Accretionary Wedge #41 Contribution: Slip-Sliding Away

I’ve been thinking about my own contribution for December’s Accretionary Wedge for over a month now (hopefully giving everyone else all the cover they’d need for late entries), but the time has come to write it up and move on.

I’ve been fairly fortunate in my time as a geologist to witness a volcano erupting firsthand in Hawaii. If I tried to tell you that I’ve directly experienced a more memorable geological event (at least to this point in my life), I’d be lying. I’ve also had the chance to feel a couple of very small earthquakes firsthand in New Jersey (Ramapo Fault), Hawaii (Kilauea Volcano), and Kansas (Oklahoma quake that triggered this Accretionary Wedge topic). I slept through an even bigger quake (M7.3 Landers, ~150 miles away) during my first field season, and saw the damage firsthand before the day was out. This past spring I saw the Mississippi River at a record flood crest from the safety of the levee near the Old River Flood Control structure and drove across the Morganza Spillway with 19 gates open, sparing New Orleans from another watery apocalypse. These last two may have been the most significant geological events I’ve witnessed firsthand. Nonetheless, the event I’m choosing to write about is a different event altogether.

The geological event that is the focus of this post is the Nardi Road/Goulais River landslide of October 13, 2003. Although this event was of a more local scope than some of the ones I enumerated above, I was able to witness firsthand the profound consequences for those who experienced it most directly. I was fortunate to be able to see and document the consequences with my Geoenvironmental Systems class less that 24 hours after the slide occurred. Mr. and Mrs. Norlin, whose safely rode out the slide in their red-roofed house (which features prominently in a number of images below, were kind enough to grant us permission to examine the slide in firsthand detail, and it must be noted that their spirits were remarkably good, despite the ordeal they had so recently survived.

141-4193_IMG
Norlin House and Suburban

.

For the most part, I’ll let the pictures do the talking – the full set of images can be seen on Flickr. The immediate triggering event for the landslide (or more accurately, a rapid, progressive series of rotational slumps) is unclear and may never be known. In a larger sense, this area was located on a cutbank of a meandering section of the Goulais River. The slump was rooted in a thick sequence of varved clays deposited at the end of the Wisconsinan Ice Age, as well as alluvial sands. There have been a number of other slides of this type in the region historically – in fact, our class had already examined the deposits of one such slide on the south shore of the Saint Mary’s River just a few miles west of Sault Ste. Marie, MI earlier in the semester. Although this event took place long before I had my first GigaPan, I did already own my first digital camera, and I shot a number of panoramic shots along with the many individual images seen below.

141-4182_IMG
Dennis Guimond’s House, next door.

.

141-4179_IMG
The Norlin’s House and a shed

.

141-4170_IMG
The Goulais River, near the toe of the slide.

.

GoulaisRiverSlideLoc GoulaisRiverSlide1
Location of the Nardi Road/Goulais River Slide (Google Earth)

.

GoulaisRiverSlideApr2005 GoulaisRiverSlideMay2007 GoulaisRiverSlideMarch2010
Evolution of the Landslide Toe, April 2005 – May 2007 – March 2010

.

141-4154_IMG
Varved glacial clays are visible in a crevasse beneath a thin mantle of sand. Detachment surface is locally dipping about 45 degrees. Faint “slickenline”-like traces were still visible in the loose sand on the detachment surface in the days immediately after the slumping event.

.

141-4164_IMG
Tension gashes formed in the “lower plate” of this detachment surface within 24 hours of the main slip event.

.

141-4181_IMG
Kelsey Anderson points out a normal fault where the “lower plate” of this detachment surface (now horizontal) has been offset within 24 hours after the main slump event.

.

141-4188_IMG
General Chaos and Mayhem, LSSU students for scale.

.

142-4223_IMG
High angle detachment surface near headwall. Note slip direction on the detachment surface is delineated by sand and soil still coating the muddy surface. Varved clay sediments make up the footwall of this block.

.

141-4190_IMG
Headwall of the slide complex. Sandy alluvial sediments and soil make up the highest layers; varved clays are lower down. The Suburban had been parked outside the carport and buried itself vertically during the event. Geology students for scale.

.

143-4314_IMG
Slicklenlines and boot prints in the lower portion of the slide.

.

143-4334_IMG
Detachment surface and varved clays near the headwall of the slump.

.

