Exciting news! The mountain my friend and I were planning to climb this month has experienced a minor eruption. Early Monday morning, Mt. Asama coughed up smoke and glowing rocks. The mountain has been quiet the last few months but swelling beneath the crater has been increasing. A medium-sized eruption can be expected soon. Ash from this weeks activity fell across several cities in the Kanto Area, including in Tokyo and over parts of Chiba Prefecture.
Asamayama, as it is known in Japanese, has a long eruption history and the current crater is actually set atop three older volcanoes. Kurofuyama is now just part of the crater rim of the original volcano. Later another cone built up in the crater of Kurofuyama, and that was in turn destroyed and replaced by Maekakeyama. Basically, the volcanic cone sitting in the old Kurofuyama crater is known as Maekakeyama, however, the whole volcano which has been coughing up smoke and lava over the centuries is known as Asamayama – currently 2,568 metres high.
Looking over the eruption history of Asama it seems to have erupted four to six times every century, including a very big eruption in 1108. During the 1700s the volcano erupted 21 times! Asama’s most famous eruption was in the summer of 1783. A great flow of lava emerged and oozed down the mountainside. Volcanic ejecta dammed the course of the Tone River – Japan’s second longest river – and many villages and hamlets were flooded. The river found a new course and went through the northern Kanto Plains causing more flooding. Where it used to empty into Tokyo Bay the Tone River changed course and now empties into the Pacific Ocean further north along the borders of Chiba and Ibaraki Prefectures. The lava flow is now a tourist attraction called “Onioshidashi” – basically Devil Push Out. I have been there two or three times.
In the last hundred years Asama has seen some major eruptions where great clouds of ash billowed from the crater. From 1899 to 1921 eruption activity was recorded almost every year and then several times a year in some years. From then until 1965 activity was recorded every two or three years. The next big bang came in 1973 and then it was quiet again until 1981 and 1982 when more great clouds of ash issued from the crater. I recall the medium-sized eruption of September 1, 2004 when a loud pop sent rocks hurtling over a kilometer from the crater. Though I didn’t see it for myself I saw photos of orange glowing clouds at night. One morning I went to get my bicycle and found a thin layer of fine ash.
My visits to Asama have mostly been from nearby although in May of 2006 I climbed up Kurofuyama with a friend and we got a clear view of the crater with white smoke billowing into the blue sky. Of all the several dozens of times I have seen Asamayama either from nearby or from far away only once have I ever not seen smoke. That was in February of 2007 when my co-worker and two friends attempted to climb to the crater. Though I had read about poisonous gases at the crater we had prepared ourselves and brought gas masks. We never needed them. First because the danger level was one, meaning it is safe to approach the crater (level 2 means you cannot approach the crater and level 3 means you must avoid entering a four-kilometre radius around the crater, which is the current danger level). The other reason was because the top of the mountain was too icy for our gear and we had to give up.
Since then my co-worker has been after me to take him back there. So just last week we were discussing the hike. Now it seems we’ll have to sneak up to Kurofuyama at night in order to hopefully get some glowing crater shots and then stay for the morning and hope to see some action. But we won’t be able to go until the 21st so we have to hope that Asamayama keeps up with the hot action but doesn’t go too wild. We don’t want to be kept out altogether if possible.