A layered lake is a little like Earth’s early oceans − and lets researchers explore how oxygen built up in our atmosphere billions of years ago

Little Deming Lake doesn't get much notice from visitors to Itasca State Park in Minnesota. The absence of oxygen in the deep layers of Deming Lake is something this small body of water has in common with early Earth's oceans. Deming Lake is meromictic, a term from Greek that means only partially mixing.