The Tatun volcanic episode ended 350,000 years ago, but in geologic terms the landscape is still young, and the geothermal activity persists. The area's abundant rainfall trickles down into the underlying strata of quartz sandstone, an ideal aquifer which fills with hot groundwater. Pressurized, the heated water returns to the surface along two fault lines-the Chinshan Fault and the Kanchiao Fault-and ushers forth as hot springs. The Peitou and Yangmingshan areas have a dozen wellheads, and these have supported hot spring culture through its long history.

Besides producing hot springs, the underground geothermal energy is hot enough to boil water and create steam. From hills above the water table, this steam issues from cracks in the rock, producing another feature of the Tatun hot spring area-steam vents.

Between Hsin Peitou and Chinshan is an 18-kilometer stretch with more than 20 areas of hot springs and steam vents. Steam billows upwards in clouds. Acidic gases issue forth and not a blade of grass survives. The noses of visitors fill with the pungent odor of sulfur.

A short way off the road connecting Yangmingshan and Chinshan is Chutsuhu. Here visitors will see steam rising from Hsiaoyukang. From the vents at its bottom to the faults at its top, the entire area is engulfed in gushing white clouds of steam-a breathtaking sight. The surrounding volcanic rock is crumbled and broken, the result of eons of rains and earthquakes, and the rubble has tumbled down its slope. The look is classic volcano. On the ground are bubbling caldrons called "ash mud holes," formed when the rock is dissolved by hot sulfurous gas and hot water from underground.

The road from Peitou to Yangmingshan passes the Takuangtsui hot spring area. To the east is the Lungfengku hot spring area, which is rich in sulfur minerals. Sulfur is the main ingredient of gunpowder, and during the Ming dynasty merchants traded with the plains aboriginals, exchanging agate, and bracelets for sulfur.

Later, during the Qing dynasty, the mining of sulfur was an important commercial activity here. During the reign of Emperor Kangxi, an adventurer named Yu Yonghe left his home in Zhejiang Province and crossed the Taiwan Strait to locate the source of this sulfur. After traveling the length of the island, he arrived at present-day Lungfengku. He wrote an account of his journey, "Record of the Small Sea Travels," and it is one of the earliest clear, eyewitness descriptions of northern Taiwan. From this account, the world of letters learned of the scenery of the Tatun area and its volcanoes.

Stories of the hot springs

If one speaks of Taiwan's hot springs, the natural place to start is Hsin Peitou, located at the foot of the Tatun volcanoes. The earliest person to utilize the springs was a German trader, who in 1893 built a club in Peitou. Two years later, in 1895, after defeat in the Sino-Japanese War, the Qing court ceded Taiwan to Japan, and Peitou was sold to the Japanese and used as a resort for soldiers.

In 1895, a Japanese businessman opened a hot spring hotel in Peitou. Then in 1901, the Taipei-Tanshui rail line was constructed, a public bath and park were built in Peitou, and the development of the hot spring area was well on its way. From 1950 to 1970, Peitou gradually changed into a red light district, and this flourished until the government ended the licensing of prostitutes in 1979.

The public bath fell to ruin after the fall of the gentle arts. In 1996, a teacher of the Peitou Elementary School set out to rescue this historic building, and started a campaign to restore it to its former grandeur. The public bath, which was founded in 1913 and was once East Asia's largest hot spring facility, is now a living testament to Taiwan's hot spring culture. Built of tile, wood and steel, its elegant exterior bears a resemblance to an English country estate. The public bath has re-opened as a hot spring museum.

Under the care of Peitou's residents, the hot springs are bringing back nostalgic visitors who seek a glimpse of the past. In the background are the million-year-old Tatun mountains. This is only natural. The histories of Peitou and the Tatun mountains are one and the same, and their fates are intertwined, combining the natural world and human culture as a single precious resource.

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Volcanic eruptions have left their mark on the Tatun Mountains. Hsiaoyoukang is still geothermally active with billowing steam vents that recall an earlier geologic era. (Sinorama file photo)