The East Terrace Site
The Past Environment

Palynologists study the plant pollen in sediment cores taken from lakes in Minnesota and nearby states. They radiocarbon date these pollen cores, which allows them to affix calendar ages to the rise and fall of pollen from different plant species. Since they know the temperature and precipitation ranges these plants grow in, they can reconstruct past climates. During the Paleoindian period in central Minnesota, the amount of pine pollen began to decrease, while oak and grass pollen increased. The climate was becoming warmer and drier, and prairie covered much of Minnesota by the end of the Paleoindian period. Water levels dropped and the Mississippi River became an important resource area for plants, animals, and humans.

The history of the Mississippi River valley is also important in this story. Through time, river channels cut into the surrounding soil and rocks to form a valley. Terraces, which are flat shelves representing past stages in this process, line the sides of the valley like steps, with the highest terrace the oldest, and the lowest the most recent. Many early Minnesotans lived in camps and villages on river valley terraces to be near water but above the floodplain. Studies by the project geomorphologist found three terraces formed at the site in this way. All camp sites at East Terrace are on the highest, or oldest, terrace, which was probably the only one formed when Native Americans lived there. The water level was higher than it is today because the river had not yet cut deep into the underlying rock and sediment. Nonetheless, it had carved deeply enough to begin molding the island across from the site. The island began to provide a possible crossing point or refuge. Rapids also developed as the water level dropped. Rushing water helped keep the river in this area from freezing over in the winter, which attracted game and their hunters.