Sunday, July 7, 2019

What I Did While I Was Out, part 2

I was out of the office for work again last week. This time I was a bit farther afield than Wyoming and the Dakotas; on the weekend of June 29–30 I was on Santa Rosa Island, one of the five islands of Channel Islands National Park. Here's a few photos from Santa Rosa:

This is a pretty representative view from the central part of Santa Rosa Island, featuring grassy and brushy vegetation over a lot of up-and-down topography.

You can't very well drive to Santa Rosa Island. Your options are boat or aircraft; I took the boat option, via the concessionaire Island Packers.

Complete with dolphin escort.

Once you have arrived, hopefully you have brought whatever you want or need, because you won't be able to hop over to the convenience store to pick up jerky and trail mix. There are no permanent human inhabitants on Santa Rosa Island anymore, let alone stores. There is almost no pavement, and the only vehicles are a few NPS trucks and such, so it's all hiking and camping for non-staff. This also means that most visitors will probably only see a small part of the island, unless they are up for some distance walking. We had access to the park vehicles, which sped up things, but even then it took a lot of driving because of the topography. Roads end up following ridge crests in many areas.

On the road.

I found the constant cool wind to make the field work very pleasant. Every trip is scenic, even when the fog has rolled in. When driving from the park facilities to various peripheral sites early in the day, we drove in and out of the clouds several times as we traveled up and down the ridges and valleys.

Looking east from the road, above the clouds and fog. Santa Cruz Island is visible in the distance.

Today the top land animal on Santa Rosa is the housecat-sized island fox. These little fellows are all over (I saw nine in one day) and they act like they own the place.

Like this one.

Santa Rosa Island is laced with canyons and valleys. Drainage isn't usually too active, but this was a wet winter, and we came across flowing water occasionally.

A canyon leading to the sea.

A canyon farther inland; this one was dry.

It's no secret that fossils have been found on the islands, most notably the "pygmy mammoth" Mammuthus exilis, but also a wide variety of plants, marine invertebrates, terrestrial and marine vertebrates, and marine microfossils.

The nearly complete 1994 specimen (cast) at the Santa Barbara Museum of Natural History (we saw another cast a couple of weeks ago). The non-dwarfed shovel next to the specimen gives an idea of scale.

Archeology is closely intertwined with paleontology here. Humans arrived on the islands by 13,000 or so years ago, and took a liking to them: shell middens dating from the latest Pleistocene throughout the Holocene are common, providing a glimpse not only at human activities and shifting food preferences, but also changes in the mollusk fauna over time. At the site that produced the famous "Arlington Springs Man", decomposed owl pellets chock-full of bones of the "giant deer mouse" Peromyscus nesodytes have been found at the same level as the human remains.

Shorelines have always attracted people; you can find a lot to eat in coastal areas, and if you have watercraft, it's a lot faster to travel by water than by foot.

Geologically speaking, the two smaller islands (Anacapa and Santa Barbara) are made up of Miocene igneous rocks with a veneer of Quaternary sediments, while the three larger islands (San Miguel, Santa Rosa, and Santa Cruz) have much longer histories. Santa Cruz Island has a lot of Jurassic metamorphic and igneous rocks exposed; the other two don't go back quite that far at the surface, but have Cretaceous or potential Cretaceous rocks at the surface. All three have marine rocks deposited during the Paleocene and Eocene, and marine and igneous rocks from the Miocene. The Pliocene is absent from all three, as far as can be told, but the Pleistocene is very well-represented with both terrestrial and marine deposition.

From the pier on Santa Rosa Island, it's easy to see the contact between the yellowish, tilted, well-bedded Beechers Bay Formation (or Beechers Bay Member of the Monterey Formation) and overlying Quaternary sediments. Incidentally, "Beechers" is pronounced and often written "Bechers", and no one is quite sure where the extra "e" came from.

And now for something completely different: Dino Fest is coming up next weekend (July 13) at the Science Museum of Minnesota. I'll be working a table, so maybe I'll see you there!

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