Gray Mountain

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DeAnza Wash begins cutting its way through the Gray Mountain horst at a narrow defile that was the easiest passage for wildlife to migrate through from the slopes of Table Mountain to the springs along Carrizo Creek.  High rock pinnacles line the wash on either side of this defile, but the pockets of flat ground hidden within the pinnacles on the south side of DeAnza Wash were perfect spots for Kumeyaay hunters to camp out and wait for game to wander by.

There are pictographs here among the pinnacles, pictographs that have lost their meaning, but one can speculate that the pictographs depict the hunt or are prayers to the spirits to lead game here.  This was certainly not a large village site but may have been a training ground for young hunters beginning to learn their craft.  But there may have been something about this site that was more than just a hunting camp.  For beyond the defile DeAnza Wash drops down from the western slopes of Table Mountain, called by the Kumeyaay mat-kusiyaay, Mountain of the Shaman.  It is one of the four sacred mountains of the Kumeyaay and no one but the spiritual leaders of the Kumeyaay were allowed upon its slopes.

Gray Mountain East
Gray Mountain East

Between Gray Mountain and Table Mountain lies a barrier of pinnacles and boulders that are all but impenetrable, a fence between the sacred and the profane.  On the northeastern slopes of Gray Mountain, the Kumeyaay were free to roam, and indeed there is an old Kumeyaay trail that runs from the hunting camp southeast along the edge of the barrier and down a canyon to the floor of Jacumba Valley.  But beyond the barrier the Kumeyaay were forbidden to tread, for this was mat-kusiyaay.  Only those in tune with the spirit world were permitted on mat-kusiyaay, for the spirits dealt harshly with trespassers.

This barrier of rock is the Gray Mountain Sill.  It lies over the hottest core of the La Posta Pluton.  Like the Broken Earth Sill, the Gray Mountain Sill found its way into an ancient fault zone of the old coastal range, mountains that rose on the edge of North American 100 million years ago to a height of over two miles or more.  Just northeast of Gray Mountain rises a jumbled pile of granodiorite higher than the rest of the sill.  This may have been a laccolith, a sheet-like intrusion of magma that was injected between layers of sedimentary rock.  The pressure of the magma was high enough that the overlying strata were forced upward and folded, giving the laccolith a dome or mushroom-like form.  From this laccolith the magma intersected the ancient fault line and forced its way both northwest and southeast.

The laccolith divides the Gray Mountain Sill into two parts, and these two parts were further divided when the Jacumba Valley graben opened up and the Gray Mountain horst was thrust upwards.  The northwestern half of the sill was lifted up while the southeastern half dropped down.  You can see the southeastern half of the Gray Mountain Sill as you travel east on Interstate 8.  This section of the sill finally disappears underground just north of old Highway 80.

There are three features along the northwestern half of the sill that are good hiking destinations for the more adventurous hikers.  First, follow the Temple Peak Loop Trail up to the saddle and take the Broken Earth Trail up past Cactus Meadow.  We will return here later but for now we climb up past the saddle on the main Broken Earth Trail.  Beyond the saddle as the Broken Earth Trail begins to drop down towards DeAnza Wash, it makes a left turn  Here, look for a trail heading off on the right.  This is the Kumeyaay Camp Trail. The Camp trail drops down on the east side of the ridge and enters DeAnza Wash about a quarter-mile upstream of the Broken Earth Trail.  Follow DeAnza Wash to where the wash is squeezed between rock walls and look for an opening through the right-hand cliff.  This opening takes you to the site of the Kumeyaay hunters camp, marked with a BLM sign.  You will find the pictographs in a tafone, a wind-carved cavity on the side of a boulder, near the sign.

From the hunter’s camp the old Kumeyaay trail heads southeast along the edge of the sill, following the path of the fault that marks the northeast side of the Gray Mountain horst.  The old trail hits a sandy drainage, follows the drainage a short distance before climbing over a small saddle, and then drops into another drainage.  This drainage heads for a narrow pass where the Gray Mountain Sill comes close to the slopes of Gray Mountain itself before squeezing through the pass and onto a plateau.  On the left side, along the side of the sill, you come to a rare sight indeed, a large granodiorite arch perched on the edge of a wall of rock.

The Stone Rainbow is the longest granodiorite arch in the area and is a genuine wonder.  While most of the smaller granodiorite arches are weathered-through tafoni formed by wind corrosion, this arch was formed by the process of exfoliation. Sheets or plates of the granodiorite bowed upwards to form arched fractures as the pressure of the overburden was released as the overburden eroded off.  Then the lower sheets broke apart and peeled off through the freeze and thaw process. Arches are rarely made from exfoliation because the exfoliation process would have to leave the arch behind as other parts of the rock peeled away. Somehow the topmost plate remained intact while the plates beneath it shattered and fell away.

