From LRG, in Intro GIS
How did dinosaurs disappear? Was it because of volcanic activity, diseases or a meteorite impact? Most clues have led us to believe that a meteorite impact near the Yucatan peninsula caused the famous massive extinction. A meteorite with a diameter of 1 km hitting the Earth’s surface would produce intense volcanic activity and a global tsunami, and send huge amounts of dust and water vapor into the atmosphere thus changing the Earth’s climate dramatically.
Collisions with objects with a 1 km diameter occur on Earth, on average, every 250,000 years. Considering the fact that the Earth is about 4 billions years old, meteorite impacts can be viewed as an important process in the Earth’s history. The study of craters may teach us many things about the Earth and our solar system, and may help us to resolve others mysteries. But before we study craters, we need to find them. Craters from a meteorite with a 1 km diameter, however, are so large that they are difficult to see from the Earth’s surface and searching can be very time consuming and expensive. Fortunately, GIS can be used to make finding craters easier.
Recently researchers in Norway used the automatic detection of circular depression in digital elevation data to locate craters with 5 to 10 km diameters. They used a template-matching technique to measure the similarity between digital elevation data and a known image. They used the following 3 types of craters as templates: 1) the simple crater: bowl-shape depression with surrounded rims, 2) the complex crater: central peak surrounded by trough and slumped rims, and 3) the peak ring crater: a central peak with several ring structures creating an annular basin. Their study shows that morphometrical DEM analysis provides a powerful and inexpensive tool for landform assessments of crater-shaped features.
The virtue of GIS is not limited to Earth. Since the morphology of meteorite craters displays similar patterns throughout the solar system, other research used GIS database to compare craters on Mars and Ganymede (the larger natural satellite of Jupiter) using data from the Galileo probe and creating a catalog that includes information on crater location, size, the state of preservation state, geologic unit, ejecta morphology and interior morphology. Such research can help us understand the different environment and surface composition of other planets too far to be reached or too hostile to visit.
References:
Krøgli Svein Olav, Henning Dypvik & Bernd Etzelmüller, 2007, Automatic detection of circular depressions in digital elevation data in the search for potential Norwegian impact structures, Norwegian Journal of Geology, Vol. 87, pp. 157-166,
Atoc 250, 2008, Natural Disaster: Meteorite impact, McGill University.
Barlow N. G., Comparison of Impact Crater Morphologies on Mars and Ganymede, Dept. Physics and Astronomy, Northern Arizona University, Flagstaff.