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November 25 and 26, 2002
At left, the previous map of the McDonald Islands; at right, the new contours as drawn by a cartographer passenger from memory and traced over the old map. | ||
Press Release by Margaret Bradshaw: Major volcanic changes to McDonald Island
Tourists aboard a New Zealand chartered ship on a 30 day visit to the remote sub-Antarctic islands of the South Indian Ocean appear to have been the first to notice that a small volcanic island in Australian waters neard Heard Island has significantly changed its shape and size. The Russian ship Akademik Shokalskiy, on charter to Heritage Expeditions, was carrying 39 passengers between Crozet and Heard Islands. It was passing McDonald Island at dawn [on November 25, 2002] when the changed profile was noticed by a passenger, Grahame Budd, who had been on the island in 1971. Comparison of old and new photographs showed that the whole northern part of the island is much higher than before, and that three quarters of the island is completely new. After a visit to Heard Island, where three of the passengers (Max Downes, Grahame Budd, and Jon Stephenson) had worked in the 1950s and 1960s, the Expedition Leader, Rodney Russ, decided to return to McDonald Island for a closer look in better light. No landings could be made because of Australian restrictions, and the surrounding uncharted waters prevented a close approach. Steaming slopes and two types of lava dome greeted the passengers. The view from the north showed that at least three separate volcanic cones had buried most of the old land surface. Another passenger, Tony Bomford, known for his mapping in South Georgia and Australia, estimated that the highest point was now 310 metres in the north, compared to an earlier high point of 212 metres on Maxwell Hill in the south. He promptly produced a sketch map of the new island with 50 metre form lines. Analysis of enlarged digital photographs taken by passengers on the second visit indicate that considerable sedimentation has occurred along the coastline, so that the formerly separate Flat Island is now joined to the main island. Several metres of ash appear to have blanketed the northern half of McDonald Island, and Macaroni Hill at its northern end has disappeared. A low-lying spit and reef now extend over a kilometre to the east of McDonald Island and are hazards to shipping. Geologist Jon Stephenson, another former Heard Island expeditioner who had climbed on Big Ben with Grahame Budd in 1963, viewed the lava domes with great interest. "The finger-like pinnacles associated with two of the domes are probably being forced out as spines by pressure from below. This may mean that the volcano is in an unstable state and could erupt violently again." An unseen vent to the south of these domes is producing an intermittent smoke plume. A larger, more rounded volcano, possibly composed of a different type of lava, now covers the central part of the island. Much of the new ground has fumaroles emitting steam. It is unclear when these new volcanic domes were formed. Earthquakes felt on Heard Island in 1992 were followed by the arrival of pumice fragments on the beaches. Volcanic activity on or near McDonald Island was reported in 1997, 1999, and 2001, but the greatly altered shape of the island has apparently not been reported. Whenever this activity occurred, it did not destroy life on the island. Penguins are still nesting up to the top of Maxwell Hill, and in patch-like colonies on the ash-covered remnants of the old land inshore of the new spit, although they have deserted Flat Island. There were also plenty of penguins and seals on the beaches, and several dozen fur seals were seen swimming offshore. The two geologists on the Heritage Expedition (Dr Jon Stephenson and Dr Margaret Bradshaw) recommend that a future visit to the island be made, despite the island being officially a closed area, so that the sequence of the new volcanic events and the composition of the lavas can be determined. | ||
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