The primary reason the Caspian Sea is often considered not a true "sea" is that it is a landlocked body of water, meaning it has no natural connection to the world's oceans.
Understanding the Classification
Geographers and hydrologists classify large bodies of water based on several characteristics, including their connection to other major water bodies, size, and salinity. While commonly called a "sea," the Caspian Sea possesses key features that align more closely with the definition of a lake, particularly its lack of an oceanic outlet.
The Defining Factor: Landlocked Status
True seas are typically defined as large bodies of saltwater connected to an ocean. The Caspian Sea, however, is entirely surrounded by land, bordered by five countries: Azerbaijan, Iran, Kazakhstan, Russia, and Turkmenistan. This characteristic of being completely landlocked is the main reason it is frequently classified as the world's largest lake.
Salinity and Water Type
Another characteristic often associated with seas is high salinity, similar to ocean water. While many lakes are freshwater, the Caspian Sea is not. As referenced, the Caspian Sea's water has a 1.2% salinity, which classes it with brackish water bodies. Brackish water is saltier than freshwater but less salty than typical ocean water.
- Freshwater: Generally less than 0.5% salinity.
- Brackish Water: Salinity between 0.5% and 3.5%.
- Saltwater (Oceanic): Generally around 3.5% salinity.
So, while its water isn't freshwater like most large lakes, its inland location is the more significant factor leading to its common classification as a lake.
Size and Historical Naming
Despite its lake classification, the Caspian Sea is enormous, covering an area of about 371,000 square kilometers (143,000 sq mi). Its sheer size contributes to its name "Sea," a historical designation that predates modern scientific classification.
Here's a simple comparison:
| Feature | Typical Sea (connected to Ocean) | Caspian Sea | Typical Lake (Inland) |
|---|---|---|---|
| Ocean Connection | Yes | No | No |
| Water Type | Saltwater | Brackish (1.2%) | Freshwater (Often) |
| Location | Coastal/Part of Global Ocean | Landlocked | Inland |
In summary, while large and saline enough to be called a "sea" historically and having brackish water, its defining characteristic of being landlocked makes it geographically a lake, and it is often listed as the world's largest lake.
