U.S. releases enhanced shuttle land elevation data

Shaded relief images of deeply eroded volcanic terrain in northeast Tanzania demonstrate the improved nature of the highest-resolution SRTM data now being released. The image at left has data samples spaced every 90 meters (295 feet); the image at right has samples spaced every 30 meters (98 feet). Credit: NASA/JPL-Caltech/National Geospatial Intelligence Agency

High-resolution topographic data generated from NASA's Shuttle Radar Topography Mission (SRTM) in 2000, previously only available for the United States, will be released globally over the next year, the White House announced today. The announcement was made at the United Nations Heads of State Climate Summit in New York.

This initial public release of topographic data for Africa will help empower local authorities to better plan for the impacts of severe environmental changes such as drought, glacial retreat, inland flooding, landslides and coastal storm surges. Datasets covering the remaining continents will be made available within one year, with the next release of data focusing on Latin America and the Caribbean.

Lower-resolution SRTM topographic data having 90-meter (295-foot) pixels were released publicly in 2003 for many parts of the world, providing a global standard for many applications. The new data increase the detail to 30-meter (98-foot) pixel spacing, now revealing the full resolution of the world's landforms as originally measured by SRTM.

"The public availability of enhanced global SRTM topographic data will greatly benefit international efforts to better understand natural processes that shape our planet, prepare for and respond to natural hazards, and anticipate and prepare for the impacts of global change," said NASA Chief Scientist Ellen Stofan. "NASA is proud to have played a critical role in creating these data that will benefit society through open data sharing."

SRTM was a joint project of NASA, the German and Italian space agencies, and the National Geospatial-Intelligence Agency. It was managed by NASA's Jet Propulsion Laboratory, Pasadena, California, for NASA's Science Mission Directorate, Washington, D.C. The newly released 30-meter topographic data products will be publicly distributed by the U.S.  

Geological Survey (USGS) along with the 90-meter data. These data are being made available via a user-friendly interface on USGS's Earth Explorer website.
SRTM flew aboard the Space Shuttle Endeavour in February 2000, mapping Earth's topography between 56 degrees south and 60 degrees north of the equator. During the 11-day mission, SRTM used an imaging radar to map the surface of Earth numerous times from different perspectives. The combination of these radar data were processed at JPL to produce a global topographic map created by bouncing radar signals off Earth's surface and back to the shuttle.

Topographic data benefit a wide variety of activities, from aviation safety to civil engineering projects. Topography also strongly influences many natural processes, such as the distribution of plant communities and the associated animals that depend upon them, weather and rainfall patterns, and the flow and storage of surface water. The data aid in better understanding, predicting and responding to flooding from severe storms and the threats of coastal inundation associated with storm surge, tsunamis and sea-level rise.

Multiple training workshops on SRTM data are planned for users in Africa. The SERVIR program, a joint venture by NASA and the U.S. Agency for International Development, is planning workshops in Eastern and Southern Africa with the Regional Centre for Mapping of Resources for Development, and in West Africa with key environmental organizations. 

The Secure World Foundation is partnering with NASA, USGS and other members of the international Committee on Earth Observation Satellites to offer online training and regional workshops to further enable users to take advantage of these data resources. JPL is a division of the California Institute of Technology in Pasadena.

Source: NASA/Jet Propulsion Laboratory

Kilauea, 1790 and today

The Island of Hawai'i, USA.

Scores of people were killed by an explosive eruption of Kīlauea Volcano, Hawai'i, in 1790. Research presented in GSA Bulletin by D.A. Swanson of the Hawaiian Volcano Observatory and colleagues suggests that most of the fatalities were caused by hot, rapidly moving surges of volcanic debris and steam that engulfed the victims. Deposits of such surges occur on the surface on the west summit area and cover an ash bed indented with human footprints.

The footprints, made by warriors and their families, appear along a major trail in use at the time. Today, the area is one of the most visited parts of Hawai'i Volcanoes National Park.
The explosive eruption resulted from the violent interaction of groundwater with hot rocks. Such explosive eruptions have happened frequently in Kīlauea's past and will probably occur in the future when the caldera collapses down to the water table, some 600 m (2000 ft) below the summit of the volcano.

The 1790 eruption of Kīlauea was explosive, and its major impacts were in the summit area of the volcano. The eruption taking place now at Kīlauea is effusive, says Swanson, producing a flow of lava that erupts without explosion. This flow is erupting from a site named Pu'u 'Ō'ō on the east rift zone, far from the summit area, and lava has to flow many kilometers (several miles) before reaching inhabited areas.

Explosive eruptions are very hazardous; the 1790 fatalities bear witness to this fact. Lava flows are not very hazardous to life but can be exceedingly destructive to property. Explosive eruptions are brief but terrifying. Lava flows often last for months or more and are captivating to the viewer. Kīlauea has both types of eruptions, but not at the same time.

Violent explosive eruptions from the summit of Kīlauea are geologically common. They are generally clustered into periods lasting a few centuries. It has been about 200 years since the most recent major explosion, which culminated about 300 years of frequent explosive eruptions. In the past 200 years, Kīlauea has produced many lava flows similar to the present one; small explosions took place in 1924 and, on an even smaller scale, during the past 6 years.

The general public is unaware of Kīlauea's explosive nature, because the volcano has erupted mainly lava flows in recent times. Kīlauea will almost certainly become explosive at some future time, producing conditions similar to those of 1790. However, according to Swanson, there is no reason to think that a period of violent eruptions will resume any time soon. The public can probably expect more lava flows in the near future, such as those of the past three decades from Pu'u 'Ō'ō.

Source: Geological Society of America