• 2022/02/07
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Ⅱ. Onsen and other Geothermal Phenomena in Kyushu

Ⅱ. Onsen and other Geothermal Phenomena in Kyushu

by: Vicki L. Beyer

About Onsen

Japan is justifiably well known for its onsen: mineral hot springs produced by geothermal forces. One-third of all the natural hot springs in Japan are located in Kyushu. Every minute of every day, 695,000 liters of onsen water rises to the surface somewhere on the island.


Hot springs especially occur in volcanically active areas like Kyushu. In these volcanic regions, molten rock is closer to the earth’s surface than in other areas. As snow melts or rain water seeps into the earth, it eventually encounters solid rock that it cannot easily penetrate and so begins to pool, forming what is known as groundwater. When the solid rock encountered by the groundwater is volcanically heated the groundwater absorbs heat from the rock, sometimes becoming exceedingly hot. Since cold water is denser than hot water, the heated water rises through the process known as convection. If the heated water can find a fault line or other fissure in the earth through which to move, it can rise all the way to the surface.


Even ordinary (i.e., unheated) groundwater can emerge from underground. This phenomenon is known as a spring and is commonly the source of a river. In the case of geothermally heated water, the phenomenon is referred to as a hot spring or, in Japanese, onsen. Since the soil in volcanically active areas generally has a higher mineral content, water seeping through that soil often picks up minerals, therefore the water of a hot spring is usually also mineral-enriched.


Some minerals have therapeutic or curative properties, so bathing in hot spring mineral water is not just a pleasant and relaxing experience but also beneficial to our health. Although it is not clear exactly when people first realized the practice might have health benefits, people in Japan have been bathing in onsen for literally thousands of years.       One legend relating to primitive onsen use is that it was hunters tracking wounded animals who first discovered the hot pools in woodlands. Apparently animals seemed to know that the hot water could ease their pain and the hunters, realizing this, concluded that the animals were messengers of the gods, sent to teach humans about this important therapy. Early Buddhist priests believed that Buddhist deities guided them to onsen. They also incorporated onsen bathing for purification into some of their ritual practices. From purification to healing, there is a strong connection.     


Japanese physicians began scientific research on the healing properties of onsen water over three hundred years ago. Based on the results of these studies, in 1948 Japan officially legislated what specifically constitutes onsen water. According to the legislation, it is water, steam or gas that emerges from the earth at a temperature above 25°C (77°F) or, if under that temperature, contains one of 19 stipulated minerals, including sulfur, sodium chloride, hydrogen ion, flourine ion, radon, radium salts, and ten others known to have therapeutic properties. If the water comes out of the ground sufficiently hot, the mineral content is not relevant for it to qualify as onsen water. But it is a given that such water will still contain various minerals.


Many public onsen baths (including hotels and hot springs resorts) across Kyushu and elsewhere in Japan will post notices of the mineral content of their water as well as information about the particular health benefits their water offers. Among the scientifically recognized health benefits are; relief from arthritis, neuralgia, high blood pressure, diabetes, skin conditions, "female complaints", gout, and general aches and pains. The onsen water can also have an anti-oxidation effect that rejuvenates the skin and in addition slows aging.


In some areas, rather than wait for the onsen water to emerge from the ground naturally, wells are dug in order to retrieve it or to ensure a steady supply. As long as the water still meets the temperature or mineral content requirements of the law, this practice is permitted, and in fact is rather common. The depth of the well depends on the location; it is said that digging anywhere in Japan you will find onsen water within 1,000 meters. Kyushu is blessed with so many natural hot springs that sinking wells is more often done merely to control exactly where the onsen water emerges.


How to Bathe


Whether you are visiting an onsen simply to get clean or for a therapeutic      restorative, in most places, it is treated as a bath, rather than a swimming pool: this      means you get naked. Many non-Japanese are somewhat alarmed by this practice, initially uncomfortable with the idea of sharing a communal bath with strangers. But once you understand the “rules”, it's not at all hard to get used to.


