Author name: nicholas-j-tosca

Of all the surface environments on our planet, alkaline lakes are among the most distinctive and significant in terms of their biogeochemistry, climatic sensitivity, and associated mineral deposits. But how does the Earth produce alkaline lakes? Fifty years ago, Lawrence Hardie and Hans Eugster hypothesised that the bewildering complexity of non-marine evaporites could be explained by common successions of mineral precipitation events, or chemical divides. Since that time, the chemical divide concept has provided Earth scientists with an enduring framework within which to integrate new advances in mineral–water equilibria and kinetics, sedimentology, and paleoclimatology. These developments are painting an increasingly detailed picture of how alkaline waters form and interact with magmatic and atmospheric CO2, now and in the distant past.

Alkaline lakes are incredibly dynamic, unique, and fascinating biogeochemical environments that have remained distinctive features of Earth’s evolving surface over much of its history. Understanding these evaporative surface waters, their exceptionally productive ecosystems, and their rare sedimentary deposits requires an inherently interdisciplinary approach at the intersection of hydrology, geology, and biology. The discipline-spanning articles in this issue evaluate the diverse characteristics that make these dry, salty, and habitable environments so valuable in unraveling the history and evolution of Earth’s surface, and in following the arc of habitability on ancient Mars. Here, in this introductory article, we summarize the characteristics and importance of alkaline lakes with the hope of attracting you, too, to join in our fascination with them.