Weird, Even Uneasy Science Beneath Two Oregon Coast Spring Break Faves: Cannon Beach, Seaside

Published 03/21/23 at 2:30 AM
By Oregon Coast Beach Connection staff

(Cannon Beach, Oregon) – It's no secret that Seaside and Cannon Beach are big, fave hotspots for spring break along the entire Oregon coast (with Coos Bay and Astoria catching up a bit, however, and Lincoln City in a close competition). Yet do you know their origin stories? (All photos Oregon Coast Beach Connection)

Real science is almost always far wilder than fiction. Star Trek couldn't hold a candle to what's really going with your favorite spots you dig for running around, hoisting kites or wading in the waves. Some mind-bending stuff is around you – maybe even a few real treasures.

Haystack Rock's Fiery, Freaky Beginning. All but a few of the headlands you see on the northern half of the Oregon coast come from something a bit spooky: a gargantuan lava flow that seared its way across proto-Oregon some 14 million years ago or so. And not just once, but dozens, maybe thousands of times. They came from a big hole in the Earth's crust about where the Idaho border is now, lumbering across 300 miles. Cape Meares, Tillamook Head and even Yaquina Head in Newport are part of this.

These lava flows were so powerful they plunged into sediment far offshore and then literally re-erupted at another location (the shoreline was maybe 70 miles inland then).

Called “invasives,” Haystack Rock was once part of a larger structure that came from this action. The rest of it eroded away, leaving the rock and its Needles. Still creepy to this day: that same hole in the crust is where Yellowstone National Park is now, and it will likely one day erupt as a super volcano. How Cannon Beach's Haystack Rock Was Created: Fiery Oregon Coast Tale

Silver Point bedrock (courtesy Jesse Jones, CoastWatch)

What Lies Beneath Seaside and Cannon Beach. Back in 2021, Oregon Coast Beach Connection was privy to a glimpse of something rare: bedrock beneath Cannon Beach. Thanks to CoastWatch - which keeps an eye on erosion, manmade issues and other aspects of changing beaches - a unique moment was frozen in time. At Silver Point, major erosion that winter ate away what little sand levels there were there and you could see the dark, almost black mudstone that's beneath the town's beaches.

This was rarely seen. Sadly, it only lasted a few days.

It's not the same black rock you see at Haystack Rock, or that which comprises Tillamook Head. That's basalt – an ancient lava flow – that made those structures, and it's about 14 to 17 million years old.

Silver Point as it normally looks, Oregon Coast Beach Connection

Seaside geologist Tom Horning said this stuff is softer than basalt as it's a conglomeration of things – many of which are much, much older than 18 million years.

The punchline here: it's the same stuff that's beneath Seaside. However, with Seaside there's about 150 feet of sand between you and the rubbly stuff below. So if you ever get a chance to see Cannon Beach's bedrock, you're looking at Seaside as well. -- Oregon Coast Storms Reveal What's Beneath Cannon Beach at Silver Point -- What is Beneath N. Oregon Coast's Seaside? Trippy Geologic Answer

Brown Waves, Whole Sand Dollars Between Seaside, Warrenton. With Seaside being the biggest hotspot for spring break on the Oregon coast, beaches are usually packed. But one beach is not: the extreme northern end of town at the 12th Ave access. Here, where the beach dead-ends at the Necanicum River (and where Gearhart begins), there's something unusual – and telling.

You'll find way more whole sand dollars here than anywhere on the Oregon coast. Part of that is fewer people and thus less broken ones. Yet there's a couple of things going on that simply bring more sand dollars onto shore.

Conversely, however, there are also a lot of whole sand dollars on parts of the Long Beach Peninsula on the south Washington coast. Brown Waves Return to N. Oregon Coast - It's a Good Thing and What Else It Means

All this has to do with the enormous amount of nutrients coming from the Columbia River, creating mass sand dollars beds just offshore. Nitrates and phosphates are much of it, according to Seaside Aquarium’s Tiffany Boothe.

In turn, those nutrients create a lot more phytoplankton as well, especially one kind that creates brown waves when there's huge blooms of it. However, nature is complex. So you'll encounter the thick, sometimes gooey brown waves all the way from Seaside to almost Astoria, but the masses of sand dollars only really happen around the Necanicum. See why here: Curious Bits About Sand Dollars on Oregon Coast / Washington Coast You Didn't Know

Hotels in Seaside - Where to eat - Seaside Maps and Virtual Tours

Hotels in Cannon Beach - Where to eat - Cannon Beach Maps and Virtual Tours

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Andre' GW Hagestedt is editor, owner and primary photographer / videographer of Oregon Coast Beach Connection, an online publication that sees over 1 million pageviews per month. He is also author of several books about the coast.

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