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Friday Rocks – “The Accretionary Wedge Is The Spice” edition

No year is complete without the crossing of at least one tectonic plate boundary, in my geological opinion. At the end of May, D and I returned to the Virgin Islands, specifically St. John and some St. Thomas. We did a lot more swimming and snorkeling with friends this time around and, thanks to my new little Olympus Tough, were able to capture some of the beautiful, vast and nicely protected underwater ecosystem of these volcanic Caribbean islands. Here is the full album and a few choice submarine pictures:

Snorkeling Maho Beach, St. John, USVI

Snorkeling Hawksnest Beach

Snorkeling Honeymoon Beach

Snorkeling Honeymoon Beach

Snorkeling off Buck Island

Snorkeling off Buck Island

The islands are not just beaches, but extinct arc volcanoes and/or accretionary wedge material associated with the convergent plate boundary between the Caribbean and North American plates. In fact, 60-70% of St. John is the Virgin Islands National Park, land donated by Laurance Rockefeller to the US National Parks Service in 1956, with well-maintained hiking trails. Friends Jon and Mo and I decided what a great idea it would be to hike the Reef Bay Trail (on the list of Top 10 Caribbean hikes and second most strenuous hike on St. John). A mile down to Reef Bay along the Reef Bay Gut (river valley), look at some old Taino petroglyphs along the way, check out sugar mill ruins and jog back up the trail to the main island road – No Problem, Mon! Lickety Split.

So, let me tell you about subtropical areas after heavy rains; they breed my (second-)worst enemy (after roaches): mosquitoes. Oh, honey, these aren’t your microscopic Houston-spring babies, I’m talking giant Vampire Mosquitoes that roam in armed gangs and have evolved to attack you no matter what permutation of permethrin-treated clothing and DEET repellent you have on or attack them with. Holy mother of dengue fever. Not ten minutes into the hike, we were swarmed by All The Mosquitoes. All of them. Each time we slowed down to look at a plant or an animal, we formed a collective landing-strip-and-buffet for the little bastards. At one stop, there were a couple of guys – one resembling Channing Tatum with a jaw and the other the middle-aged love child of Hemingway and Hunter S. Thompson, who both turned out to be Beltway journalists – asking if we had any bug spray, which I reluctantly parted with. We needs it, precious. In essence, we had to keep going, but I did manage to get a few good pictures of lovely stuff that grows in virgin Caribbean forest. For instance, a gigantic wild bromeliad, which as my dad loves to point out, is from the same family as pineapples:

Bromeliad

Also along the trail are ruins of a few slave-trade-era plantations, mostly just foundations now with the forest and weathering processes taking over. Before getting all the way to the bottom of the trail, you can veer off to the west for a short hike to see the Upper Waterfalls and Taino petroglyphs. The falls weren’t very spectacular during our visit, but the low water level allowed a good view of the rock carvings theorized to pre-date Christianity, made during the northward travel of native South Americans to North America via the Caribbean Islands (the ones that stayed became known as Taino). Here’s an example of a petroglyph – pretty sure it’s a depiction of an alien and a chupacabra:

Reef Bay Petroglyphs

At last, we got to the unforested, fresh, mosquito-free Reef Bay, where sit the ruins of an old sugar mill. Sugarcane plantation + slave labor = sugar for European consumption, and yet another reminder that, for tiny-assed nations, England, Holland and Denmark covered a lot of ground and wreaked even more havoc in the colonial era. From a very detailed description of the Reef Bay Trail by Gerald Singer:

… One side of the boiling room housed the boiling bench and the row of copper boiling pots where the cane juice would be boiled down into a wet raw sugar called muscavado. The fires were fed from the outside of the building. Bagasse would often be burned to provide heat for the boiling operation. The muscavado would then be dried and packed into 1,000 pound barrels called hogsheads. Sailing vessels bound for Europe would arrive in Genti Bay to pick up the shipments of sugar.

A number of Reef Bay Trail guides encourage you to check out the ruins. Take as an example this TripAdvisor tip: “The remains of the sugar mill at the end of the trail deserve your thorough exploration.” What they neglect to tell you is that the “thriving bee hive which is neat” inside one of the buildings has grown to epic proportions. There I was admiring a giant gear while thinking about the poor workers who were forced to operate it before steam power came along, when a bee suddenly stung the back of my neck, I grabbed it out of my neck before it got too far, the damned bee then got wedged between my index and middle finger, and it stung me on my middle finger before falling to its death. This was followed by Jon’s and my tragicomic discovery that I am not allergic to bees and don’t need an epi pen after being stung by one. (All while Mo was off splashing in the waters of Reef Bay, completely oblivious to my misfortune.)

