“I Can Feel The Boulders Rolling”

I have to admit that my first thought in the few seconds of this video was, “What the fuck are you doing, you fool? Get away from the wash!”

Then I discovered the person filming the video is a USGS hydrologic technician, and I was like, “Oh, right. Carry on, then.” This is definitely one of those don’t-try-this-unless-you’re-a-paid-professional sort of things. Much like climbing down into the craters of active volcanoes FOR SCIENCE.

These floods are scary dangerous things. Too many people don’t appreciate the power of water. But just watch that video. Look at the sediment load that water’s carrying. Listen to the roar. Consider they could feel boulders bouncing in the flow, just standing there at a relatively safe distance on the bank. Note the size of the channel these occasional floods have carved. It’s not a good place to be standing when the water comes pouring in.

And it comes fast, and hard, and without much warning. Flash floods have appeared in the desert on clear, bright, sunny days when the nearest rain is a hundred miles away. The moment you hear a rumble and a roar, it’s time to get the hell to higher ground.

Unless, of course, you’re a scientist, in which case you know how to do crazy dangerous things relatively safely. In which case, carry on.

Donors Choose: Final Stretch!

Right. So remember how I said I’d match two $50 donations? And remember how we had two challenges going on, so I kinda figured I’d split my fundage between the two of them?

Heh heh heh whoops. Left it too late. We are down to one unfunded challenge, thanks to your awesomeness. So I put down the complete matching donation on that one. Here ’tis:

Mah Contribution to the Cause

I also want to mention, strictly as an observation, that the only person currently beating us on Freethought Blogs is Jen McCreight, and she has traffic that is an order of magnitude greater than mine. Which, I think, just goes to prove that geologists don’t just rock, they are very gneiss, not to mention the schist.

Thank you, I’ll be here all week.

So, Ms. C’s library project only needs $97. We can do that. In fact, we don’t even need big donations to do it. Here’s a chance for those folks who can only afford tiny donations to make a huge difference. $5, $10, more, less, whatever – it all adds up. The Donors Choose Challenge ends Saturday, so time is of the essence. Get thee to my giving page.

But we’re not stopping there.

I’ve added two projects. They’re not cheap projects. But you know what? These projects will allow kids to get out in the field. They’ll get their hands on geology right out in the field, in Great Basin National Park. Field trip!

There’s nothing like a field trip for making a future geologist. I want to get these kids out in the field, people. I want to make this happen for them. And I believe you guys can do this.

So here they are:

1. Discovering the Wonders of Nevada. “Every year we take 150 fourth graders on an overnight field trip to Great Basin National Park. Our school is a Title One, 100 percent free or reduced lunch school. Our parents are hard working and very supportive, but can’t always provide the enrichment activities their children need. The fourth grade students look forward to the “Ely Trip” every year.” $1006 to go.

2. Exploring the Wonders of Nevada. “Every year we take 150 fourth graders on an overnight field trip to Ely Nevada. For many of our students, this is the first time they have been in a rural setting. Our school is in a lower working class neighborhood. Our students are well-behaved, enthusiastic kids who could use a little “boost.” Our parents are very supportive but can’t always provide the supplies needed for the school year.” $357 to go.

All right? Let’s do this thing. Again, you don’t have to be Aunt or Uncle Moneybags. Little amounts count. Every single dollar gets these kids closer to an experience with geoscience that will stay with them throughout their lives.

So. Incentives. I shall give thee incentives, because this is something we should all do together.

1. I’ll write a short story for the highest donor. You can even choose the subject, if you like, and you’ll get a paper copy complete with autograph, if you wish. You’ll have to give me until the end of the year, because I’m stupid enough to try NaNo this November, but I’ll have it written and sent to you in January. Yes, I will haul my arse to the hated post office just for you.

2. The second-highest donor will get a personally-collected hand sample. That’s right! I’ll post a list of places I’m going this summer (once I know what they are!), and you tell me what hunk o’ beautiful geology you want me to package up and mail to you.

