Banner with a view looking east from Raptor Ridge of the San Pasqual Valley.

Highland Valley Trail

San Pasqual Valley near Rancho Bernardo and Escondido, California
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The Highland Valley Trail follows the south side of San Pasqual Valley for about 2 miles (Figure 1). The photo gallery below provides highlights of scenery, ecology and geologic features along the trail. The photo tour below starts at the Highland Valley Trail Staging Area (located near the intersection Highland Valley Road and Pomerado Road, near Interstate 15). The trail roughly follows Highland Valley Road before turning into Sycamore Canyon. The trail ends near a parking area for the San Dieguito River Parks Headquarters.

The trail is an easy path to walk, but be aware the route is very popular for mountain bikers. A mild problem with this hike is the distant highway noise, but as you hike farther east along the trail, the volume of the sound diminishes, especially when you turn the bend and continue into Sycamore Canyon. Despite the noise, the scenery is fantastic, especially if you like large boulder-covered landscapes and views of the scenic valley and surrounding mountain peaks. This is an excellent trails to see spring wildflowers of the coastal sage plant community.

The trail passes along hillsides covered with coastal sage scrub and mixed oak and grassland habitats. Willow- and sycamore-dominated riparian habitat occurs along the streams. Along the trail you can see trees and stumps burned by the 2007 Witch Creek Fire that burned through the area. Fortunately several areas of the oak forest survived the fire along the trail and with the assistance of many people and organizations, the remaining wild lands ecology is being slowly restored.

Click on images for a larger view.
Map of the western part of San Pasqual Valley showing the location of the Highland Valley Trail, Mule Hill Trail, and other trails in the area.
Fig. 1. Map of trails in the San Pasqual Valley showing the location of the Highland Valley Trail.
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Following the Highland Valley Trail, West To East

The photo gallery below roughly follows the Highland Valley Trail starting at the east end at the Highland Valley Trail Staging area (Figures 2 to 5). The trail starts by basically cuts along the southern slope of the San Pasqual Valley, passing around an active Christmas Tree farm and plant nursery (Figures 6 to 10).
Entrance to staging area on Highland Valley Rd.
Fig. 2. Entrance to staging area on Highland Valley Rd.		 Kiosk at the trail head for the Highland Valley Trail.
Fig. 3. Highland Valley Trail Staging Area kiosk.		 View of Interstate 15 from near the parking area for the Highland Valley Trail.
Fig. 4. View of Interstate 15 from the staging area		 Important wildlife corridor sign near the trailhead for the Highland Valley Trail.
Fig. 5. Highland Valley Trail near the trailhead parking.
View looking across fields and Highland Valley Road to the wetlands along the San Dieguito River.
Fig. 6. View of the wetlands along the San Dieguito River.		 View looking east along the Highland Valley Trail across the Pasqual Valley wetlands area.
Fig. 7.View looking east along the Highland Valley Trail.		 View west along Highland Valley Trail toward Bernardo Mountain in the distance.
Fig. 8. View west along trail toward Bernardo Mountain.		 View of a grassy hillside and barren dirt fields along the Highland Valley Trail in the vicinity of a Christmas Tree nursery.
Fig. 9. Christmas tree farm along the trail.
Panoramic view of the San Pasqual Valley from along the Highland Valley Trail.
Fig. 10. Panoramic view of the western end of San Pasqual Valley near the Christmas tree Farm. Bernardo Mountain is to the left. Mule Hill is to the right of Interstate 15. The distant ridgeline of Palomar Mountain rises above and beyond the Escondido Mesa area near the center. Starvation Mountain is on the right above the trail.
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Entering A Land Of Large Boulders

Among the attractions about this hike, there are many massive boulders amids the oak forest, grasslands, and sagebrush along the trail. The rocks themselves preserve an interesting history of their igneous origins and how weathering and erosion, including processes involving many wildfires over thousands of years, have gradually shaped the boulders and the landscape along the valley. Figure 11 illustrates a boulder that has been split, possibly by the roots of a plant that once expanded in a crack as it grew and absorbed water from infrequent rains. Many split boulders similar to this once can be observed along the trail.

The rock itself is composed of a type of granite called tonalite, an igneous rock that formed when massive bodies of molten material rose and crystallized in massive plutons of an ancient volcanic arc that existed here in Cretaceous time, roughly 120 to 100 million years ago. These igneous bodies intruded more ancient seafloor rocks. Fragments of these older rocks are preserve as inclusions (also called xenoliths, meaning foreign rocks). These rocks appear as dark patches of rock embedded in the younger light-colored tonalite.

