Measuring about 400 miles (640 km) from east to west, it is an important water source for agricultural irrigation in the Plain.
Rather it consists of a volcanic pile of the Quaternary Snake River Group basalts.
In the eastern Snake River Plain, the Snake River lies near the southern edge of the plain, about 40–50 miles (64–80 km) southeast of the ranges of central Idaho.
For about 100 miles downstream from Milner Dam in the vicinity of Twin Falls an estimated total volume of approximately 200 billion cubic feet (5.7 km3; 1.4 cu mi) of water enter the Snake River from gigantic springs on the north side of the canyon.
Consequently, the gravity and weight of the water in the basalt layers north of the river drives the huge springs.