Finding Fault

A panorama of the Topanga portion of the Santa Monica Mountains reveals a dramatic story of geologic upheaval. That's the Backbone Trail in the middle, traversing an uplift fault, or anticline, made of layers of sedimentary stone that were once on the sea floor but are now at the top of a mountain. All Photos © 2015 S. Guldimann

Many Malibu residents were awakened on Sunday morning to the ominous rattling and shaking of an earthquake. The magnitude 3.32 temblor was centered in the Santa Monica Mountains on a fault under Latigo Canyon. That’s not surprising, because the mountain range’s dramatic beauty was sculpted out of the earth by seismic forces, and that process is far from over. The architect is still at work.

Here's a closer look at the Topanga anticline, with the sandwich-like layers of up-ended sedimentary stone clearly visible.

Malibu has two major earthquake faults: the Malibu Coast-Santa Monica Fault and the Point Dume Fault. The first runs east-west through the city, while the Dume fault, located just offshore, extends northward out toward the Channel Islands, which are actually the highest peaks in the submerged westernmost portion of the Santa Monica Mountains.

This is a USGS map showing the location of the October 25, 3.32 magnitude Malibu quake. The network of red lines indicates various local earthquake faults.

The Santa Monica Mountains are a sort of sandwich tray that a careless giant dropped and hastily attempted to reassemble. They are comprised of heavily faulted and folded ocean floor sediments, liberally interspersed not with mustard or ketchup, but with lava formations known as the Conejo Volcanics, and with a jumbled assortment of alluvial soils and landslide material to garnish the dish.

The volcanic intrusions in the Kanan Dume area of the Santa Monica Mountains are visible  for miles. Saddle Rock, the one that looks like a giant hitchhiker's thumb, can be seen from the top of the Santa Susanna Mountains and was reportedly an important Chumash landmark.

In many parts of the Santa Monica Mountains, Miocene-era shales and sandstone are full of marine fossils, lifted far above the ocean floor and left to weather on the mountain tops.  

Fossilized sea shells like these scallops, or pecten, occur in the Topanga  Formation—Miocene-era sea floor sediment that is common in the eastern Santa Monica Mountains.

In other parts of the range, rain and wind have excavated spires and domes of lava, which emerge from the layers of sediment like massive sculptures. And all through the mountains erosion continues to carve canyons and reshape the land, while landslides rearrange the canyons and coastline. 

Sandstone Peak, the highest point in the Santa Monica Mountains at 3111 feet, technically ought to be called Andesite Peak. It's made of red stone that may resemble sandstone, but is actually volcanic, not sedimentary.

For a place that evokes peace and tranquility in the public imagination, Malibu is a surprisingly violent and dramatic place, at least it is in geologic terms. Although, according to a 2005 California Department of Parks and Recreation report on Malibu Creek State Park, the Santa Monica Mountains actually display “relatively low seismic activity, compared to the regionally high seismic levels in Southern California.”

Corral Canyons fantastic rock formations are made of soft sedimentary rock created from alluvial soils and twisted into bizarre shapes by the seismic activity. The caves were formed through a combination of erosion and wind action. 

Relative is the operative word. There are plenty of smaller faults—offshoots of the main faults in the same way that the main faults are generated by the San Andreas Fault, the massive boundary between the Pacific and North American plates, that have the potential to wreak havoc.

The bluffs at Point Dume preserve a record of violent seismic activity. This cliff is made of layers of soft sea floor sediment that have been forced up at an angle.

At Westward Beach, the sedimentary rock is folded and rolled—a sort of geologic burrito, rather than a sandwich. Clifftop homes perched on top of these cliffs may boast stellar views and command fabulous prices, but are at increased risk from earthquakes, landslides and even wave action, and are ultimately fairly impermanent in the scheme of things. 

The two main plates are what is called a strike-slip fault: the Pacific plate is moving north, taking most of Southern California with it, but it isn’t a smooth transition. The plates grind and catch as they move. Somewhere along the line the plates developed a massive kink, called the Big Bend. This geological phenomenon accounts for the shape of Southern California. It's why the Santa Monica Mountains form a transverse mountain range, running east-west, instead of north-south, and why Point Dume faces south instead of west, giving Malibu residents and visitors an unusual view of the sun rising and setting over the Pacific, and confusing travelers on Pacific Coast Highway—officially a north-south highway, but one that actually runs east-west.