141-4178_IMG
Evidence for late-stage lateral shearing. These horizontal slickenlines were formed as a cluster of maple trees was dragged laterally toward the end of the slide sequence.

.

142-4241_IMG
Trace “fossil” where a tree trunk indented the varved clay sediments of this block.

.

142-4259_IMG
Tree trunks with clay from the impact above.

.

142-4266_IMG
The “Birch Tree Block”

.

141-4191_IMG
Another great day in the field.

.

You can also consider this the final call for submissions for Accretionary Wedge #41. I’ll be writing up the summary post next (tomorrow).

Geology Office Hours – 19 Dec 2011

Here’s the video of yesterday afternoon’s Geology Office Hours Google+ Hangout. Our main topic was advice for geology undergrads looking to apply to grad school, but we also began to answer a really big question about how the Earth has differentiated.

A reminder that the Geology Office Hours hangouts are now on holiday break. Next one is scheduled for Thursday, January 5, 2012.

Upcoming Google+ Hangout: Advice About Grad School for Undergrad Geology Majors

By now, you’re probably well aware that I’ve been holding “Geology Office Hours” hangouts on Google+ most Monday and Thursday afternoons at 4:00pm CST (2200 GMT). The topics are usually unplanned and tend to go wherever the participants interests lie on any given day. We’ve had some great conversations on topics as diverse as the unfolding eruption sequence at El Hierro, approaches toward teaching geologic time to diverse audiences, the likelihood of fracking causing the early Movember Oklahoma earthquakes, and whether submarine volcanic eruptions could go Plinian, to mane just a few. I’ve been very pleased with the results and I intend to continue these hangouts for the forseeable future (after a holiday recess – more below).

Google+ Hangouts Promo ImageAfter last Thursday’s hangout +Brian Schrock commented: “Maybe we could do an office hour sometime regarding grad school for us undergrads. I always seem lost in the grad school process despite all the help my professors are giving me.” I think that’s a great topic for one (or more) of these hangouts, so I’m designating it as the primary topic for this Monday’s hangout. Ideally I’d like to have a couple of other geology profs and/or current grad students share their experiences and insights, in addition to as many undergrads with questions as possible. I’ll plan to record the Hangout for those that can’t make it. Also, if there’s enough interest, possibly we’ll repeat this topic sometime in the new year.

For those interested in participating, you’ll need a Google Plus account and a computer (desktop/laptop/Android smartphone), ideally with either a built-in or USB webcam (I’ve had great results with a Logitech 720p Webcam Pro 9000). If you haven’t done a hangout before, read up on Hangouts and make sure to install the required Google Talk add-ons ahead of time (you’ll be prompted to do this).

Finally, I’m going to take a two week break for the holidays from my regularly scheduled hangouts after Monday’s hangout. If there are big geological events in breaking news I may hold an ad hoc hangout or two, as necessary. Otherwise, hangouts will resume on Thursday, January 5, 2012.

On the Passing of Arnold Bouma

Although my specialty in geology is not as a sedimentologist, I did do my Ph. D. thesis in a basin full of turbidites (looking at provenance of conglomerate clasts). Thus, the news of yesterday’s passing of Arnold Bouma gives me a reason to tack on one more set of geology field photos of the Bouma Sequences I knew best. In memoriam…



Turbidites, German Rancho Formation, Salt Point State Park, California
Launch Full Screen Viewer | View in Google Earth 4.2+ | Take Snapshots & Comment

.

Bouma Sequences

.

IMG_4600

Field Exam

It’s all fine and good to enjoy the breathtaking geological vistas of our National Parks, but what drives the student of the Earth is reading her rocks to attempt to understand her past. So go ahead and get your noses up against this outcrop and do your best to interpret what you can see here. This is a “no hammer” outcrop. Take as much time as you need and place your answers in the comments.



Weathered Sedimentary Rocks near Ticonderoga, NY
Launch Full Screen Viewer | View in Google Earth 4.2+ | Take Snapshots & Comment

.

IMG_8507

.

Good luck and may the force be with you!

Framing the Bride

Some brides are so beautiful they can’t fail to draw your attention. So it’s no wonder that no matter where I roamed in Yosemite Valley my camera was repeatedly drawn to Bridalveil Falls.

239-3979_IMG
From the Bridalveil Falls parking area

.

239-3958_IMG
Beside the Merced River

.

239-3978_IMG
Further downstream, beside the Merced River

.

