Most life was wiped out, and the creatures that did survive huddled in small pockets of open water, where hot springs continued to bubble up. This was Snowball Earth â a deep freeze that began around 715 million years ago and held Earth in its icy grip for a good 120 million years. There are no other comparable glacial periods on Earth.
Lake Barkley Lake Levels. The lake's level is fluctuated from summer to winter for flood control purposes. Summer pool (359 ft. sea level) is normally reached by May 1. The water level begins dropping gradually on July 1, and winter pool (354 ft.) is reached by December 1.
Norris Dam is a straight concrete gravity-type dam. The dam is 1860 feet (570 m) long and 265 feet (81 m) high. Norris Lake, the largest reservoir on a tributary of the Tennessee River, has 33,840 acres (137 kmÂ²) of water surface and 809 miles (1302 km) of shoreline. The dam has a maximum generating capacity of 132,000 kilowatts.