Geography Reference
In-Depth Information
of impact structures may be, in certain conditions, the basic diagnostic criteria
of impact origin, superior over petrographic and mineralogical proofs.
In particular, our diagnostic methods based on the geometry of impact
craters have allowed us to discover and add to the Catalog more than 40
potential astroblemes in Rudny Altai [1], as well as to better constrain the
genesis of ten craters in Madagascar, Northern Italy, and Siberia. The impact
craters identified only according to morphology are assigned validity grade 2
in the Catalog [1], which means ―potential craters‖ in the five-grade (0 to 4)
scale of I. Zotkin and V. Tsvetkov [69].
We study the morphology of impact structures by shaded relief modeling,
using NASA data arrays of SRTM (Shuttle Radar Topography Mission) and
ASTER GDEM (Global Digital Elevation Model) (Figure 29), with the digital
mapping technology as described above.
Figure 29. Figure 29. Probable astrobleme Volchikhinskaya: a) GIS-EISC shaded relief
model (ASTER GDEM data), b) lower-resolution shaded relief model (SRTM data).
The new method of detecting impact craters consists in selecting optimum
foreshortening of an image, or illumination parameters and shadow depth, to
fill the gaps caused by modification of impact craters affected by erosion,
deposition, tectonism or volcanism.
This image processing procedure allows detecting RS in a series of
elevation models, as well as collecting evidence for standard elements
diagnostic of CRSs. The procedure of CRSs identification includes several
steps [61]:
