• Dokdo in the East Sea
  • Educational material
  • Junior High School Version
Critical Thinking[Teacher Notes]
Which was formed first? Ulleungdo or Dokdo?
It’s easy to simply think of Ulleungdo and Dokdo as small islands in the East Sea.
But there is more to the story than that. When seen underwater, their true form becomes clearly evident.
Ulleungdo and Dokdo may look like two separate islands above the waterline, but in fact the two are connected deep below the surface. How, then, did these two islands come to be?
Which island do you think was formed first?
I think Dokdo was formed first. Dokdo was probably a big island that was eroded away over time by the constant waves!
Ulleungdo is bigger, so it probably was formed first!

Teacher Notes
Ulleungdo and Dokdo look small above the surface, but they are actually very large islands when seen from below the waterline. Ulleungdo and Dokdo are two separate islands above the waterline, but, in fact, the two are connected deep below the surface. This is because Ulleungdo and Dokdo were formed through similar volcanic activity.
Between Ulleungdo and Dokdo, which island was formed first? It is easy to think that the larger Ulleungdo was formed first, but in fact Dokdo was formed earlier. Ulleungdo was formed about 2.5 million years after Dokdo. Dokdo was originally a much larger island, but over time eroded to its current shape and size.
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