Which Central Asian desert lies east of the Caspian Sea and mostly in Turkmenistan?

The Central Asian desert east of the Caspian Sea and mostly in Turkmenistan is the Karakum Desert.

The Karakum occupies roughly 70 percent of Turkmenistan, covering about 350,000 square kilometres. It forms a broad east–west belt immediately east of the Caspian Sea, with the Amu Darya delta and the Kyzylkum region farther northeast. The name is commonly translated as “Black Sand,” contrasting with Kyzylkum, or “Red Sand.”

The desert contains several geographical divisions, including the Trans-Unguz Karakum, the Central Karakum and the southeastern Karakum. Rainfall is scarce, generally around 70–150 millimetres annually, and the population is sparse. Nonetheless, rivers descending from the Hindu Kush feed oases such as Mary and Tejen, where irrigation supports agriculture.

One famous modern landmark is the Darvaza gas crater, popularly called the “Door to Hell,” which has burned since 1971. The Karakum Canal, begun in 1954 and completed in 1958, also crosses the desert. Kyzylkum is the main distractor here: it lies chiefly in Uzbekistan and Kazakhstan, across the Amu Darya from the Karakum.