Submitted by Spaceman9800 t3_yrqb9i in Washington
I know about the famous Eastern Washington flood Basalts, but I'm curious if there are similar areas of exposed volcanic rock in Western Washington, perhaps around Mt. Rainier or Mt. St. Helens?
Comments
Zhenja92 t1_ivuzd06 wrote
I did a series of maps about the basalt flows a few years back for Nick Zetner, a geology professor at CWU. Here is a link to one of the maps that shows the full extent (I have maps showing the active flow in each year - but the brown shows the full area). https://www.dropbox.com/s/cipb9c7odsn5zv0/10_5madike.jpg?dl=0
AcclaimedGroundhog t1_ivv0k3l wrote
There is some columnar basalt at Narada Falls in Mount Rainier National Park, if I remember correctly.
PuzzleheadedOnion841 t1_ivv1lvk wrote
There is a beautiful section of columnar andesite up at Mt. Baker on the road to Artist Point. Can also be found around Rainier. So if you're just looking for volcanic rocks and not specifically basalt, you're in luck. There are also some great pillow basalts near deception pass and in the Olympics.
oblio3 t1_ivv4xkl wrote
If there are others like me who are discovering an interest in geology (in my case well after my school years), Nick Zentner has a few different series on YouTube.
The I-90 Rocks series he did and posted under the hugefloods name was a great entry point for me. Highly recommend for some easy to consume videos about familiar areas.
If you like them, he goes deeper on other channels.
Accurate_Humor948 t1_ivv5bt5 wrote
There’s columnar basalt up Reecer creek road north of Thorp
aimeec3 t1_ivvc5sl wrote
My years of taking NW Geology courses are finally gonna pay off!!!!
So Washington is geologically speaking actually many different "islands" pushed together. The coastline when dinosaurs walked the earth was actually in Montana. Over time as the pacific plate was subducted under the N American plate it also brought along Islands. Those Islands couldn't be subducted and instead become part of the N American plate. The subduction zone moved west and repeated this until you get the coastline we have now. Now, the flood basalt happened by huge fissures opening up on the East side of the Cascades about 17 million years ago. Now, by then the Cascades were formed so the basalt couldn't reach Western Washington except through the Columbia River Valley. So to answer your question most of Western Washington is silica based while eastern Washington is basalt, except in the Columbia River Valley and one other weird little outlier.
This outlier is a series of tunnels near Mt St Helen's where there was a period of basaltic flow about 2000 years ago. This 300 year period is the only time Mt St Helen's or any Cascade volcano history thay flowed basalt as opposed to the thicker more explosive silica. Geologists have absolutely no idea why or how this happened. You can visit the tubes know as the Ape Caves now. I highly recommend it as a spring/summer activity as the road up to it is closed in the winter.
Sorry for the Geology lesson.... I have had this information stored in my brain vault and saw my chance to finally use it. Hahaha
sarkarnor t1_ivvdwuj wrote
Thank you! I have recently been looking for geology stuff on yt.
BarnabyWoods t1_ivvfwsn wrote
There are a number of places in the Olympics where pillow basalt is exposed. Pillow basalt forms when lava erupts under the sea. One place you can see it is along Hurricane Ridge Rd.
Nixx_Mazda t1_ivvodnf wrote
I found my pictures of some of the stuff at Mt. Baker. Took these in 2003.
Nixx_Mazda t1_ivvoqvp wrote
Cool.
In college I took Geology 101 and we took a field trip down to the south end of Lake Sammammish. You can find fossils right off the freeway.
oblio3 t1_ivvplxu wrote
Not exposed on the surface but Ape Cave near Mt. St. Helens is basalt: https://wa100.dnr.wa.gov/south-cascades/ape-cave
"Ape Cave formed about 2,000 years ago, when an 8-mile-long lava flow known as the Cave Basalt poured down the southern flank of Mount St. Helens. As it flowed, parts of the lava started to cool, forming a hardened crust and creating an insulated tube for the still-molten lava flowing inside. Scientists estimate that the lava in the Ape Cave tube continued moving for as much as a year. Eventually, the last of the molten lava drained out through the hardened tube, leaving the interior empty. Over time, sections of the hollow tube collapsed from above, creating several natural skylights. The largest of these collapsed sections now forms the entrance to the cave."
Nick Zentner on Ape Cave: https://www.youtube.com/watch?v=Uks7Fq67YOk
Obvious_copout t1_ivvvfw3 wrote
Hwy 26 to Pullman has some great basalt! But you can find it anywhere along the Columbia river gorge in central Washington.
chriskabob t1_ivvwz5n wrote
There are some nice pillow basalts exposed both at Washington Park in Anacortes, and on Rosario Point in Deception Pass State Park. There's some nice columnar andesites up near Heather Meadows at Mt. Baker. If you just want to see some volcanic rocks, head to our local volcanos.
pwdrchaser t1_ivxj4c6 wrote
Can we ask for your expertise on granite geology? I’m located in SW WA and am looking for granite formation near me whether in OR or WA. So far closest I’m able to come to is the Hwy 2 corridor in the central cascades, but looking for closer access.
aimeec3 t1_ivyaduq wrote
Well all of the Cascades are silica/granite. You just have to find places where the soil has eroded away or where roads have been blasted through the mountains. It's harder to find open granite formations in western Washington because of all the trees. There is Granite Mountain off of I-90 or going up past Paradise on Mt Rainier is always a good bet.
pwdrchaser t1_ivyb1uu wrote
How about closer to Portland area? Seems like mostly basalt from what I have seen.
aimeec3 t1_ivybzxq wrote
Portland is right on the Columbia River delta that the Eastern Washington flood basalt flowed through to get to the ocean. If you go closer to to Mt Hood there should be some outcroppings here and there along the road. But if you want to see large batholiths then NE Oregon in the Elkhorn mountains or SW Oregon near Medford and Granite pass.
Again the reason we don't see as many large granite formations are because of the trees and soil covering them up. So you have to find where it as been eroded away or where there has been massive uplift.
pwdrchaser t1_ivydfz1 wrote
Awesome. Thanks!
robe_ot t1_ivykoyg wrote
Folks have already mentioned the pillow basalts on display in the Olympics, but it should also be pointed out that the eastern Olympics seen from Seattle are part of the Crescent formation which is made up of oceanic basalt. Look into the Siletzia story. There was a Hawaii or Iceland-like island that formed off the coast of Oregon millions of years ago and eventually accreted onto the western coast of North America. This means the northeastern and eastern Olympics are geologically quite distinct from the interior and western Olympics. In my mind you can kind of sense it when you peer into the range from atop peaks like Mount Ellinor and Mount Townsend, or even standing on Hurricane Ridge.
Optimal_Bird_3023 t1_ivywquu wrote
Came to say this. Between Yakima and Ellensburg you can see a lot of basalt layering. The Yakima canyon is beautiful.
ribrien t1_iw3pwro wrote
Worth the drive if you’re looking for rocks
hockey_stick t1_iwaipo6 wrote
If you're up for a walk on the beach, the flood basalts you mentioned in Eastern Washington can also be seen at Cape Disappointment State Park near Ilwaco. North Head Lighthouse sits on top of the basalt flow, but you can also go down to the beach to see where those basalt flows met the ocean.
[deleted] t1_ivuycml wrote
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