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Widely considered the most spectacular peak in South America, Yerupajá is so steep that it has seldom been climbed. The best climbing approach is from the southwest, the face seen in this view. Yerupajá is locally known as El Carnicero (“The Butcher”) because of its blade-like ridges, typical of mountains that have been heavily eroded by glacial ice. Other features created by the erosive effect of flowing ice are small glacial lakes, which often vary in color due to different amounts of fine mud being fed into them by meltwater from under the glaciers. During the ice ages, the glaciers advanced many kilometers outward from the cordillera, occupying all the surrounding valley floors (all of which lie above 3,000 meters), producing U-shape valleys.
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In contrast to the gentle topography of the Sentinel Volcanic Field, Oatman Mountain (upper left) rises from the Gila River channel to an elevation of approximately 560 meters (1,837 feet). While Oatman Mountain is located close to the Sentinel field, it represents an earlier phase of volcanic activity in the area. Volcanic rocks comprising Oatman Mountain were more viscous, leading to shorter, stronger flows that are weathered into stream channels and scarps on the mountain slopes. The mountain is a popular hang gliding destination due to abundant thermal currents rising from the surrounding desert floor and lava surfaces.
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This astronaut photograph of polar mesospheric clouds was acquired at an altitude of just over 200 miles (about 321 kilometers) in the pre-dawn hours (18:24:01 Greenwich Mean Time) on July 22, 2008, as the International Space Station was passing over western Mongolia in central Asia. The dark horizon of the Earth appears at the bottom of the image, with some layers of the lower atmosphere already illuminated by the rising Sun. The higher, bluish-colored clouds look much like wispy cirrus clouds, which can be found as high as 60,000 feet (18 kilometers) in the atmosphere. However noctilucent clouds, as seen here, are observed in the mesosphere at altitudes of 250,000 to 280,000 feet (about 76 to 85 kilometers).
Astronaut observations of polar mesospheric clouds over northern Asia in June and July are not uncommon. The crew of the International Space Station acquired this image and many others in support of research for the International Polar Year. Some researchers link increased observations of these clouds to changes in global climate. Polar mesospheric clouds have been the subject of extensive observation and research from space by the Swedish satellite Odin, launched in 2001, and more recently by NASA’s Aeronomy of Ice in the Mesosphere (AIM) satellite system beginning in 2007.
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Several monuments are visible in this image, including the large Red and Bent Pyramids built by Snofru, first king of the Fourth Dynasty, which lasted from 2575–2465 BC. Other visible monuments include the pyramid complexes of Amenemhat III and Sesostris III, both kings of the Twelfth Dynasty (1991–1783 BC). Both of these complexes are poorly preserved, due to both the unstable ground conditions and the dismantling of the limestone blocks forming the outer pyramid casings during later historical periods.
The Bent Pyramid (image upper right) is so called because the slope of the outer face was lessened halfway through construction, leading to a distinctive “bent” profile. Scholars have offered different explanations for why this was done: perhaps to decrease the mass of the pyramid to prevent its collapse or to reduce the work necessary to complete it. The Red Pyramid to the north (image center) was built after the Bent Pyramid, and is named for the coloration of the building stone at the structure’s core. Compare the shadows of the Red and Bent pyramids in the image to see the different profiles of the structures (easier to see in the large image.) An irregular, dark feature to the southeast of the Bent Pyramid is not a shadow cast by a monument; it is an irrigation area extending into the desert.
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This astronaut photograph highlights three islands in the group: Bush Key, Hospital Key, and Garden Key, which is the site of Fort Jefferson. Fort Jefferson is a Civil War-era fort, perhaps most notable for being the prison of Dr. Samuel Mudd, who set the broken leg of John Wilkes Booth following Booth’s assassination of President Lincoln. The fort itself is currently undergoing extensive restoration to prevent collapse of the hexagonal outer walls (image left). The islands stand out due to brown and light tan carbonate sands visible above the Gulf of Mexico water surface. Light blue-green irregular masses in the image surrounding the islands are coral reef tops visible below the water surface.
