The Hakkoda volcanic complex (Hakkoda, Hakkodasan, Hakkoda Mountains) are an active volcanic complex in south-central Aomori Prefecture on N Honshu Island, Japan.  Its highest peak, Mount Odake is 1,584 m.  The complex is built inside and around a 9 km diameter caldera created by a series of multiple VEI 7.0 starting 869 ka.  There are at least 17 stratovolcanoes and cones making up the complex.  They are generally grouped into N and S groups.  The N group is located on the rim of the caldera.  The S group predates the caldera. 

The forested Hakkoda Mountains attract climbers, skiers and sightseers.  They offer extensive backcountry skiing.  The mountains are not technically challenging but do present deadly dangers in terms of volcanic gasses, harsh winter weather and avalanches.  The same harsh winters provide heavy snowfall that makes the mountains a prime destination for backcountry and mountain skiers. 

The Hakkoda Mountains are collectively called Mount Hakkoda or Hakkoda.  The word is a description of the shape of the mountains.  ‘Hakko’ means ‘eight armor’, as the 8 peaks resemble helmets.  The ‘da’ part means ‘field’ and describes the flat plateaus between the peaks. 

Hakkoda is a particularly deadly group of mountains.  In recent years, volcanic gasses killed people training on the mountains.  It was also the site of the Mount Hakkoda disaster in Jan 1902 when a group of Imperial Japanese Army solders got lost in a blizzard.  They were climbing the mountain on the way to Tashiro Hot Spring.  199 did not make it home.  The troop movement was done in the prelude to the Russo-Japanese War.  The Imperial Japanese Army thought it necessary to secure a route through Hakkoda Mountains in the event that railroads were destroyed by the Russian Navy.  The regiment stationed at Aomori had a large number of men who did not have experience in climbing mountains in the snow.  They also did not have guides.  That combination proved deadly.

Total journey was 20 km.  The first two days went slowly.  Weather changed on day three, with a blizzard that dropped deep snow on the mountains, high winds, and a temp of -41° C.  The unit did not show up at their destination and a 60-man rescue party was launched.  Search and rescue operations lasted for months, involving tens of thousands of military and villagers.  193 of the 210 froze to death en route.  Another 6 died within two months of rescue.  Most of the survivors lost limbs due to frostbite. 

The immediate area is sparsely populated, with less than 1,000 within 10 km of the caldera.  This balloons to over 475,000 within 30 km.  Most of these are 19 km NNW of the caldera in coastal Aomori City.  There are over 1.9 million within 100 km. 

JMA lists Aomori City’s population as 303,000 as of 2011.  It is located on the N shore of Honshu, facing Aomori Bay to the N.  There are a pair of large rivers flowing through the city.  The city backs into Towada Hachimantai National Park to its immediate S.  The park gets over 2.6 visitors/year (2009).  There are multiple hot springs in the city.  Aomori is the regional commercial center for the Aomori Prefecture.  Agriculture and fishing are small contributors to the economy.  There is a decent manufacturing sector.  Services account for nearly 80% of all economic activity. 

Climate has a cold, humid continental climate with short, warm summers and long cold winters with heavy snowfall.  Average annual temperature is around 11° C, with average highs in August 22.5° C and lows in Jan -2° C.  Average precipitation is 135 cm/year.  Average snowfall is 57 cm/yr.   

As with the rest of Japan, activity at Hakkoda will be reported by the Japan Meteorological Agency (JMA), though it is not actively monitored for volcanic activity.  The entire nation has robust and active seismic coverage that should be sufficient to report activity. 

Regional Calderas

Muraoka in a 1989 paper noted that there are at least five calderas within a 40 x 40 km area between Towada and Hakkoda.  Both of these were previously well known.  The other three, Okiura, Yunosawa and Ikaigaseki are newly discovered using remote sensing data.  The five calderas will be listed roughly by age, youngest first.  Towada, Hakkoda and Ikaigaseki are all thought to be Crater Lake-type collapses.  Yunosawa and Okiura are both Valles-type collapses.  All five calderas formed within the last 3.5 Ma.  There may be a sixth caldera slightly overlapping the NE corner of the Towada caldera.  It is nominally named the Nenokuchi caldera and if it exists, is about the same size as neighboring Towada.  The additional caldera is invoked to explain a couple ignimbrites that are not tied to any of the five known caldera systems. 

