Paleohydrology

Echo Lake sediment core Click to enlarge. (25 KB)

The fluctuation of water levels in lakes and mires reflects, in large part, changing amounts of available moisture. For this reason, the sediments from lakes and mires provide a key to understanding climates of the past by recording long-term changes in water levels. Sediment cores (such as the one from Echo Lake, New Hampshire, on the right) can be used to document past shoreline levels within lake basins, and radiocarbon dates and fossil pollen stratigraphies indicate the ages of these past lake levels. Periods of time when lake-levels were lower than modern represent times when the climate was drier. By using lake-level data from many lakes in New England, across North America, and even around the globe, we are able to document the changing patterns of precipitation and evaporation since the last glacial period (21,000 years before present).

Lake level dynamics

Crooked Pond in southeastern Massachusetts was one of our recent study sites. The illustration here represents a cross-section through the pond, and illustrates the changes in water levels and sediment stratigraphy since 16,000 years before present. Dark brown mud accumulates where water is deep and still in the lake center, but near-shore in shallow water waves and currents cause sand (yellow) to be deposited. As water levels rise and fall, sand layers are buried as evidence of periods of shallow water.

Coastal Studies     Geoarchaeology     Paleoclimates     Vegetation Dynamics