Stanford Advanced Field Methods Class

LocationMapWelcome to the class blog for Stanford Field Class GES 190: Ultramafics in the Field. This class is taught by Prof. Jessica Warren at field locations in northern California and southern Oregon. This site includes blog entries written by students during the classes in Autumn 2012 and Autumn 2014.

In 2014, the class spent 9 days in the Trinity Ophiolite in northern California, camping by Kangaroo Lake. During that time, we conducted a terrestrial laser scanning survey of rock outcrops, using equipment provided by UNAVCO. We subsequently spent a few days at the Siskiyou Field Institute in southern Oregon, analyzing the datasets and doing some additional fieldwork. In 2012, the class spent a week in the Trinity Ophiolite of northern California, followed by a week in the Josephine Peridotite of southwestern Oregon.


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Day 12: A visit to Crater Lake National Park (Katrina Zamudio)

Today we took a full day break from the classroom at the Deer Creek Center in order to visit Crater Lake which is about 2.5 hours away. We woke up to another soggy, cold morning, ate breakfast, packed lunch and then got in the Suburbans.

The drive included our third stop at Dutch Bros. Coffee this trip and an episode of carsickness, but after a few hours we pulled up to the park. At our first stop, Megan gave us an introduction to the geology behind Crater Lake. We learned that in addition to Basin and Range faulting, there is faulting related to the formation of the caldera that is Crater Lake.

In short, Mt. Mazama stood where the lake now resides. After the magma chamber underneath Mt. Mazama was emptied in a climactic eruption event about 6800 years ago, the ground quickly and dramatically subsided resulting in a series of steep normal faults in a ring pattern. This was because there was no longer material underneath Mt. Mazama to support it’s load. This resulted in the caldera that ultimately became Crater Lake. Over time, the caldera widened as a result of erosion and filled with snowmelt to become the 1900 ft deep lake we see today.

Crater Lake from the rim. So blue! So deep!

Crater Lake from the rim. So blue! So deep!

When I saw the lake for the first time, my jaw dropped. It is much bigger than anything I imagined and the water is so blue and so still. I’ve never seen anything like it. After lunch at some picnic tables, we drove around the entire rim of the volcano and made several stops while we filled out a worksheet Megan prepared for us. The stops included viewing a rhyodacite outcrop near Cleetwood Point, a welded tuff named Wineglass Tuff, and Phantom Ship, the throat of an andesitic volcano that got plugged, cooled and eroded in the shape of a creepy ship. Today there is andesitic volcanic activity in the center of the caldera (under the water).

Phantom Ship from the rim of Crater Lake.

Phantom Ship from the rim of Crater Lake.

After we wrapped up at Crater Lake, we got back in the Suburbans and headed back towards Selma. We stopped at Elmer’s Diner in Grants Pass and I ate my weight in french fries and blackberry cobbler with ice cream on top. Tomorrow is the last full day before we drive back to Stanford!

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Day 10: First Look at the TLS Data (Uju Ugwu-Oju)

Today, we showered. Finally, we washed off days of accumulated field grime and it was glorious! Our clothing wasn’t left out of the cleansing action – we did our laundry in a local laundromat in Cave Junction, Oregon. With an hour and a half to kill while our clothes were being cleaned, we visited some of the shops in town. There was quite the selection of New Age paraphernalia.

From noon till 5:30pm, we worked in the classroom at the Deer Creek Center. We got to take a look at the data we collected from our TLS surveys. It was incredible to see the 3-D point cloud of Kangaroo Lake so easily manipulated with the click and scroll of the mouse. The only downside would be the dizziness that comes with being too zealous in rotating the figures.


Laura, Katrina and Chris hard at work.

We spent our time in the classroom working with the data using the RiScan software. This was in order to get the feel of how to use it and how best to dictate and control the view and color scale of the figure in order to make useful interpretations.



RiScan software showing a sample point cloud.  As opposed to this being an Acer ad.

Jessica explained that the goal of getting us to map manually, digitally and performing the scanning project was to get us thinking about different data collection methods and which method was most appropriate on a project-to-project basis. There would be a worksheet for us to complete before the end of the class with that purpose in mind.