The type of caldera tells us a lot about what the system looked like before the collapse.  The Crater Lake-type collapses all took place at large composite andesite stratovolcanoes.  Precaldera volcanoes typically are about three times the radius of the caldera.  Caldera forming tuffs are typically dacites.  There is a chemical difference between Valles-type and Crater Lake-type erupted magmas. 

Finally, the older calderas are not necessarily a good prospect for geothermal energy exploration.  In this region, the only two calderas with active hydrothermal systems are Okiura and Hakkoda.  Most of the high temperature springs are concentrated in the actual calderas. 

The Towada caldera is the most recently active.  It is a squarish depression, 11 km across, long recognized as a caldera.

Hakkoda caldera was also previously known mostly from its prominent NE wall.  The SW caldera wall was thought to be concealed by younger volcanic structures of the N and S Hakkoda volcanoes.  A new interpretation has the S Hakkoda volcano itself as the S rim of the caldera.  The caldera itself is 13 x 9 km.

The Okiura area has long been known for an active hydrothermal system including many hot and boiling springs.  Remote sensing led to a 1981 proposal that the Okiura caldera underlies the region.  It measures 17 km in diameter and is a highly eroded Valles-type depression with ring faults.  It is roughly 18 km NW from Towada, 18 km SW from Hakkoda. 

VOGRIPA lists two massive eruptions out of Okiura.  The oldest of these was a 1.5 Ma VEI 7.5 that ejected the 300 km3 Aoni Tuff (andesite – rhyolite).  The second listed eruption was a 450 ka VEI 6.2  10 km3 Jizodaira Ash.  Thick deposits of the Aoni Tuff are mixed with lake sediments in the Okiura caldera.

Basin topography and central cones in the Ikarigaseki area were also identified via Landsat imagery.  Its topography is similar to that of Hakkoda, though more eroded.  The basin is described as a Crater Lake-type caldera, elliptical measuring 12 x 8 km, and nested completely inside the N portion of the larger Yunosawa caldera. 

The Nijikai Tuff surrounds the Ikarigaseki caldera.  It is estimated at 35 km3 and dated around 2.5 Ma.  Intracaldera tuffs are rare in Crater Lake type calderas, but they are found in the Ikarigaseki caldera.  The material shows hydrothermal altering. 

The Yunosawa caldera is a 15 km circular depression.  Its N rim has been partly obscured by deposits from the neighboring and younger Ikarigaseki caldera.  The eroded S rim is all that is visible.   It is located perhaps 18 km W from Towada, 12 km SW from neighboring Okiura.  The oldest Obiakiyama Tuff from Yunosawa is estimated at 300 km3, and is the largest volume erupted from the five calderas.  It is dated at 3.5 Ma.  Like Okiura, it also has ring faults and is considered to be a Valles-type collapse. 

Regional Volcanoes

The following list of neighboring volcanic systems is gathered from the JMA National Catalogue of the Active Volcanoes in Japan (Fourth Edition).  JMA maps of the region show extensive volcanism.  Inactive systems will be mentioned only in passing, it that.  All of these volcanoes erupt primarily andesites to basaltic andesites with some minor dacites. 

Note that we will briefly describe 6 active volcanoes within 100 km of Hakkoda carried on JMA’s National Catalogue of the Active Volcanoes of Japan (The Fourth Edition) in the following section.  Needless to say, the region is intensely volcanic.  JMA carries at least another 20 volcanoes within the same area on their regional maps.  Most of these have an entry in their database Quaternary Volcanoes of Japan, active 2.6 Ma to present. 