Jon: “How do you feel?”
Me: “I just got stung by a f-ing bee, Jon. How do you think I feel? No, I’m not in shock, really more startled than anything else.”
Jon: “Ok. It’s ok. Let’s walk this way in the ruins.”
Me: “Are you out of your mind? Do you want me to get stung again?”

Point made, bee. Your sacrifice was not in vain. I’m outta here.

Seriously, by that point, I was hot, sweaty, mosquito-bitten, adrenaline-ridden and kinda irritated at the local who witnessed my bee sting and suggested dabbing pee (yes, human urine) on it, and just wanted to leave. Except, as you probably guessed, the only way out was to climb back up the 15-20° incline we had just come down. We made it back up in pretty good time (despite the triple distractions of more mosquitoes waiting for us, my thudding heart and helping look for someone’s lost dog) and Jon’s brother was gracious enough to pick us up at the top of the trail, after a short wait when we were devoured by even more mosquitoes.

An artist’s rendition of my trek down to Reef Bay and back. Click to enlarge.

Then we went to Wagapalooza, a benefit for the St. John Animal Care Center and the Cruz Bay equivalent of the parade of the Krewe of Barkus. Apparently, the phenomenon of dogs in costumes with the annual crowning of royalty knows no national borders. Don’t forget to spay and neuter your pets, folks, even the mosquitoes!

Wagapalooza 2014

I highly recommend the Reef Bay Trail when mosquitoes aren’t out by the thousands, but if you’re looking for a quicker, drama-free option, there is always the Lind Point Trail which you can hop onto in Cruz Bay and leads to three beautiful beaches, including Salomon, Honeymoon and Caneel. Honeymoon Beach is my favorite (it’s where we saw the turtles):

Honeymoon Beach

We also took the opportunity to cruise around St. Thomas on a Wet Woody’s charter, stopping at some nice beaches and coves to swim and snorkel. God, I love fast powerboats and this one was a sweet ride. This trip also gave us some of the best views of outcrops of accretionary wedge, which is:

A wedge- or prism-shaped mass of sediments and rock fragments which has accumulated where a downgoing oceanic plate meets an overriding plate (either oceanic or continental) at a subduction zone. The sediment is generally marine sediment that has been scraped off of the downgoing plate by the overriding plate. However, sediment from the overriding plate can also contribute to the accretionary wedge. Fragments of rock from the colliding tectonic plates can also accumulate in an accretionary wedge. The sedimentary rocks which form at accretionary wedges are deformed, faulted, poorly-sorted mixtures which are often referred to as “mélange” (which means “mixture” in French).

The Virgin Islands are directly south of the Puerto Rico trench, which itself is located at the transition between the subduction of the North American plate beneath the Caribbean plate to the east and a transform plate boundary (where the two plates shear past each other) to the west. Two items of interest here: 1) There is more translation than contraction at the Puerto Rico trench, which is good or St. John may be an active volcano, and 2) movement along the southern Enriquillo–Plantain Garden fault zone of the strike-slip system to the west caused the big 2010 earthquake in Haiti.

Here’s a spectacular outcrop of dipping mélange. Can you imagine living in one of those houses and being able to walk out everyday and stand on such beautiful structure? *sigh*

Wet Woody's Boat Ride

Jodorowsky’s Dune, a documentary about a really pretty but pretty bad conceptualization of one of my favorite science-fiction novels, Dune, which was ultimately and thankfully directed by David Lynch, was in the news when we were in the Virgin Islands. As we cruised past this mélange outcrop, I explained the mechanics of subduction zones to my friends, closing it with, “The accretionary wedge is the spice,” which I thought was tremendously clever, but fell on deaf ears. (I think D heard me and understood, but ignored it, as usual.) Worm = mélange = accretionary wedge = spice. Get it, get it? Ok. Good.

***

Vacations with good friends, good food and beautiful rocks and water. Can’t ask for much more. Except for lots less mosquitoes and no bee stings.

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1 comment… add one

  • Blair June 20, 2014, 5:42 PM

    I get it (spice).

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