There was no hiking today.


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Day 9: On the road again (Laura Zalles)

We woke up bright and early Tuesday morning to chirping birds, a light breeze, and… ash? The forest fire smoke that came in the previous night had deposited a thick layer of grime over our tables, tents, and, to my dismay, utensils. Luckily, that didn’t matter as much this particular morning, as our first stop on the day’s journey was for the most important meal of the day, no personal utensils: breakfast at the Hi-Lo Cafe in Weed, CA (home of the best biscuits around!)


With stomachs growling, we stuffed food, equipment, and duffel bags into the two remaining Suburbans, quietly grieving the loss of TA Nik’s truck. Finally, we made it to the Hi-Lo and were greated by heaping piles of eggs, pancakes, hashbrowns, and, of course, biscuits.

Zalles photo 5

Pleasantly stuffed, we crammed back in the cars and started our two hour drive to Deer Creek, our next site. The car ride was mostly uneventful and, unfortunately, mostly geology-less. I rode with Maxine, TA Katie, Chris, and Philomena, and conversation ranged everywhere from state dialects to pet photos to the finer details of films starring Nicolas Cage. One fun geology-related tidbit: in response to a wonderful roadcut displaying distinct layers of what appeared to be marine sediments, Chris noted that President Eisenhower may have supported geology more than any other US president, without even realizing it: he established the interstate highway system!

During the drive, we crossed over into the Josephine Peridotites, a body of peridotite rocks representing the “mantle” portion of a large, 180 million-year-old ophielite. An ophielite is a group of rocks that includes portions of the mantle, such as our ultramafic peridotites, and portions of the oceanic crust such as pillow basalts. The Trinity peridotite, where we spent the last week, is also part of a larger ophiolite body. These ophiolites were originally accreted by a subduction zone. This same subduction zone also created the more recent volcanism that forms the Cascades Volcanic Region that includes Mt. Shasta. When we drove up I-5 on the way to Oregon, we could see the effect of both the “collision zone” from the subduction, which caused the accreted sediments on one side of the highway, and the volcanism caused by the shifting subduction margin on the other side. Because the angle of subduction (between the North American Plate and the relatively young Juan de Fuca Plate) is low, the spacing between the accreted terrain and the volcanoes is larger than it would be had the angle of subduction been greater. This is because volcanism always occurs at the point where the subducting plate, in this case the Juan de Fuca Plate, is a certain depth beneath the overriding plate, the North American Plate.

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Day 8: Hi-Tech v.s. Old-fashioned (Philomena Gan)

It’s almost 200 years since William Smith first published his geological map of Britain, still generations of geologists, whether learning or learnt, range through rough terrains with pens and boards, assigning each different lithology a new colour, taking a strike and dip wherever they can, marking good bedding-cleavage relationships onto rain-stained paper. Yet 200 years have passed from industrial revolution to digital era, geologists have been able to take advantage of every advance in technology-such as today, we are going to try out digital mapping! With collision-absorbing case protected nexus tablets, no other complicated mapping equipment to fuss with, we are ready for the day!

The magical tool we are using today is called ‘collector’, a ArcGIS product that can be easily downloaded from Googleplay or App Store. With pre-edited functions and loaded GPS, all we need is to go to a place, select the type of the outcrop (e.g. ‘exposed boundary’), write some notes(e.g.’an intrusive boundary between peridotite and gabbro’), press ‘start streaming’, walk along the exposed boundary and press ‘pause streaming’ at the end of outcrop, you should be able to find a beautiful line on the screen, and able to check immediately the plausibility of the line by looking at the aerial photo on which the line is drawn. Spent loads of times on Facebook and Tinder (Maxine had a good time ‘No’-ing firefighters 30 miles away), it didn’t take long before we start to draw gabbro dykes and mark pyxoxene crystal foliations in peridotites all over the place.

