Chapter
10
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A Caspian Chronicle: Sea-Level Fluctuations
Between 1982 and 1997
Patricia Wood Dickerson
Office of Earth Sciences
NASA Johnson Space Center
Houston, Texas USA
Abstract
In the present episode of sea-level change, waters of the Caspian regressed to their lowest level in 1977; by 1985 there were clear indications that transgression was under way, and over the past twenty years sea level has risen 2.6 m. The effects of relative fall and rise have been most visible along the northern shore and in Kara-Bogaz-Gol Gulf, where topographic relief is subdued. By the time of the Shuttle-Mir missions, however, effects of rising sea level could also be seen in areas of steeper topography, such as Gorgan Bay on the southeastern coast and around Apsheron Peninsula. The photographs of this series (Figures 2-7, Table) are in clockwise progression from the Volga River delta in the northwest to Apsheron Peninsula in the southwest.
Citation for the published article
Dickerson, P. W., 2000. A Caspian chronicle: Sea-level fluctuations between 1982 and 1997, in Dynamic Earth Environments: Remote Sensing Observations from Shuttle-Mir Missions (K. P. Lulla and L. V. Dessinov, eds.), John Wiley & Sons, New York, pp. 145-148, 266, 280-281.
Links to Color Images
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Figure 10.1
Shaded relief map of Caspian region. Locations numbered 2 to 7 correspond to Figures 10.2 to 10.7. (Modified from U.S. Geological Survey, 1996.) |
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Figure 10.2
Volga River delta. The Volga is the largest river in Europe and drains an area of 1,380,000 km2. (A) April 1994 (NASA photograph STS059-218-064). Astrakhan (A on the southwest side of the delta) and Volgograd (V at the right-angle bend in the river) appear as gray patches in this northwestward view. (B) May 1996 (NASA photograph NM21-035-043). In the two years between these two photographs, the islands south of the delta have become submerged. Interdune areas along the delta margins appear wetter as well. Several areas of change have been marked with arrows to facilitate comparison. See also Fig. 19.2 in color insert. |
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Figure 10.3
Ural River delta: NASA photographs (A) October 1994 (STS068-202-069); (B) May 1996 (NM21-740-055). The Caspian has also encroached upon the delta of the Ural River, the headwaters of which are in the southern Ural Mountains. Although it can be difficult to distinguish water from vegetation, there are differences (arrows). The most notable differences are in the southernmost lobe-for example, the widths of channels separating subaerial islands. In view (B) sunglint lends emphasis to submerged areas and one can see that exposed dredge spoil east of the main channel has decreased markedly (C). Along the shorter, western canal the banks that were exposed in 1994 were almost entirely submerged or eroded two years later (at A). Sunglint also highlights what appears to be a network of levees-possibly roads or canals-that have been flooded east of the river channel (at B). |
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Figure 10.4
Buzachi and Mangyshlak Peninsulas: NASA photographs (A) May 1985 (STS51B-031-060); (B) May 1996 (NM21-740-076). Between these two southeastward photographs, taken seven years apart, the most striking difference is in Sor Kaydak (SK) and Sor Mertvyy Kultuk (SMK); the salt flats (sor) stretching to the east and southeast of the peninsula were dry in 1985 and inundated in 1996. On Buzachi Peninsula (B) much of the western shore has been flooded. |
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Figure 10.5
Gulf of Kara-Bogaz-Gol, Turkmenistan: NASA photographs (A) April 1985 (STS61A-200-034); B) April 1994 (STS059-L17-073); (C) January 1997 (NM22-735-050). A Turkmen legend holds that the Caspian separated from her husband, the Black Sea, which brought down a curse from Allah upon the Caspian. Their offspring Kara Bogaz would never cut its umbilical cord with its mother, and the Caspian would forever have to feed water to the bay (St. George, 1974). (A) In 1985, not long after flow between the Caspian and Kara-Bogaz-Gol Gulf was partially reestablished, there was still little water in the bay; bright, reflective salt deposits occupied much of the area. Note the peninsulas along the southern bay margin (arrow). (B) A channel, visible in this southwestward view, was dredged through the spit in 1992 and rising Caspian waters spread over the bay floor (see Chapter 16). The spits and peninsulas along the south coast were significantly smaller in 1994. (C) By January 1997, when this detailed view was taken, the island north of the largest peninsula had virtually disappeared and much of the peninsula had been inundated (arrow). Of the two anvil-shaped promontories along the southern shore in the 1994 view, one has become an island and the other has lost the eastern point. |
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Figure 10.6
Gorgan Bay, Iran. (A) April 1982 (NASA photograph STS003-010-586). Taken five years after the 1977 lowstand, this southwestward view of the fault-controlled southeastern Caspian coast portrays a narrow inlet to Gorgan Bay with a squat promontory just north of the channel. Note the western limit of Gorgan Bay waters, as well as the position of the Iran-Turkmenistan shoreline extending northward from the inlet. (B) November 1995 (NASA photograph STS074-708-035). By 1995 bay waters had transgressed westward, parallel to the Elburz Mountains, increasing the area of the bay by roughly one-half; the spit that defines the northern bayshore is longer and narrower owing to the westward flooding (arrow). Waters also encroached upon the eastern shore, widening the channel into the bay and changing the shape of the promontory. A lagoon, with a narrow outer bar (arrow), now covers what had been beach. |
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Figure 10.7
Apsheron Peninsula, Azerbaijan: NASA photographs (A) April 1991 (STS036-089-050); (B) May 1996 (NM21-735-078). Rising waters are a concern for petroleum production facilities on- and offshore around the Apsheron Peninsula. Subtle changes due to rising sea level can be seen along this coastline, where topographic relief is higher, by comparing the two views (arrows). |