This old USGS map shows liquefaction risk (green) and landslide hazards (blue) in the Point Dume Quadrant. The Point itself is shaped by the Malibu Coast Fault. My dad used to to say that when you are standing on the top of the headlands and looking out to sea you are looking straight towards Antarctica, and there's nothing in between except water.

The Big Bend also generates numerous smaller faults, including the Malibu faults, and the blind thrust fault that generated the 1994 Northridge Earthquake.

The National Park Service created this map of geology in the Santa Monica Mountains. Red represents Conejo volcanics, beige is the Topanga formation. The dotted line that runs through Point Dume is the Malibu Coast Fault. There are a couple of other major faults on the map that weren't discussed in the article, the Boney Mountain Fault, which is responsible for the most rugged and highest portion of the mountain range, is one of them. Here's a link to a version with higher resolution.

While the media frequently warns about the “Big One,” a rupture of the main San Andreas Fault, which could potentially cause a catastrophic magnitude 8.2 earthquake, the smaller local faults, like the ones under Malibu, also have the potential to generate devastating earthquakes—up to a magnitude 7—more than enough to turn Malibu into a disaster zone.

An earthquake fault is why Malibu Bluffs Park is open space and not an industrial development. In 1987, General Motors abandoned plans for a three-story 85,000-square-foot research facility not because the Coastal Commission and local activists objected to the loss of key recreational and environmental land but because an active fault was identified on the property. "Geologists have known of the main Malibu fault for many years," a May 10, 1990 Los Angeles Times article states. "But in the last few years, evidence has been found to indicate that it is active and more extensive than previously realized. Among the significant recent discoveries are two splays or splinter faults off the main Malibu fault that have been active within the last 11,000 years—the benchmark for what constitutes an "active" fault in California. The first discovery of an active splinter fault in 1987, forced General Motors Corp. to abandon plans for construction of an $11-million advanced design center across Pacific Coast Highway from Pepperdine University."

Among the numerous "smaller" faults running through the area with that potential is the  Elysian Park Fault, discovered in 1987 following the 5.9 Whittier quake. According to the Los Angeles Times, it is a blind thrust fault that extends all the way from Whittier, through Downtown Los Angeles, and out to Point Dume, without ever breaking the surface. The probability is high that there are still undiscovered faults of this type throughout the area. A significant earthquake is just a matter of time.

A seismic sensor monitors activity in the Santa Monica Mountains at the National Park Service's Circle X Ranch in the western Santa Monica Mountains.

The City of Malibu offers a variety of emergency preparedness materials and classes, including CERT training for adults and teens and a family emergency preparedness workshop that covers essentials like first aid. Ready.gov, FEMA's emergency preparedness site, is another good place to start, and there hundreds of other websites out there devoted to everything from advice on securing furniture, to the best ways to store food and water. 

Having an emergency plan, and supplies that include food for humans and pets, water, medicines, flashlights, warm clothes, and a battery-powered radio can be the difference between an adventure and a fiasco.

The October 25 earthquake made beds shake and shelves rattle, but was too small in magnitude do cause significant damage. Next time, we may not be that lucky. 

The Santa Monica Mountains rise abruptly and dramatically from the Camarillo Plain. They tell an epic and constantly evolving story of upheaval and change in which humans are only a footnote.

The Sting

A honeybee gathers pollen from lavender flowers. Most of Malibu's insects are relatively benign, but summer is peak season for stings and it can be helpful to know what's out there and how to deal with any unfortunate encounters. Photo © 2014 S. Guldimann

“Beware the Jabberwock, my son!

      The jaws that bite, the claws that catch!

Beware the Jubjub bird, and shun

      The frumious Bandersnatch!”

—Lewis Carroll, Jabberwocky

Around here, shunning the ichneumon, velvet ant, and especially the tarantula hawk might be sound advice, too.

