Lake Chewaucan, which occupied the Summer Lake and Abert Lake basins of south-central Oregon, was one of these pluvial systems.

At its maximum extent, it was far larger and deeper than the shallow remnant lakes and dry playas that mark its former extent today.

The Paisley 5 Mile Point Caves are carved into a rimrock ridge above what was once the shoreline of Lake Chewaucan.

The caves are solution cavities formed by geological processes in the volcanic rock, opening as south-facing shelters that look out over the basin.

In the Pleistocene, they would have overlooked a lake ecosystem — water, aquatic birds, fish, and the plants and animals that concentrate wherever reliable water exists in an otherwise arid landscape.