28 −74.81 −110.57 1 1 1 0.5 0.5 4 No 69 350 14 1.33 13 −75.00 −110.43 0.5 1 1 0.5 0.5 3.5 No 70 750 30 1.14 132 −74.89 −111.26 1 1 1 0.5 0.5 4 No 71 2300 51.5 1.15 1197 −75.60 −110.70 1 1 1 0.5 1 4.5 Yes 72 3200 58.5 1.13 2149 −76.52 −112.02 1 1 1 1 1 5 Yes 73 250 15.5 1.07 12 −77.21 −111.92 1 0 0.5 0.5 1 3 No 74 1025 36 1.00 261 −77.72 −112.64 1 0.5 1 1 0.5 4 No 75 300 16 1.13 15 −77.67 −114.04 1 0.5 1 0.5 1 4 No 76 625 26 1.17 83 −77.80 −115.00 1 1 1 0.5 1 4.5 No 77 650 12 1.18 18 −78.08 −115.37 1 0 0.5 0.5 0 2 No 78 400 10.5 1.33 9 −78.11 −115.93 1 1 0.5 0.5 0 3 No 79 350 13.5 1.25 13 −78.93 −115.69 1 0 0.5 1 1 3.5 No 80 325 20.5 1.28 27 −79.68 −113.53 1 1 0 1 1 4 No 81 200 6 1.40 1 −80.38 −115.11 1 0.5 0 1 1 3.5 No 82 125 4.5 1.25 0 −80.38 −115.11 1 0.5 0 1 1 3.5 No 83 150 10 1.22 3 −80.34 −116.40 1 1 0 1 1 4 No 84 1750 31.5 1.10 341 −80.30 −117.49 1 1 1 1 1 5 No 85 800 20 1.22 63 −80.37 −118.90 1 0.5 1 1 1 4.5 No 86 750 18.5 1.31 50 −80.73 −117.56 1 1 1 1 1 5 No 87 150 10.5 1.33 3 −80.81 −118.65 1 1 0 1 1 4 No 88 225 13 1.36 7 −80.87 −120.70 1 0 0 1 1 3 No 89 100 9 1.25 2 −80.27 −117.62 1 1 0 0 0 2 No 90 150 10.5 1.33 3 −80.41 −118.65 1 1 1 1 0.5 4.5 No 91 550 29.5 1.19 94 −80.62 −120.12 1 0.5 1 1 1 4.5 No 92 250 12.5 1.27 8 −79.96 −120.20 1 1 1 1 0.5 4.5 No 93 150 10 1.22 3 −79.24 −119.18 1 1 0 1 0 3 No 94 100 8 1.00 1 −79.37 −119.00 1 1 0 0 0 2 No 95 125 7.5 1.14 1 −79.78 −115.18 1 0 0 0.5 0.5 2 No 96 100 8.5 1.13 1 −78.46 −120.28 1 0 0.5 1 1 3.5 No 97 1000 28.5 1.19 159 −77.54 −118.28 0.5 1 0.5 0.5 0.5 3 No 98 2600 49.5 1.11 1250 −76.96 −117.78 1 1 1 0.5 1 4.5 Yes 99 3850 58 1.11 2542 −76.07 −115.94 0.5 1 1 1 1 4.5 No 100 1350 27.5 1.29 200 −76.73 −125.76 1 1 1 1 0.5 4.5 Yes 101 1100 21 1.21 95 −76.93 −125.73 1 1 1 1 0.5 4.5 Yes 102 1050 20 1.11 82 −77.11 −125.89 0.5 1 1 0.5 0.5 3.5 Yes 103 2400 39 1.17 716 −77.32 −125.97 1 1 1 0.5 0.5 4 Yes 104 1100 22 1.20 104 −77.46 −126.85 0.5 1 1 0.5 0.5 3.5 Yes 105 550 29 1.15 91 −79.24 −128.12 0.5 0 1 0.5 0.5 2.5 No 106 600 17 1.27 34 −81.34 −125.35 1 0.5 0 1 1 3.5 No 107 150 11.5 1.30 4 −82.36 −127.50 1 1 1 1 1 5 No 108 600 25.5 1.13 77 −83.98 −133.02 1 0 1 0.5 0.5 3 No 109 500 39 1.11 149 −84.31 −131.87 1 0.5 1 0.5 0.5 3.5 No 110 125 11.5 1.30 3 −81.82 −128.45 1 0.5 1 1 1 4.5 No 111 100 8 1.29 1 −81.20 −129.58 1 1 0 0 0 2 No 112 550 42 1.15 190 −81.62 −130.38 1 0 1 1 1 4 No 113 275 28.5 1.19 44 −81.87 −130.76 1 0 0 