Humboldt Sink

Headlines like this one (above) brings to mind a hypothesis I've had for many years pertaining to the western US being hot and dry.

Mississippi alluvian fissures are draining water from the river. This isn't the first time water drained suddenly from a location. 

If you look along California and Nevada, you find two major fault lines, the Pacific Plate and the Walker Play. Any seismic activity could create fissures, draining water into extensive lava tube caves from all the volcanic areas in the west. This also would explain the deep water hole called Devil's Hole in Death Valley. It contains fish found in Lake Titecaca in Bolivia. In fact, when there are earthquakes in Mexico and Central America, the water in Devil's Hole sloshes. 

As well, as water receded, many creatures could have taken to the underground in search of survival. There are reports of oil drilliing in California in the 1930s that entered voids that held water, much like Blind Frog Ranch on the Discovery show, "Mystery at Blind Frog Ranch."

In fact, the Amargosa River in Death Valley runs underground in areas where Pantamint Lake and Lake Manly once sat. 

They were reportedly seen upon occasion with large creatures like those from Megafauna, like Mammoths. If such creatures and people went underground and have adapted to water-filled caves with occasional outtings, this would fit that scenario. 

The west wasn't a desert when these ancient pluvian lakes pooled in the valleys. 

A group of MIT researchers has discovered that the American west must have dried up just about 8,200 years ago – and that it did so relatively rapidly.

With no actual reason for the west to heat up, but the lakes dried out fast, the only conclusion is that seismic activity created fissures, draining the lakes in a very seismically active region. Without the lakes, it heated up.