Caspian Sea: the largest lake in the world

One of the most interesting natural features on Earth, the Caspian Sea is the largest body of inland water on the planet, challenging the traditional classifications of being both a sea and a lake. Located between Europe and Asia, this enormous sea has many other unique qualities as well, such as its extraordinary salinity, distinct geography, biodiversity, and economic and political importance for the five surrounding countries.

Geography of the Caspian Sea

The Caspian Sea is located in the heart of the Caspian Sea region, at the crossroads of continents, and is bordered by five countries: Kazakhstan to the northeast, Turkmenistan to the east, Iran to the south, Azerbaijan to the west, and Russia to the northwest. The Caspian Sea extends over an area of 745 miles (1,200 kilometers) from north to south and covers a surface area of about 143,200 square miles (371,000 square kilometers), and holds the title of the largest inland body of water in the world. To illustrate, this means that its surface area is roughly equal to that of Japan. The Caspian Sea basin, which includes a vast catchment area, is fed by many rivers, most notably the Volga River, which flows into the northern Caspian Sea. Smaller rivers such as the Ural also contribute to the flow of water, enriching the sea with freshwater inputs.

Caspian Sea formation

The formation of the Caspian Sea has evolved over millions of years. Unlike oceans, this body of water is not the result of plate tectonic motion or continental drift. Rather, it arose through a combination of tectonic activity, geological processes and climate change. During the Late Cretaceous, about 70 to 60 million years ago, the area that now includes the Caspian Sea was part of the ancient Tethys Sea, a vast ocean separating the giant continents of Lorasia and Gandwanna. Over time, as the tectonic plates moved and collided, the Tethys Sea began to crumble and shrink, giving rise to smaller basins and seas, including the Caspian Sea region. The gradual convergence of the Eurasian and Arabian tectonic plates has led to the rise of mountain ranges, including the Caucasus Mountains to the west and the Alborz Mountains to the south. These mountain ranges served as natural barriers, trapping the waters and forming a basin that eventually became the Caspian Sea. At the same time, Earth's climate has been fluctuating over millions of years, causing periods of glaciation and global warming to change sea levels and rainfall patterns. During icy periods, large ice sheets formed, trapping water and causing global sea levels to drop. This has cut off the Caspian basin from the oceans and reduced the volume of flow from rivers. During periods of interglacial warming, melting ice sheets and increased rainfall led to rising sea levels and increased freshwater flow from rivers. These fluctuations in sea level and freshwater inputs have affected the size, depth and salinity of the Caspian Sea over time.

Unusual salinity

The Caspian Sea is also characterized by unusual salinity, compared to typical oceans and seas. It basically presents the characteristics of both fresh and salt water bodies. Unlike most seas, which have open connections to the ocean and experience regular tidal flows of salt water, the Caspian Sea is largely surrounded by land. This limited exchange with oceanic waters limits the flow of salt water into the Caspian Sea basin. On the other hand, the Caspian Sea receives large amounts of fresh water from various rivers, including the Volga, the Urals and the Kura. These rivers carry fresh water from distant mountain ranges and vast plains, reducing the salinity of the Caspian Sea. The Volga River, in particular, is the largest source of fresh water in the Caspian Sea, making up the majority of its flows. Despite the flow of this fresh water, the Caspian Sea does not exhibit the low salinity levels that characterize most freshwater lakes. Instead, it maintains a moderate salinity level, averaging about 12 ppm. This makes the water of the Caspian Sea saltier than fresh water (with a typical salinity of 0.5 ppm) but less salty than the ocean, which has an average salinity of 35 parts per thousand.

Biodiversity and environment

The average salinity levels in the Caspian Sea make it a good habitat for species that have adapted to saltwater conditions. Beneath the Caspian Sea is a range of fish species, including sturgeon, whose eggs produce a delicacy known as caviar. Other residents include the Caspian seal, the only aquatic mammal living in the sea, and the Caspian gull and Caspian Kharshna, which find refuge along the beaches. Unfortunately, biodiversity in the Caspian Sea faces many threats, ranging from overfishing to habitat degradation. The exploitation of energy resources, such as oil and natural gas, has led to environmental concerns, affecting both marine life and coastal ecosystems. Conservation efforts led by organizations such as the United Nations Environment Programme (UNEP) seek to protect the delicate balance in the Caspian Sea and ensure the sustainability of its resources for future generations.

Economic importance

The Caspian region is of enormous economic importance due to its abundant natural resources and strategic location. Countries along the Caspian coast have invested heavily in acquiring these energy resources and leveraging their offshore assets to support their economies. The region is known for its vast reserves of oil and natural gas, which attracts international oil companies and stimulates the growth of a booming energy industry. As a result, offshore oil rigs are deployed to drill in the area. The Caspian Sea also supports the burgeoning fishing industry, providing livelihoods for coastal communities. Sturgeon fishing, in particular, has been a traditional practice for centuries.