A plume of ash, estimated six miles (10km) high and three mile wide is seen after a volcano erupted in the Puyehue-Cordon Caulle volcanic chain, about 575 miles (920 km) south of the capital, Santiago June 4. (Ivan Alvarado/Reuters)

The eruption of the Puyehue-Cordón Caulle volcano in the Andes mountains of southern Chile that began on 4th June 2011, provided some spectacular images of the force of nature, as ash covered the landscape resulting in at least 3500 people being evacuated from the surrounding rural communities.  The volcano, some 870 km south of the capital Santiago, which hasn’t been active since 1960 when it erupted after an earthquake, sent its plume of ash 6 miles high across Argentina and toward the Atlantic Ocean. Within days the ash cloud reached cities all around the Southern hemisphere, as far away as Cape Town in South Africa and cities in Australia, forcing airlines to cancel hundreds of international and domestic flights and causing travel chaos.

Courtesy Nasa Earth Observatory - image taken by satellite on June 13

Dramatic pictures appeared in the media across the globe, notably in the Boston Post’s Big Picture. By 18th June the ash cloud had circled the Earth: the Chilean civil aviation authority said that “the tip of the cloud that has travelled around the world has more or less reached the town of Coyhaique”, about 600 kilometres south of the Puyehue-Cordón Caulle. As recent as 1st July, ash in the atmosphere was still disrupting flights at the Buenos Aires airport in Argentina. Fascinating data emerged as the eruption was being monitored from outer space.

The azure-blue waters of the Nahuel Huapi Lake, Bariloche, Argentina, as we saw it in March, 2010.

One of the first towns to be hit was San Carlos de Bariloche, just across the border in Argentina, in the province of Río Negro. My interest in the eruption of this volcano was heightened by the fact that it was in March of 2010 that I joined a group of people on a hiking trip to Patagonia, starting in this very same Argentinean town in the foothills of the Andes on the southern shores of Nahuel Huapi Lake, whose azure-blue waters provided a setting such that this region of lakes and mountains has often been referred to as the “Swiss Alps” of Argentina or Argentina’s lake district. The lake’s name is derived from Araucanian Indian meaning “island of the jaguars”.  It was discovered in 1670 by the Jesuit priest Nicolás Mascardi, who built a chapel on the lake’s Huemul Peninsula and established an Indian reducción (work mission).

In this combination photograph, Lake Nahuel Huapi is seen in a file photo from August 17, 2009 (top), and on June 8, 2011 with pumice and ash accumulated on its shore from an eruption of the Puyehue Volcano across the border in Chile. (Chiwi Giambirtone/Reuters)

A further set of Boston Globe Big Picture photos illustrate a dramatic transformation in the landscape since the eruption took place, as the volcanic ash fallout spread far and wide, covering everything as far as the eye can see. The very same blue waters of the Nahuel Huapi we had swum in, after arriving at the Petunia Campsite in Bariloche, were now unrecognizable, as ash blanketed its surface, as illustrated in this video clip. I caste my mind back to the early morning of 10th March, 2010, as we rose from our slumber in the bus transporting us on our overnight journey from Buenos Aires to Bariloche along route 40, still some hours from our destination, the highway following the valleys along the River Limay towards its source on the eastern side of the Nahuel Huapi.  As we gazed through the insect-splattered windscreen across the pampas landscape towards the north-west, a volcano came into view in the distance. Initially we had thought this was none other than the Osorno volcano, the volcanic peak north of Puerto Varas, the Chilean town we would be visiting later, in the course of our tour.

Upon reflection however, I realized that this could conceivably be any one of a number of volcanoes scattered along the border between Chile and Argentina, possibly even the Puyehue-Cordón Caulle volcano in the Parque Nacional Puyehue in Chile, which had now erupted so dramatically.

A boat covered by volcanic ash sits docked on the bank of Nahuel Huapi Lake, also blanketed in volcanic ash, in Villa La Angostura in southern Argentina, Thursday June 16, 2011. (Federico Grosso/Associated Press)