Prior to the middle of the 20th century, it was normal for men and women to bathe together, although since that time the norm has shifted. Now the sexes are separated, although some onsen resorts still have designated pools, usually outdoors, for mixed bathing.


If you’re staying at an onsen resort or hotel, you will be supplied with a cotton yukata robe and an onsen towel, usually made of thin Turkish toweling, measuring around 32-by-86 centimeters (about 12-by-34 inches). You can change into the yukata in your room before going to the bath, but each bath (men’s side and women’s side) has an separate room for changing so you can also enter wearing your street clothes, taking the yukata with you to wear after the bath. Even if there’s nothing written in English, it’s not difficult to determine which side of the bath to go into. The color coding is the same as for restrooms: blue for men and red for women.


The changing room contains shelves holding baskets (or sometimes small lockers) where you put your clothes after removing them. Everyone is very discreet, minding their own business as they change.


Once everything is off, you’re ready to move into the next room, the bath itself. If you’re feeling a bit self-conscious, women might find that a handy aspect of the dimensions of the onsen towel is that it can be pressed against one’s chest and drapes all the way down to below the crotch, allowing for a modicum of modesty. Men often just bunch up the onsen towel and hold it at crotch level, or tie the towel loosely around their hips. The bath is typically a large room, often very steamy thanks to the onsen water, which can be a boon for those who are still feeling shy.


Before you go running straight for the bathtub, which is usually one or more very large pools of steaming water situated at the back of the room, first you must wash. You will see a row of “washing stations”, spigots below mirrors, usually with a shelf for      soap and shampoos, and low plastic seats in front of them. Pick an empty spot, grab yourself a small round washtub, rinse off the plastic seat and sit down. Fill your washtub with hot water from the spigot and pour it over yourself, taking care not to fling the water about, especially not onto your fellow bathers, and repeat until you’ve fully rinsed. Some washing stations have showers—again you should be careful not to splash others.


Once you’re ready, you can soap up and scrub. Many people use their onsen towels as a washing cloth, rinsing it and wringing it out once finished. Because the towelling is usually very thin, it’s very effective and is practically dry once wrung out.


When you’ve finished washing and completely rinsed off you’re reading to get into the bathtub. You can use your wrung-out onsen towel again for that modesty ploy, if you need to, but do not allow your towel into the water. Roll it up and set it on the rim of the tub, or fold it and place it on top of your head (this one is more popular with men than women bathers).


Once you’ve eased yourself into the bath, which can take some time since the water is usually at least 40°C (104°F), you have nothing to do except relax; enjoy the heat and the healing power of the water. Your fellow bathers may want to try to chat, or they may leave you alone. Nobody is loud or rowdy in an onsen.


When you can’t stand the heat anymore, go back to your washing station and give yourself a cool rinse before getting back in, or trying another bath, if there are multiple tubs. If there’s an outdoor bath, known as rotemburo in Japanese, be sure to give it a try, soaking and stargazing go particularly well together. In brisk winter, the rotemburo is often blanketed in clouds of billowing steam. Mountain onsen areas can be snowy in cold seasons and relaxing in a tub of steaming hot water while gazing at the snow around you is an unforgettable treat.


When you’ve finished bathing, give yourself one final rinse and towel off. Even your wet onsen towel, once wrung out, will be surprisingly absorbent, allowing you to get reasonably dry before you return to the changing room. Hair dryers and various amenities are provided to use as you dry off and wrap yourself in your yukata.


After your soak, it’s a good idea to have a cool drink. Reportedly, 30 minutes in a hot bath takes the same toll on your body as sprinting 1,000 meters (about 1,100 yards) and if the minerals in the water include any salts, you may become dehydrated.


If you really cannot handle being naked in hot water with strangers, many large hotels have family baths that you might be able to use to bathe privately. Special private bath rooms for an additional fee are also becoming more common, although of course they are much smaller and may lack the atmosphere of a large onsen bath. Inquire at your accommodation to learn what options are available.