3. I’ll match 4 (count them, 4) donations of $50. So you $50 folk get to double your money! Don’t let that stop you from donating more, of course! And if you guys manage to fund these projects before I can whip my credit card out, you can each pick a project of your own for me to donate to.

4. Starving Students Offer: Those of you too strapped for cash to manage more than small donations can still get a little something! Send me an email telling me what you’re studying, why you chose your major, and why you donated, and I’ll showcase you guys on the site. Plus, I’ll write a poem for the person whose note makes me punch the air and shout, “Yes! Science can haz future!” Same caveats apply as the short story deal.

5. I’ve also got some super-snazzy Mount St. Helens posters, so all who have donated to any of our projects and want their names in for that have a chance at winning one of Mother Earth’s great works of art. Yahoo knows me as dhunterauthor.

We’ve got until Saturday, my darlings. Make it so.

Why I Love Scientists: Kraken Kraziness Edition

This exchange happened recently on Twitter, retweeted by Brian Switek, and exemplifies why geologists and paleontologists generally get along. I present it to you in its full glory: scientists making fun of the kraken story. Enjoy!


Encouraged by recent media attention given to the #Kraken "study," I am now working on "Pegasus landing traces" study for next year's GSA.
Anthony (Tony)Martin
Moreover, the "Pegasus landing traces" precede Hyracotherium in the fossil record, which proves that horses are secondarily flightless.
Anthony (Tony)Martin
@ It's amazing what tracks can tell us! Our footprint collection has what looks like baby Pegasus tracks. Social behavior?
Andrew A. Farke
@ @ @ When you all find the flying trilobite nests, I will laugh maniacally.
Glendon Mellow
@ @ Agreed, and we need at least 3-4 talks about how all of those "theropod feathers" in China are actually equine.
Anthony (Tony)Martin
@ @ It's all so obvious, isn't it? Nature News, here we come!
Anthony (Tony)Martin
@ @ Nature News. . .heck, we're going for Nature! With feathers, it can't fail.
Andrew A. Farke


You Call Those Evil Volcano Lairs?

They’re quasi-evil. They’re semi-evil. They’re the Diet Coke of evil…

Erik Klemetti may sneer at the Geological Society of London’s Top 5, but Mt. Erebus? Sure, he’ll have well-dressed minions, but he’ll also be too ice-bound for true evil. Jessica Ball’s on to something with Pagan Island, but her evil lair will be overrun with tourists within six months. Garry Hayes has a beautiful evil setting in Mount Shasta, but everyone knows you can’t rely on Lemurians to carry out one’s plans for world domination. Silver Fox isn’t disclosing the location of her evil lair, which is wise, but it’s not even a volcano. You can’t have an evil volcano lair if there’s no volcano.

No, the truly evil geologist knows there’s only one volcano that qualifies as an Evil Volcano Lair.

Olympus Mons. Image Credit: NASA

It’s three times the height of Everest. What evil geologist wouldn’t want their lair located in the tallest volcano in the solar system? And at 370 miles wide, there’s plenty of room for an evil empire to spread out. This will be critical as plans for world – nay, solar system – domination come to fruition. Since Olympus Mons covers an area the size of Arizona, no henchmen have to worry about doubling-up.

Olympus Mons relative to Arizona. Image Credit: NASA/JPL

It has a total of six calderas in its summit, which are up to two miles deep. These are idea for placement of death rays and lasers and other implements necessary to the proper functioning of an evil empire.

Olympus Mons Calderas. Image Credit: ESA/DLR/FU Berlin (G. Neukum)

And the volcano’s outer edge is an escarpment up to five miles high, with a wide moat roughly one mile deep encircling. Every lair should have a moat. We don’t even have to dig one, thus freeing my henchmen for other nefarious tasks.

As an added evil bonus, Olympus Mons’ extreme elevation means that any pesky do-gooder secret agent types will not be able to parachute in. There’s not enough atmosphere up there for a parachute to slow their decent. I don’t expect them to land. I expect them to die

And a thick dust layer will bog down any rovers my nemesis manages to sneak up there. This will not be a problem for me and my evil lair construction equipment because I am an evil genius. I’d tell you my plans for overcoming the technical obstacles, but then I’d have to kill you.

