Sweet Rocks in the San Juan Islands

If you like orcas, Canadian layered bar cookies, and rocks that are related to said cookies, read on!

Like many families in 2020 and 2021, mine had multiple false starts trying to plan this vacation during the brief periods of 2020 when society was trying to come to grips with how much we’d have to shut down to protect our communities. But finally in July 2021 the van Stolks made it happen. We loaded up a rental car and boarded the ferry to Friday Harbor on San Juan Island to kick off four days of hardcore relaxation.

My sister and I decided to surprise our parents with a whale watching tour with Maya’s Legacy. We thought it would be a nice nerdy cruise with naturalists even if, as the staff said, we weren’t guaranteed to see whales. Boy were we ever the luckiest though! More on that later. We left from Friday Harbor and cruised around the path on the map below.

Map of our wildlife tour itinerary – see top right for spoilers 😉

The boat cruised past the north coast of Flattop Island to admire the varied lounging positions of happy harbor seals. While we were at it I also admired the stunning layered rocks the seals were sunning on. These neat layers of nearshore sandstone, cobble conglomerate, shale, and storm deposits were laid down on some foreign coast during the Cretaceous period. That foreign coast collided the western shore of North American in the late Cretaceous between 100 and 84 million years ago. This process is very similar to what I wrote about in my post about the Oregon Coast – we meet accreted terranes once more. The San Juan Islands are a whole series of geologic immigrants, separated by five large thrust faults.

So I looked up this formation when I got home in my handy “Roadside Geology of Washington” and had to laugh. That layered formation is part of the Nanaimo Group. If that name is familiar, you likely know it from a layered Canadian treat with a nutty chocolate graham cracker crust, vanilla custard, and chocolate ganache.

A very scientific comparison (c) Courtney.

The rocks in the Nanaimo formation (pronounced nuh-NYE-moh) occur north of the most northerly thrust fault in the San Juan Islands, the Haro Fault. This fault shares a name with the Haro Straight – the boundary between Canada and the US. These rocks on Flattop island have more geologic allegiance to the Canadians than to the rest of Washington State, but with desserts like Nanaimo bars in the game you can’t blame them.

The sediments that make up the Nanaimo group eroded off of a large accreted terrane/mini-continent named Wrangellia that makes up most of Vancouver Island and southern Alaska (think of the Wrangell Mountains) as it was colliding with North America between 90 and 65 million years ago. Coarser sediments were deposited when sea levels were lower, and fine grained sediments were laid down as sea levels rose. Between the sporadic movement of the terrane and other causes of sea level change such as glaciation, the sea levels varied enough to result in frequent flips of sediment type.

Not my MS paint cross section – Steven Earle of Malaspina College drew this cross section of the deposition of the Nanaimo Formation.

After greeting the seals and the rocks at Flattop Island our captain Dave aimed for a pod of orcas he heard was northwest of Sucia Island. This small island looks like an absolute paradise for kayak-camping, and is made of the Eocene sedimentary rocks that got eroded from the mainland side of the Salish Sea and layered on top of the Nanaimo group. These rocks are the orange layer labeled “tertiary rocks” on Steven Earle’s image above. Dave threaded the boat past the high stone reef north of Sucia Island where more seals sat with their heads just above the waves. We join a couple other tour boats as they followed a family of orcas on the hunt! There was one more professional hanger-on in contrast to us tourists- a NOAA scientist with a net trailed behind the pod in a little boat to scoop up anything interesting left over from their prey.

Lee the naturalist ID-ed the whales by comparing their fins to a digital yearbook of locals. This family was Biggs orcas (formerly known as transient orcas), distinguished by their preference to hunt mammals like seals and smaller whales. We followed this family for a little while, all starry-eyed about beating the 80% chance of seeing the Puget Sound’s most famous residents. Then Lee and Dave decided to take a risk and turn the boat west to try and find another pod they had heard of. The boat made a beeline towards the oh-so-scenic Phillips oil refinery. But here in shallow water we found more orcas!

Tours have limits on how close we can move towards them in a boat, but the whales kept swimming closer. And closer. Eventually Dave killed the motors on the boat so we wouldn’t have a chance of hurting them. We lost sight of them for a moment until the boat started rocking and a HUGE male orca appeared within a wave beside the boat. A second later, in the next wave, we saw the face of a juvenile harbor seal who knows he’s in big trouble. He dove away and in close succession the large male, two adults, and two juvenile orcas started circling the boat. But where was the seal now?

Turns out he was an intelligent and resourceful seal, so he lodged himself safely between our boat’s propellers where the whales couldn’t grab him.

He rested there for 10 minutes or so while the guide considered shooing him away. He ended up disappearing on his own accord. The guide said he dived and can out-compete the whales in a breath-holding contest. The whales eventually moved west with us in search of an easier dinner. I loved how the baby whales were frolicking around doing little belly flops out of the water! Talk about an ideal day.

Last but not least – a review of Nanaimo bars. After consulting with my mom (an authentic Canadian), she says that the one I bought was about 6 times the size of the Nanaimo bar she grew up with. This makes so much sense! I couldn’t come close to finished the bar in one sitting – the white layer has a texture in between cake icing and fudge. Basically pure sugar sitting on top of a coconut, chocolate, and almond crust. Topped with a layer of chocolate ganache. A delicious sugar overload to share with friends.


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