Sunday, February 12, 2012

The unbelievable bathymetry of Mavericks

The window for the Mavericks surf contest is open through the end of March, and at any time the selected contestants can be given 24 hours to head to California for the big-wave competition.

The contest has only been held seven times since 1999. The surf spot has only been known to the general public since 1990, after a photograph taken by a friend of Mavericks pioneer Jeff Clark (who first surfed it alone as a teenager in 1975) was published in Surfer magazine.

It is one of the largest and heaviest waves in the world (which makes the fact that Jeff Clark paddled a half-mile out to sea to surf it alone for years all the more impressive).

Surfline, itself a pioneer in the world of predicting surf, has an outstanding special feature presentation on the mechanics of Mavericks and the interaction of water and geology that produces its monster waves. It was produced and written by the late Sean Collins, the founder of Surfline, who was single-handedly responsible for changing the way surfers around the world check conditions before heading to the ocean, and published on November 16, 2011 -- only a month before he left this life at the age of 59.

The thirty-page analysis features beautiful aerial photographs and especially underwater bathymetry images showing the unique underwater terrain that channels wave energy from the largest northwest Pacific storms into the lineup at Mavericks. The word "bathymetry" (Greek for "the measurement of the deep") refers to the same science as topography, but underwater. Slide 8 of the Surfline analysis of Mavericks explains that:
Swells approaching Maverick's from the North Pacific will first pass over the continental shelf, and the distribution of swell energy along the coast will be determined by swell interaction with the topograph of the ocean floor (bathymetry). Swell energy will always turn towards shallower water (refraction), and swell direction and swell period will be contributing factors of how much the swell will refract.
Willard Bascom (1916 - 2000), a pioneering oceanographer and scientist and author of the excellent Waves and Beaches: the dynamics of the ocean surface (1964), whom we have met before in this previous post, explains refraction in that book by saying:
Refraction simply means bending. As waves move into shoaling water the friction of the bottom causes them to slow down, and those in shallowest water move the slowest. Since different segments of the wave front are traveling in different depths of water, the crests bend and wave direction constantly changes. Thus the wave fronts tend to become roughly parallel to the underwater contours. 70-71.
Underwater bathymetry imagery released in 2007 from the USGS and Cal State Monterey Bay revealed an amazing complex of dramatically curving reefs that channel the wave energy into the patch of ocean located off of Pillar Point (at the northern boundary of Half Moon Bay) where Mavericks breaks when the swell energy is powerful enough and the swell direction is right.

Slide 14 of Sean Collins' Surfline presentation of the Mechanics of Mavericks shows the critical portion of this underwater reef complex. The text on that slide reads:
The unique bathymetry extending about a mile offshore is the secret to the big surf at Maverick's. Recent side-scan sonar surveys by the USGS and the Seafloor Mapping Lab at California State University at Monterey Bay have revealed a very interesting swirling pattern of shallow reef that extends westward off Pillar Point. These swirling grooves in the reef off Pillar Point act like a huge magnifying glass to merge and focus extra wave energy from adjacent deeper water toward the shallower reef. The unique patterns in the ocean floor were created by long-term erosion and historic seismic activity of the local San Gregorio Fault system. Another possible cause is huge icebergs during the last Ice Age that may have helped to grind out these grooves -- a similar phenomenon that also occurred on the Hudson Shelf near New York.
The fantastic curving patterns can be seen in the NOAA/USGS imagery from this website shown in the diagram below. You can see how the deep channels on either side of the Mavericks lineup create refraction that cause waves to bend towards the shallower ridge in between the channels, focusing the wave energy.

The origin of these graceful curving reefs, like other geological features on earth, invites various explanations. Like a popular mystery story (such as the stories of Sherlock Holmes, or Scooby Doo and the gang), there are explanations which generally fit into the popular assumptions and preconceptions of the powers that be, but these explanations may or may not stand up to scrutiny. The conventional explanations will generally involve tectonic forces, such as the idea that they were caused by "long-term erosion or historic seismic activity of the San Gregorio Fault system" cited above.