Where to Go


With so many of Japan’s onsen located in Kyushu, you’ll be spoiled for choice. Sometimes small towns have built up around onsen, with many traditional Japanese-style inns (ryokan), or even large hotels, catering to visitors who come to "take the waters". In other cases, there may be just a single onsen ryokan at the site of a more remote hot spring.


Ryokan usually include two meals (dinner and breakfast) in the tariff, as do some hotels. A popular trend with meals at these establishments is to feature the freshest possible local produce, providing a wonderful opportunity to sample the local cuisine. Increasingly, ryokan and hotels are offering various options in terms of sleeping arrangements (e.g., bed or futon) as well as choices regarding the number and style of meals they serve. However, a menu is rarely offered to diners and is usually fixed. If you have dietary restrictions, consult your accommodation in advance. Most can prepare alternatives that will accommodate your needs.




In Fukuoka Prefecture, one of the largest onsen towns is Harazuru Onsen, located in the southeast of the region, on the banks of the Chikugo River. According to legend, the hot spring was first identified nearly a century and a half ago by a fisherman on the river who noticed that there was one particular spot on the riverbank where snow never accumulated. The onsen's water is slightly alkaline and sulfurated, qualities which are good for beautifying skin. It is also said to relieve frozen shoulders and other joint stiffness, as well as helping digestive complaints, diabetes, gout and other illnesses.


There are more than a dozen hotels and ryokan at Harazuru, some even overlooking the river. The size of the bathing facilities, and whether they have an outdoor rotemburo, varies depending on the size of the hotel or ryokan itself.


The town operates a "ryokan cooperative" that can help travelers choose the right accommodation to suit their budget and personal style: www.harazuru.jp/ (Japanese language only).


Many hotels and ryokan also allow "day spa" visits by people in the area who wish to enjoy the baths of the facility but do not want to stay overnight. Tsuruwasennen is a pleasant day spa just a short distance from the southwest bank of the river.


These days even onsen visitors who come for the primary purpose of bathing want other entertainment and activities as well. There are a number of historic shrines and temples nearby, as well as a bustling farmer's market that many visitors enjoy. There are also various river activities available. One popular summertime evening activity is watching the cormorant fishing on the Chikugo River. Using birds to dive from fishing boats into the river and return with their catch, attracted by the light of flaming torches, is an ancient form of fishing in Asia. There are few places left in Japan where this technique is still practiced, making this a rare and unique experience.




Saga's Ureshino Onsen is known for its historic connections, having apparently been      visited by Empress Jingu (169-269AD) after she returned from campaigning in Korea. She is said to have declared "ah, ureshino!" (Ah, I am happy!) when bathing here, giving the area its name. The onsen water of Ureshino is particularly famous for being good for the skin. It is slightly alkaline and contains sodium bicarbonate, which makes it fizz gently. Nestled in the mountains of southwestern Saga, right on the border with Nagasaki, it was popular in the early 19th century with Philipp Franz von Siebold, a German doctor working for the Dutch East Indies Company in Nagasaki. Today, a Germanic-looking building on the banks of the river is a day spa called Siebold-no-Yu.


There are several hotel and ryokan choices in Ureshino offering sumptuous onsen bath facilities and tasty meals made with local ingredients. Among the particular dishes you can expect to be served is yu-dofu (tofu cooked in onsen water), a local speciality. Other activities you can enjoy in the area include exploring on a rented bicycle, perhaps into the nearby tea plantations or to Todoroki Falls. Hizen Yume Kaido is a theme park that recreates Ureshino in its Edo Period (1603-1868) role as a post town on the Nagasaki-kaido. There are street performers in period costume, including princesses and      samurai, as well as a spectacular ninja show and period craft workshops where you can try a hands-on experience.




The most geologically active part of Nagasaki Prefecture is the Shimabara Peninsula where the Unzen volcanoes are located (see “Volcanoes”). It follows that there are also excellent onsen in this area. The two best known onsen districts are Unzen Onsen and Obama Onsen.


Nestled in the mountains south of Mount Unzen, the Unzen Onsen is an area known for its acidic mineral hot springs, as well as for the steamy fumaroles (see explanation below) and pervasive sulphur smell that can give the whole district an other-worldly atmosphere. The entire town, much of it spread across the wooded hillside, seems to be powered by steam.


