The Mystery of Lost Lake of the Cajon Pass

It is not known to many people, but it is still possible to use the old highway up through a portion of the Cajon Pass. Present day highway 15 runs well above old 395 and Historic Route Highway 66. Such rustic areas as Blue Cut and Halls Ranch (Yes my Family again), and Sullivan's Curve still exist.

As you drive up the badly surfaced road from Devore (Use the Kenwood Exit from the Northbound 15 and make a left, pass under the 15 and then make a right on Cajon Blvd [old 395 & route 66]) you notice that for the most part you are driving on what would be the southbound lanes of the old 4 lane highway. As you come around the curve at Blue Cut you notice that there is now a mountain sitting over the right-hand lanes into the center divider. You might think that this is ample proof that the San Andreas Fault zone is alive and moving. But you would be wrong. It is actually the San Jacinto Fault Zone that straddles the highway. The San Andreas is still one mile ahead.
Two Faults zones so close together and visible? As you proceed north you notice that the entire area between the faults is moving to the north and at different speeds. Only 2 or 3 inches a year, but they are moving. So much so, that railroad crews from both the Union Pacific and Burlington Northern Santa Fe, have to go out twice a year and reset the tracks. Otherwise, the train tracks would bend out of shape, just like old 395 has.

As you proceed, you will see a sign that says 'Lost Lake'. It also says private road so most people ignore it and just keep heading up towards Sullivan's Curve. Sullivan's Curve by the way, is a favorite Train Watcher area and has also been the scene of several major train accidents over the years. The best way to get into this area is to exit highway 15 at Cleghorn Pass Road, make a left under the freeway if you are going north bound that is and then make a right on the first roadway you see. This will take you back to a triple track bypass area, a small yard, and the beginning of the lower end of Sullivan's Curve.

But if you take the time to make the left turn onto the dirt road and cross the triple set of tracks that tend to hide it's route, you eventually find a quiet little area that should not exist. For there are no streams, creeks or rivers that feed into Lost Lake. The water seeps up from beneath the ground. A direct result of two major earthquake faults zones passing within a half mile of each other.

Some say that Lost Lake has no bottom, that it feeds directly from the center of the earth. The water is also very cold, below freezing even in summer time. Fire crews have used its water supply to help fight fires, and they have never noticed a drop in water levels. It always stays the same, even in heavy rain seasons. And snow fall has no effect on it. But it has never frozen either.

Lost Lake is surrounded by lush grassy vegetation, some what like what you might see back in Kentucky or Tennessee. In fact Kentucky Blue Grass grows all around the lake.

As you drive further into the narrow valley you realize that both fault zones are coming together. All of a sudden you run into a wall of a mountain that blocks your way. You can climb up this 500 foot high rock fall and look out over the valley you have just passed through. To the northwest are the 10,000 peaks of Mt Baldy, Cracka Ridge and the Mountain High Ski area. As you hike through the area you become aware of how insignificant you are amongst the grander of the Fault Zones, the Mountains and the trees.


Never said it was drained! I said it was low enough to ride the motorcycle across. It is a sag pond on the San Andreas fault. My boyfriend was a geology major and gives a lecture at the lake once a year as part of a Cal State San Bernardino class discussing the subduction zone where the Pacific Plate dives under the North American Plate. He has studied the lake and surrounding area since 1958. the earthquake you are most likely referring to was the 1857 quake that caused a rip in the topography of the surrounding area. The Fort Tejon earthquake of 1857 occurred at 8:20 AM PST Jan 9. Length of surface rupture was 225 miles with a maximum offset of 30 feet. They estimate it was about a 7.9 quake. Things change you know. I saw the water in the Santa Ana River splashing up over the bridge to Riverside by Fairmont Park in 1968 and now there is hardly any water above the surface. The Santa Ana River also wiped out the town of Agua Mansa when the water filled from bank to bank on Jan. 31st of 1862. Things change.

wow someone can copy and paste

no you did say that ur boyfriend did ride across the bottom of what u wrote above...

I love how you put that pawn in check with the facts. Not only did you do your homework but got the research to back it up, I even heard about the Santa Ana river flood. I heard that huge boats were sailed through there after it happen. I find this very interesting considering I live so close by.

if u go up to lake now 7/07/16 u can see bottom whole lake only 2-3 feet deep no crack from eartquake no monster fish no mystery

Lost lake is now dried up except for a small puddle. It's gone.

I was born at night , but what kind of motorcycle runs underwater?...

The valley was under water in prehistoric times. Underground hot springs and cold water streams still exist throughout the area. While the water table flows between tens and hundreds of feet below the surface, it does not go to the Earth's core. It does go deep enough to be very cold and very pure.

Volcanic activity occurred in ancient times ... small cinder cones can be seen in the high desert. Far as I know, what little volcanic activity occurred there ceased many many hundreds ...indeed, thousands ... of years ago

Yes, divers have explored the area. Sheriff search and rescue trained up there and have made many trips to recover vehicles and bodies. The lake is not bottomless; that is an urban legend started by the fact Lost Lake's source is not visible above ground.

It has not been developed because it is small ... too small to support formal recreational facilities. It could not generate enough money to make it worthwhile.

Hope this helped answer your questions.

er seepage in an area of tectonic depression in
the San Andreas Rift Zone, a linear valley in
the Lone Pine Canyon. Dr. Ray Weldon conducted a
detailed study of a series of stream terraces associ
ated with Cajon Creek in the region of Lost Lake
(Weldon and Seih, 1985). The work identified progressi
ve offset of radiocarbon dated, late Pleistocene
and Holocene deposits and landforms by the San Andreas
fault that yielded a set of slip rates spanning
the past 14,400 years. Near Lost Lake they deter
mined a slip rate for the San Andreas fault of ~24
mm/yr for the past 14,400 years and inferred that this
slip rate had remained
relatively constant during
that period of time. The primary da
ta utilized was the identification
of a series of stream terraces
associated with Cajon Creek that had been progre
ssively offset by the San Andreas fault.

Due to the drought (I assume) the lake is at a very low level and gets worse every time I visit. I do volunteer cleanup at the lake and I have never seen it so low.


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