• Dokdo in the East Sea
  • Educational material
  • High School Version

2. Dokdo’s Geography and Ecology

Understand Dokdo’s formation and geographical characteristics
Understand Dokdo’s climate and ecosystem
Critical Thinking
Dokdo was formed by underwater volcanic eruptions. A volcanic island is fundamentally different in its geological makeup than other islands. How do Dokdo’s geographical characteristics affect its climate and ecosystem? What types of unique life forms can be found on Dokdo?

Dokdo’s Formation

Seodo, Dongdo
Dokdo’s shape was carved by centuries of waves!
Dokdo’s base was formed by volcanic activity!
* The height of the mountain has been exaggerated and scaled up by a magnitude of four in relation to the width of the base.
Originally, the Korean Peninsula and the Japanese archipelago were part of the eastern end of the Eurasian Plate. Approximately 23 million years ago, the Eurasian Plate collided with the Pacific Plate and formed what is now the Korean Peninsula. The resulting depression between the Korean Peninsula and the Japanese archipelago formed the East Sea.
Dokdo and Ulleungdo were formed by hardened lava from the seabed some 2,000 meters below sea level. Its base began to form about 4.6 million years, and the island broke the surface of the water roughly 2.7 million years ago. Originally a singular island, Dokdo began separating into two as it was eroded by water around 2.5 million years ago. It is believed to have taken its current shape some 2.1 million years ago as wind and water erosion continued to reshape the island.
Dokdo is the oldest of the volcanic islands of Korea. It was formed approximately 2.5 million years before Ulleungdo and about 2 million years prior to Jejudo.
Activity 1
Compare Dokdo, Ulleungdo, and Jejudo, and confirm which island formation is the oldest.

Dokdo’s Geographical Characteristics

Dokdo is greatly influenced by the seas and feature a variety of marine topographical formations. Its bedrock consists of volcanic rocks. Thus, Dokdo’s geological characteristics consist of hardened volcanic ash (tuff) and alkaline volcanic rocks such as trachyte and basalt. Although they may look hardened, they are in fact extremely porous and easily worn or crumbled.
Dongdo’s summit is relatively flat compared to other areas, and is home to a lighthouse and a guard tower. The soil layer is about 20-30 centimeters deep and accommodates a variety of plant life. Dokdo’s coasts are mostly made up of steep marine cliffs around 30 meters in height, which are difficult for plant life to grow on. Conversely, Seodo’s summit consists of sharp ridges. However, the area southwest of the summit is relatively flat and features a soil layer capable of supporting plant life. A natural water reservoir is located in the northern area and is a source of drinking water.
Common geographical features found on Dokdo includecolumnar joints , fault lines, and wave-cut platformsalong the coastal terrain. In addition, severe wind erosion accounts for the wide distribution of panholesthroughout the island, visible in a variety of areas. Even today, Dokdo is continuously changing due to the effects of water erosion.

Dokdo’s Seabed

Dokdo’s SeabedSource : Korea Hydrographic and Oceanographic Administration
East Sea, Ulleungdo, Mt. Anyongbok, Dokdo
Ulleungdo and Dokdo are part of a mid-ocean ridgethat connect below the ocean surface. Dokdo’s seafloor topography consists of a base approximately 20-25 kilometers in diameter and that reaches 2,000 meters below sea level. On the seabed rests a flat plain between Ulleungdo and Dokdo, and Mt. Anyongbok is in this area.
The entire seabed consists of various mountain ranges, and they are named after important figures in Dokdo’s history. Two underwater mountains roughly 15 kilometers and 55 kilometers southeast of Dokdo are Mt. Simheungtaek (second Dokdo underwater mountain) and Mt. Isabu (third Dokdo underwater mountain).
As Ulleungdo and Dokdo are part of the same mid-ocean ridge and composed of trachyte, they are considered to be qualitatively similar. On the other hand, Japan’s Oki Islands are composed of gneiss and are unrelated to volcanic activity, making them fundamentally different.
Activity 2
Mt. Anyongbok can be seen in the same mid-ocean ridge as Ulleungdo and Dokdo. Locate Mt. Isabu and Mt. Simheungtaek in the same ridge.
Ulleungdo, Mt. Anyongbok, Dokdo, (  ), (  )