A more detailed example of a conventional explanation for such extreme curving geological features can be found in the Highly Allocthonous website of geologist Chris Rowan, where such plunging folds are explained as a "tale of orogenies past," in which tectonic forces lift parallel layers upwards (causing them to bend), and then other forces cause the fold axis to become tilted to some degree. When the tilted bent layers are sheared off, the folded layers present dramatic hairpin bends that represent the top of the uplifted layers. Mr. Rowan entitles his post "12 folds a-plunging" and provides numerous photographs of examples from around the world (all of them above the current ocean surface).

This blog post from professional geologist Michael Welland (author of Sand: the Never-ending Story, 2010) discusses the extreme curved reefs off the California cost near Half Moon Bay and links to the Highly Allocthonous post about "plunging folds" as a likely explanation for the bathymetry that gives rise to the waves of Mavericks. While the Highly Allocthonous post does not directly mention the reefs off of Pillar Point, the other examples it offers of "plunging folds" certainly makes it appropriate for Mr. Welland to argue that the mechanism described for the curving patterns in "12 folds a-plunging" are the same forces that created the bathymetry at Mavericks, and Mr. Welland concludes that the Pillar Point reefs are "clearly 'folds a-plunging' in the sea-floor off San Mateo County."

There are some significant details, however, which call into question this explanation for the origin of the severe curving reefs near Half Moon Bay. First, there is the question of the distinctive reef composed of concentric circles indicated by the white arrow in the imagery from CSU Monterey Bay below (this is the same imagery as that in the image above, but colored to indicate depth, with red being shallower and blue deeper water depths, and yellow indicating depths in between blue and red):

It is difficult to imagine a scenario in which the concentric circles of the reef indicated by the arrow could have been created by uplifting of layers which were later tilted and sheared off.

In fact, the more one considers that explanation, the less satisfactory it appears in light of the reef patterns depicted in the sea-floor imagery. Note, for example, that the curves are clearly further apart at the point of greatest "hairpin turns" rather than closer together as we might expect if they were actually caused by tectonic uplifting.

Further, a close examination of the topography will reveal that the terrain in question is deeply scored and jumbled, and that it appears that wide bands have been "planed out" in this deeply scored terrain to create the graceful curves, but that some of the scoring lines clearly continue on the "other side" of the "planed out" bands.

For instance, in the image above, the reader can examine grooves and scoring inside each of the circled areas which appear to have once belonged to a continuous piece of land which was later divided by some force that carved out a deep and smooth channel right down the middle. Not only are these channels significant to surfers at Mavericks (since they act to bend the wave energy towards the central ridge), but they are also important clues to the mysterious underwater terrain off the California coast.

The fact that something appears to have cut across the existing terrain and left deep grooves like this indicates flow of something -- the most likely suspects being liquid or viscid flows, either lava, glacial ice, or water. In each case, it seems clear that the terrain was not under the surface of the ocean when the lava, ice, or water carved these channels. The curving patterns are certainly indicative of flowing liquid or viscid forces as well*.

The image below from Google maps shows that the graceful curving reefs that create the Mavericks break are part of a larger patch of underwater ridges that stretch north of Pillar Point towards Montara and south into Half Moon Bay itself, but which are most extreme in the area of the Mavericks break.

The darker area contains swirling patterns as well as "feathered" ridges that seem to end in a series of parallel points, resembling quite remarkably the patterns of the sacred moko of the Maori of Aotearoa (New Zealand).

The reader can click on the image to zoom in and see the details, or even better to visit Google and conduct a search on their maps for "Half Moon Bay, California" -- selecting the "satellite" imagery view rather than the "map" imagery view in the upper-right corner of the map will bring up the sea-floor images seen above.