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The image is highly oblique—taken from an angle looking outwards from the ISS, rather than straight down towards the Earth—and this perspective provides a sense of topography along the southern edge of Greenland. The exposed dark grey bedrock along the southwestern coastline has been carved by glaciers into numerous fjords, steep-sided valleys that drain directly into the ocean. The white cloud cover surrounding the island likely mingles with some sea ice and icebergs calved from glaciers. A band of high-altitude cirrus clouds (light grey) casts shadows on the lower stratus cloud deck in the lower third of the image. The thin blue layer of Earth’s atmosphere is visible spanning the top third of the image from left to right.
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This detailed astronaut photograph features Lipari Island and the northern portion of Vulcano Island. Tan, speckled areas on both islands are urban areas and towns. Lipari is the largest of the Aeolian Islands, and it is a popular tourist destination due to its rugged volcanic topography and beaches (several boat wakes are visible around the islands). White pumice beaches and caves are located along the northern and northeastern coastlines of Lipari; black sand beaches derived from lava flows can also be found on the island. The most recent eruptive activity on Lipari took place from approximately AD 580–729.
Vulcano Island is comprised of two calderas—large craters formed when explosive eruptions empty a volcano’s magma chamber, and the overlying material collapses into the resulting void. Caldera della Fossa occupies the north, and Caldera del Piano occupies the south. The volcanic cone of La Fossa, located within the Caldera della Fossa, has been the site of much of the historical eruptive activity on the island. The last eruption on Vulcano Island took place during 1898–1900.
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Sunglint images reveal great detail in surface water—in this case the marked difference between the smooth outline of the Amazon and the jagged shoreline of the Uatumã River. The jagged shoreline results from valley sides being eroded in relatively hard rocks. Because the Amazon flows in its own soft sediment, its huge water discharge smoothes its banks. The Uatumã River in this area has become a ria, a dammed valley. Sediment from the Amazon has created the dam. Another dammed valley is visible at bottom center of the scene.
Although no smoke plumes from forest fires are visible in the view, two kinds of evidence show that there is smoke in the atmosphere. The coppery color of the sunglint is typically produced by smoke particles and other aerosols scattering yellow and red light. Second, a small patch of cloud (image right) casts a distinct shadow in the atmosphere. The shadow is visible because smoke particles in the surrounding sunlit parts of the atmosphere are reflecting light back to the camera.
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The green slopes of Monte Epomeo are enclosed by urban development (light grey speckled areas) that rings the island. The last volcanic activity on Ischia took place in 1302. The neighboring island of Procida (top right) was formed from the same magma sources as Ischia, and likely shared the same volcanic “plumbing system.” Today, Ischia is a popular tourist destination due to its hot springs, hot mud baths, and the hiking opportunities afforded by Monte Epomeo. Several boat wakes are visible around both islands in this astronaut photograph.
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The urban area of Tunis is located on a flat coastal plain, and is distinguished in this astronaut photograph from the surrounding desert by the pattern of grey and tan buildings and the dark street grid. The city is bordered by an evaporating saline lake to the northeast known as Sebkhet Arina (upper left). Evaporite minerals such as halite (sodium chloride, or table salt) and gypsum produce the white deposits. They surround the darker lake center, where there is more moisture. The western urban-rural fringe is defined by a range of low hills (lower left). On the western side of these hills, dark green agricultural fields are visible.
To the southeast of the city is Lake Tunis, a lagoon that people have significantly altered from its natural state. For example, it is completely closed off from the Mediterranean Sea except for two channels, and has been since Roman times. The general lack of water circulation and input of nutrients from wastewater have altered the ecosystem, allowing reef-forming marine worms to become established; the reefs further stifle water circulation. The wastewater also causes eutrophication (overly fertile waters that trigger algae overgrowth) and occasional fish kills.
