Naoto-san and I arrived in Kumamoto Prefecture on a chilly February Thursday for a short 2-day field trip to the Kyusendo Cave (球泉洞). Before the trip, I had learned that this was where stalagmites had been previously collected back in 2019. After the great flood of Kumamoto in 2020, the devastation of towns and roads near the cave prevented access to the cave. Now, five years onwards, we finally get the chance to revisit old sites and continue past research.
Entrance to the Kyusendo Cave (球泉洞)
Our primary objective this time was to revisit the previous sampling sites
to check on cave conditions and to sample the water in the surrounding
environment for carbon and oxygen isotopic measurements. As we made our way to
the sampling sites, we had to descend deep underground using ladders. As we
ventured further inside, water started seeping from the marble walls, and we
encountered underground waterfalls and rivers.
Descending ladder after ladder to get to our sampling sites
Through comparisons with old photos, we were able to identify the previous
sampling sites. We carefully set up funnels and bottles to collect dripwater
from the hanging stalactites while trying to avoid bumping into the hundreds of stalactites hanging from the ceiling above. Since it was the dry season, flow rates were low,
so we had to leave the bottles in the cave to collect water overnight. We also sampled
water from the underground waterfall and river. As we bottled up the water, we
took note of the cave’s temperature, humidity, and carbon dioxide concentration,
giving us a picture of environmental conditions underground.
Naoto-san setting up our dripwater-collecting funnel and vials. Watch out for the stalactites!
On the second day, Yokoyama-sensei joined us in the cave to collect the
bottles we placed the day before. We walked back to the sites where we left our
bottles yesterday, passing two Kumamon, the ever-present mascot of Kumamoto
Prefecture, on our way there. We were happy to find that all our bottles had been
filled to the brim with dripwater. With the teamwork and experience we had
built up the day before, we quickly packed up our samples and climbed back out
of the cave. After a quick lunch at a nearby restaurant, we drove around to nearby
spots to sample water from rivers in the area, wrapping up our field trip at a
beautiful waterfall.
Group picture with caving Kumamon
