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    Vanuatu's Lopevi Volcano released a plume on 3 May 2007 (center of photo) that was captured by NASA's Aqua satellite. The US Air Force Weather Agency reported an extensive area of vog resulting from the volcanic eruption. When gases from a volcano - particularly sulfur dioxide - react with oxygen, water, dust, and sunlight, volcanic smog (or vog) results. Besides Lopevi and its neighboring islands, this image shows the volcanic plume blowing westward away from the volcano. The plume appears as a small, mostly opaque puff of gray-beige. The resulting area of vog, which appears as a more transparent, dingy-gray haze, dwarfs the diminutive plume. Lopevi is a stratovolcano composed of alternating layers of solidified lava, hardened ash, and volcanic rocks. One of the island nation's most active volcanoes, this volcanic island is only about 7 km (4 mi) wide. Eruptions have been recorded at Lopevi since the middle of the 19th century. Vanuatu's two major islands of Espiritu Santo and Malakula appear in the upper left. Image courtesy of NASA.
    A thick blue haze stretches over the South Pacific archipelago of Vanuatu on the morning of 12 April 2010. The haze is volcanic fog - vog - emitted by the Gaua and Ambrym Volcanoes. Both are known for producing volcanic plumes rich in sulfur dioxide. This gas reacts with moisture in the air to create small droplets (called aerosols) of sulfuric acid, which scatters blue light, coloring the plume. This overview image shows the plume extending for thousands of kilometers to the northwest (upper left) and southeast (lower right) of the islands. Photo courtesy of NASA.
    A higher-resolution view of the previous Vanuatu Archipelago image showing the two active volcanoes of Gaua and Ambrym. Vanuatu's two major islands of Espiritu Santo (top) and Malakula (bottom) appear in the center of the image. Photo courtesy of NASA.
    The thick, steam-rich plume from Guau Volcano blows directly northeast in this natural-color satellite image acquired on 24 April 2010. The thick steam is brighter white than the surrounding lower-altitude clouds. Vegetation is green, as is Lake Letas. Vegetation to the south and west of the volcano, damaged by ash and acidic volcanic gases, is dark gray-brown. Photo courtesy of NASA.
    Periodically active volcano Mt. Manaro is the dominant feature in this shaded relief image of Aoba (Ambae) Island, part of the Vanuatu Archipelago located 2,250 km (1,400 mi) northeast of Sydney, Australia. The 1,496 m (4,908 ft) high Hawaiian-style basaltic shield volcano features two lakes within its summit caldera, or crater. Two visualization methods were combined to produce the image: shading and color coding of topographic height. The shade image was derived by computing topographic slope in the northwest-southeast direction, so that northwest slopes appear bright and southeast slopes appear dark. Color coding is directly related to topographic height, with green at the lower elevations, rising through yellow and tan, to white at the highest elevations. Image courtesy of NASA.