Showy Swirls Around Jeju Island

The highest point in South Korea is not the Taebaek Mountains which run along the country’s east coast. Instead, it is found atop a volcanic peak on Jeju Island, about 100 kilometers (60 miles) south of the Korean Peninsula. During the winter of 2026, the winds blew across the island in just the right way, spinning the clouds in its wake.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this image of swirling clouds and colorful, turbulent water near Jeju Island on February 19, 2026. The island rises about 1,950 meters (6,400 feet) above the sea surface. At its center is Hallasan, a shield volcano that last erupted in the 11th century and which contains a remarkable network of lava tubes.

Trailing, offset spirals, called von Kármán vortex streets, form when a fluid passes a large, isolated, stationary object. If the winds are too weak, the clouds simply pass smoothly by, and if the winds are too strong, the vortices cannot maintain their shape. In the sweet spot, with winds between 18 and 54 kilometers (11 and 34 miles) per hour, clouds trace airflow in counter-rotating vortex patterns. Although the underlying physics is the same, the appearance of the vortices can vary: sometimes they appear wispy, as is the case here, and other times they form more sharply defined parallel rows, as they did in the same location the day before.

The sea, as well as the atmosphere, was turbulent near Jeju Island in mid-February. To the west, a large plume of sediment from the coast of China’s Jiangsu province has made the waters murky. Although brown sediment-laden water is present year-round in shallow coastal areas, large plumes like this are common in winter. Research suggests that seasonal changes in currents and vertical mixing of the water column could explain the large winter plumes.

NASA Earth Observatory image by Michala Garrison, using NASA MODIS data EOSDIS LANCE and GIBS/Worldview. Story by Lindsey Doermann.

• Global Volcanism Program, Halla. Accessed February 23, 2026.
• NASA Earth Observatory (February 24, 2024) Sediments spread over the Yangtze Bank. Accessed February 23, 2026.
• NASA Earth Observatory (November 16, 2008), Cheju Island, South Korea. Accessed February 23, 2026.
• UNESCO World Heritage Convention (2018) Jeju Volcanic Island and Lava Tubes. Accessed February 23, 2026.
• Weather Underground (December 2019) Swirls, Loops, and Small Vortices: The Science Behind Von Karman Vortices. Accessed February 23, 2026.