This detailed astronaut photograph features two stratovolcanoes—Pico de Teide and Pico Viejo—located on Tenerife Island, part of the Canary Islands of Spain. Stratovolcanoes are steep-sided, typically conical volcanoes formed by interwoven layers of lava and fragmented rock material from explosive eruptions. Pico de Teide has a relatively sharp peak, whereas an explosion crater forms the summit of Pico Viejo. The two stratovolcanoes formed within an even larger volcanic structure known as the Las Cañadas caldera. A caldera is a large collapse depression usually formed when a major eruption completely empties the magma chamber underlying a volcano. The last eruption of Teide occurred in 1909.

Sinuous flow levees marking individual lava flows are perhaps the most striking volcanic features visible in the image. Flow levees are formed when the outer edges of a channelized lava flow cool and harden while the still-molten interior continues to flow downhill. Numerous examples radiate outwards from the peaks of both Pico de Teide and Pico Viejo. Brown to tan overlapping lava flows and domes are visible to the east-southeast of the Teide stratovolcano. Increased seismicity, carbon dioxide emissions, and fumarolic (gas and smoke) activity within the Las Cañadas caldera and along the northwestern flanks of the volcano were observed in 2004. Monitoring of the volcano to detect renewal of activity is ongoing.

Large wildfires that began in July continued to burn in interior Alaska in the first week of August 2009. These images from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite on August 2 show some of the state’s largest blazes and the thick pall of smoke they were creating. The top image is a natural-color (photo-like) view of the area, while the lower image combines visible, shortwave-, and near-infrared light to make burned areas (brick red) stand out better from unburned vegetation (bright green). In this kind of false-color image, the bright pink areas along the perimeters of the fires are often a sign of open flame.

According to the August 3 report from the Alaska Interagency Coordination Center, 483 fires had burned across the state so far this year, affecting about 2.4 million acres. The Railbelt Complex was the largest one burning in August, at an estimated 462,298 acres. The Tanana River appears to be creating a natural firebreak at the northern edge of the fire, which is spreading to the south. To the east, the smaller Wood River Fire (107,634 acres) has bright pink spots along both its northern and southern perimeters. Both these fires, as well as the Big Creek Fire (145,652 acres) and Little Black One Fire (292,907 acres) along the Yukon River, were triggered by lightning.