Olympus Mons is loaded with lava tubes, which provide ideal locations for cunning and complicated traps. Some of the tubes will be quite large, which will give our lair the proper deep, dark, sinister cave ambiance. Ambiance is important, and should never be underrated in an enterprise of this sort.

One may even find water-saturated zones in the sediments beneath the volcano, which will still be toasty warm due to residual heat from the magma chamber and the geothermal gradient. This ensures my henchmen will always have access to hot showers without diverting critical energy resources away from the death rays, lasers, et al. As dirty henchmen lead to an unhappy evil empire, this is an important consideration. Then again, who needs henchmen when you can have… robots! So perhaps I shall keep all of the hot water for my own personal use.

Olympus Mons is suitably close to Earth for climactic takeovers to be easily launched, yet far enough away that the place will not be overrun daily by pesky secret agents. Viruses can be mutated by leaving them outside the protective shell of the ship while in transit, thus ensuring victory over Earth’s population. And additional funds to finance the evil empire can be obtained by selling transport and renting facilities to scientists, who will not be able to pass up the chance to personally investigate the Red Planet. Geologists will be given a discount, of course.

With Olympus Mons as my evil volcano lair, nothing shall stop my evil plans. Nothing!

Information and images filched from: Wikipedia, NASA’s Mars Exploration Program, ESA’s Mars Express, and the NSSDC Photo Gallery. Special thanks to the creators of Austin Powers and Dr. Horrible’s Sing-Along Blog. Stay evil, my friends!

Accretionary Wedge #38: Back to School (Hogwarts, No Less!)

The 38th edition of the Accretionary Wedge is up at Anne Jefferson’s place. She’s done a marvelous job, and so have all of the geobloggers who took her back-to-school theme and ran with it. There’s even a Harry Potter motif! This is the edition that inspired the post that ended up nominated for Open Lab, and there’s far better stuff than mine over there. Go enjoy!

Why are you still here? Oh. Right. Some of you have never seen the Accretionary Wedge before. A few brief explanations would appear to be in order, then.

The Accretionary Wedge is a geology carnival that began way back in 2007, which is practically the Cambrian by intertoobz standards. Every month, the host picks a theme, and then the rest of us scramble to write up something suitable. I got a little weird, actually. Next month it’s probably Barbies. Look, we take our science seriously, but that doesn’t mean we don’t get whimsical with our topics. A good time is had by all, and no matter how odd the topic, there’s a lot of gorgeous geoscience involved.

As for the name, an accretionary wedge forms when marine sediments get scraped off oceanic plates as they subduct beneath continental ones. All sorts of stuff ends up jumbled together. What better name for a geoblog carnival, then, amiright?

Right. Now that you know all about it, go immerse yourself in all the wonders over there.

Right. I Want to Try Something.

There’s a Welsh phrase I love very much: “Like killing snakes.” Means “very busy.” I’m like killing snakes right now. The start of the Winter Writing Season is always like throwing a grenade into the middle of my life, and this time, I decided to go nuclear, what with starting the Geokittehs blog with Evelyn, joining Freethought Blogs, offering to do some of the social media work for Burien Little Theatre, and participating in the Skepticism 101 panel at GeekGirlCon. And I’m not going to tell you the major cell phone carrier I work tech support for, but I’ll put it like this: we’re getting the iPhone 4s, which means they’ve closed the vacation calendar, opened up overtime slots, and are basically expecting us to be like killing snakes at a snake farm in which some mad strange person has been giving the snakes fertility drugs.

As I said, busy.

And that won’t leave as much time as I like for in-depth research for meaty geology posts. Not that we won’t have meaty geology posts. We will, at least a few. I’ll also be highlighting my beloved geobloggers as the weeks go by, because they deserve to be known and you’ll be happy to know them. But I’ll also need topics I can do as a hit-and-run. Which brings me to a somewhat pathetic cry for help.

