File:Vog from Ambrym Volcano, Vanuatu (MODIS 2017-03-16).jpg

English: The island of Ambrym lies in the South Pacific Ocean in the Republic of Vanuatu about 2,000 km (1,200 miles) east of Australia and 1,600 km (1,000 miles) north of New Zealand. Covered in jungle, this triangle-shaped island is home to a massive and active volcano. Ambrym volcano stands 4,377 feet (1,334 meters) above sea level and is home to two active craters, Marum and Benbow. The website, Volcano Discovery (volcanodiscovery.com) describes the volcano in these words, “Ambrym’s caldera is a wide, impressive moon-like landscape containing an ash plain, cut by innumerable erosion gullies and containing several active craters and recent lava flows".

The Volcanic Ash Advisory Center Wellington (VAAC) issued advisories on March 3 and 4, stating that Ambrym was experiencing continuous low-level ash emissions. Such low-level emissions are also often accompanied by heavy degassing, including toxic gasses such as sulfur dioxide. When sulfur dioxide, dust, and other volcanic pollutants mix with water vapor and oxygen in the presence of sunlight, volcanic smog (“vog”) is created. At ground level, vog appears much like haze, and can cause a number of health issues, particularly respiratory issues such as sinusitis and allergies.

On March 5, 2017 the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite captured a true-color image of vog from Ambrym volcano spreading across the South Pacific. The vog appears as a pale blue-gray haze, with thinner and more diffuse edges than the nearby bright-white clouds.