Kashgar has a rich cultural history dating back thousands of years, having served as an important hub along the Silk Road. The rising of this remarkable landscape dates back even further.
A modern view of the remote oasis in China, located at the western end of the Tarim Basin and the Taklimakan Desert, is visible in this image acquired on July 23, 2014, by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite. The image is false-color infrared (bands 3, 2, 1) to better highlight the composition of Earth’s surface. Urban areas appear gray, including the famed city of Kashgar in the bottom-right corner. Networks of roads are interspersed with buildings, which appear as rectangles in various shades of blue and purple.
Not all of the notable features in this image were shaped by humans. The long, light-colored ridges running horizontally are active folds—areas where the land is deforming upward as landmasses collide. In this case, India is pushing northward into Eurasia. The folds rise up to absorb the convergence of land (3 to 8 millimeters per year) between the Pamir Mountains to the south (China) and the Tien Shan ranges to the north (Kyrgyzstan). The southern ridge is the Kashi Fold, and the Atushi Fold lies to the north.
The folds appear various colors due to distinct rock formations with different mineral abundances. The green-yellow color across the Atushi Fold, for example, is likely related to a higher concentration of gypsum compared to the lighter tan and darker grey-brown areas. In general, the lighter-colored areas within the folds are mostly floodplain sediments—siltstones and sandstones about 1 to 5 million years old. The dark beds flanking the folds are thick conglomerates, generally less than 1 million years old.
The folds are uplifting relatively quickly on a geologic timescale at a rate of about 1 to 3 kilometers per million years. In spite of the rapid uplift, large areas of the folds have been beveled almost flat by small rivers that were more active during the last Ice Age. Today, rivers bounded by irrigated farmland (red in this image) cut through these folds in narrow gorges. The long gray area at the base of the image is the Kezilesu River, which means “red river”—a name that stems from its turbidity.
The forces deforming the region’s landscape occasionally give rise to earthquakes. In 1985, a magnitude-7.4 earthquake occurred on a branch of the Pamir Frontal Thrust fault. The quake destroyed about 85 percent of Wuqia County (northwest of this image) and left 15,000 people homeless.
References and Related Reading
- Chen, J. et al. (2007, March 28) Quantification of growth and lateral propagation of the Kashi anticline, southwest Chinese Tian Shan. Journal of Geophysical Research, Solid Earth, 112 (B3).
- Li, T. et al. (2013, August 27) Quantification of three-dimensional folding using fluvial terraces: A case study from the Mushi anticline, northern margin of the Chinese Pamir. Journal of Geophysical Research, Solid Earth, 118 (8), 4628-4647.
- Li, T. et al. (2012, August 7) Equivalency of geologic and geodetic rates in contractional orogens: New insights from the Pamir Frontal Thrust. Geophysical Research Letters, 39 (15).
- NASA's Jet Propulsion Laboratory (2016, December 12) ASTER: Kashgar, China. Accessed January 13, 2017.
NASA Earth Observatory image by Jesse Allen, using data from NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team. Caption by Kathryn Hansen based on image analysis by Doug Burbank (University of California Santa Barbara) and Jessica Thompson Jobe (University of Texas El Paso).
- Terra - ASTER