Your mission, should you choose to accept it, is to provide me with quotations. I loves me some quotations. Give me your favorite geology and/or science quotes. Bring me the ones that inspire you, get right down into the core of you and light a bright little fire. And what I shall do with those quotes is use them as a jumping-off point for posts. Who knows what will come of them? Who knows what I will make of them? Only way to find out is to place them in my hands and see where they take us.

But that’s not all!

Perhaps there’s a subject you’d like me to pontificate about. Perhaps you’d like my opinion on some matter. Perhaps you’d like to show me something outrageous and see if it gets up my nose far enough for the Smack-o-Matic to come off the wall. Believe it or not, I’m not nice all the time. You might like me when I’m angry. You can have a look through the archives, now that our own Jason Thibeault has managed to migrate them over, and see. I figure a good rant’s like a brisk run: good for the blood on occasion. We might want to engage in one at some point.

And if you have pictures of some very delectable geology you’d like to throw my way, I could do up a nice showcase of same. Perhaps you want to tell me a little about your field work, or a particular bit o’ geology you know and love. Write me up a paragraph or two, send me a photo, and we’ll display it here. Yahoo knows me as dhunterauthor. I’m not at all hard to find.

That should maintain this establishment’s reputation for quality whilst I’m also engaged with trying to lock some fiction into a full nelson and get it pinned to the page.

Thank you in advance, my darlings, for your kind assistance.

And while we’re on thanks, go over and show Jason some love. He worked his heart out getting the archives online here, whilst he was also responding to others’ pleas for help, and he deserves a tanker truck full of his preferred beverage. Muchas gracias, Jason!

Donors Choose: We’re Rocking It!

Well, of course we are, we’re lovers of geology.

You, my darlings, have been remarkable. Two days in, and you’ve already got two projects funded. I can’t tell you how proud I am of you!

The teachers have sent you all lovely thank-you notes, and I shall post them here:

Project 1: Women and Hands-on Science. Funded!

Dear Karen, Mayen Davis, Anne, Yahoo! and The DonorsChoose.org Team, 

My students and I would like to thank you again for your donations to our science education. I have already told them about the donations and they are ecstatic. I believe that with the right tools we can teach our young girls that education is the key that will open many doors for them in the future. Many of the girls are convinced that science just isn’t fun. With these materials, I can show them just how fun and exciting science can be and possibly spark new ideas for their future careers!Thank you again. You are making a difference in the lives of these girls.

With gratitude,
Ms. D

You see what a difference you’ve made, there? These are young women who are about to discover what we already know: that science is incredible good fun. You’ve just given them a key to the wonders of the world.

Project 3: Geology Rocks! Funded!

Dear Andrea McCormick, Mrs. Patten,, Maureen Ilg, Nora, Joe and The DonorsChoose.org Team, 

I just wanted to express my sincere gratitude for your generous donations. The Geology Centers and activities will have a significant impact on my students. We now have the opportunity to have more interactive and engaging lessons.

I plan to use the geology kits to help students identify the three main rock types, how they are formed and the characteristics of each. The center activities will allow the students to explore geology concepts independently and reinforce what they are learning in class.

I can’t wait to show my students the rock samples and get started on some hands-on experiments and projects!

With gratitude,
Ms. B

You’ve just got some young hands on science, my darlings!

We still have two projects to fund:

Project 2: Science Rocks! $303 to go

Project #4: Rock Out: Learning About Rocks, Minerals and Geology. $254 to go

The way you lot are going, I don’t imagine it’ll take you long. Let’s do this thing!

Now, you might have noticed by now that the menfolk are vastly outnumbered by the womenfolk in the donation department. You, there, you with the Y chromosome. Yes, you! Step up and represent. Let’s get some equality going here!

At the Beginning of the Universe…

there was geology.

Oh, I know, some folks will tell you it was physics. Yes, there was that, too. And there might be a few who argue for chemistry, and we’ll grant them chemistry. Of course those things were there. Can’t have a universe without them. Not a universe like ours, anyway.