While we have multiple posts on Japanese volcanoes, most of them are a long way from Hakkoda.  The two closest are our Sept 2025 Chokai and our 2021 Towada post (18 km S). 

As usual, all distances will be measured from Hakkoda. 

Osorezan 75 km NNE 

Osorezan, is a 828 m high volcano partly occupying a 5 km diameter caldera on Honshu 75 km NNE from Hakkoda.  The caldera is partly filled with a shallow lake that drains though the N caldera wall.  The system has been active for at least the last 1.46 Ma.  Initial activity built a large stratovolcano that created a somma 680 ka.  There were four VEI 5.7 – 4.8 eruptions 370 – 240 ka which created the caldera.  Each of these ejected around 1 km3 of dacite. 

Post caldera activity built pyroclastic cones and domes starting 80 ka.  The system has an active hydrothermal system with hot springs.  The only report of historic activity was published in 1787 which reported fires and clouds at the summit.  Earthquake swarms were detected during the second half of the 20^th Century.  There is a magma body below the volcano. 

Iwaki 49 km W

 Iwakisan is a 1,625 m andesite / basaltic andesite stratovolcano located some 49 km W of Hakkoda.  It is called the Fujisan of the Tsugaru district.  The cone is topped by a 2 km crater filled with a dome.  There are at least six explosion craters around the summit.  There are three more domes on the W and S flanks.  The summit has an 800 m collapse crater on the NE side.  Avalanche deposits to the NE of the volcano has hummocky topography.

It is one of the more active volcanoes on Honshu, with seven magmatic eruptions 10 – 2 ka.  Most of these were associated with dome building.  One produced a tephra.  Since 1571 AD, there have been at least 25 phreatic eruptions.  Most of these are listed as uncertain eruptions.  The confirmed ones are listed as VEI 2’s.  Activity since 1972 has been mostly seismic, with an increase in fumarole activity reported in 1978. 

Akita – Yakeyama 79 km SSW  

The 1,366 m Akita – Yakeyama (Catalog 25 / Map D23) is located some 79 km SSW from Hakkoda.  It is the most recently active of a group of coalescing volcanoes.  It is immediately W of Hachimantai volcano.  The main volcano, Yakeyama has a small dome in its 600 m wide summit crater.  The Tsugamori volcano to the E is a stratovolcano of similar height with a 2 km crater breached to the NE.  The Kuroshimori dome is 4 km S of Yakedake.  There are several thermal areas.  One of them, Tamagawa Spa on the W foot is strongly radioactive.  The last magmatic eruption formed the Onigajo lava dome in the summit crater 5 ka. 

There were multiple eruptions since the Onigajo eruption.  Five of them 1250 BC – 1678 AD, three more in the 19^th Century, and eight in the 20^th Century.  The most recent of these were a pair of phreatic events in 1997.  All the 20^th Century activity other than the first in 1929 were VEI 1 eruptions.  1929 was a VEI 2.  All the older eruptions listed by Smithsonian GVP were VEI 2 events.  This may be due to the remoteness of the system.

Hachimantai 79 km S 

The Hachimantai volcanic group (Catalog 26 / Map D22) is a field of scattered vents located some 79 km S of Hakkoda thought to be active before the Holocene.  The 1,613 m summit is an undulating plateau of andesitic lavas with steep slopes on its edges.  There are circular craters near Komonomore and Mokkodake in the center of the plateau.  Craters are youthful looking but have not been dated.  Japanese experts believe it to be of possible Holocene age.  While there are no historic eruptions known, there are active solfataras on the W and S flanks.  Smithsonian GVP lists a pair of confirmed eruptions 9.9 and 7.3 ka.  