Cruising along the Google Maps imagery up and down the California coast will show that the extended dark rough patch near Mavericks that resembles a moko in its swirling pattern may be more extreme than those found elsewhere, but that it is by no means alone. Other such patterns rise up out of the otherwise much smoother continental shelf at various points, including further north near Bolinas (also near a significant headland like Pillar Point accompanied by a wide bay) and further south near Morro Rock (again, a prominent headland and one which in this case features an obvious volcanic extrusion). See the images below.

In the image above of the long dark scored reefs off the coastline near Bolinas, California, note the same hairpin curves and feathering found at Mavericks, and also note the very distinctive concentric circle pattern which is even more pronounced than the concentric ring pattern pointed out at Mavericks in the images above.

The detail of the Bolinas pattern reveals very clear evidence that these "moko" patterns that seem to rise up at certain points along the California coast may be indications of volcanic activity in the ancient past. The concentric circles of the Bolinas "rough patch" form a complete ring (unlike those off of Pillar Point / Mavericks), and the USGS / CSU Monterey Bay imagery appears to indicate steeply beveled sides to the ring, giving it a very clear crater-like appearance.

Moreover, the deeply scored and darker sea-floor both here and at Half Moon Bay / Mavericks seems to indicate volcanic flow. The image below of another such "rough patch" off the coastline just south of Morro Rock (further south along the California Coast from Half Moon Bay, south of Monterey and Carmel and Big Sur) reinforces this conclusion:

This kind of "washboard" terrain is very characteristic of ancient volcanic action, and is reminiscent of the terrain around Fort Irwin and the Mojave Desert that was discussed in this previous blog post. Note that again we find a volcanic-looking rough patch protruding from the otherwise smoother seafloor in the vicinity of a prominent headland -- Morro Rock sticks out into the Pacific in much the same way that Pillar Point does. It would be redundant to include an image of it here, but another such patch can be observed at Point Año Nuevo not far south of Half Moon Bay.

The interesting thing about these mysterious patches of heavily scored volcanic-looking ground is that they are surrounded by much smoother seafloor. In fact, looking at them for a long time will give the distinct impression that these rough patches themselves are partially filled up with the same thick silt and sand that blankets most of the adjacent seafloor. Let's return to the imagery around the Mavericks surf break and see.

Just south of Half Moon Bay, at San Gregorio State Beach (where highway 84 intersects the Pacific Coast Highway or Highway 1) there is another small "rough patch" that clearly appears to be surrounded by silt. These patches are starting to give the impression that the entire ocean floor off the Northern California coast is really rough and washboard-like, but most of it is drowned in silt.

A close-up look at the swirling ridges that lead in towards Mavericks gives the same impression: it appears that the long "feathered" ridges disappear into a deep layer of silt. In other words, these ridges probably continue on below the surface that we can see: they were formed first and then buried later in silt.

A closer examination of the concentric terrain feature near Mavericks will reveal the same thing: it is probably a crater very much like the one shown above at Bolinas, but since it is deeper and more deeply buried in silt, only the upper edges of the lip of the crater can be seen, and these do not form a complete circle above the silt as the crater at Bolinas does (the Pillar Point crater is probably a complete circle, but some of its lip is below the level of the silt that flowed in later).

What could explain these amazing terrain features? The conventional explanations are quite inadequate. The hydroplate theory of Dr. Walt Brown, however, provides a scenario which appears to fit the evidence quite satisfactorily.

We have already seen in previous posts that Dr. Brown's theory envisions the continents sliding away from the initial rupture (and the rapidly rising Atlantic floor, which sprang upwards after the escaping floodwaters removed enough sediment) and towards the newly formed Pacific Basin (which buckled downwards in compensation for the upward-springing Atlantic floor, "sucked" towards the Atlantic on the other side of the globe as if the underside of the Pacific floor were connected through the earth by long cables to the underside of the Atlantic).