Because of its mountain-side location, Unzen Onsen enjoys four distinct seasons, each offering different scenery to be enjoyed alongside your hot springs soak. As with most onsen towns, there are many choices of accommodation, many including onsen baths. The Unzen Tourist Association can help visitors make their choice.


Unzen Onsen has been a popular destination with foreign tourists since the 1880s, just a couple of decades after Japan opened itself to the modern world. Then, as now, hiking and otherwise enjoying the natural surroundings were popular activities when visitors are not bathing. One of Unzen Onsen’s most popular natural phenomena will be discussed in more detail in the next section.


Obama Onsen is a seaside onsen town with plenty of hotel and ryokan choices featuring onsen baths. The town sits on Tachibana Bay with the Unzen volcanoes behind it, boasting      heart-stopping sunset views and super fresh seafood. Obama Onsen has a history dating back to 713 AD and plenty of historical nooks and crannies to explore around town. It also has some of the hottest onsen water in the country (often above boiling point). There’s plenty of it too; over 15,000 kiloliters (15,000 tons) of water per day.




As the home of Mt. Aso, Japan’s most volcanically active area, Kumamoto has numerous onsen, including many located inside the Aso caldera.


One of the largest onsen areas inside the caldera is Uchinomaki Onsen in the northwest, with six different hot spring water sources. Among the minerals in the onsen water are trace elements of lithium, which particularly relaxes bathers (as if the hot water itself wasn’t enough). There are a number of ryokan and other accommodation options to choose from. Uchinomaki Onsen is also host to a large number of day bathing facilities, for those who want a good soak, but don’t need to stay overnight.


In Minami Aso, one historic onsen is striving to make a comeback after suffering substantial damage in the 2016 earthquake. Known as Jigoku Onsen due to its sulphur content and fumaroles, Suzume-no-Yu sits high on the flanks of Eboshi-dake. From the middle of the Edo Period (1603-1868) the spring was mined to extract sulphur for other uses; no one thought of attempting to bathe there. In the latter part of the Edo Period, samurai class individuals began to visit for the water’s therapeutic effect. By the middle of the 19th century, anyone was permitted to visit and it became a popular resort, often catering to guests for extended stays in search of a health cure.


Suzume-no-Yu is a very unique hot spring. The acidic water contains so many different minerals that it’s difficult to characterize. Another unusual feature is that while the hot spring water emerges from the ground at 98°C (208°F), you might find a spring of completely cold water very nearby.     


The 2016 earthquake and a subsequent landslide badly damaged Suzume-no-Yu, blocking the road and stranding 70 people who had to be airlifted out. The spa was closed for two years while the road was reopened and repairs could be commenced. But the seventh generation of the Kawazu family who operate the onsen are determined to rebuild. While waiting to get back up the mountain after the earthquake, Makoto Kawazu visited onsen facilities in the Tohoku region to learn from their experience at rebuilding after a natural disaster and he has leveraged that information to formulate a reconstruction plan for Suzume-no-Yu.


At present there are still no overnight facilities, but the onsen re-opened in April 2019 to day visitors, who can enjoy new indoor baths or spend time in the original outdoor bath, with its natural bottom through which the onsen waters emerge. A new cold plunge pool stands ready to help bathers cool off. Eventually the ryokan and restaurant will be reopened, offering new, modernized facilities.


Sitting between Mt. Aso and the Kuju Massif is Kurokawa Onsen, an onsen town featuring a large number of public rotemburo baths, each in its own distinctive natural setting. Many of the baths belong to ryokan, so there are lots of choices for overnight stays here too. If you’re looking to really get away from it and experience “dolce far niente” (the sweetness of doing nothing), this is the perfect place.


One of Kumamoto’s more unique onsen is Shimoda Onsen on Shimoshima island in the Amakusa island chain. While ordinarily hot springs in Japan are categorized as volcanic or non-volcanic, Shimoda Onsen has the distinction of being neither, instead being regarded as a “special” hot spring. Geologists believe the heat beneath the earth’s surface creating the onsen water is generated by the friction on a fault line running through this area.