Iwatesan 92 km S 

Iwatesan (Catalog 27 / Map D31) is located 92 km S from Hakkoda.  It is another symmetrical stratovolcano (2,038 m) when viewed from the E.  From the W, an older cone is visible with a 2 x 3 km caldera.  Initial activity built the Nishi-Iwate volcano 700 ka.  Activity migrated E to form Higashi-Iwate volcano. It collapsed at least seven times over the last 230 ka.  The most recent of these are somewhere between 739 and 1615 AD.  Yashuidake is the (mostly) basaltic summit cone of Higashi-Iwate.  It is topped with a 500 m wide crater and rises well above, burying the E rim of the caldera.  That caldera is breached by a narrow gorge on the NW.  The central crater is partly filled with a lake.  A young lava flow from Yashuidake descended into the caldera.  A fresh-looking 1732 lava flow traveled down the NE flank.

Smithsonian GVP lists multiple eruptions from the system, with at least 21 between 8.5 – 2.0 ka.  Only 8 eruptions over the last 2.0 ka, with the most recent listed eruption in 1934.  On the other hand, Bulletin reports list at least six episodes of volcanic tremor and earthquakes 1995 – 2000, with the most recent of these being Nov 1999.  None of these resulted in any increase in reported hydrothermal or volcanic activity, though inflation was observed in 1998. 

Akita – Komagatake 102 km SSW 

Akita – Komagatake (Catalog 28 / Map D29) is a 1,637 m stratovolcano topped with two calderas located 102 km SSW from Hakkoda.  The N caldera is 1.2 x 1.0 km.  The S caldera is 3.0 x 2.0 km.  They were formed in a pair of explosive eruptions 13.5 – 11.6 ka.  The post caldera Onamedake cone in the N caldera produced lava flows to the N and E.  It has a 100 m summit crater.  There are a pair of post caldera cones, Medake and Kodake in the NE corner of the S caldera.  Minamidake pyroclastic cone is also located in the the S caldera.  The floor of the caldera is covered with lava flows.  Some of this lava flowed down the W flank of the volcano from the SW rim of the caldera. 

The volcano was active 10.8 – 0.5 ka, with 11 confirmed eruptions.  Some of these were powerful, with a pair of VEI 4 and at least three VEI 3 eruptions.  There were three eruptions 400 – 1100 AD in the VEI 2-3 range.  Renewed activity began with a VEI3 in 1891, and three more eruptions 1902 (VEI 1), 1932 (VEI 2) and 1970 (VEI 2).  The small historic eruptions took place from cones and fissure vents inside the S caldera.  The 1932 eruption is considered to be phreatic.

The Smithsonian GVP Bulletin Reports on Akita – Komagatake start with the Sept 1970 eruption from the Medake cone, active through Jan 1971.  It built a new cinder cone with a lava flow from the foot of the new cone.  There were hundreds of Strombolian explosions at times daily during this eruption.  Fumaroles were active following this eruption, with a short-lived plume observed above the volcano in Dec 2011.  Seismicity in the area increased late Dec 2011 but quickly returned to normal levels. 

Hakkoda Volcanic Complex

The volcanic complex consists of at least 17 stratovolcanoes and lava domes.  These are divided into two groups, Kita – Hakkoda to the N and Minami – Hakkoda to the S.  The two groups of volcanoes are relatively closely spaced andesitic stratovolcanoes.  Hakkoda is located some 20 km SSE from Aomori in the N coastline.  It tops out at 1,533 m. 

Timing of activity at Hakkoda has been relatively complex, with construction of the first group of small stratovolcanoes and domes at Minami – Hakkoda starting 1.7 – 1.1 Ma.  Massive caldera forming eruptions took place N of Miniami – Hakkoda 869 – 470 ka.  Following these eruptions, activity shifted a bit S, between the center of the new Hakkoda Caldera and the center of the Minami – Hakkoda group, building a new group of stratocones and domes centered on the S rim of the new caldera, Kita – Hakkoda.  Note that these periods all overlapped in time.  Activity at Hakkoda even overlapped with that of neighboring Okiura caldera 18 km SW. 

The center of the Hakkoda caldera is located N of the Kita Hakkoda group, and N of Hakkoda volcano itself.  The resurgent activity obscured the location of its S rim.  The Minami Hakkoda volcanoes are more eroded than those of Kita, meaning they are likely to be older.  The Hakkoda Welded Tuff covers Minami Hakkoda volcanoes.  Kita Hakkoda volcanoes are is built on top of it.  Both volcano groups and the caldera combine to form a broad caldera system. 

