Dokdo is a volcanic island that is formed by lava which erupted about 2,000m underwater. It was formed between the early and the late Pliocene in the 3rd phase of the Cenozoic Era, between about 4.6 million to about 2.5 million years ago. Considering that Ulleungdo Island was formed about 2.5 million years ago, Dokdo is about 2 million years older than Ulleungdo Island.
Dongdo preserves two old volcanic craters
and has a relatively flat peak,
whereas Seodo has a sharp, cone-shaped peak.
Its geology is alkali volcanic rocks,
especially basalt and trachyte.
The soil is residual soil which has
weathered from the peak of mountain
and very steep with over 30° grade. The soil is sandy loam in dark or reddish brown color.
Dokdo’s climate is typical oceanic climate that is largely influenced by temperate current. Dokdo’s average temperature is around 12°C. The average temperature of the coldest season (January) is 1°C and that of the hottest season (August) is 23°C. Dokdo is generally very windy and the average wind velocity is 4.3m/s. The wind blows from southwest in summer and from northeast in winter.
Dokdo is often foggy and has 160 or more cloudy days in a year. Also, it rains
about 150 days in a year. About 85% of the days in a year are either
cloudy or rainy/snowy to make this region relatively moist. It rains
about 1,240mm a year. In winter,it snows very often and heavily.
With strong sea wind and infertile rocky soil, not many plants can
survive in Dokdo. It is where migratory birds stop by or rest for
a while on their way to the final destination. It is biologically
and geographically very important and allows us to study
the history and distribution of biological organisms in Korea.