But geology was hiding within those things. As stars came together, as they began forging elements, as those elements exploded out into the universe and gravity gathered them together again, geology, like life, looked at all that lovely physics and chemistry and said, “Yum! I can do something interesting with that.” And oh, it did.

People think of geology as an earth science, and yes, earth’s where humans figured it out. Right there in the name, geo, planet earth. But other planets have rocks. And the elements that formed the earth were, like the elements that form us, born in the stars. Biology will still be biology when it’s applied to aliens. Geology is still geology when applied to other worlds, and we’ve beaten life twice now: there were rocks before critters, and we’ve gotten our hands on space rocks before space critters. So there.

So that post I linked to up above, that’s a post I want you to go read. Because my friend Ryan at Glacial Till, who is doing absolutely scrumptious things with meteorites, he’s teaching you geology from the beginning. Right from the beginning of time. And there’s another lesson within, one he didn’t state explicitly but is there, like geology at the beginning of time, hiding in plain sight all along. And the lesson is this:

You don’t have to give up the stars to study the earth.

You wanna be a geologist but study outer space? You can do that. Absolutely, you can. What are the inner planets called? Rocky planets, thankyouverymuch. What are asteroids? Rocks. Big ol’ space rocks. Moon’s got rocks. There’s rocks everywhere, all over solar systems, and sometimes, those rocks land on us. Sometimes, we land on them.

So yes, you can have your geology and whatever else you like. You can have your geology, and your astronomy, and your physics, and your chemistry, and your biology, too. You can have it all. Why do you think I love geology so very, very much? Because it’s got everything.

So get over to Ryan’s place. Let him show you where geology began, and where it will take you next.

Ryan's First Meteorite: "NWA 2965- Exposed interior of the meteorite. Also shown is a polished sample from a different portion of NWA 2965." Filched with permission of author.


Tomes 2011: All Science All the Time Edition

Oh, dear. I think I just heard the sound of bookshelves screaming in anticipation. Poor overloaded darlings. They’ll just have to toughen up and take it, or rely on e-readers to lighten their load. We’ve got some excellent books on tap this edition.


The Stuff of Thought

There are two things Steven Pinker always combines that I adore: the science of the mind, and language. This book delivers both in copious amounts. A few myths are dispelled, quite a few more insights given, and there’s an entire chapter on metaphor that should have any self-respecting writer screaming for joy.

The chapter on names shall greatly interest those following the Nymwars Saga.

And it’s all delivered in the gorgeous, clear, playful prose Steven’s known for. There’s absolutely nothing not to love in this book that I could find.

It’s meant to be third in a trilogy: the first two were The Language Instinct and Words and Rules. But if you haven’t read the other two, no worries. This one stands comfortably alone. That’s not to say you shouldn’t read all three, especially The Language Instinct, which is fantastic.


Crater Lake: Gem of the Cascades

This is a reasonably comprehensive and utterly enthralling book on Crater Lake. I’ve read a lot about Mount Mazama and the eruption that created Crater Lake, but this book contained a lot of things those other sources didn’t. It covers everything from its discovery to its future. The color illustrations are delicious, the geologic information clearly presented and easy to understand without being melodramatic or simplified beyond toleration, and the little info boxes and explanatory diagrams add to rather than distract from the whole. I dipped into it during our Oregon trip, meaning to skim a bit. I finished it before we’d left for home. It’s that easy to read, but I didn’t finish it feeling like I’d been spoon-fed: my brain felt pleasantly full of completely intriguing information. And it certainly made visiting Crater Lake more interesting.

I really can’t recommend this one highly enough. And, bonus, the 3rd edition is practically up-to-the-minute.

Source is moi.

Where Terranes Collide

Okay, so I had to snap a photo of it to get a cover image, and it’s rather hard to find, but if you have any interest whatsoever in the North American Cordillera, then the effort to acquire this book shall be rewarded. It was written by C.J. Yorath, who worked for the Geological Survey of Canada for a great many years. The man knows his stuff. He knows it so damned well that even if you are a grammar guru, you will be able to forgive the occasional typos.

