Environmental parameters controlling stalagmite growth in tropical areas: New insights from cave monitoring at Petruk Cave, central Java, Indonesia

[摘要] To elucidate environmental parameters controlling stalagmite growth in tropical areas, we conducted cave monitoringthroughout a year in Petruk Cave, central Java, Indonesia. We compared stalagmite growth rate with the cave’s environmentalparameters, air temperature, drip rate, calcium concentration of the drip waters, and pCO2-air. We found arelationship where stalagmite growth rate is fast (slow) when pCO2-air is low (high) during dry (rainy) season, suggestingthat pCO2-air controls stalagmite growth. Note that this is a first study that reports that dramatic pCO2-air reductionoccurring during dry season in a tropical cave controls stalagmite growth. Additionally, we discuss the mechanism ofpCO2-air fluctuation. Monitoring results show that pCO2-air fluctuation is divided into two phenomena: seasonal fluctuationsand daily fluctuations. Dramatic pCO2-air reduction during the dry season is likely to result from a decline ofplant activity due to little rainfall. On the daily scale, pCO2-air reached to the minimum around 6 a.m. and maximumaround 2–4 p.m., although it is not obvious whether this is due to plant activity or cave ventilation. Also, dynamic pCO2-air reduction was observed following cave ventilation driven by the sudden drop of outside air temperature due to adownburst during severe rain. This suggests that heavy rainfall in short duration is also one factor that controls caveventilation and pCO2-air.

[学科分类] 地质学