Where was Lake Hitchcock?

At the end of the last ice age, about 20,000 years ago, a lake formed in the Connecticut River Watershed. The lake extended up the valley from a natural dam formed from the accumulation of gravel and sand left by retreating ice sheets at what is now Rocky Hill, CT. This lake extended beyond St. Johnsbury, VT, a distance of over 200 miles.

During its existence, 15-12,000 years ago, Glacial Lake Hitchcock probably looked like many of the brilliantly blue glacial lakes seen today in Alaska and the Canadian Rocky Mountains (picture to the left). The unusual color of these lakes is due to the suspension of fine silt and clay particles in the water. Fine particles absorb all but blue wavelengths, giving the water its blue appearance. (Source: University of Massachusetts Biology Department)

How is a delta formed?

A delta is a geologic formation in deposit of sand and gravel formed wherever a swift stream or river empties into a lake, ocean, or slower river, so called because its triangular shape resembles the Greek letter delta.

How do we know all of this? By exploring a varve!