The water of Shimoda Onsen is more than 51°C (124°F) and contains sodium bicarbonate and chloride. It is popular with visitors seeking relief from digestive disorders, muscle and joint pain, diabetes, gout and even hemorrhoids. There is also a public foot bath near the visitor's center, allowing foot sore day trippers to enjoy a brief soak. The Amakusa Islands are semi-tropical, so in addition to relaxing in the baths, visitors can enjoy diving, sea-going boat rides, hiking, local pottery and visiting sites associated with the area’s Christian history (see “Ocean and Islands”).




Oita is often referred to as the onsen capital of Japan, and with good reason. This prefecture has more hot springs and produces more onsen water than anywhere else in the country. Oita sits on two east-west fault lines that contributed to the existence of the volcanoes at nearby Mt. Tsurumi as well as Mt. Aso and the Kuju Massif. These volcanic peaks are said to power all that hot water coming out of the ground in Oita.


Oita’s best known onsen town is coastal Beppu, where over 100,000 kiloliters of onsen water gushes from 2,700 different sources every day. Eight different primary hot springs have been identified in Beppu, so this area became better known as “Beppu Hatto” (eight onsen resort). Beppu has a long history as a hot springs destination and became known as a health resort during the Kamakura period (1192-1333) when a sanatorium for wounded soldiers was established at Kannawa, one of Beppu’s eight major onsen.


As Beppu is a large port city, it can be challenging (though not impossible) to find a      traditional hot springs resort environment, but finding soothing, therapeutic onsen baths is certainly no problem. There are even inexpensive self-catered options perfect for extended stays. These are particularly popular with Japanese people seeking the health benefits of onsen bathing and healthy steam-cooked food. For non-Japanese visitors, this kind of accommodation makes a good base for a thorough exploration of the area.


Another type of onsen experience available in the Kannawa district of Beppu is the steam bath, also popular as a curative. Kannawa Mushiyu was founded in 1276 by Ippen Shonin, a Buddhist monk who has several historical associations with hot springs. Visitors wearing yukata, segregated by gender, spend about 20 minutes per session lying in a steam room, the floor of which is strewn with medicinal herbs, sweating out toxins and being healed. At a nearby temple is a collection of crutches left behind by patrons of the steam bath who no longer need them.


For a more rustic, authentic hot springs experience, head into the mountains behind Beppu. Nestled in the valley below Mt. Yufu, is the onsen town of Yufuin, popular both for its hot springs and its delightful, laid-back atmosphere.




Kagoshima is also home to plentiful hot springs, thanks to its many active volcanoes.


Kirishima Onsen and Kirishima Shrine Onsen are two onsen towns high in the Kirishima mountains, where visitors can enjoy hiking and other outdoor activities by day and relax in a soothing mineral bath at night. There are known to be around nine different hot spring sources in the area, each producing onsen water with different health benefits. If you’re looking to try all of them, you are fortunate that many offer not only accommodation but also day spa visits. At Kirishima Shrine Onsen, there is even a special ticket available that gives entry to any three baths, the perfect excuse to sample a few. If you’re looking for a unique bathing experience, ask at your accommodation for directions to Saiko-no-Iwafuru Me-no-Yu, a natural pool of hot spring water a short distance from Kirishima Onsen.




Miyazaki is the most tropical of all Kyushu’s prefectures, yet it shares the Kirishima mountains with Kagoshima. Just across the northern prefectural border from Kagoshima is Ebino Kogen, where Miyazaki boasts the highest altitude onsen resort in Kyushu. This is another area that is very popular with hikers and mountain lovers, perfect for anyone who enjoys a good long soak after a day on their feet. In the foothills to the east of the Kirishima mountains runs a river called Yunomoto (meaning “source of hot water”) and in the Nishimorokata district there are a couple of small onsen inns where visitors can be pampered, with a very local experience. The hot spring water in this area is highly carbonated; just imagine bathing in champagne (or locally they say imagine bathing in ramune, an early form of soda pop).


