Friday, December 23, 2016

Korea Tour : Jeju Volcanic Island and Lava Tubes (2)


Mt. Halla Natural Reserve: Unique Geography and Ecology


Jeju Island has an oval shape and is 70 kilometers from east to west and 30 kilometers from north to south. It is 1,847.2 square kilometers in area, about three times as large as Seoul, the capital city of Korea. At the center of the island is Mt. Halla, a volcano rising 1,950 meters above sea level, and the mountain’s gentle slopes descend from its peak all the way down into the sea, making the island look like one big mountain. The area covering 151.35 square kilometers around the mountain (about 8.3 percent of the entire island) has been designated as a natural reserve.


The overall shape of Mt. Halla is simple, but it features the diverse topography and geology of a volcanic mountain, including a lake-filled crater at the summit, a cluster of rocky cliffs to the southwest of the summit composed of rock pillars with bizarre shapes (columnar joints formed by cooling of lava), and 40 or more parasitic cones. The mountain has a wide range of climate conditions and distinct vegetation distributions along altitudinal gradient, displaying magnificent landscapes varying by season and location.

Baengnokdam (White Deer Lake), an oval-shaped crater lake at the summit of Mt. Halla, has an east-west diameter of 700 meters and north-south diameter of 500 meters. It is 111 meters deep and 1,720 meters in circumference. 
 


On the whole, Mt. Halla is an aspite-type shield volcano (a volcano with gradual slopes formed from fluid lava flows traveling across a broad area of land), but its steep summit has the characteristics of a lava dome (a mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano). Mt. Halla is unique in that it is a shield volcano which erupted on a continental tectonic plate. Shield volcanoes are not common all over the world, taking up less than 10 percent of the world’s volcanoes. Furthermore, most other shield volcanoes occur in oceanic plates.
 


The mountain is a habitat for a wide variety of plants from its base up to the top. It has the distinct vertical distribution of flora along its slopes from subtropical to temperate and polar plants. Its flora encompasses various species growing in a wide range of climate zones from the northern limits of the subtropical zone to the southern limit of the polar zone.
 


Mt. Halla is a habitat for more than 1,800 plant species, almost half of over 4,000 species growing in Korea; it is in itself a virtual ecological park and botanical garden. Especially noteworthy are a variety of arctic-alpine plants including many endemic species and the forest of Korean fir (Abies koreana) on the slopes near the summit.
 




The arctic-alpine plants inhabiting Mt. Halla include 33 species endemic to Jeju Island, one genus endemic to Korea, 56 species for which Jeju is their southern range limit, and three species for which the island is their northern range limit. These plants are valuable plant genetic resources of excellent research value.
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