Monday, January 19, 2009

Making mountains


We live near Topanga State Park, in the western part of the Santa Monica Mountains. The Santa Monica Mountains begin just above downtown Los Angeles, and run westward to Point Mugu in Ventura County. These mountains are unusual in that they are a Transverse Range, running east-west rather than north-south. They are one of only two such Transverse Ranges in North America.

Yesterday we took a hike along the East Topanga Fire Road. The road runs along the top of the ridge on the eastern side of Topanga Canyon, from the main entrance of Topanga State Park at Trippett Ranch, south to an overlook onto the Pacific Ocean.



We always take a short cut to begin, taking a steep dogtrack up a hill through an oak grove, until we emerge on the wider Fire Road. The trail is wide enough for a truck to pass, although only Park Service vehicles are allowed. Mountain bikers and horseback riders use the trail alongside hikers.

At the top of the first rise, a bench invites hikers to rest a moment and take in the view. From here, the trail goes about 6 miles to its end at the Parker Mesa Overlook. We've gone to the overlook before, but not for several years. Our goal was modest - we would walk until we got tired of it, conserving enough energy to walk back.

The natural landscape here is called Coastal Chaparral. Plants include black sage, California buckwheat, ceanothus, scrub oak, manzanita and chamise. On a day like yesterday, with a clear sky and a bright sun and 80 degree weather, the resinous oils in these plants warm and rise up to perfume the air.


In January it's a bit early for the spring flowers. On this hike, we saw a few early blooms. Big shrubs of Ceanothus cuneatus, or Buck Brush, were covered with delicate clusters of white flowers.

One of the amazing things about these mountains is the geology. The Santa Monica Mountains are relatively young as mountain ranges go. They were caused by the collision of two of the earth's plates - the Pacific Plate, which forms the pan of the Pacific Ocean, and the North American Plate. The Pacific Plate pushes beneath the edge of the North American Plate, heaving it up and buckling the rocky crust of its surface. This began near the end of the Miocene Epoch, a mere 5 million years ago.

This collision of the earth's plates is visible even on a short hike like ours.

The oldest of Topanga's rocks are of the Chico Formation, created about 90 million years ago, during the Cretaceous Era. These rocks were created as sand, gravel, limestone, silt and conglomerates built up in layers by the actions of ancient oceans. They are tan and finely grained, and contain the fossils of ancient snails and squid and other sea life.

Past the bench, the road curves down around a huge golden sandstone boulder that juts out of the brush. We always call this rock "Lioness Rock" because we think it resembled a sleeping cat. Past Lioness Rock, the trail curves and runs along the eastern side of the ridge, below a cliff of crumbling tawny rock, subject to rock falls during rainy seasons. It overlooks great tilted boulders folded into the earth forming Santa Ynez Canyon below.


Here the overhanging cliff shades the path, and the air is still cool. We met up with our friends John and Foster, biking down the gentle incline as we ascended. They had gone out early and were heading for home.

Here on the shady side of the ridge, a small California bay tree was starting to bloom.

The elevation of the Fire Road on this ridge is between 1400 and 1600 feet above sea level. After a time skirting the east side of the ridge, we reached a saddle, where you could see East into Pacific Palisades, with the meandering development of Palisades Highlands, and West into Topanga Canyon, where Topanga Canyon Boulevard threads its way through the folded mountains.

That's the road I drive to work everyday. I should remember to look up at this peak where I'm standing, next time I'm in the car.

Past the saddle, the trail winds on the Topanga side of the ridge, and we're exposed to the mid-day sun. As we look south, we can see the length of the trail as it winds toward the Outlook.

Here, the rocks are grey and crumbly. They may be part of the Martinez Formation from about 50 million years ago during the Paleocene and Eocene Epochs, dark grey or greenish siltstone and dark brown sandstone.


Beyond and around the curve, boulders of pinkish mauve sandstone rise above the trail. These are part of the Sespe Formation, dating from about 25 million years ago during the Oliogocene Epoch. They have the characteristic reddish coloring from the presence of iron oxides in the rock. The Sespe Formation is also dramatically displayed in Red Rock Canyon, but here on the East Fire Road, it bulges up in a great outcropping.


There is a dramatic difference in the plants that grow here on these pink rocks. The boulders are shaped and runnelled with channels by water run-off. Perhaps there are springs that bubble up here, because, unlike other parts of the ridge, riparian plants such as oaks and toyon, small succulent plants and tiny ferns nestle in the folds of the rocks.

The pink rocks give way as the trail steepens and turns. Here is a striking rock formation, where dark siltstone and shale rocks are interspersed with white deposits. I am not a geologist, but when I read about these mountains, I wonder if these rocks were part of the Topanga Formation, which took place 10-12 million years ago, where ancient eruptions sent magma through cracks and fissures in the sedimentary rocks, and blasted bombs of volcanic boulders onto the landscape.

Here deposits of white-colored rock thread through darker rock, as deposits of basalt bulge among them.

We climbed to a broad place where the trail turns eastward and rises steeply. It was perhaps another mile or so to Parker Mesa Outlook, but from here this view stretched before us.

That's Catalina Island beyond. The sun glittered on the waves. Our water bottles were drained by half. Our feet and legs were tired. We turned and looked at the distance behind us. It was here we decided to turn back. Parker Mesa Outlook could wait for another weekend.

Here's the view from the walk back. This is looking back to where we turned around. You can see, near the upper right hand corner of the picture, where the trail rises sharply and then disappears into a fold in the hills, the place where we turned back. And you can see how the trail curves round the hill. The steep dog-track in the center of the picture is a little branch-off trail for more adventurous climbers than we are.

The way back was daunting on the uphill stretches. At the saddle at the top of this rise, the trail switches to the eastern side of the ridge, where we were grateful for the shade and the cooling breeze.

By the time we reached home, my face was flushed and red, and our legs felt like jelly. Even now, a day later, I can feel the muscles in my legs.

We'll go again, next weekend, and see if we can make it farther.


Here are samples of the different kinds of rocks we saw. You can see the pinky-mauve rock at center; the dark basalt on the right; a chip of white stone on the bottom, and a chunk of crumbly brown sandstone veined with darker blue shale on the left. The Santa Monica Mountains are still being formed today, as geologic forces continue heaving upward, rotating minutely clockwise, as the earth continues its growth

6 comments:

Kate said...

Love the photos and the geologic description of these natural wonders. Sounds like a lovely day out and about in nature.

I was reading Sharon's blog post today at www.owlinmaine.blogspot.com and the contrast in terrain/weather is striking. Isn't it great that in this great country of ours there is so much variation?

Makes life interesting, no?

phd in yogurtry said...

They are one of only two such Transverse Ranges in North America.


Oh the things I have learned reading your blog! You've got some breathtaking photos. That basalt bulge is amazing. I love interesting rock formations. Makes me feel very small and insignificant.

I am a Tornado ~ proven fact! said...

sounds like a perfectly lovely day.

JCK said...

I adore your Topanga. It is special.

Beverly said...

Glennis, I feel like you took me right along with you. Except I don't have jelly legs. ;-)

What a beautiful and fascinating place.

Gary Rith Pottery Blog said...

you live there????? you have spring flowers??????? that is just so UNFAIR