Basket of Boulders
Basket of Boulders

Beyond the Stone Rainbow the old Kumeyaay trail begins to cross a plateau of alluvium that has washed down from Gray Mountain and was trapped behind the Gray Mountain Sill.  Here the fault of the horst is buried, not to be seen again until it reappears in the canyon on the plateau’s far eastern side.  As the old trail begins to cross the plateau, a game trail takes off to the north next to a rocky draw.  It is a fairly well-used game trail.  What would be attracting enough of the wildlife in the area to make such an obvious trail?

The draw is rocky so the trail says well east of the draw but becomes indistinct as you leave the rocks and the wildlife has more room to wander.  But they all funnel northwest, west of the Black Boulder and east of the granodiorite boulders of the sill.  They lead to a curious feature, a large oval depression in a flat slab of granodiorite.

This is a weathering pit or panhole.  Originally a shallow depression on top of the horizontal granodiorite slab, it first collected windborne grains of sharp-edged feldspar and mica which swirled inside the depression, similar to how a tafone forms but horizontally instead of vertically.  Rainwater then collects inside the growing depression and chemically weakens the bonds inside the rock, creating more loose grains of weathered rock to swirl and abrade the depression even further.  Gradually this particular panhole grew large enough to form a natural tank, collecting enough rainwater to last several weeks after a heavy rain.  The Gray Mountain Natural Tank attracts thirsty wildlife from all around while the water lasts.  The Gray Mountain Sill contains several smaller panholes, but these dry up faster than the Gray Mountain Natural Tank so this watering hole gets more visitation.

Just east of the Gray Mountain Natural Tank is a curious outcrop of black rock.  The Black Boulder stands out from the tans and grays of the surrounding granodiorite.  A closer examination shows the Black Boulder and its surrounding pile of rock look more like basalt than granodiorite.  Was this the result of the more recent volcanic activity that occurred in the area a mere 20 million years ago?  And if so, why didn’t this small eruption of basalt grow into an even bigger volcano like its nearby cousins?

Heading back to the Broken Earth Trail and to Cactus Meadow, as the Broken Earth Trail begins its climb towards its junction with the Kumeyaay Camp Trail, another trail forks off to the right and follows the ridge up towards the southwestern end of the Broken Earth Sill.  This is the trail that leads to the top of Gray Mountain’s western peak.  But first the Gray Mountain Trail comes to the edge of the Broken Earth Sill.  Here the Basket of Boulders cross-country route forks off to the right and follows a flat slab of stone westward to an overlook that looks down into the Basket of Boulders.  From there a not-so-obvious route heads down into the Basket of Boulders and out the other side, pausing for views from the top of the Bee Cliffs before angling down to rejoin the Broken Earth Trail.

The Gray Mountain Trail instead heads left, angling away from the Broken Earth Sill and across the valley that divides the ridge of Gray Mountain proper from the Broken Earth Sill.  There are ducks and cairns marking the route, but while sometimes the route is obvious, there are other times it is not so obvious and one has to hunt for the cairns that mark the continuation of the trail.  The trail crosses the valley, for a brief time follows the drainage, until it comes to a group of boulders.  Circle the boulders and the trail begins to climb steeply up the ridge.

Eventually the trail makes its way to a flat shoulder high on the ridgeline where you are confronted by a fin of broken rock.  Here the choice is to head right and follow the base of the broken rock cliff eastwards.  This choice gives you a fine view of Jacumba and the Interstate 8 offramp far below.  Or you can head left and traverse a slope of scattered boulders that will hide you from the view of the Interstate.  Both routes converge upon the final western summit of Gray Mountain.  But upon scanning the view from the top of the western summit it becomes apparent that this is not the highest point of the Gray Mountain horst.

The eastern summit of Gray Mountain looms higher, but it is ringed by rocky cliffs and a healthy barrier of cholla.  It is possible to climb to the eastern summit.  Peakbagger.com lists 13 ascents in the past twenty years, but the western summit is the most accessible from De Anza Springs Resort.

The view from the top of Gray Mountain also reveals the three large volcanic cones bordering the Jacumba graben, as well as three other smaller volcanic features.  By far the largest volcano, towering higher than Gray Mountain itself, is Table Mountain to the northeast.  You can see why the Kumeyaay named this mat-kusiyaay, the Mountain of the Shaman.  Its black volcanic soil seems to fill the sky with a grim, foreboding visage.  But that is a topic for another day.

There is a faint trail the leads northeast down from the western summit of Gray Mountain, angling down the western side of a ridge, eventually leading to the Stone Rainbow.  That route has no ducks or cairns and is a route for those with cross-country experience.  For the more advanced hiker, this would make for an adventurous loop that could take in all of the interesting sights of the Gray Mountain area.  But the hike to the top of Gray Mountain’s western summit may be adventurous enough for one day, so take the marked Gray Mountain Trail back to the resort.

DeAnza Springs Logo
DeAnza Springs Logo

1951 Carrizo Gorge Rd.

Jacumba, CA 91934

619-766-4301

Stay@DeAnzaSprings.com

1951 Carrizo Gorge Rd.

Jacumba, CA 91934

619-766-4301

Stay@DeAnzaSprings.com

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