However technology did not prove to be omnipotent, there are still things that we need to do in person. Firstly, the delaying GPS gave us many amusements of watching ‘my location’ point doing some random walks when we are actually standing still. The same problem also means we have to manually drag dykes to smooth lines instead of just save the tangling zigzags as displayed on screen. And a good app it is, strikes and dips still need to be measured by hand, not quite as easy as just leaning the tablet to the rock!

After a good play with tablets in the morning (and collected many useful data) and had lunch under the same tree we had lunch with

Taking a break from digital mapping, we watch as the smoke rolling over the hills.

Taking a break from digital mapping, we watch as the smoke rolling over the hills.

our first day in Kangaroo Lake, we sat back in our campsite and started finishing our map in the afternoon. Back to the old-fashioned colouring pencils! Slowly but effectively filling up the blank mylar, it offers a satisfaction with which the auto-coloured lines on digital screens cannot compare. As the map’s filled up, we realise that we are completely engulfed by smoke produced by the forest fire-wind’s finally working against us after endorsing us a whole week of clear sky. Nik left us after dinner to return to Stanford. Thanks for all the joy you brought us! We are also leaving Kangaroo lake tomorrow for Oregon, and hopefully can escape this suffocating smoke. The bloody moon it produced is quite a view.

Today I had a good compare and contrast between the Hi-Tech mapping and the Old-fashioned way. It’s very difficult to say which one is better: apparently they have their own advantages and weaknesses. Long essays can be written on this topic, however one day’s experience is enough for me to say: when combined, Hi-Tech and Old-Fashion can produce the best geological map on the world.

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Day 7: 2nd Mapping + TLS Day (Uju Ugwu-Oju)

Today, the class was split evenly into two groups. One spent the day finishing up the terrestrial laser-scanning (TLS) project, and the other – of which I am a part of – did more field mapping. The mapping group started the day hiking up the gabbro cliff face adjacent to the path to Kangaroo Lake. With our maps nearly completed, we were at liberty to make several stops that involved re-visiting areas that we needed further clarification on. Our first series of stops were on the very gabbro cliff face on which we had begun the day.  There was a lot of hammering away tirelessly at the rock surface to procure the perfect rock sample (in the case of our TA, Nick) and on all our parts, there was more study of the rock to ascertain the temporal relationships of the units. The final decision was that the tonalite and diabase were around the same age. This was based on evidence of mixing of the two magmas (This would mean they were both near liquid at similar times).

Mixing of diabase (dark-colored) with tonalite (light-colored).

Mixing of diabase (dark-colored) with tonalite (light-colored). Note curved nature of  diabase rock denoting mingling when they were both in a more liquid state.

Other evidence of the age relationship included outcrops in which tonalite cut across diabase, as well as outcrops that showed the reverse relationship. Generally, a rock is younger than the rock it cuts across. Therefore, the appearance of both cross-cutting relationships suggests they are co-evals.

La dee dah

Tonalite cutting across Diabase. Note more relatively straight nature of the tonalite as opposed to curved edges, suggesting more of a cutting than a mingling.

We ended the mapping day early having finished our maps by 1pm. We went down to camp and spent the rest of the day finishing up worksheets in the office tent. The TLS group made it back by 5pm. Tonight, we dined on a meal of sausage, red beans and rice accompanied with a Shanghai egg dish and a fruity vegetable salad. Our meals have reached a surprising level of sophistication. We should probably all co-author a book on cooking in the field.

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Day 6: Fun with Terrestrial Laser Scanning (Chris Kremer)

Last night, strong gusts pummeled our tents, and so when we journeyed up the trail this morning, we feared that the tripod-mounted targets we had been using for terrestrial laser scanning (TLS) the other day had blown over. Our campsite lies on the opposite side of Kangaroo Lake from the field site, and as some of us made our preparations for bed yesterday evening, we saw the headlamps of hikers exploring the rock faces on which we had placed some of our targets, which consist of pivoting red reflecting disks mounted on tripods.

