Siayan is one of the Batanes Islands. Also known as Ditarem Island in the native language, the island is about 1/2 mile to 3/4 miles in diameter and lies about 5 miles (8 km) north-northeastward of Itbayat Island. The closest island is Mavulis Island which is about 1Template:Frac miles north-northeastward of Siayan. There are several detached rocks off Siayan's northeast side, rendering the channel between it and Mabudis unsafe for larger vessels.
Siayan has an elevation of 538 ft (164 m) and is listed as an inactive volcano by the Philippine Institute of Volcanology and Seismology.
- University of Georgia, Yami culture of Taiwan, Retrieved on 2010-08-24
- U.S. Coast and Geodetic Survey, Department of Commerce. United States Coast Pilot, Philippine Islands Part I, p. 39. Washington Government Printing Office, 1919.
- PHILVOCS, List of Inactive Volcanoes in the Philippines. Retrieved on 2010-08-24.