The forward edge of the Americas would have experienced tremendous friction, enough to create heat sufficient to melt granite and produce massive amounts of magma, which later spilled out as immense lava flows (the Columbian basalts of Washington and the volcanoes of the Mojave area are two examples of evidence of this activity). Such friction and melting could explain the volcanic-looking deeply scored "washboard" terrain that we see in places along the front-edge of the drifting continent (the California coast and the continental shelf).

As the continents slid, they buckled and thickened. Later, when the continents finally ground to a halt, the floodwaters poured off of them towards the ocean basins, dumping massive amounts of sediments into the ocean basins. The waters pouring off the continents carved immense canyons as they cascaded over the edges of the continental shelves: the Monterey Canyon that was discussed in this previous blog post is one such canyon, as are the canyons of the Ganges Fan and the Indus Fan and the canyons found under the sea at the mouths of some of the largest rivers in the world such as the Amazon and the Hudson.

At that time, when those canyons were formed, the sea level was much lower than it is today (that's why those canyons could be carved by rushing water -- today they could not be carved because they are under the ocean). Note that another mighty submarine canyon yawns below the lip of the continental shelf just west of Mavericks and Half Moon Bay as well. Look just left of the large red letter "M" in the word "Mavericks" in the image below from this NOAA website about National Marine Sanctuaries in the United States.

The sediment-rich waters flowing off of the continent may well have blanketed the washboard features so deeply that they only protrude in certain places along the California coast. It seems that at places where a large promontory (such as Morro Rock, or Pillar Point) shielded some of the silt flow, less sediments were deposited and some of the fingers of volcanic reef could poke through the silt. This silt likely hardened into sedimentary rock over the centuries before the sea levels rose to cover the continental shelves (the hydroplate theory explains that the continents were much higher relative to the seas immediately after the flood for some hundreds of years, before their great weight caused them to sink down and the ocean floors to rise).

The graceful curving patterns could have been caused by lava flow from the original lava activity that created the rough volcanic terrain, but it is much more likely that they were planed-out later while the continental shelves were still above sea level (based on the fact that some of the original grooves and scoring are interrupted by the broad channels that must have been scooped-out later).

These channels may have been carved out by glaciers which covered North America during the Ice Age that was caused by the temporarily higher continents and lower warmer seas (the warm oceans producing much more precipitation, which fell as snow and ice over the colder higher land masses). We know that glaciers reached these latitudes in California, as Yosemite Valley further inland is an obvious product of glacial carving.

An astute reader might wonder how the silt filled these glacial channels, if the silt was deposited by waters flowing off the continents right after the flood and before the Ice Age. It is possible that waters were trapped in the Great Central Valley of California long after the initial flood, later breaching and rushing out to the Pacific (just as other trapped waters later breached and carved the Grand Canyon, depositing tons of sediments in the Gulf of Mexico in the process, as Walt Brown explains in his book, which contains an entire chapter on the Grand Canyon).

The exact mechanism that carved the graceful channels in the original deeply-scored washboard is not certain at this time, but it appears likely to have been either glacial ice or sediment-rich water, and possibly later lava flows although this mechanism appears less likely*. The bottom line is that the mechanisms proposed by conventional geology appear quite inadequate, while there are several options which fit the general outline of the hydroplate theory. Note that the hydroplate theory was around long before the undersea images became available in 2007.

Thus, the incredible undersea terrain that produces the mighty waves of Mavericks appears to be yet another piece of geologic evidence that is very difficult to explain using conventional geologic theory, but which fits rather nicely within the predictions of the hydroplate theory.

The only question is, did the Polynesians (who gave the world surfing in the first place) somehow know about the distinctive undersea swirls that produce the gigantic waves at Mavericks, and incorporate these patterns into their tattooing? If so, perhaps they knew about this "undiscovered" surf break centuries before it became known again in the 1990s! But that is a mystery for another day.

* Note: since publishing this post, I have come to believe that hogbacks are the most likely explanation for these dramatic underwater features -- see this post, published 02/16/2012.