1 1 3 No 114 350 29 1.07 58 −82.41 −134.85 1 1 1 0.5 0.5 4 No 115 150 10.5 1.33 3 −81.10 −132.52 1 0.5 1 1 1 4.5 No 116 400 31.5 1.25 78 −81.36 −133.60 1 1 1 0 0.5 3.5 No 117 100 6 1.40 1 −81.64 −134.55 1 0 0 0 1 2 No 118 250 15.5 1.07 12 −81.55 −135.48 1 0 1 1 0.5 3.5 No 119 550 21.5 1.15 50 −80.35 −131.14 1 1 1 0 1 4 No 120 250 11.5 1.30 6 −80.50 −134.03 1 0 1 1 1 4 No 121 950 36 1.12 242 −80.23 −134.29 1 0.5 1 1 0 3.5 No 122 250 30.5 1.03 46 −79.57 −132.88 1 0 0 0.5 0.5 2 No 123 325 23.5 1.24 35 −80.40 −136.32 0.5 0 1 1 1 3.5 No 124 400 29 1.00 66 −80.08 −138.89 0.5 0.5 0 1 0.5 2.5 No 125 275 32.5 1.10 57 −79.39 −137.82 0.5 0.5 1 1 0.5 3.5 No 126 125 17.5 1.19 8 −79.67 −138.15 0.5 0 1 0.5 0.5 2.5 No 127 250 19 1.11 18 −79.76 −139.69 1 0 0 0.5 0.5 2 No 128 400 24 1.18 45 −78.70 −137.18 0.5 1 0 0.5 0.5 2.5 No 129 300 10.5 1.33 6 −78.61 −137.87 0.5 0 1 0.5 0.5 2.5 No 130 600 25.5 1.13 77 −78.39 −139.25 1 0.5 1 1 0.5 4 No 131 425 39.5 1.08 130 −79.00 −142.10 1 0.5 0 0.5 0.5 2.5 No 132 700 31 1.00 132 −78.15 −140.91 1 0.5 1 0.5 0.5 3.5 No 133 675 22 1.00 64 −77.91 −140.89 1 1 1 0.5 0.5 4 No 134 2600 52.5 1.06 1406 −73.71 −126.54 0 1 1 1 0.5 3.5 Yes 135 400 28 1.15 62 −74.69 −127.78 0.5 1 1 0.5 0.5 3.5 No 136 200 4.5 1.25 1 −75.98 −128.21 0 1 1 1 0.5 3.5 Yes 137 1700 47.5 1.16 753 −76.11 −128.64 0 1 1 1 0.5 3.5 No 138 325 16 1.13 16 −75.80 −128.57 0 1 1 1 0.5 3.5 No 139 1500 19.5 1.17 112 −75.98 −129.11 0 1 1 1 0.5 3.5 Yes 140 450 5.5 1.20 3 −75.90 −129.29 0 1 1 1 0.5 3.5 No 141 1800 36 1.06 458 −75.98 −132.31 0.5 1 1 0.5 0.5 3.5 Yes 142 900 21 1.00 78 −76.24 −132.63 0.5 1 1 0.5 0.5 3.5 Yes 143 400 5 1.00 2 −76.22 −133.14 0 1 1 0.5 0.5 3 No 144 600 13 1.17 20 −76.27 −135.11 0 1 1 0.5 0.5 3 Yes 145 950 18.5 1.18 64 −76.27 −136.12 0 1 1 0.5 0.5 3 Yes 146 800 9.5 1.11 14 −75.88 −137.95 0 1 1 0.5 0.5 3 No 147 275 19.5 1.17 21 −75.62 −138.08 0 1 1 0.5 0.5 3 No 148 600 8.5 1.13 9 −78.09 −153.87 1 1 1 1 0.5 4.5 No 149 450 21.5 1.15 41 −78.13 −155.26 1 1 1 1 0.5 4.5 No 150 775 23 1.19 80 −77.88 −153.60 1 1 1 1 0.5 4.5 No 151 275 16.5 1.06 15 −77.89 −154.81 1 1 1 1 0.5 4.5 No 152 100 7 1.33 1 −78.19 −157.00 0 1 1 0.5 0.5 3 No 153 125 18 1.25 8 −82.11 −154.71 0 0 1 0.5 0.5 2 No 154 100 16.5 1.06 5 −81.96 −157.64 0 0 1 0.5 0.5 2 No 155 150 24 1.18 17 −81.53 −163.39 1 1 1 0.5 0.5 4 No 156 225 15 1.00 10 −78.00 −165.52 0 0.5 0.5 1 0.5 2.5 No 157 100 12 1.18 3 −77.18 −164.77 0 0.5 0.5 