Typically the limestone has cracks which help to guide the flow of water, but there may also be porous parts where water is stored for a few years.
Water dripping through the cave may come from cracks in bedrock, or more slowly through the pores.
Ideally, a sample will accumulate regular, parallel layers, allowing the investigator to study its growth through time, and see changes in environmental conditions.
These speleothems grow in caves within limestone rock.
Because of this, and their growth over thousands of years, speleothems have emerged as one of the most important sources of information about climate and environmental change over the last few hundred thousand years.
Th for young samples, although this problem becomes less significant or even insignificant with increasing age.
Closed-system behavior can be judged by pétrographic considerations, stratigraphic ordering of ages, and Pa concordance.
For example, the summer patterns of East Asian monsoon activity gradually change over thousands of years as the Earth’s orbit wobbles.
Likewise changes in the abundance of carbon atoms, or the amounts of particular elements can be analysed and interpreted, for example in terms of changing aridity.