Beyond the the Christmas Tree farm, the character of the hiking trail changes, and the landscape becomes more wild. The trail dips into a small canyon where it crosses a bridge over spring-fed stream (Figures 12 to 17). Be aware of poison oak along the trail. Beyond the stream, large boulders become more abundant along the trail (Figures 18 to 28).		 A large boulder appear split down the middle.
Fig. 11. Split boulder of tonalite (a granitic rock) that includes dark inclusions.
Zoom view of Starvation Mountain from the Highland Valley Trail.
Fig. 12. Zoom view to east of Starvation Mountain.		 View of an intersection of two trails. The Highland Valley Trail goes into the oak forest to the left.
Fig. 13. Highland Valley Trail bears left into forested area.		 A small wooden pedestrian bridge crosses a small creek in an oak forest.
Fig. 14. Bridge crossing stream in oak forest area.		 Poison Oak - leaves of three, let it be!
Fig. 15. Poison oak: "Leaves of three, let it be!"
View of a small clearwater stream flowing through a forested area.
Fig. 16. Spring-fed stream in oak forest.		 View of a small rocky gravel bar along a small stream.
Fig. 17. Gravel bar beneath the bridge displays a mix of rocks.		 View of lots of rounded boulders and outcrops standing out on a sagebrush covered slope with an oak forest beyond the rocks.
Fig. 18. Boulders along the trail.		 View of a hillside with of rounded boulders and outcrops standing out on a sagebrush covered slope with an oak tree and Bernardo Mountain in the distance.
Fig. 19. Boulders on a hill with Bernardo Mountain.
A step-like series of granite boulders and outcrops rise above a sagebrush covered slope.
Fig. 20. More boulders and outcrops along the trail. 		Granite boulders and outcrop with a view of San Pasqual Valley in the distance.
Fig. 21. More boulders and outcrops along the trail. 		Low rocky outcrops on a grassy slope crossed by the Highland Valey Trail.
Fig. 22. Outcrop next to a small spring-fed stream		 Two small round grinding mortar holes on the lichen-stained surface of a granite outcrop.
Fig. 23. Indian mortar grinding holes on a granite outcrop.
Close up foew of the granitic rock (tonalite) with several dark inclusion of gabbro inbedded in it.
Fig. 24. Dark gabbro inclusions in granite (tonalite).		 A disk-shaped dark inclusion that appears stretched during partial melting before the surrounding granite crystallized.
Fig. 25. A partially melted and stretched inclusion in granite.		 Several disk-shaped dark inclusion that appears stretched during partial melting before the surrounding granite crystallized.
Fig. 26. Stretched inclusions in the granite host rock.		 A large boulder outcrop surrounded by oak trees and very green grass in the foreground.
Fig. 27. More boulders and outcrops along the trail.
A large granite outcrop and boulders along the dirt trail. One of the boulders has a flat top, and Highland Valley Road appers above it. The rural San Pasqual Valley and surrounding mountainous ridges are in the distance.
Fig. 28. Panoramic view looking east along the San Pasqual Valley from near boulder overlook area at a high point along the Highland Valley Trail.
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Figure 28 shows a panoramic view of the San Pasqual Valley from a high point along the trail. East of the high point, the trail passes through rolling grasslands and coastal sage and patches of oak forest that survived the 2007 Which Creek Fire (Figures 29 and 37). It is easy to spot the remains of charred tree stumps along the trail. More large boulders and outcrops appear along the trail, including a particularly large split boulder on the pedestal of a granite outcrop (Figure 32). From this section of the trail it is possible to get distant views of the granite boulder and outcrop-covered slopes of the distant peaks along Raptor Ridge, Starvation Mountain, and Sycamore Ridge that rise above the south side of San Pasqual Valley.
View of the Highland Valley Trail and Highland Valley Road cutting through grassy meadows with forest and mountain peaks in the distance.
Fig. 29. Looking east across grasslands along the trail.		 Another view of the Highland Valley Trail and Highland Valley Road cutting through grassy meadows with forest and mountain peaks in the distance.
Fig. 30. View west along trail and Highland Valley Road 		A larg granite boulder or outcrop surrounded by oak trees with agricultural field in the valley in the distance.
Fig. 31. Large boulder with agriculture fields in distance.		 An outcrop of granite with two large head-shaped boulder balanced on top that had obviously split apart in the past.
Fig. 32. Two-Faced Split Boulder.
View of the boulder and outcrop-covered mountainside and peak of Raptor Ridge beyond a forest in the foreground.
Fig. 33. Zoom view of Raptor Ridge.		 Two distant rocky mountain peaks with Starvation Mountain being on the right.
Fig. 34. Zoom view of Starvation Mountain (right).		 View of the trail lined with sagebrush and mountains in the distance.
Fig. 35. Starvation Mountain and Sycamore Ridge (right)		 View of the dirt trail winding along the sagebrush covered hillside with Highland Valley Road running along the valley below.
Fig. 36. Trail view west along Highland Valley Road.
Panoramic view of hills surrounding San Pasqual Valley with Highland Valley Road and the Highland Valley Trail crossing a grassy slope.
Fig. 37. Panoramic view of San Pasqual Valley along the Highland Valley Trail through grasslands along Highland Valley Road.
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Sycamore Canyon