Minami Hakkoda

Minami Hakkoda volcanic group is located some 7 km SW from Hakkoda.  These volcanoes were active 1.7 Ma – 300 ka.  There is some disagreement over the beginning of activity here, ranging 1.7 – 1.1 Ma.  These erupted andesite, basalt and dacite.  The highest peak is a composite stratovolcano topping out at 1,516 m.  The Osegawa pyroclastic flow deposits erupted as part of Minami Hakkoda 900 – 800 ka around the Osegawa River.  Being the oldest volcanoes, this group is the most eroded of Hakkoda volcanoes and domes.  It is also the least studied, with little available in the literature. 

One oddity about this group is it is located in the NE sector of the still active Okiura caldera.  Activity in this part of the caldera group migrated NE.  By location, these cones and domes could be described as resurgent activity in Okiura, but all the literature groups them with Hakkoda instead. 

Caldera formation

Hakkoda Caldera is a broad pyroclastic flow plateau active 900 – 400 ka.  Volume estimates for various eruptions vary wildly between 253 – 50 km3 of dacites.  The eruptive products were widespread, with the largest, variously dated 790, 770 and 650 ka being found up to 830 km on the Osaka Plateau from its source.  That particular eruption began as a Plinian eruption and transitioned to eruption of a pyroclastic flow.  Widespread distribution of the ignimbrite upwind against the prevailing westerly winds are typical of an ignimbrite ashfall concentric distribution pattern.

VOGRIPA lists multiple VEI 7 class eruptions from Hakkoda 869 – 470 ka.  The oldest of these 890 ka was a VEI 7.0 that ejected at least 100 km3 of the Kokumoto 6a pumice.  The 840 ka Kokumoto 5a eruption was a VEI 7.0 that also ejected 100 km3.  The last of this string was the 790 ka Kokumoto 3 eruption, a VEI 7.0 that ejected 100 km3.

The largest eruption was a VEI 7.4 770 ka that ejected the 253 km3 Hakkoda 1 / Kokumoto 1 / Imakuma 1 igminbrite.  It was followed after an extensive period of repose by the 470 ka Hakkoda 2 / Imakuma 2 ignimbrite.  This eruption was a VEI 7.0 that ejected another 100 km2.  The two most recent eruptions 125 and 115 ka were VEI 6.1 and VEI 6.0 respectively.  They both ejected 10 km3. 

Kita Hakkoda

Kita Hakkoda volcanic group was active 400 ka – 1600 AD.  It erupted andesite, basalt and dacite.  The complicated structure of the mountains consists of five smallish stratovolcanoes and four domes what were partly obliterated by the caldera ringwall.  These volcanoes and domes include Hinadake, Takadaotake, Tamoyachidake, Maedake, Narusawadaichi, Sennintai, Iodake, Kodake, Idodake, Akakuradake and Odake volcanoes. 

The highest of these is Sugayu-dake, located on the S part of the ringwall.  It is a flat cone with an elliptical crater, 150 m in diameter and 50 m deep.  Akagura-dake is the ctneral cone, located off center, also with a 500 m elliptical crater, destroyed on the NE side.  Tamoyachi-dake is the third.  These three are considered parasitic cones.  Takota-Odake is a fourth cone 1,515 m high, with an explosion crater on its NW side.

The Ido-dake, Maye-dake and Akagura-dake domes are all andesite.  There are several explosion craters present.  The most active of these hosts the Shinyu hot spring, solfatara and fumarole.  There is an active solfatara at Idodake. 

Hakkoda Odake, Ido dake and Tsurugi dake domes all have well-preserved craters.  Akakuradake has a 1 km wide explosion crater breached to the N.  The Akagura-dake dome is relatively isolated to the S.  Hot springs are found at several locations within the caldera. 