I was on a walk recently with visitors from Colorado. They marveled at how few biting bugs we have in the Santa Monica Mountains. It’s true, mosquitoes and black flies are mercifully few, but we still have quite a few stingers, many of them strange enough to be entirely at home in Wonderland. 

Let’s meet some of them, shall we?

With Scorpio, the largest and brightest of the summer constellations, dominating the night sky, it seems appropriate to start with this celestial creature's terrestrial counterparts. Although we tend to describe them as bugs, scorpions aren't insects, they're arthropods in the family Arachnida. Although there are four scorpion species in the Los Angeles area, the varieties most often found in Malibu are Paruoctonus sylvestrii, the common California scorpion; and Vaejovis spinigerus, the striped-tailed scorpion.

Paruoctonus sylvestrii, the common California scorpion, zeroes in on supper. This was a fairly large specimen—almost two inches long. Photo © 2014 S. Guldimann

Our scorpions rarely exceed two inches in length, but they are fierce nocturnal predators, able to subdue insects nearly their own size. Fortunately, they aren’t reportedly aggressive towards humans and prefer to avoid confrontation. In fact, although scorpions are common in the Santa Monica Mountains, many residents have never seen one.

The best way to spot these elusive arthropods is at night with an ultraviolet light, because the scorpion’s entire exoskeleton fluoresces under UV light—a recent theory proposed by biologist Douglas Gaffin of the University of Oklahoma suggests the fluorescent pigments may act as a light receptor for the scorpion—an eyeless way of seeing. Here's a link to a 2012 article in New Scientist.

An inexpensive UV flashlight makes it easy to spot scorpions at night. Although, ignorance is perhaps bliss. I was astonished to discover just how many scorpions are out there and I have no intentions of ever sitting on the ground again at night. Photo © 2014 S. Guldimann

I’ve been on several nighttime scorpion walks in the Santa Monica Mountains and I am astounded to find how many scorpions are out there. The fact that stings are so uncommon is a testament to the shy and retiring nature of these reclusive hunters.

Most stings occur when humans inadvertently disturb scorpion hiding places, including woodpiles and garden furniture. Scorpions have also been know to seek shelter in shoes left out overnight on the doorstep or in the folds of beach towels and other laundry left out to dry.

None of Malibu’s scorpion species are regarded as a dangerous and both the common scorpion and the striped-tail are apparently popular species in the pet trade. Both have a painful sting—victims compare it to a wasp sting—but it only poses a health hazard to individuals with severe allergy to the venom. 

Scorpions are beneficial, eating many times their own weight in insects, so peaceful coexistence—whenever possible—is the best way of dealing with them. Besides, they're all around us, whether we know it or not. 

There's another seldom seen Malibu resident with a painful sting: the soil centipede. This beastie is a type of Strigamia centipede. It's fast moving, lives under rocks and garden pots and will bite anything that it senses is a threat. Soil centipedes are eyeless and don't actually have teeth or stingers—they "bite" their prey—and the hand of any gardener unlucky enough to come in contact with them—with a pair of specialized legs that are used like fangs and connect to venom sacs in the body. It's a painful bite but reportedly not dangerous.

The soil centipede just wants to be left alone. For something that is nearly six inches long and bright red it's remarkably good at keeping out if sight and  moves fast when disturbed. Its first line of defense is to get out of the way, rather than to bite, although it does that with fierce efficiency if it feels threatened. This centipede was under a potted plant, where it was living a (presumably) happy life eating insect larvae. I carefully put the pot back and left it to go about its business. Photo © 2014 S. Guldimann

Scorpions and centipedes are all very well, but the serious sting awards go to three members of the wasp family. These insects are usually shy and reluctant to sting, but when they do they have a formidable weapon.