1 0.5 2.5 No 158 1400 34 1.13 318 −85.96 −163.98 0.5 1 1 0.5 0.5 3.5 Yes 159 400 10.5 1.33 9 −78.39 167.56 0.5 1 1 1 0.5 4 Yes 160 325 16.5 1.20 17 −78.50 166.04 0 1 1 1 0.5 3.5 Yes 161 1600 29 1.07 264 −78.61 165.08 0 1 1 1 0.5 3.5 Yes 162 2050 39.5 1.14 628 −78.73 163.67 0 1 1 1 0.5 3.5 Yes 163 2250 33 1.13 481 −77.78 168.67 0 1 1 1 0.5 3.5 Yes 164 1800 29.5 1.19 307 −77.70 166.83 0 1 1 1 0.5 3.5 Yes 165 1250 21 1.10 108 −77.49 166.78 0 1 1 1 0.5 3.5 Yes 166 425 22.5 1.14 42 −77.23 167.68 0 1 1 1 0.5 3.5 Yes 167 350 20.5 1.16 29 −77.18 166.94 0 1 1 0.5 0.5 3 Yes 168 750 16.5 1.20 40 −74.58 164.22 1 1 1 1 0.5 4.5 Yes 169 600 26.5 1.21 83 −73.80 169.69 0.5 1 1 1 0.5 4 Yes 170 950 33.5 1.09 209 −73.42 164.70 0 1 1 1 0.5 3.5 Yes 171 1550 34.5 1.16 362 −72.78 169.89 0 1 1 0.5 0.5 3 Yes 172 750 17.5 1.19 45 −71.93 170.41 0 1 1 1 0.5 3.5 Yes 173 500 25.5 1.13 64 −76.45 −165.16 0 0.5 0.5 0.5 0.5 2 No 174 450 34.5 1.09 105 −76.37 −166.16 0 0.5 0.5 0.5 0.5 2 No 175 450 13.5 1.25 16 −76.12 −72.41 0.5 1 1 1 0.5 4 Yes 176 400 9.5 1.38 7 −73.68 −78.91 0 1 1 0.5 0.5 3 No 177 550 20 1.22 43 −73.70 −79.43 0.5 1 1 1 0.5 4 Yes 178 300 17 1.27 17 −74.67 −78.72 0.5 1 1 1 0.5 4 Yes Average 621 21.3 1.18 121 −77.56 −120.28 0.69 0.69 0.71 0.74 0.57 3.40 The final column identifies whether the cone was a previously recognized volcano (Yes) or a new discovery (No). Most of the previously identified volcanoes are catalogued in LeMasurier et al. (1990).
- Table 3.
Statistical comparison of the morphologies of the cones identified in this study identified as volcanoes
Height (m) Average diameter (km) Axis ratio Volume (km3) Confidence factor (a) (b) (a) (b) (a) (b) (a) (b) (a) Average 701 940 21.9 17.1 1.19 2.11 144 150 3.75 Standard Deviation 641 670 10.7 11.6 0.09 0.81 345 371 0.56 Median 475 810 20.5 15.3 1.17 1.98 42 31 3.5 Minimum 100 100 4.5 2.3 1.00 1.13 0.5 0.2 3 Maximum 3850 3030 58.5 63.3 1.44 5.23 2542 3086 5 Comparison with: (a) those from a global database of shield volcanoes; and (b) Grosse et al. (2014). The two are similar, apart from the long-short axis ratio; our cones are, on average, more circular than shield volcanoes elsewhere. This could be linked to specific glaciovolcanic eruption mechanisms, but is most likely a data bias due to our detection methods excluding more elliptical edifices.
A new volcanic province: an inventory of subglacial volcanoes in West Antarctica
