Forest Road 10 to Battleship Rock.  Red = rim; purple = public road.  There is a Forest trail from the rim to Jemez Falls that I haven’t been on for 30 years.

Valles Caldera South Rim
FR 10 to Battleship Rock

Introduction.  The southwest corner of the rim of the Valles Caldera extends from Forest Road 10 along a fairly level stretch of rim.  A set of cliffs at its west end renders the rim rather ragged.  At an obscure point, the rim plunges down the cliff side of San Diego Canyon to Battleship Rock.  The Santa Fe National Forest owns this section of the rim, and administers it as multiple use; grazing, logging, hunting, motorized trail use, cross country skiing, and hiking are all permitted uses.  This report addresses the west end of the south rim.  Part of this stretch—Township 18 North, Range 3 East, Section 9—is a Forest Service Research Natural Area.

Access: Forest Road 10 goes south from State Road 4 through Vallecitos de los Indios.  A road sign and many mailboxes mark the junction.  It is a good dirt road usually suitable for passenger cars.  The road extends up over the rim, and down to the village of Ponderosa.  It ends on State Road 4 near Jemez Pueblo.

Immediately at the rim is the junction of FR 10 and FR 135, which runs west along the rim.  Within about a mile, FR 135 turns south and proceeds down Cat Mesa.  The rim part of the road is generally level and passable, with several parking places along the way.  Past the turn to the south, FR 135 becomes very rough in spots that require an industrial strength vehicle.

Description: The western half of the south rim of the Valles Caldera is quite level.  It formed of air-fall pumice from the last of the Valles eruptions, so it has no lumpy cones like those forming the eastern half.  At the top of the rim line, earlier ash-flow tuff forms a narrow line of sheer orange cliffs.  At various times following the collapse of the Valles Caldera, the resulting bowl filled with water, forming sequential crater lakes.  Over millennia, headwall erosion of San Diego Canyon crept up to the rim, finally breaching it at Battleship Rock and draining the lakes.  Two streams from within the caldera meet at Battleship Rock and exit the caldera—the East Fork of the Jemez River drains the south half of the crater and the San Antonio River drains the north half.  The rim of the caldera is defined as the watershed divide of waters flowing into and away from the caldera.  Therefore, the rim crosses San Diego Canyon at Battleship Rock.

From State Road 4, Forest Road 10 passes through the little community in the Vallecitos de los Indios and ascends the south wall of the caldera.  Where FR 10 tops the rim, FR 135 turns westward parallel to the rim through a sickly forest of ponderosa pines.  Some are dog hair stands so thick one would have trouble walking through them.  The Forest Service thinned some areas along the road, probably for fire control.  In about a mile, FR135 reaches the remnant line of tuff cliffs and turns south down to Cat Mesa.  The rim continues west as a sharp line of cliffs.  Where cliffs protrude out over the rim are some nice views back into the caldera where the ridge of Los Griegos dominates the south rim.  Rabbit Mountain is in the far distance.  The canyon of the East Fork directly below becomes deeper as one proceeds west.

   
The caldera, looking west to Los Griegos.  The light   The canyon of the East Fork comes into view.
 spot, upper left, is a pumice quarry.

  
Tent rocks of the earlier ash-flow tuffs.                 Looking west past tuff cliffs to Canon de San Diego

In the 1930s, the Forest Service set aside an entire township here as the Monument Canyon Research Natural Area.  Except for FR135, neither roads nor trails cross the research area.  However, game trails are numerous, as are research tags on various features of the landscape.  The rim is passable for a while, but becomes rocky and brushy, and the side toward the East Fork becomes sheer cliffs.  However, the forested little hummocks and rills behind the row of cliffs are pleasant enough to walk through.  At intervals, the cliff line breaks where the views become quite spectacular.

  
The rim of Cat Mesa is passable for a while.         Looking northwest up the canyon of the San Antonio.

Our goal was to find the point where the rim descended the side of Canon de San Diego down to Battleship Rock.  As we neared the west end of the row of cliffs, they became truly formidable and the views even more sweeping.  The west rim curled around to the north, enclosing the canyon of the San Antonio River where State Road 4 comes down to Battleship Rock.  We could see the profile of the caldera rim as it descended into San Diego Canyon to Battleship Rock.  It looks steep but not impassable.

The rim line we followed eventually became heavily wooded and rather featureless.  We found our drop off point by identifying the UTM coordinates on the topo map and locating that place on the ground.  It was very steep, but it appeared that a game trail went down at this point.  Also, a road off Cat Mesa came up to this place, with a hunting camp at its end.

The view of the west rim of the caldera as it descends into Canon de San Diego.  The little peak just to the right of the cliff, called Cerro Colorado, is on the rim.

In truth, unless the Valles Caldera Rim Trails become wildly popular and public demand integrates them into a National Trail, it is unlikely that the Forest Service would build a trail down this slope.  (Even more unlikely is that they would build a trail up the other side, which has formidable cliffs.)  There may also be a policy that prohibits trails through a research natural area.

There is an alternate route from Cat Mesa to Battleship Rock.  A trail descends from FR 135 to Jemez Falls, from which another trail goes down the canyon of the East Fork to State Road 4 at Battleship Rock.  It is a nice route but doesn’t have spectacular views like the Cat Mesa cliffs above San Diego Canyon.

Dorothy Hoard  July 2007