The female Netelia ichneumon wasp has a painful sting, used to subdue caterpillars.  It's been described as comparable to the sting of a yellowjacket or a bee. However, this is a beneficial wasp and it is reportedly only aggressive if handled. The Netelia in the photo is a stingless and benign male that somehow ended up in the house. This species is largely nocturnal, and often drawn to porch and garden lights. Photo © 2014 S. Guldimann

The velvet ant is actually a wingless wasp, and like its distant relative the Netelia it also has an impressively painful sting. Biologist Justin Schmidt, who has been stung by just about everything possible, famously developed a pain scale for insect stings. If the sting of the yellowjacket—the most common and aggressive stinging insect in Malibu and just about everywhere else in North America—is a 2 on the 1-4 Schmidt pain scale, the velvet ant is probably a 3. Children are at the greatest risk for encounters with this wasp, since it's brightly colored, pretty, furry and tempting to touch. Fortunately, allergic reactions are reportedly relatively rare. Like the ichneumon wasp, only the female of the species stings. The male is small, winged and easily mistaken for some sort of inconspicuous fly. Photo © 2014 S. Guldimann

Of all the Malibu-area bugs that bite or sting, the tarantula hawk—or pepsis wasp—is the queen. This wasp has a sting described by insect biologist and sting pain index creator Justin Schmidt as "Blinding, fierce, shockingly electric. A running hair dryer has been dropped into your bubble bath."  That's enough to make anyone cnidophobic. The wasp in the photo is feeding peacefully on milkweed nectar, and is shown only a little larger than life. Despite that legendarily horrific sting, it's not an aggressive species, but I was glad that I had a telephoto lens and didn't have to get too close. This wasp is usually rather rare in Malibu, since development has increasingly eliminated tarantula habitat, but for some reason, 2014 seems to be a banner year for the species. Most stings happen when the victim accidentally disturbs, steps on, or brushes against a wasp. Wearing gloves while gardening can help prevent unpleasant encounters. Photo © 2014 S. Guldimann

All three wasps are eye-catching and have vivid coloring, probably intended to warn would-be predators to stay away. It's a warning humans would do well to heed. The Tarantula Hawk has the distinction of being second only to the bullet ant on Schmidt's pain scale. He rates the sting of this wasp as a 4, and adds “…immediate, excruciating pain that simply shuts down one’s ability to do anything, except, perhaps, scream. Mental discipline simply does not work in these situations.” 

This spectacular insect really does prey on tarantulas, which is why it is armed with such a formidable weapon. The female tarantula hawk paralyses the tarantula with her sting and lays her eggs in the unfortunate arachnid, which she will drag to a preselected and prepared hole or burrow, where it will serve as a food source for the next generation of tarantula hawks. And you thought Malibu politics were nasty. 

On a practical note, wearing gloves and shoes while working in the garden can help prevent some encounters with stingers. Many Malibu bee stings happen on the beach, where bees congregate on the wet sand to find salt. A pair of flip flops can help prevent beech bee stings, but some bites and stings are unavoidable—yellowjacket wasps win the award for general orneriness and often appear to sting without provocation, and even in Malibu in the middle of the worst drought in decades, mosquitoes are still out for blood.

Anyone experiencing swelling, hives, breathing problems, or any other sign of a serious allergic reaction from any type of sting should seek immediate emergency medical assistance. Even without a serious allergic reaction, stings can be surprisingly painful and, in some cases, take days to stop hurting or itching.

It's a good idea to keep Benadryl in the first aid kit for sting emergencies. Anyone with sting allergies should make sure they have an up-to-date EpiPen on hand, as well. Here at the Malibu Post we like  "sting ampules."  These are tiny, individual tubes of benzocane that are easy to carry and can be applied to give temporary relief from all kinds of stings. I've never seen them at a store, but Amazon sells a cheap and effective brand).  Cortizone cream, Caladryl lotion and the kind of first aid cleansing spray or wipes with Benzalkonium Chloride and Lidocaine are also  helpful. Ice helps reduce the pain and swelling from most types of sting, although some respond better to heat. In all cases prevention is much preferable to any sting remedy, no matter how efficacious.

The beautiful and deadly tarantula hawk embodies the dichotomy of the insect world: they share our world—or, rather, we share their world, since there are a lot more of them than there are of us, but often they inspire fear because they appear strange or have the ability to defend themselves with powerful chemical weapons. Most stinging "bugs" are beneficial and serve an important function in the local ecosystem. Learning to coexist is important, and offers us a look at a world as weird and alien as anything in fiction, and sometimes also a glimpse of something rare and surprisingly beautiful.


Suzanne Guldimann
29 July 2014