Where on Earth...? MISR Mystery Image Quiz #12: St. Petersburg

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This Multi-angle Imaging SpectroRadiometer (MISR) natural-color image of Russia's St. Petersburg was captured by the instrument's nadir camera on May 31, 2002, and covers an area of 244 kilometers x 249 kilometers. The image has been rotated such that north is toward the bottom. Answers to the questions are provided.

1. The location of a city is indicated by the pale gray-colored pixels in the upper left. Three of the following four statements about this city are true. Which statement is false?

   1. No city with a larger population is located within 4 degrees latitude.
   2. The city was established about 300 years ago.
   3. There are hundreds of bridges within the metropolitan area, of which only one is a drawbridge.
   4. A linear feature connecting the island to the right of the city with the mainland supports automotive but not rail traffic.

   • Answer: C is false.
     The image has been rotated such that north is toward the bottom. The city in the south eastern portion of the image is Russia's St. Petersburg, which is the most northerly large city in the world at almost 60 degrees north latitude. The closest city with a larger population, Moscow, is south of St. Petersburg by more than 4 degrees (at 55.75 degrees north). St. Petersburg was established along the banks of the Neva River by Peter the Great in 1703. This marshy, low-lying area possesses many rivers and islands, and about 300 bridges, of which more than twenty are drawbridges. The island connected with the north shore of Petersburg is called Kotlin Island and is the home of the famous naval fortress of Kronstadt. The road built upon a tidal barrage connecting the island with the mainland is open to road traffic but does not support a railway.

2. A large blue water body extends along the top portion of the image. Three of these four statements about it are true. Which statement is false?

   1. The shores provide an important habitat for at least one type of seal.
   2. Dreissena polymorpha, an invasive pest species, has been found in these waters.
   3. These waters are more salty than most other seas.
   4. Forest products account for at least half of all cargo leaving one of the major ports along the shoreline.

   • Answer: C is false.
     The water body extending along the top portion of the image is the Gulf of Finland. These shores are home to the Grey Seal and the Ringed Seal. The bivalve Dreissena polymorpha has been recorded in the eastern parts of the Gulf of Finland since the 1980's. The Gulf of Finland is a low salinity marine environment, and one of the freshest enclosed seas in the world. Over half of all cargo leaving the Finnish port of Hamina are forest products.

3. Another large body of water stretches along the left-hand portion of the image. Three of these statements about this water body are true. Which statement is false?

   1. Its maximum depth is less than 300 meters.
   2. There is an active monastery on one of its islands.
   3. It is the main source of freshwater for the region and is currently threatened by pollution.
   4. Its basin is of tectonic origin and was formed through movements of the Earth's crust.

   • Answer: D is false.
     The waters stretching along the left are part of Lake Ladoga. Despite being somewhat shallow (the maximum depth of the lake is about 230 meters), Lake Ladoga is the largest freshwater lake in Europe and the primary source of drinking water for St. Petersburg. Pollution from various industrial and agricultural materials threaten the Lagoda water supply. The large island of Valaam (apparent in the lower-left of the image area) houses a monastery dating from the 12th century remains active. The origin of the lake is related to the recent glacial history of the area and not to tectonic deformations of the Earth's crust.

4. Extending from the bottom center of the image to the water's edge in the upper right quadrant is a curvilinear boundary separating darker shades of green on the left from lighter hues of green and brown on the right. Three of the following four statements about this feature are true. Which one is false?

   1. It coincides with a political border.
   2. It is associated with an escarpment more than 500 meters in elevation.
   3. It demarcates areas characterized by historically different logging practices.
   4. It is traversed by a river in which salmon and trout migration has been affected by the construction of a hydroelectric plant.

   • Answer: B is false.
     The curvilinear feature coincides with the southern portion of the border between Russia and Finland. The maximum elevation in this region is less than 200 meters. For much of the 20th century, Russia's westernmost border served as a barrier to international interaction, and the forests in this region were largely excluded from the international trade in forest products. In contrast, forests along the Finnish side of the border have been more intensively exploited during the past century. The Vuoksi River crosses this border at the twin cities of Imatra, Finland and Svetogorsk, Russia, and then flows onward toward Lake Ladoga. The Imatrankoski power station and dam which was constructed between these towns in the 1920's has hindered salmon and trout migrations along this route.

Image credit: NASA/GSFC/LaRC/JPL, MISR Team.
Text acknowledgment: Clare Averill (Acro Service Corporation/Jet Propulsion Laboratory).