| Location: The Sinks, Limestone Canyon, Irvine Open Space Reserve, – Santa Ana Mountains, California Distance: 9 miles (out and back) Peak Elevation: 1,475 feet Elevation Gain: 1,500 feet Difficulty: Moderate Caution: Sun exposure, rattlesnakes, ticks, mountain lions |
The Sinks are a mini–Grand Canyon in Irvine’s backyard. I’m not sure if I’d call it a mini–Grand Canyon, maybe a baby grand. The massive sinkhole reveals the red sandstone cliffs of Limestone Canyon. From the eastern viewing deck, you have excellent views of the 20-million-year-old rock layers. The Irvine Open Space Preserve typically restricts access to this protected natural area, except for select access days. Register in advance for the rare chance to view this natural wonder.
| Directions to Trailhead | Hiking Directions | Butterfly Habitat Island | Limestone Canyon | Limestone Ridge | The Sinks | Plan Your Visit | Video Tour |
Directions to Trailhead
| From the 5 freeway, exit Jamboree Road and head northeast. Continue on Jamboree for 5.9 miles. Turn right onto Santiago Canyon Road and drive 4.6 miles. Make a right at Hicks Haul Road. After a few hundred feet, turn right into the Augustine staging area. |
Hiking Directions
| Trailhead: From Augustine Staging Area, head southeast on Limestone Canyon Road. 1.09 miles: At the junction, turn left and climb the Limestone Spur Trail. 1.31 miles: At the junction, turn right onto Limestone Ridge Trail. 4.50 miles: You have reached the east viewing platform for the Sinks. Follow the trails back to the staging area. |
Butterfly Habitat Island
At first, I thought I was imagining a large number of butterflies fluttering along the first mile. I didn’t realize this is a butterfly habitat island. By protecting this natural space and planting the correct plants, this creates an idyllic habitat for these colorful winged creatures. There are big yellow ones, tiny orange triangles, lime stripes, big dots, purple dots.
Limestone Canyon
The path begins harmlessly enough, along the shadeless Limestone Canyon Trail. In fact, there’s zero shade among the green foothills of this trek. In spring, the hills are still green. The sandy and pebble-strewn path cuts through the short squat green chaparral and occasional yucca bloom. There are little dots of orange and purple blooming to the side and even on the rarely used trail. During raptor nesting season, Irvine Ranch Conservancy closes some trails to protect red-tailed hawks, owls, Cooper’s hawks and red-shouldered hawks.
Limestone Ridge
Then from the junction to the Raptor Trail, there’s a bit of a climb. The first bump has about five tiny switchbacks. The single track starts to undulate and roll up and down with the contours of the hill slopes. The ascents up the little bumps are not too intense. Your heart rate will get going a bit. And you do need to concentrate on some of the downhills.
Along this low ridge, you may see white chick lupine and big green lizards. There are also large patches of spiny cactus pads. This section is pretty windy and you can spot red-tailed hawks and red-shouldered hawks riding the thermals. By the way, when you hear an eagle screeching on TV, it’s actually a red-tailed hawk since eagles squawk.
The Sinks
There are two viewing decks for observing the Sinks, one in the west and one in the east. From Limestone Ridge, you can see the Sinks up close at the eastern platform. Around 40 million years ago, this area was under water. Then, the land uplifted because of tectonic plate forces. Around that time, a large chunk of land collapsed into a sinkhole, revealing the ancient rock. Diagonal bands are visible in alternating layers of white and pink rock. These are rocks from the end of the Eocene epoch when the earth rapidly cooled.
Plan Your Visit
- Registration: The Irvine Open Space Preserve at Limestone Canyon is accessible on the first Saturday of every month. Register online at the Irvine Ranch Conservancy’s Let’s Go Outside Each event has limited spaces.
- Gates: The gates are only open from 8 am to 2 pm. You will receive a citation if you are on the Irvine “scheduled program only” trails before 8 am or after 2 pm. Failure to remove your vehicle from the Augustine staging area by 2 pm will subject you to citation.
- Cancellation: If your plans change and you cannot attend, cancel your registration to open your spot to another visitor.
More to See in the Irvine Open Space Preserve
Video Tour of Limestone Canyon