Jeju Island is molten paradise
Jeju Island from the air. Picture: Jeju Tourism

Few locations illustrate the force of Mother Nature's tantrums as intimately as South Korea's Jeju Island, where more than 360 volcanoes exist within an area of just 1846sqkm.

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Jeju Island's volcanoes are responsible for the drama that shaped a coastline of lava rock formations long ago. Plus, and this is an important plus, a large-scale lava tube system which includes the formidable Manjanggul, the longest lava tube in the world.

Lava tubes form during violent volcanic activity. As molten lava rolls across the land like a fiery highway the outer surface cools and hardens while the inner lava flows on, leaving a tunnel behind, which in Manjanggul's case extends almost 8km.

In some places, Manjanggul broadens to about 23m or rises up to 30m high. The fact that you can venture deep inside this lava tube sends the wow factor soaring several degrees. And, once inside, the remarkable state of preservation gives a clear impression of events that occurred between 200,000 to 300,000 years ago.

Lava flow-lines are visible along Manjanggul's internal walls. These bear witness to the volume and frequency of each lava flow. There is ropy lava underfoot, the result of hot lava roughing up previous deposits. Stalactites appear where temperatures increased as the lava rolled through narrowing sections of the tube and partially melted its ceiling. The stalactites then dripped to the floor to form stalagmites.

Similarly, hot deposits oozed through adjacent lava tubes. These formed the so-called lava "toes" and other fanciful formations to be seen on the walls and on the ceiling. Any rock fragments or boulders that tumbled down into the flowing mass were swept up and trapped forever as lava "balls" or "benches".

Jeju Island. Picture: Jeju Tourism
The public can safely walk through the lava tube for a distance of at least 1km, at which point the world's biggest lava "column" stands frozen in the act of pouring through the ceiling from a second lava tube above Manjanggul. This spectacle alone merits a visit to Jeju Island.

Then there's the rugged coast. Here, nature's imagination seemed charged with destruction as violent geological forces knocked the coastline asunder, leaving black beaches and lava rock sentinels arranged in a visually disturbing way.

The Jungmun Daepo coastline is particularly striking, and gives a clear demonstration of what happens after molten lava rolls into the sea. In short, it cools rapidly, solidifies, contracts and cracks vertically. The result: rectangular and hexagonal- shaped columns spreading along the Jungmun Daepo coastline like a folding screen for a distance of about 2km.

I'm not the first visitor to be enthralled by Jeju Island. Last year it ranked among the finalists (along with our Great Barrier Reef and Uluru) in the New 7Wonders of Nature competition, a global web-based search to recognise the seven most wondrous natural sites in the world.

And in 2010 nine of Jeju Island's geological sites were designated UNESCO Global Geoparks. Along with the lava tube system and the lava rock formations, Seongsan Ilchulbong Tuff Cone and Mt Hallasan are prominent features on UNESCO's list.

First a few words about Seongsan Ilchulbong Tuff Cone, a product of hydro-volcanism.

About 5000 years ago, an underwater volcano erupted in the shallow seabed off Jeju Island's eastern coast. The interaction of hot ascending magma with sea water followed by successive deposits of ejected volcanic ash produced the steep-sided tuff cone we see today.

Seongsan means "gigantic castle", an appropriate name because, viewed from sea level, the 99 rocky peaks surrounding the tuff cone's crater create the appearance of a turreted castle which seems to float and almost hang in the sky.

Ilchulbong means "sunrise peak". As the easternmost point of Jeju Island it is first to greet the dawn. Not surprisingly, this is a popular spot at sunrise, especially on New Year's Day when Seongsan Ilchulbong attracts vast numbers of visitors.

It is particularly rewarding to climb the 180m to Seongsan Ilchulbong's castled heights and the ascent is achievable in a short space of time with little effort. Five hundred or so well-constructed steps take you straight to the crater, with spectacular views along the way.

Once at the summit, the basin-like interior of the tuff cone is almost pastoral - a lush green meadow in sharp contrast to those fiery beginnings long ago. Despite its great age, however, Seongsan Ilchulbong provides a clear base for the interpretation of eruptive and depositional processes of hydro-volcanoes for scientific research.

As for Mt Hallasan, at 1950m this is the tallest mountain in South Korea. It is also a dormant volcano and widely recognised by scholars for its research value.

Hallasan is also known as Mt Yeongjusan, meaning "mountain high enough to pull the galaxy". A hike to its 500m-wide crater lake requires thought and preparation. The weather can be changeable but well-developed hiking trails give access to the mountain's vertical ecosystem of plants at different altitudes.

The lure of nature is a powerful force. Add magma and nature seems bigger, bolder, more powerful.


FACT FILE

• Jeju Island is 130km from the southern coast of Korea. Frequent flights depart from Seoul Gimpo Domestic Airport and take about an hour. visitkorea.or.kr

• Adventure World has a three-day, two-night Jeju Island and Lava Tubes tour starting from $371 per person twin share. adventureworld.com.au

Margaret Turton travelled courtesy of Korea Tourism Organization.

The West Australian

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