This image shows the huge plume¹ of sulphur dioxide that spewed from Chile's Puyehue-Cordón Caulle Volcanic² Complex, which lies in the Andes about 600 km south of Santiago. After lying dormant³（休眠的，静止的） for more than 50 years, a series of rumbling⁴（隆隆声） earthquakes signalled the beginnings of this major volcanic eruption⁵. On 4 June, a fissure⁶ opened, sending a towering plume of volcanic ash and gas over 10 km high. Several thousand people were evacuated⁷ as a thick layer of ash and pumice fell（浮岩羽） and blanketed a wide area. Airports in Chile and Argentina were closed as a result.

The image was generated on 6 June using data from the Infrared⁸ Atmospheric⁹ Sounding Interferometer on Eumetsat's MetOp-A satellite. As the eruption continued, the image shows how strong winds initially¹⁰ swept the broad plume of sulphur dioxide northwards and then eastwards¹¹ across Argentina and out over the southern Atlantic Ocean.

Strong westerly winds are common in this region because it lies within the belt of the 'Roaring Forties'. Since there is little land south of 40º, higher wind speeds can develop than at the same latitudes¹²（纬度） in the Northern Hemisphere.

Interestingly, over the South Atlantic, the plume take a sharp turn to the north as a pressure system causes the wind to change direction.

The Puyehue-Cordón Caulle complex is a chain of volcanoes that includes the Puyehue volcano, the Cordilera Nevada caldera and the Cordón Caulle rift¹³ zone. This event appears to have stemmed from the rift zone（裂谷带） and is the most serious since the eruption of 1960, also from the same vent¹⁴（发泄，出口） .

Chile has more than 3000 volcanoes, of which around 80 are currently active.

The image represents sulphur dioxide concentrations within the full vertical¹⁵ column of atmosphere. It was generated using data from the interferometer（干涉仪） , which was developed by the French space agency CNES for MetOp-A.