Volcanoes near Usulutan, El Salvador are featured in this image photographed by an Expedition 23 crew member on the International Space Station. The Pacific coastline of much of Central America is marked by a line of active and quiescent volcanoes known to geologists as the Central American Volcanic Arc, or CAVA. The volcanoes result from the upward movement of magma generated along the subduction zone between the Cocos and Caribbean tectonic plates; frequent earthquakes also occur along the plate boundary. This photograph includes four stratovolcanoes — a type of volcano associated with active subduction zones — located near the midpoint of the CAVA in El Salvador. Scientists believe while all of the volcanoes shown here have been active during the Holocene Epoch (approximately 10,000 years ago to present), only the 2,130-meter-high San Miguel (also known as Chaparrastique) has been active during historical times. The most recent activity of San Miguel was a minor gas and ash emission in 2002. The steep conical profile and well-developed summit crater are evident at left, along with dark lava flows produced by San Miguel. Immediately to the northwest the truncated summit of Chinameca volcano (also known as El Pacayal) is marked by a two-kilometer-wide caldera, formed when the volcano’s magma chamber was emptied by a powerful eruption followed by collapse of the chamber’s roof. Like its neighbor San Miguel, Chinameca’s slopes host coffee plantations. Moving to the southwest the eroded cone of El Tigre volcano is visible. According to scientists, El Tigre volcano formed during the Pleistocene Epoch (1.8 million to approximately 10,000 years ago) and is likely the oldest of the stratovolcanoes depicted in the image. Usulutan volcano is located directed to the southwest of El Tigre. While the flanks of Usulutan have been dissected by stream flow it still retains a summit crater that is breached on the eastern side. Several urban areas – recognizable as light gray to white regions contrasting with green vegetation and tan fallow agricultural fields – are located in the vicinity of these volcanoes, including Usulutan (upper right) and Santiago de Mara (lower right).
Beirut Metropolitan Area, Lebanon is featured in this image photographed by an Expedition 16 crewmember on the International Space Station. The capital of Lebanon, Beirut is located along the southeastern shoreline of the Mediterranean Sea. According to geologists, the metropolitan area is built on a small peninsula composed mainly of sedimentary rock deposited over the past 100 million years or so. The growth of the city eastwards is bounded by foothills of the more mountainous interior of Lebanon (sparsely settled greenish brown region visible at upper right). While this sedimentary platform is stable, the country of Lebanon is located along a major transform fault zone, or region where the African and Arabian tectonic plates are moving laterally in relation to (and against) each other. This active tectonism creates an earthquake hazard for the country. The Roum Fault, one of the fault strands that is part of the transform boundary, is located directly to the south of the Beirut metropolitan area. Other distinctive features visible in this image include the Rafic Hariri Airport at lower right, the city sports arena at center, and several areas of green and open space (such a large golf course at center). Also visible in the image are several plumes of sediment along the coastline — the most striking of which are located near the airport. The general lack of vegetation in the airport may promote higher degrees of soil transport by surface water runoff or wind.
Aeolian Islands, Italy are featured in this image photographed by an Expedition 17 crewmember on the International Space Station. The Aeolian Islands formed from a chain of volcanoes in the Tyrrhenian Sea to the north of the island of Sicily. The islands have been studied by geologists and vulcanologists since the 18th century, and were accorded UNESCO World Heritage Site status in 2000 in recognition of their continuing value to study of volcanic processes. Two types of volcanic eruption, Vulcanian and Strombolian, were defined based on study and observation of geologic processes on the islands of Vulcano and Stromboli (not shown). This detailed view features the island of Lipari and the northern portion of the island of Vulcano. Tan, speckled areas on both islands are urban areas and towns. Lipari is the largest of the Aeolian Islands, and is a popular tourist destination due to its rugged volcanic topography and beaches (several boat wakes are visible in the image 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 between approximately 580-729. The island of Vulcano (right) is comprised of two calderas — large craters formed when explosive eruptions empty a magma chamber, followed by collapse of the overlying material into the newly-formed void — the Caldera della Fossa to the north and the Caldera del Piano to the south. The volcanic cone of La Fossa, located with 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.
www.FreeScienceLectures.com Building on the success of the two rover geologists that arrived at Mars in January, 2004, NASA’s next rover mission is being planned for travel to Mars before the end of the decade. Twice as long and three times as heavy as the Mars Exploration Rovers Spirit and Opportunity, the Mars Science Laboratory will collect Martian soil and rock samples and analyze them for organic compounds and environmental conditions that could have supported microbial life now or in the past. The mission is anticipated to have a truly international flavor, with a neutron-based hydrogen detector for locating water provided by the Russian Federal Space Agency, a meteorological package provided by the Spanish Ministry of Education and Science, and a spectrometer provided by the Canadian Space Agency. Mars Science Laboratory is intended to be the first planetary mission to use precision landing techniques, steering itself toward the Martian surface similar to the way the space shuttle controls its entry through the Earth’s upper atmosphere. In this way, the spacecraft will fly to a desired location above the surface of Mars before deploying its parachute for the final landing. As currently envisioned, in the final minutes before touchdown, the spacecraft will activate its parachute and retro rockets before lowering the rover package to the surface on a tether (similar to the way a skycrane helicopter moves a large object). This landing method will enable the rover to …