For a more tropical onsen experience, try Aoshima Onsen, a seaside onsen town near the famous sacred island of Aoshima. Here visitors find a laid back atmosphere and bright sunshine, with some of the larger hotels providing stunning ocean views.    


Many onsen towns have public foot baths available for weary travelers. These foot baths are usually long sunken troughs with onsen water flowing through them and lined with benches. Anyone is welcome to remove their shoes and socks to sit and soak their feet for a while at no charge. If you've been walking around sightseeing, this can be a very welcome and soothing respite (until you realize you don’t have a towel; it’s wise to always carry a small one with you). As an example, Ureshino has Siebold's Fussbad, while at Obama Onsen, Hot Foot 105, overlooking the shore, is Japan’s longest foot bath. You guessed it—105 meters (345 feet) in length, it also has facilities for steaming local seafood or vegetables, if you fancy a bit of self-catering. Even Kagoshima Airport has its own foot bath, what a way to wait for your flight! Or, they say if you dig a hole on the beach at Sakurajima, it quickly fills with hot water—a self-made foot bath.


Other Geothermal Phenomenon in Kyushu


Another result of geothermal forces in Kyushu is the existence of fumaroles, mudpots, and even geysers in some places.


A fumarole is an emission of steam, and sometimes noxious gases, from underground through a crack or fissure in the earth's surface. The steam is basically onsen water that is so hot that it has vaporized before emerging from the ground. Many volcanically active areas have fields of fumaroles, areas where the volcano's heat and the fractured landscape produce multiple vents for the steam and other gases.


Where the emission contains some liquid, but not enough to form a stream, the water often mixes with the surrounding soil, particularly that which is clay-like, to become mud. The farthest reaches of the mud sometimes cools and hardens, forming a rim that creates a pool of mud which appears to boil, as water and vapor continue to rise from below the surface. This phenomenon is usually referred to as a mudpot. The mud can be white, gray, green or red, depending on the minerals it contains.


A geyser is an eruption of boiling water out of a fissure with such energy that it shoots high into the air. It is believed that geysers are the result of water collecting in a chamber situated very close to volcanic magma, so that it heats easily. When the chamber is full of water that reaches boiling level, the expansion this causes forces the water to rise quickly through fissure (effectively a tube) and shoot out of the ground until the water chamber has emptied or cooled. Many geysers erupt on a fairly predictable schedule, signs of the limited size of the chamber and a steady flow of groundwater into it.


The Japanese like to refer to areas with plentiful fumaroles, mudpots and geysers as "jigoku" (hell). Indeed, between the steam and the frequent smell of sulfur in the air, these areas do seem to conform with the images of the underworld held by most cultures. Kyushu is host to two of these fascinating spots where we can observe the earth's energy up close and personal, in Unzen and Beppu.


The Unzen Jigoku sits almost exactly in the center of the Shimabara Peninsula, due south of Mt. Unzen. Trails, and in some areas, elevated walkways, allow visitors to take a walk through hell without any danger, or risk of eternal torment. Almost nothing can grow in this rocky landscape where fumarole steam vents leave sulfur deposits and mudpots boil. The steam is particularly evident if you're visiting on a cold day, but visiting in the heat of summer perhaps provides an even greater appreciation of the hell-like conditions.


At the beginning of the 17th century, shortly after Tokugawa Ieyasu consolidated all of Japan under his control, he began to persecute Christians, seeing the religion as a potential threat to his government. Christianity, a relatively new import to Japan at the time, was strongest in Kyushu and the Shimabara area was predominantly Christian. The Unzen “hell” was used to torture Christians and get them to renounce their faith (or die). American movie director Martin Scorsese portrayed one such incident in the opening scenes of his 2016 movie "Silence" (based on the 1966 novel by Japanese writer Endo Shusaku).


A popular snack for visitors to these regions is hard-boiled eggs, prepared using the steam or boiling water emerging from hell. In many parts of Kyushu with fumaroles, using the steam to cook is a long-standing and common practice. It is considered particularly healthy because of the mineral content of the steam.