Setting up the scanner unit in preparation for a scan

Setting up the scanner unit in preparation for a scan

Any disturbance of a given tripod, even a minor one, can make it useless as a target if it is unleveled. This is because TLS creates three-dimensional images of extremely high resolution. If we had lost any one of our six targets to even a minor disruption, the effectiveness of our target array would have been reduced. Had more than three of the six targets been eliminated by a gale or a camper, it would have been impossible to stitch together the scans we were making today with the ones made yesterday. We were relieved, however, to find that all of our targets were in place and still level, and so we commenced work. As our class has divided into two field teams, the other team mapped today, while my group made scans.

Our main purpose of performing TLS work in the Kangaroo Lake area is to understand the intrusive relationships between gabbro and peridotite. We have already mapped the surface expressions of the two rock formations using paper and pencil. Now, we would like to use highly detailed scans of rock outcrops to understand what the formations might look like below the surface. In geology parlance a “dike” is a planar rock feature that forms when a magma or hydrothermal fluid permeates a rock and precipitates minerals in very large cracks.

Ken configures a scan on his laptop while Katrina contemplates an outcrop of gabbro and peridotite

Ken configures a scan on his laptop while Katrina contemplates an outcrop of gabbro and peridotite

At Kangaroo Lake, we see dikes of the mafic igneous rock gabbro in the ultramafic rock peridotite (a mafic rock has large amounts of magnesium and iron; an ultramafic one has even more). Though we approximated the features as planar on our paper maps, the dikes undulate and so are not strictly planar. We believe TLS will help us understand how the dikes curve and change orientation under the surface and will in turn provide us with a greater understanding of the behavior of mafic and ultramafic rocks in the upper mantle.

Over the course of the day, my group made eight scans of the local topography and several rock outcrops of interest. Though our friend Ken from UNAVCO kindly showed us how to operate the TLS technological suite the other day, many of us were a little rusty on the operational procedures, especially those involving the computer control of the scanner. Still, the most challenging aspect of the work was rapidly but carefully assembling, disassembling, and relocating the scanner for each new scan. We wanted to collect as much data as possible, but adjusting target reflectors, configuring scans, and measuring the relative positions of targets required diligent coordination among the members of our group. The work was successful but exhausting. By the time we had returned to camp, we were too tired to wash off at Kangaroo Lake and opted instead to work on our respective paper maps.

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Day 5: TLS Introduction Day (Maxine Luckett)

Today we spent the day learning about TLS (Terrestrial laser scanning). Many thanks to Ken Austin from UNAVCO who drove down from Washington yesterday with $200,000(!!!) in ground based LIDAR equipment for us to use. We started the day with a short introduction to UNAVCO and TLS. These scanners utilize infrared lasers to scan topography recording the reflected light waves. With multiple reading and georeferencing tools this system can produce precise and accurate 3D renderings of the earth’s surface. In out case we are going to attempt to use the reflection images to locally distinguish between the gabbros, peridotites, and other rock types we see in this area.

Ken Plugging in the Riegl Scanner

Ken Plugging in the Riegl Scanner


Ken and Katie using range finders across the lake.

Ken and Katie using range finders across the lake.

To start off we took the (heavy) equipment down to the Western shore of Kangaroo Lake. Ken started up the equipment and began with a rough panoramic shot of the lake, ourselves included (TLSelfie!). Safety wise, the IR waves are eye safe and human safe. Mounted on top of the scanner is a nice camera which takes corresponding pictures. These pictures can then be used to true color the point clouds that the scanner produces, well if you don’t move. Note: Everyone’s offset to the left, Uju’s Usain Bolt lightning pose, Ken’s deliberate move out of the picture to show how the true coloring can screw up, and my pretty pink parasol.

Let's take a TLSelfie!

Let’s take a TLSelfie!

After the rough scan we were sent off to scout target sites. The targets are 16.5 cm discs that are very red and highly reflective mounted on large tripods. The disc can be rotated and tilted to accurately face the scanner from whatever position. There are also three GPS units which can be mounted atop the targets to gather very accurate location data. To knit together multiple scans, the software needs there to be at least 3 shared tiepoints between scans. Because we wanted to tie this afternoon’s scans of the lake with the scans we would perform over the next two days up on the peridotite slope, we sent three targets up to the ridge to serve as tiepoints. The other three we positioned on the north, east, and west sides of the lake. The particular scanner we were able to use is a long range scanner, able to take images up to 1250 m away! The distance across the lake was over 500 m, so the scans we performed this afternoon were performed on a <950 m basis (the scanner would only collect data from that far away.

