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  • Thanks to Subaru for partnering with us on this SciShow mini series. The all new 2020 Subaru Outback

  • helped us stay comfortable during filming.

  • [♪INTRO]

  • Stefan: Welcome back to Washington! This is the final

  • episode in our mini-series about the geology of Olympic National Park!

  • Alexis: So far, we've talked about Mt. Olympus and

  • an ancient that transformed Washington and now, it's time for one last story.

  • Stefan, let's hit the beach!

  • Stefan: Oh yeah!

  • Stefan: Last week when we were at Rialto Beach, you

  • might have noticed a bunch of cool rock towers in the background. Those are called sea stacks,

  • and these beaches in western Washington are famous for them.

  • Alexis: But these rocks don't just look cool. They

  • also tell a fascinating story about how this landscape has changed over the last few centuries.

  • Alexis: Welcome to Ruby Beach!

  • Stefan: We figured that while we were in Washington, we should

  • visit at least two place that have sea stacks. I mean, like, when in Romeright?

  • Alexis: Something like that. Anyway!

  • Alexis: So, behind us, are some of Ruby Beach's

  • famous sea stacks. Sea stacks can be made of all kinds of rock, but the ones here are

  • generally made of the sedimentary rock breccia and mostly-volcanic conglomerate.

  • Basically, that means they're made of a bunch of rocks that got cemented together.

  • Stefan: Meanwhile, the ones over at Rialto Beach are made

  • of volcanic basalt, sedimentary sandstone, and conglomerate, depending on

  • where you look.

  • Alexis: Exactly what the stacks are made of doesn't

  • matter that much, but the important thing to know is that these sea stacks are made

  • of harder rock than the stuff you tend of finding on the mainland. And that's important because

  • of how sea stacks are formed in the first place.

  • Stefan: Sea stacks form because of something called

  • preferential erosion.

  • You start off with a headland, or a piece of the coast that juts out into the ocean.

  • As the ocean waves come in, they get bent around the headland and end up hitting the

  • coast in specific spots. And that's where the trouble starts. Or the fun.

  • If the area where the waves hit is made of softer rock, or made of a rock that contains

  • some kind of fracture, the waves will erode it.

  • That leads to small indents in the headland, and then small caves, and then eventually,

  • the water cuts straight through. And then you're left with a sea arch!

  • Stefan: You can find sea arches all over the place,

  • but it's not like erosion stops once that arch is formed. The waves continue to

  • erode the rock, and over time the arch can get bigger until it eventually collapses into sea stacks.

  • Alexis: But the rock composition isn't the only

  • variable. According to a cool model published in 2014, the beach in front

  • of the sea stack is important, too.

  • The model found that really wide beaches tend to prevent sea stacks from forming, because they

  • act as protective barriers. Basically, the waves crash against the beach and don't

  • actually hit the headland.

  • Meanwhile, really narrow beaches can encourage sea stacks to form. In that case, the water

  • picks up all the sand and other sediment, and it rubs against the headland kind of like sandpaper.

  • So erosion happens faster.

  • Over all, this means that, if Ruby Beach were a lot wider, we might not have these rocks

  • to look at!

  • Stefan: So, the sea stacks at Olympic National Park

  • are really cool, but that's not the only place you can find them.

  • They're all over the world, from Scotland to Australia. And when you do find them, they can tell you somethings about the place you are visiting.

  • Alexis: For one, at the most basic level, you can

  • learn where the coastline used to be. Because anywhere there's a sea stackwell, that

  • used to be part of the mainland!

  • Stefan: Sea stacks also tell you that waves are mainly

  • approaching the coast head-on, rather than on an angle. When the waves come in sideways,

  • they erode mostly one side of a headland, and that makes it a lot harder for sea stacks to form.

  • Alexis: And finally, sea stacks tell you that there's

  • a sort of balanced system happening here. Kind of like we talked about in the Mt. Olympus

  • episode earlier on this trip!

  • If you find a sea stack, you know there's a good amount of sediment moving around

  • and eroding the cliffs, but not so much that it forms a wide protected beach that prevents erosion.

  • So, generally, when you find a sea stack, there won't be some kind of huge sprawling

  • beach stretching way out into the water.

  • Stefan: Instead, you're more likely to see something

  • like this!

  • Stefan: So while sea stacks are pretty cool, but they won't

  • last foreverprobably not more than a few hundred years, depending on how big they are

  • and what they're made of.

  • Alexis: They're a reminder that the land around

  • you is constantly changing, and that there's a lot you can learn if you know what to look for.

  • Stefan: Butthere's one more thing we

  • should mention about sea stacks. Because while they are really nice to look at, they are

  • also kind of dangerous.

  • Alexis: It's true. Like, in the late 1800s, one

  • ship near Rialto Beach got caught in some rough waves and foggy weather. Someone on

  • the board saw a sea stack through the fog and thought it was another boat, so they decided

  • to steer toward itand ended up crashing.

  • Stefan: There have actually been over a hundred

  • shipwrecks off the coast of Washington, due to sea stacks, rough waters, tons of fog,

  • and reefs are hiding just under the waves. So while these are nice

  • to look at during the daytime

  • Alexis: We're going to stick to dry land. And on

  • that note, we should probably head back to the car and tell Hank we're about done here!

  • Stefan: That sounds great! So until next time, thank you

  • for joining us on our road trip!

  • Alexis: Thanks to Subaru for partnering with us for this three-part road trip series, and for lending the support of an all-new 2020 Subaru Outback.

  • Stefan: We had to drive a lot to make these episodes, both

  • inside Olympic National Park and out, and all the features of the outback help make our trip a lot easier.

  • My favorite feature was the roomy cargo space! We fit our luggage and even film gear easily.

  • And with the hands-free power rear gate, I didn't have to put my bags down on the wet

  • ground to open the door. Which is always a struggle, right?

  • Alexis: If you want to learn more about the 2020 Subaru

  • Outback, you can check out the link in the description.

  • [ ♪OUTRO ]

Thanks to Subaru for partnering with us on this SciShow mini series. The all new 2020 Subaru Outback

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ワシントンはいかにして船の墓場になったかSciShowフィールドトリップ #3 (How Washington Became a Ship Graveyard: A SciShow Field Trip #3)

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    林宜悉 に公開 2021 年 01 月 14 日
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