Beppu has eight hells (as if one wasn't enough), all within the city limits. A meguri (course) visit to all eight is a popular activity for visitors. Because these sites are in built-up areas, they are all fenced in and cordoned off with restricted walkways and sometimes sculpted gardens where an admission fee is charged. While this inevitably makes them more touristy locations, completing the meguri is still a great way to gain a greater appreciation of the geothermal forces at work, as well as of the variety of effects they can produce. In addition to observing the phenomenon, you can sometimes smell the gases or hear the escaping gas or breaking mud bubbles, there’s a lot to take in.


A combined ticket will get you into seven of the eight hells. Among the popular souvenirs sold at each location is a T-shirt reading (in Japanese) "Every day is hell".


●Tatsumaki Jigoku (Tornado Hell) - The feature of this "hell" is its geyser, which erupts every 30 to 40 minutes for 6 to 10 minutes. This is one of the most frequently erupting geysers in the world. To protect visitors, and nearby buildings, a stone barrier has been erected around three sides of the area where the geyser spouts, and there is also a stone plate across the top that keeps the water from flying too high into the air. If not restricted, estimates suggest the water could reach as high as 50 meters (165 feet),       but even at four and a half meters or so (about 15 feet) the spouts are still a pretty impressive sight. The discoloration of the stones of the barrier indicate that there must be some iron among the minerals in the water. The gurgling sound before and during the eruption is also particularly intriguing, an indication that both water and steam are competing to emerge from the opening. Apparently the 20 or so eruptions each day put      out about 600 kiloliters (about 600 tons) of water.


●Chinoike Jigoku (Pool of Blood Hell) - The name says it all. This 1,300 square meter pool is the color of tomato soup, but since probably no one was familiar with      tomato soup when the pool was found, more than 1,300 years ago, calling it a pool of blood makes more sense. The slurry in the pool takes its color from the iron oxide, magnesium oxide, calcium oxide and silicic acid it has picked up on its way into the pool. The pool is about 30 meters (98 feet) deep and the water that fills it is believed to come from about 180 meters (590 feet) below ground. About 1,800 kiloliters of water bubbles into this pool daily, three times the amount emerging from the Tatsumaki Jigoku's geyser. The water's temperature is 78°C (176°F), far too hot to get into, but there is a foot bath of water from the pool that has been cooled to a more tolerable temperature. A popular souvenir of a visit to this hell is a skin cream made with the iron-laden mud of the pool.


●Kamado Jigoku (Cooking Pot Hell) - This site gets its name from a legend that the steam emitting from these vents was used to steam the rice offered to the guardian god Ujigami during a festival at the nearby Hachiman shrine. The water in the pools here is around 90°C (194°F), which is certainly hot enough for cooking. There are several different pools and mudpots at this one location. How natural phenomena in such close proximity can be so widely varied is a fascinating sight. Moving clockwise, the first vent is a very small pool of brown slurry. Next is a steam vent where, it is said, if you blow cigarette smoke into the steam, it will double in volume. A statue of a red oni (demon) standing on a tradition pot lid towers over the vent. The next pond is water of brilliant cobalt blue, with crusty white silica deposits formed around its edges. A wooden stand invites visitors to have a drink of the onsen water (Careful! It's still about 80°C     /176°F) or take a short moisturizing steam bath on your hands, feet, or throat. Next is a small collection of mudpots with thick mud walls that make them look a bit like cooking pots. They bubble from time to time, not because they're boiling but rather because of the water or air being forced into them from below the earth. The next pond is a mystery even to the geologists. It changes color suddenly and unpredictably several times a year, ranging from dark blue to light green. What color might it be on your visit? The final pool is reddish in color, similar to the Chinoike Jigoku. A sign nearby explains that it used to be gray, but over many years changed to its current color, an example of oxidation in action. There are also three foot baths available here, containing water from three different sources on this site, the most popular of which has a sandy bottom.


