About half a million years ago, the Clearwater Valley was filled by a lake backed up by a lava dam near Hemp Creek.

It is unknown where the water goes that escapes through the lava dam.

The river eventually overflowed the lava dam and eroded down into it, draining the lake and forming Benham Falls.

Most lava dams lasted for around 10,000 to 20,000 years.

However others have proposed that the lava dams were much more ephemeral and failed catastrophically before overtopping.

This lava dam is over 300 m (1,000 ft) in thickness and about 2 km (1.2 mi) wide where it impounds the lake.

Thus emplaced, the shape of a lava dam resembles an elongated blob, wedged in the valley bottom.

A lava dam created a broad shallow lake in the area of the Raft River during late Pliocene time, over one million years ago.

Prospect Dam is a former lava dam in the Grand Canyon of Arizona, United States.

It was the oldest and tallest of several former lava dams in the Grand Canyon.