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Mt Diablo Big Summit Loop





by Transit & Trails


Wildlife Sightings

by iNaturalist


Length: 6.4 miles
Difficulty: Moderate
Duration: Halfday
Created by kueda

I moved to the Bay Area from New England in 2003 and haven't looked back! In the intervening years I've explored many of the local trails and parks, always with an eye toward plants, mushrooms, wildlife, and all things living. Oh, who am I kidding, dead things are pretty cool too. Whether I'm feeling the heat on top of Mt. Diablo or cooling my feet at Abbotts Lagoon, nothing makes me feel more alive than being outside.

Good for:
  • Views
  • Wildflowers
  • Chaparral
  • Forests and Woodlands
  • Grasslands
  • Trail Hiking


Spectacular views of rolling hills, rock-speckled fields adorned with rare wildflowers, and a chance to see eagles and tarantulas on the same trip. What's not to like? Well, there's the searing heat and steep inclines, of course, but hey, that's what keeps the crowds away. This hike shows off a number of Mt. Diablo's higher elevation habitats to great effect, along with sweeping views in every direction.

You can start this loop at Juniper Campground, the summit, or a pullout on Summit Rd where the North Peak trail begins (Devil's Elbow), but this description will start at Juniper Campground.  After the winding drive up the mountain, take a moment, have a drink, and review your route.  Start hiking up the Juniper Trail from the parking lot.  You'll pass under oaks, over rocks, and through some of the chamise chaparral you drove through on the way up. Check out the placards on the mountain's geology and take in the fine views of the San Ramon Valley to the southwest.  In late spring, keep an eye out for California larkspur, a tall plant with modest white flowers that grows only in central California.
The trail cuts through the lower summit parking lot, through some more chaparral, and descends to a hairpin turn in the road where there's a small pullout and a map.  From here start on the North Peak Trail.  In addition to awesome rock pillars and a fine spread of wildflowers in spring and early summer, you should have a wonderful view of Morgan Territory, the Altamont wind mills, the Central Valley, and, on the clearest of days, the snowy peaks of the Sierra.
As the trail curves down and to the north, it passes through an oak forest that provides welcome shade in the summer and some lush ferns, fritillaries, and Chinese houses in the spring. When the trail reaches a fire road you've arrived at Prospectors Gap. Turn left and very soon after take another left onto Bald Ridge Trail.  This will take you on a winding, rocky descent toward Murichio Gap.  On the way you'll continue giving up that hard-earned elevation from Juniper Trail, but take heart! Along the way you may see rare flowers like two-lobe clarkia in the shaded oak forest, or the extra-rare Mt. Diablo jewelflower and Mt. Diablo bird's beak, two tiny flowers that grow in the rocky, exposed parts of this trail… and almost no where else on Earth! Even if you don't see any flowers, you'll definitely have spectacular views down Bald Ridge toward Eagle Peak and Mitchell Canyon. Keep an eye toward the sky for Golden Eagles, and your other eye on the trail for rattlesnakes and horned lizards!
When the trail hits a 4-way intersection, you've arrived at Murichio Gap.  You might want to hop up on the rocks right in front of you for a nice view.  When you're done, take a left and start heading southwest on Meridian Ridge Road.  You'll start going downhill quite steeply pretty soon. Try not to pity any poor hikers you meet coming up this hill, because you'll be in for it soon yourself. In the winter this part of the park features numerous blooming manzanita, and in the spring, the heady fragrance of buckbrush fills the air. You'll start seeing some more grassland plants like mule's ears, poppies, baby blue eyes in the spring, and some seep-spring monkeyflower if the creek is flowing.
When you arrive at Deer Flat your downhill times are sadly at an end, and it's time to climb the switchbacks uphill back toward Juniper Camp.  They're actually not so bad.  Take a break and watch a butterfly patrol its territory. Your reward at the top should be a brisk breeze and a view of rolling grassland to the southwest.  From here it's a flat stroll back to Juniper Camp. If it's late summer / fall and you've finished your hike around sunset, drive out slowly along North Gate Road and look for male tarantulas! They're out looking for mates, and can often be seen crossing the road.  Don't run them over! And try to resist the urge to pick them up: a drop of even a few feet can do great harm.  They're more fragile than they look.
Logistics: depending on your level of fitness and your propensity to take pictures of every little flower, this could take anywhere between 3 to 5 hours. It is quite steep and in the summer temperatures can exceed 100 F, so bring more water than you think you'll need, even more if it's hot. Poison oak is present in most parts of the park, but it rarely drapes across the trail. Though infrequently encountered, rattlesnakes are present too, and are especially active in the late spring. Give them a wide berth and you'll be fine. Bathrooms and water can be found at Juniper Camp and at the summit, but otherwise there are no facilities along the trail.

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