Hachiman Dake volcano group is part of the Hakkoda Mountains.  It is located some 10 km NE from Hakkoda.  The peak tops out at 1,020 m and erupted basaltic andesites 2.5 – 1.4 Ma.  It is unclear if this volcano is part of the Kita Hakkoda group, as it seems to be on the outer periphery and far too old.

Eruptions

There are hot spring systems associated with the N Hakkoda volcano.  While there are no historic eruptions, ashfalls continued up to a few thousand years ago.  Fumarole activity is still present at the Sukayu hot springs.  Temperatures of the hot springs and acidity decrease with distance from the volcano center. 

While Hakkoda has not been historically active, its hydrothermal system continues to be both vigorous and deadly, with volcanic gasses responsible for deaths in 1997 and 2010.  In the most recent of these, volcanic gasses (H2S) caused the death of a female junior high student picking mountain herbs and vegetables near Sukayu.  In 1997, a group of Japanese Ground Self Defense Force members in ranger training entered a hollow at the NE foot of the volcano.  CO2 accumulated there (CO2 is heavier than air) killed them.

The rangers were operating in the dark and slipped into a small depression, 18 x 11 m and 8 m deep.  Their rescuers also slipped into the depression.  The men were hospitalized and three did not make it.  The depression did not have live plants in it and leaves on plants surrounding it were dead.  The local fire station mentioned many holes and depressions on the volcano that emit sulfurous acidic gasses.  Local farmers reported dead animals in the depressions. 

The previous activity was an earthquake swarm Aug 1986.  The largest of these was a M 4.8 that caused minor damage at Kayanochaya and other neighboring villages.

JMA carries 8 eruptive events from Hakkoda.  All of these were from the Kita Hakkoda volcanic group.  The 5 most recent of these were all phreatic.  The three oldest were magmatic, two of which had phreatic components.

The two most recent phreatic eruptions took place 1400 – 1600 AD.  They produced two separate tephra falls.  A third phreatic eruption around 1300 also produced a tephra fall.  All three of these took place at Jigokunuma.  A fourth phreatic eruption took place around 500 AD from the Odake summit.  The earliest pure phreatic eruption also took place likely from the Odake summit 0 AD. 

The latest eruptive products from the Jigoku-numa hot pool on the SW foot of Odake volcano of the Kita-Hokkoda volcanic group were examined in 2000.  The pool is 80 m in diameter.  There were three tephra layers produced by phreatic eruptions from the pool.  The tephras do not extend more than 200 m from the pool.  The explosions took place no deeper than 50 m beneath the hot pool and were driven by explosion of a confined pocket of steam in the active hydrothermal system.  Other than providing heat, there was no magma or juvenile material involved.  The hydrothermal system is still active and similar phreatic explosions can happen again. 

Three older eruptions were all magmatic.  All were from the Odake summit.  All produced tephras.  All were large enough to have barely measurable eruptions volumes.  The oldest of these 4.8 ka started as a magmatic eruption, went through a phreatic phase and ended as a magmatic eruption.  The 4.2 ka started as a phreatic and transitioned to a magmatic eruption.  It produced the largest amount of tephra.  The final magmatic eruption was purely magmatic in 3.1 ka. 

Tectonics

The following is reproduced from our Sept 2025 Chokai post, as it describes the region relatively well. 

Tectonics of N Honshu are driven by the subduction of the Pacific Plate beneath the Okhotsk Plate at the Japan Trench E of Honshu.  The Okhotsk Plate is a wedge-shaped minor tectonic plate that extends N to include all of the Kamchatka Peninsula, and W to mainland Siberia.  It S end is in the vicinity of Tokyo, bounded by the Philippine Sea Plate offshore and the Amur Plate to the S and W.  In many places, this is described as the North American Plate.  As tectonics here is driven by subduction, the region is prone to megathrust earthquakes, the most recent of these being the M9.0 2011 Tohoku earthquake.