There were a lot of ups and downs in this book – up one set of mountains and down another, from the Rockies to the coast. He takes you on a field trip through the chaos of a subduction zone, and it’s one hell of a ride. Then, he introduces you to the people behind the data. I love the paeans to the geologists he’s known and worked with. And I love the inside look at the way geology happens – arguments over data, banging on rocks, the rough stuff that the public doesn’t get to see before beautifully polished results are printed. This felt like being an insider. And now I’m going to have to go hunt down his other books…



I dearly love Oliver Sacks. I dearly love music. I dearly loved Oliver Sacks talking about music. This book is a total treat. If you’ve ever read any of Oliver’s work before, you know his prose is like really good chocolate and that the subjects he explores are fascinating. This exploration of music and the brain caused me some difficulties, because I had things I was supposed to do and didn’t do them. Went to lie abed and read.

There are so many incredible stories in here: of how music affects people who are so damaged it seems nothing can reach them, of how music affects us, the weird things and the wonderful things music can do. I have to admit that it scared the crap out of me at times: when you’re reading Oliver Sacks, you realize just how many things can go drastically wrong with a human brain. But it also delighted me right down to my toes. If you have any love of neuroscience, music, or stories about human beings doing remarkable things, you’ll delight in this book, too.


Road Guide to Mount St. Helens

I’m not actually going to say much of anything about this book. It’s not because it’s bad – far from it. It’s a wonderful, handy little guide suitable for slipping into a pocket or purse as you explore Mount St. Helens. Pick up a copy at the visitor’s center at Silver Lake on your way up.

But I won’t tell you all about it, because you can go read it for yourself, right now. Just click the link above. The authors were kind enough to put in online, for free.

So go on, then. Go have a read. Just this once, your wallet and your bookshelves will both be sighing with relief, and you’ll still get to enjoy a good book.

Prelude to a Catastrophe: Silver Lake

Let’s have a road trip, shall we? Yes, I do know we were in the middle of Oregon, getting ready to shove our noses against some particularly delicious road cuts, but this is a virtual car – we can skip states in the blink of an eye.

So hop in. We’re on our way to Mount St. Helens today. The skies are very nearly clear – by Washington state standards, anyway. Warm sun mingles with a cool breeze that snickers about autumn’s imminent arrival. You’ve got your nose plastered to the car window as we drive up Spirit Lake Memorial Highway from Castle Rock. All you’re seeing at this point are low hills and a flat bit of valley, plastered with green stuff. Biology is a perennial problem for geologists round here. You can barely see the hills for the trees. And you can’t even tell we’re driving along the shore of a lake. But here it is: visible in satellite views, anyway.

View Larger Map

We turn off at the Mount St. Helens Visitor’s Center. Lovely building, quite a lot of nice displays, and a nice nature trail along Silver Lake.

And you’re just burning for your first glimpse of Mount St. Helens her own self, but the clouds aren’t cooperating. That’s quite all right, because I want you to focus on the lake for a bit. Maybe it’ll help if I tell you Mount St. Helens created it.

Silver Lake, looking east.

This isn’t the best place to be if you don’t like (geologically) frequent lahars. The Toutle River, which has its origins on the north and west flanks of St. Helens, passes by just a bit north of here. It has a distressing habit of frequently channeling lahars. Some of them happen when Mt. St. Helens has a bit of an eruptive episode. Others happen when debris dams holding back bodies of water like Spirit Lake fail. Next thing you know, there’s quite a lot of rock-filled mud sloshing round the place. Happens all the time.

Now you’re looking for deposits from the 1980 eruption, aren’t you? Don’t bother. Even if the riotous vegetation wasn’t hiding all the lovely geology, you wouldn’t see much. 1980, for all it left a mark on us, didn’t really touch Silver Lake. Those lahars kept themselves to the river channel, and only left deposits about two meters thick. A mere six feet. Nothing a river can’t clear out in thirty years.

