As water drips from the ceiling of a cave, minerals can accumulate on the cave floor and form stalagmites. When the stalagmite grew, changes in its chemistry reflect how the climate above the cave shifted in the past. During cold and dry periods in Earth’s history, stalagmite growth is uncommon due to the reduction of source water. The analysis of stalagmites that grew during these times can help fill in gaps present in our climate records and aid in better understanding how climate will change in the future. Using a stalagmite that grew in Portugal during one of the coldest segments of the last ice age, we can observe how factors affecting the water cycle shifted and how vegetation intensity changed. Current research has found that through this cold period, until the stalagmite stopped growing, vegetation density above the cave site decreased. In addition, Portugal’s regional climate went through millennial-scale fluctuations of wetter and dryer conditions, with an overall trend towards warmer average temperatures. These results have implications for early human migration to southern Portugal and how the region responds to warming climatic conditions.

Graphic design collaboration featured in EOS:
Poster presented at GSA north central meeting 2023