One of the interesting things about this particular subduction margin is the distribution of volcanic centers.  Normally, volcanic systems are randomly distributed along active plate margins.  Volcanoes here have formed in conspicuous groupings.  Recent volcanic systems are about 50 km wide and spaced with 80 km gaps.  This line is parallel with the Japan Trench.  The descending Pacific Plate is perhaps 150 km beneath the volcanic front.

The low velocity zones beneath Honshu are not continuous.  Rather, it is divided into what was described by Tamura, et al in 2002 as Hot fingers in the mantle wedge.  Localized hot melting bodies may exist and extend into the back-arc side where temperatures are 200 – 300° C higher than that of neighboring mantle.  Low velocity zones do not exist in the gaps between volcanic centers.  They do exist under all the volcanic centers, along with some locations where volcanic activity has not yet begun.  Magma in these locations is thought to be accumulating near the Moho depths as it makes its way to the surface.  The total volume of magma supplied from the mantle likely exceeds the volume of materials erupted so far. 

In this part of Honshu, magma addition to the crust causes vertical uplift.  Honshu has an undulating topography at about the 80 km interval.  This correlates strongly with the thermal structure of the underlying mantle wedge.  The volcanoes are located at topographic highs and over the low velocity zones, leading to describing these zones as fingers. 

Conclusions

Hakkoda is a robust, highly active volcanic system that is part of a caldera cluster in N Honshu.  The most recent round of activity built a group of smallish stratovolcanoes and domes centered on the S rim of the caldera.  Most recent activity were phreatic explosions from a crater on the flank of one of the volcanoes.  It has an active and dangerous hydrothermal system, filling local depressions with volcanic gasses CO2 and H2S.  There is a known magma body beneath the complex.  Consider this an active, potentially dangerous system. 

Additional information

Volcanic activities of the Hakkoda volcano after the 2011 Tohoku earthquake, Yamamoto & Miura, Dec 2014

Correlation of the Hakkoda – Kokumoto tephra, a widespread middle Pleistocene tephra erupted form the Hakkoda caldera, northeast Japan, Suzuki, et al, Dec 2005

Petrological variation of large – volume felsic magmas from Hakkoda – Towards caldera cluster:  implications for the origin of high-K felsic magmas in the northeast Japan Arc, Kudo, et al, Feb 2007

Stratigraphy and source caldera of pyroclastic flow deposit during the latest Pilocene to middle Pleistocene in the southeastern foot area of the Hakkoda caldera, northeast Japan, Kudo, et al, Han 2006

Carbon dioxide emissions from soils at Hakkoda, north Japan, Perez, et al, Apr 2003

Nationwide geothermal exploration survey project (2^nd step) with special reference to the Hakkoda area, Japan, Muraoka, et al

Temperature gradient map of the Hakkoda geothermal area, Okubo & Muraoka, 1988

On the volcanoes of Japan, III, B Koto, B. Medial Zone of Volcanoes, i. Northern Japan (continued), 1893

Tephrostratigraphy and vegetational changes since latest Pleistocene time in the North Hakkoda Mountains, northern Japan, Tsuji, et al, (The Quaternary Research) 21 (4) p. 301 – 313

Geology of the Hakkoda-san district, Takarada & Muraoka

Volcanoes and tephras in the Japan area, H Machida, May 2002

Assessment of geothermal resources of the Hakkoda geothermal area, 1990

Volcano by Region (Index map of Quaternary volcanoes), JMA 

National catalogue of the active volcanoes in Japan (the fourth edition), JMA

Active volcanoes of Japan <volcanoes which have erupted within the past 10,000 years or with vigorous fumarole activity, JMA

Exploration geology of clustered calderas in the Hakkoda volcanic field, Japan, H Muraoka, 1989

The eruptive products from Kigoku-numa hot pool in Kita-Hakkoda volcano group, northeast Japan:  eruption style, magnitude and age, Kudo, et al, Dec 2000

Palynological study of the latest Pleistocene deposits on Hakkoda mountains, Miura & Yamanaka, Mar 1980