Dokdo’s Climate

Currents Near Dokdo in Summer/Winter, August, FebruarySource : National Geographic Information Institute
Korea is located in the mid-latitudes. The average annual temperature range is between 8 and 14 degrees Celsius, and features both temperate and subarctic climate characteristics. Temperatures are lower inland and to the north, and the temperature difference between summer and winter is sizable. The climate is characterized by cold, dry winters and hot, humid summers. However, the climate in Ulleungdo and Dokdo is mainly influenced by the ocean currents. The East Korea (Tsushima) Warm Current and the North Korea (Liman) Cold Current have the greatest effect on Dokdo’s climate. Dokdo is mainly affected by a warm ocean current in the summer, which mixes and circulates with the North Korea Cold Current in the winter near Ulleungdo. Dokdo’s average temperatures are never below freezing even during the coldest month of January and never above 24 degrees Celsius even during August, the warmest month.
Ulleungdo and Dokdo’s temperatures are around 12 degrees Celsius on average and relatively mild compared to similar regions. Ulleungdo and Dokdo have comparable average monthly temperatures with January and February being the coldest and August being the warmest.
Statistically, Ulleungdo and Dokdo see heavy rainfall during the summer months. The monsoon season brings rain in July, while the frequent typhoons in August and September are responsible for most of the rainfall.
Dokdo is affected by strong winds throughout the year. Depending upon the season, Dokdo encounters northeasterly and southwesterly winds. Wind speeds are high and turbulent through most of the year from January to August, and are moderate around October.
Activity 3
Note the average monthly temperatures and precipitation for Ulleungdo and Dokdo in the following graph.
Temperature, Precipitation, Average monthly temperatures, Average monthly precipitation
Ulleungdo climate (1981-2010)
Dokdo climate (2004-2010)

Dokdo’s Ecosystem

Ⓐ Tartarian aster (Aster spathulifolius Maxim), Ⓑ Giant knotweed (Reynoutria sachalinensis), Ⓒ Taito-gome (Sedum oryzifolium Makino), Ⓓ Stonecrop (Sedum takesimense), Ⓔ Spoonleaf yellow loosestrife (Lysimachia mauritiana Lam.), Ⓕ New Zealand Spinach (Tetragonia tetragonioides)Source : Cultural Heritage Administration
Dokdo is relatively humid throughout the year, with either fog or rain about 85% of the time. In addition, its soil salinity is very high due to the constant strong sea winds, making it unsuitable for plant life. Flora in Dokdo is tolerant of harsh conditions, but there are fewer varieties than on the mainland. The trees on the island are also relatively small in size. Including trees, there are some 50-60 different types of plant species growing in Dokdo. These include Tartarian aster, Giant knotweed, Stonecrop, Broomrape, Curly dock, Holly fern, Spoonleaf yellow loosestrife, and New Zealand Spinach.

Dokdo’s Marine Life

Ⓐ Abalone, Ⓑ Black-tailed gull, Ⓒ Seaweed, Ⓓ Sea chubs, Ⓔ Rockfish, Ⓕ SquidSource : National Fisheries Research and Development Institute, Lee Dong-woo
The following marine life are known to live around Dokdo: Butterfish, filefish, trout, cod, pollock, Pacific saury, blowfish, squid, octopus, shark, parrot fish, flounder, striped breakfish, sea chub, rockfish, pearl-spot chromis, yellowtail, kelp greenling, kelp, seaweed, turban shell, sea cucumber, abalone, and others
Dokdo is home to about 93 different insect species, most of which are small with weak flight capabilities.
The island also serves as an important stopover point for migratory birds. Around 139 different bird species sightings have been confirmed. The main species include the black-tailed gull, petrel, shearwater, white wagtail, and island sparrow. Of these, the black-tailed gull, shearwater, and petrel are protected under the Dokdo Natural Protected Area ordinance.
About 370 different species of invertebrates and 223 species of algae are also found in and around Dokdo. In 2005, a marine flavobacterium called (Donghaeana Dokdonensis was discovered in Dokdo. Also known as “Donghae Dokdo,” it was introduced in a scientific journal in 2006.

marine cliffs
Marine cliff – Coastal cliffs that are formed by wind and water erosion
Marine cliff
columnar joints
Columnar joints - Parallel, prismatic columns that resulted from rapidly cooling lava, causing shrinkage cracks to form in a hexagonal pattern
Columnar joints
wave-cut platforms
Wave-cut platform - A flat bedrock formed by wind and water erosion
Panhole – A depressed, erosional feature found on flat or gently sloping rock
mid-ocean ridge
A general term for an underwater mountain system that consists of various mountain ranges
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