●Oniyama Jigoku (Demon Mountain Hell) - A sign at the entry informs you      that the pressure of the steam coming out of the vent here is enough to pull one and a half train cars. But what's really noteworthy is that the geo-thermal heat is used to create a year-round tropical environment suitable for breeding crocodiles. There are several dozen crocodiles on site, with public feedings at 10:00 am on Wednesday, Saturday and Sunday and 2:30 pm on Saturday and Sunday.


●Shiraike Jigoku (White Pond Hell) - This place doesn't feel like hell at all. At first it seems like a pretty Japanese garden with a pond as its central feature, but      that pond is filled with steaming bluish-white water. The water, which is 95°C      (200°F) when it comes out of the ground, contains chloral natrium, silicic acid and calcium bicarbonate. Although it appears clear when flowing, when pooled it becomes milky. The heat from this water is used to create a small tropical fish aquarium containing piranha and other unusual tropical fish.


●Oniishi Bozu Jigoku (Oniishi Monk’s Shaved Head Hell) - Initially this hell looks like a garden situated on a gently sloping block. But visitors soon encounter mudpots containing pale gray mud from which, now and then, bubbles emerge. If a      bubble gets large enough, it can look like the shaved pate of a Buddhist monk, which is how this hell got its name. Although the site is roughly the same size as Kamado Jigoku, the mudpots here are all consistently the same color. It's almost hypnotic to watch the bubbles emerge from the mud, grow and then burst, forming concentric rings in the mud. Visitors have another chance for a foot bath at this hell too.


●Umi Jigoku (Sea Hell) - This hell features a steaming pool of aquamarine water that almost looks like it could reside inside a volcanic caldera. In addition to the striking color, a result of iron sulfate in the water, a wicker basket of eggs cooking as they dangle      into the nearly boiling water is an unusual sight. Nearby are a couple of small reddish mudpots and a large lake known for the tropical lily pads that grow on it in summer, some reaching a diameter of about 1.5 meters (about 5 feet). The variety of lily is not native to Japan and the plants only survive here because of the geothermally-warmed water.


●Yama Jigoku (Mountain Hell) - Packed with fumaroles and small pools of steaming colored water, a visit to this hell is not included in the combination ticket. It is effectively a small zoo of about 20 types of animals, kept comfortable by the heat generated from the fumaroles.


Sand baths seem almost dull in comparison with the dynamic geothermal forces of fumaroles, mudpots and geysers. But the chance to be buried in beach sand that has been naturally heated by the hot groundwater beneath it, is a memorable experience. The best known sand baths are to be found in Beppu, Oita and Ibusuki, Kagoshima.


"Bathers" don a cotton yukata and wrap a towel around their hair before lying in a shallow trough which has been dug into the beach sand. Attendants then shovel the naturally heated sand over the bather's prone body, often mixing the freshly dug hot sand with cooler sand to ensure just the right temperature and packing the sand around the body just so, in order to achieve maximum therapeutic effect. Once the bather is packed in, there is nothing to do but relax and enjoy, just as with a regular onsen bath.


The sand is surprisingly heavy, but not intolerable. The weight of the hot sand on the body is supposed to have a massage-line effect. Indeed, the heat emanating from the sand is extremely soothing, as is lying within sight and sound of a beach. On a clear day, Shikoku Island, some 30 kilometers (19 miles) away, can be seen from the Beppu Beach Sand Bath.


As we have seen in this review, onsen and other geothermal phenomenon produce a lot of energy. We've also seen some examples of how that energy has been used to cook food and heat animal care facilities and even gardens in Beppu. So, are there other ways the energy of the earth can be used?


The first attempt to use geothermal heat to produce electricity in Japan took place in Beppu in 1925. By 1990, there were 12 geothermal power stations across the country.      Although each is quite small and they do not produce a significant amount of the country's power, by 2011 the number of these small geothermal plants had increased to 18, most of them in the Beppu area. Since popular opinion has turned against nuclear power after the 2011 Fukushima nuclear meltdown, efforts to further exploit geothermal power have been significantly expanded and Beppu in particular has concrete plans to open up to 30 more small geothermal power plants in the future.