The Zagros Mountains in Iran offer a visually stunning topographic
display of geologic structure in layered sedimentary rocks. This scene
is nearly 100 kilometers (62 miles) wide but is only a small part of
similar terrain that covers much of southern Iran. This area is actively
undergoing crustal shortening, as global tectonics moves Arabia toward
Asia. Consequently, layers of sedimentary rock are folding much like a
carpet will fold if pushed. The convex upward folds create structures
called anticlines, which are prominently seen here. The convex downward
folds (between the anticlines) create structures called synclines, which
are mostly buried and hidden by sediments eroding off the anticlines.
Layers having differing erosional resistance create distinctive patterns,
often sawtooth triangular facets, that encircle the anticlines. Local
relief between the higher mountain ridges and their intervening valleys
is about 1200 meters (about 4000 feet).
Salt extrusions and salt "glaciers" are another set of geologic
features readily evident in the topography. Salt deposits, likely created
by the evaporation of an ancient inland sea, were buried by the sediments
that now make up the layers of the anticlines and synclines. But salt is
less dense than most other rocks, so it tends to migrate upward through
Earth's crust in vertical columns called "diapirs." The compressive
folding process has probably facilitated the formation of these diapirs,
and the diapirs, in turn, are probably enhancing some anticlines by
"inflating" them with salt. Where the diapirs reach the surface, the
salt extrudes, much like lava from a volcano, and the salt flows. Two
prominent salt flows are evident in the same valley, leaking from
neighboring anticlines, just north of the scene center.
This shaded relief image was created directly from an SRTM elevation
model by computing topographic slope in the north-south direction.
Northern slopes appear bright and southern slopes appear dark.
Elevation data used in this image were acquired by the Shuttle Radar
Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched
on February 11, 2000. SRTM used the same radar instrument that comprised
the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar
(SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994.
SRTM was designed to collect three-dimensional measurements of the
Earth's surface. To collect the 3-D data, engineers added a 60-meter-long
(200-foot) mast, installed additional C-band and X-band antennas, and
improved tracking and navigation devices. The mission is a cooperative
project between the National Aeronautics and Space Administration (NASA),
the National Geospatial-Intelligence Agency (NGA) of the U.S. Department
of Defense (DoD), and the German and Italian space agencies. It is
managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's
Earth Science Enterprise, Washington, D.C.
Size: 98.1 kilometers (60.8 miles) by 148.1 kilometers (91.8 miles)
Location: 27.3 degrees North latitude, 54.5 degrees East longitude
Orientation: North toward the top
Image Data: Shaded SRTM elevation model
Date Acquired: February 2000