Rhodolith Beach on Udo Island, Jeju

Basic information

Designation

Natural Monument No.438

Category

자연지형

Designated year

2004

Location

제주시, 제주특별자치도— 제주특별자치도 제주시 우도면 연평리 2215-5 등 지선에 인접한 공유수면

Coordinates

33.502677, 126.940800

Beaches and sand dunes mostly composed of shell sand are found in many places along the northern coast of Jeju Island. However, that the beach in Udo Island is composed not of shells but of rhodoliths (red algae nodules), which makes it very valuable for academic study. The rhodoliths vary greatly in size, with diameter ranging from 1cm to 5-8cm. The Rhodolith Beach of Udo Island stretches 300m and has width of 15m, forming stark contrast with the black basalt in this area. The beach was formerly known as a coral sand beach, but studies have revealed that the sand is made up of red-algae nodules rather than coral. Rhodoliths are a species of calcareous algae that deposits calcium carbonate in cells or walls between cells through photosynthesis. Nodules living underwater usually have diameter of approximately 4-5cm, spherical shape, and bumpy surfaces. In most nodules, the internal tissue and reproductive organs are intact. They are found in many parts of the United States such as Florida and the Bahamas, usually near sunken rocks. Since it is rare for an entire beach to be composed of red algae nodules, however, the Udo beach is very important for academic study.

Location