The Highland Valley Trail turns to the south and follows Sycamore Canyon Road to the south for less than a mile where the trail ends at the headquarters for the San Dieguito River Park (Figures 38 to 54). Sycamore Canyon Road is unpaved and floods during wet periods, so be cautious. There is a parking area near the end of the trail. Figure 39 shows a massive boulder of the trail that is deeply pitted at its top and smoother toward its base. The boulder reflects how the landscape is slowly wearing away over centuries of drought, fires, and episodic rains that erode away the degraded granite bedrock. In many places in cuts along trails and roads in the area it is easy to see the deep weathering profile where wetting and drying cycles over time break down the bonds between crystals in the granitic bedrock. In many places, the degrade granite easily crumbles into sand when crushed in your hand.

Figures 40 to 42 show bedrock that is different than the granite (tonalite) exposed in most other area. There is a pocket of older rock along Sycamore Canyon that pre-dates the igneous plutons of Cretaceous age. Figure 41 shows a fine-grained bluish metamorphic rock called blueschist. In this image you can see where veins of white granite filled fractures (dikes) in the blueschist host rock. The blueschist may have formed from ancient seafloor sediments that experience great heat and pressure as it was carried downward in an ancient subduction zone. The large block of it here escaped being destroy or completely melted when the Cretaceous-age plutons formed in the region. It is a rock called a migmatite, a rock metamorphic rock that has undergone partial melting. Rocks like this are commonly found along the margins of large igneous intrusions.

The trail through Sycamore Canyon is relative quiet, so you will here the wind through the trees and birds chirping. The creek bed is lined with a recovering riparian habitat, dominated by sycamores and oaks. Unfortunately, non-native eucalyptus has taken over sections of creek bed (Figure 44).

You will find a picnic table at the end of the trail. The headquarters with for the San Diego River Park is a short walk past the end of the trail.

The road intersection sign stands out at the intersection of Highland Valley Road and Sycamore Canyon Road.
Fig. 38. Highland Valley Road and Sycamore Canyon Road.

 A large, weathered boulder rosies above the sagebrush along the Highland Valley Trail.
Fig. 39. Weathered to top of a granite boulder along trail.		 A gray boulder of blueschist rises above the sagebrush along the trail
Fig. 40. Pre-Cretaceous metamorphic rock outcrop.		 Close-up view of the blueschist (migmatite) block along the trail shown in Figure 40.
Fig. 41. Blueschist with granite dikes (migmatite).
Rounded outcrops of gray rock (blueschist) on a hillside below trees.
Fig. 42. Migmatite outcrop on slope above trail.		 The dirt trail cutting across a hillside diminated by sagebrush.
Fig. 43. Highland Valley Trail along Sycamore Canyon Road.		 View of the dirt trail and road passing along a grove of eucalyptus trees along the stream bed.
Fig. 44. Sycamore Creek is more like Eucalyptus Creek.		 View of the dirt trail crossing the unpaved road in Sycamore Canyon.
Fig. 45. Highland Valley Trail crosses Sycamore Creek Rd.
Boulder and brush-covered slope on a hillside along the trail.
Fig. 46. Boulder covered slope in Sycamore Canyon.		 The dirt path running along the valley with a boulder covered slope in the distance.
Fig. 47.Highland Valley Trail in Sycamore Canyon.		 The rocky and tree covered peak of Sycamore Ridge east of Sycamore Creek valley.
Fig. 48. Sycamore Ridge east beyond Sycamore Creek.		 View of mixed tree and shrub vegetation along Sycamore Creek.
Fig. 49. Mixed riparian habitat along Sycamore Creek.
A picnic bench under an oak tree with a grove of young sycamore trees.
Fig. 50. Picnic table at end of Highland Valley Trail.		 A white rail fence borders a drivewat that leads to the building for the headquarters of the San Diego River Parks.
Fig. 51. San Dieguito River Parks Headquarters.		 View of a building partly obscured or hidden behind trees.
Fig. 52. San Dieguito River Parks Headquarters.		 A view of a forested valley with the peak of Woodson Mountain in the distance.
Fig. 53. View of Woodson Mountain behind SDRPH.
Panoramic view showing mixed trees and shrubs along Sycamore Creek near the Highland Valley Trail.
Fig. 54. Panoramic view along lower Sycamore Creek showing the mixed riparian vegetation along the stream valley.
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San Dieguito River Park, Coast To Crest Trail And Other Trails At San Pasqual Valley: SDRP map and brochure, 2 p. (link)
https://gotbooks.miracosta.edu/fieldtrips/San Pasqual_Valley/Highland_Valley_Trail.html 3/19/2021