Not that it didn’t get interesting. Here’s a nice USGS photo of a house on the riverbank near Tower Road, not far from here, that shows how much damage was caused even thirty miles from the volcano:

USGS Photograph taken on July 16, 1980, by Lyn Topinka.

See how the paint got stripped and the windows busted out on the first floor? And the poor tree trunks are a bit scoured. Roads didn’t fare well, either – State Route 504 wasn’t exactly drivable two miles upstream of the Coal Bank Bridge.

USGS Photograph taken July 5, 1980, by Robert Schuster.

Certainly no shoulder now, is there?

I’m showing you these images to impress upon you the power of a lahar, and as a prelude to telling you this: the one that created Silver Lake was a hell of a lot bigger.

The lake’s only 2,500 years old. One day, around the same time Greece was starting to really come into its own and the Buddha was holding up flowers and waiting for one man to smile, Mount St. Helens had an episode. It’s called the Pine Creek eruptive period. Oh, baby, she blew. Pyroclastic flows everywhere, and four lahars. We’re especially interested in PC1, the lahar that created the placid little lake we’re viewing.

Silver Lake, looking west.

Mount St. Helens has a habit of unleashing debris flows that dam up lakes. She’d dammed Spirit Lake (or possibly an ancestor thereof), but hadn’t done a thorough job of it. The debris dam failed repeatedly. The first massive outburst scooped up all the lovely loose alluvial and volcanic deposits it encountered and mixed them up in a nice, thick lahar that went thundering down the Toutle River. PC1, as it’s known, was historic, the largest ever to travel down the river. Above Coalbank Rapids, it discharged at 200,000-300,000 meters per second. To put that in some perspective, imagine the middle bit of the Amazon racing down the Toutle River valley at flood stage. Now imagine it isn’t merely water, but a slurry of rocky mud. That’s huge. Far larger than those paltry little lahars we witnessed during the May 1980 eruption.

And when it reached Coalbank Rapids, it found itself facing the same problem as a stadium crowd stampeding out the exit at a sold-out concert: a constricted egress. All that mud had nowhere to go but up-valley. It spread out, burying the landscape under thick sediment and rock, and a little tributary creek named Outlet Creek discovered it suddenly didn’t have an outlet anymore.

It wasn’t strong enough to cut through that enormous quantity of debris, so it ponded behind the lahar. Silver Lake is, in fact, a lahar-margin lake, and a rather large example of the breed. It’s over fifteen square kilometers. But before you get too impressed, keep in mind it’s only about 5 meters (16ft) deep at its deepest. Some measurements have it shallower. If you stand there waiting for a catastrophic flood as the lahar dam fails here, you’re going to be desperately bored. They actually had to install a weir and a drainage channel in 1971 because it got backed up in stormy weather.

Silver Lake shore, looking east

So, as you look east hoping for a glimpse of St. Helens, keep in mind you’re looking toward the spot where a ginormous lahar wreaked havoc a geologic moment ago. Go diving – okay, probably more like wading – in the east bit of the lake, and you can find that old lahar under all the detritus. Down here at the western end, where the lahar didn’t reach, it’s mostly clay, silt and sand, with a bit of peat. I swear this lake’s aspiring to become a coal field someday.

The little basin it fills is surrounded by mid-to-late Eocene volcanics, lots of basalts and basaltic andesite. This area’s seen a lot of volcanism as continents collided. Kick around this quadrangle (pdf), and you’ll even find our old friends the Columbia River Basalts, along with the birth of the Cascades and plenty of deposits from Mount St. Helens her own self.

And there she is, the grand old girl, just barely peeking out from the clouds at last:

Mount St. Helens from Silver Lake

We’ll kick round here a bit longer, among the birds and dragonflies and peaceful marshy lake life, before we get back in the car and head up the road to see firsthand just what a lahar does to your nice new house.


Scott, K.M., 1989, Magnitude and frequency of lahars and lahar-runnout flows in the Toutle-Cowlitz River system: U. S. Geological Survey Professional Paper 1447-B (pdf).