239-3995_IMG
From Inspiration Point

.

This is Thursday’s entry in @GeoEvelyn‘s Geology Picture of the Day geomeme. And in case you hadn’t guessed it yet, the geologic feature in question is a hanging valley.

Some Swell Gypsum Veins

One of the big news items out of the #AGU11 meeting was confirmation that Mars rover Opportunity had recently discovered the most unambiguous evidence yet of water on Mars. The evidence? A vein of gypsum, nicknamed “Homestake”. The vein takes its name from the Homestake Gold Mine in the Black Hills of South Dakota, where an open pit beautifully exposes some Tertiary felsic dikes crosscutting Precambrian metavolcanic rocks. Although the “Homestake” gypsum vein on Mars (below) is unlikely to contain significant quantities of elemental gold, it was a nonetheless a metaphorical bonanza because it is the best evidence yet that water once flowed underground on Mars in ways very similar to well understood processes here on Earth.

Homestake Gypsum Vein
“This color view of a mineral vein called “Homestake” comes from the panoramic camera (Pancam) on NASA’s Mars Exploration Rover Opportunity. The vein is about the width of a thumb and about 18 inches (45 centimeters) long. Opportunity examined it in November 2011 and found it to be rich in calcium and sulfur, possibly the calcium-sulfate mineral gypsum.” –NASA
Image Credit: NASA/JPL-Caltech/Cornell/ASU

.

Back here on Earth you may be more familiar with veins filled with quartz or calcite. But make no mistake, if you find an environment on Earth that resembles Mars, you can find plenty of gypsum veins here, too. I had the good fortune to GigaPan just such an area on the south side of the San Rafael Swell two summers ago. The GigaPan below (and subsequent photographs) illustrate a variety of gypsum veins, as well as some nice faults, crosscutting the Jurassic Summerville Formation (itself composed mostly of shale and bedded gypsum evaporites).

.

IMG_5024
Large Gypsum Vein and Smaller Veinlets, Jurassic Summerville Formation, Southern San Rafael Swell, Utah
IMG_5023
Smaller Gypsum Veinlets Closeup, Jurassic Summerville Formation, Southern San Rafael Swell, Utah

.

This post also serves as my Tuesday entry in Evelyn Mervine’s “GeoPicture Week” geomeme.

Call For Posts: Accretionary Wedge #41 – “Most Memorable/Significant Geologic Event That You’ve Directly Experienced”

A little over a month ago, while my geoblogging juices were really flowing, a late night rumble inadvertently inspired the theme for this month’s Accretionary Wedge. My own blogging pace has slacked off since then and perhaps yours has too, what with the pressures of the end of the semester and #AGU11. With any luck though, we’ll all have a chance to take a little time between final exams and the holidays to revisit our geoblogs and spread some geological holiday cheer.

Right, then. Your mission, should you choose to accept it, is to relate the story of the most memorable or significant geological event that you’ve directly experienced.

Let’s be clear about this – Accretionary Wedge #27 previously asked for the most important geological experience in your life and most of the submissions focused on the events that had the most significance in introducing one to geology – been there, done that; that’s not what we’re looking for this time.

What we seek for Accretionary Wedge #41 is an account of a geologic event that you experienced firsthand. It could be an earthquake, a landslide, a flood, a volcanic eruption, etc. (but don’t feel compelled to stick to the biggies – weathering, anyone?) – some geologic process that you were able to directly observe and experience. The event itself need not have been dramatic or life threatening, or it may have been. The event may have taken place before you were trained as a geologist or since (or maybe you don’t have any geologic training at all). Ideally, it’s something you can describe from firsthand experience, even if you didn’t experience it at ground zero. Events that my have happened while you were at a safe distance, but of which you were able to directly experience the aftermath (while the geologic evidence was still fresh) are certainly acceptable (perhaps you’ve been involved in relief or research efforts immediately following a major geological event). And by all means, don’t limit yourself to a single event if you’ve experienced more that one!

The story you weave is, of course, up to you. Pictures are always a plus (bonus points for audio or video) – you know we’re all adrenaline junkies on one level or another. I’m posting this call during the waning hours of the Paleozoic (time’s almost up, trilobites) but you have until the beginning of the Anthropocene to get your submissions posted. I’ll do my best to gather it all together sometime before Pangea Ultima gets together.

Landslide damage

This blog post will self destruct in 5… 4… 3…