ナショナルジオグラフィックのインスタグラム(natgeo) - 9月28日 04時06分

Photo by @shonephoto (Robbie Shone) - We're following the work of a group of scientists from the Tunisian Geological Survey and European Research Institutions (UK, Germany, Austria) who are looking at changes in rainfall patterns through time. One of their field sites is on Djebel Serj which hosts some of the largest caves in Tunisia.
Similar to trees, stalagmites often contain annual growth layers which record small variations in the hydrology. They provide unique records of past climate change over thousands of years. Pictured here is a slab taken from the middle of a stalagmite. The track down the middle was created when tiny samples were micro-milled for oxygen and carbon analysis.

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