Over the course of the afternoon, we performed 3 different scans of the lake. One each from the western, northern, and eastern parts of the lake. We also made sure to be able to see the targets up on the ridge. Below is an glimpse of what our knit together lake shot false colored by height.

All three scans of the lake in one. false colored by height in the RiScan software.

All three scans of the lake in one. false colored by height in the RiScan software.

Altogether it felt like a productive day, and I’m excited that my group, the ammonites, will be doing our TLS day tomorrow. Hopefully we get to see some neat stuff.

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Day 4: Daunting Dunites Don’t Deter (Chris Kremer)

A viscera-jouncing drive over dirt roads brought us to Eunice Bluff, our second field area in the vicinage of Kangaroo Lake. Sparse pine growth surrounded our cars, suggesting that peridotite comprised the dirt-covered bedrock, as it can produce highly alkaline soils that hamper the growth of most plants. Peridotite is an ultramafic rock (that is, a rock highly rich in magnesium and iron) and is understood by geologists to comprise most of the Earth’s mantle. As Katrina and Laura have related in their posts, one of our class’s purposes is to assess the geology of the Trinity Ophiolite, of which the rock formations of Kangaroo Lake and Eunice Bluff are a part, to gain greater insight into the geology of the mantle. We visited Eunice Bluff in particular because it features rocks that were also formed in the upper mantle but are uncommon at Kangaroo Lake.

We took a scenic and chilly hike uphill from the cars. Along the way, we passed by two muddy ponds that California’s drought had drastically shallowed. Then, after an hour of swatting at manzanita plants and tripping over roots, we had found it: gorgeous, orange outcrops of lherzolite, dunite, and harzburgite. Geologists group both lherzolite and harzburgite under the rubric of “peridotite,” but the two rock types differ in that lherzolite contains the mineral clinopyroxene, while harzburgite does not.

Both rock types consist of minerals that commonly occur in igneous rocks (rocks that form from magmas) but they have commonalities with classic metamorphic rocks. All harzburgites and lherzolites originated in the mantle and so have had a billions-year long history of high-temperature and high-pressure conditions before ending up on the continental crust, where geologists can map them. For a long time, the genesis of dunites was much murkier than that of peridotite, and, as Professor Warren informed us as we ascended the hand-scratching, boot-gripping ultramafic formations, we would learn how our favorite olivine-rich rock had come to be.

Peridotite generally weathers to an orange color, while dunite weathers to a tan or dun (hence the name “dunite”).

Peridotite generally weathers to an orange color, while dunite weathers to a tan or dun (hence the name “dunite”).

The eight of us hunched over hand samples, squinted through loupes, and pined for lunch as we contemplated the structural relationships we observed among the lithologies described above. Through Professor Warren’s guidance and tutelage, we observed that lherzolite rarely occurred in exposed rock surfaces directly next to dunite, and that dunite seemed to form channel-like features in the harzburgite and lherzolite host rock. We inferred that these channels were the cooled, hardened products of magma flow upward through the upper mantle toward mid-ocean ridges, where volcanic ocean crust forms.

An “island” of harzburgite flanked by two converging dunite melt channels.

An “island” of harzburgite flanked by two converging dunite melt channels.

While one might interpret the dunite to have crystallized from the magma flowing through these channels, this was not so. We learned that dunite formed due to the reaction of clinopyroxene in lherzolite with two other minerals, not as the result of the crystallization of dunite from a hot magma. As magma flowed upward through the channels, the pyroxene in lherzolite near the channels was effectively leached away, leaving behind harzburgite. We spent the remainder of the afternoon using this model as the basis for interpreting other ultramafic outcrops at Eunice Bluff. Each student chose a feature that he/she wanted to discuss and presented his/her interpretations to the rest of the group.

At the end of the afternoon, bedraggled but geologically inspired, we marched back down the hill toward the cars. To celebrate our great scientific successes, the group supped on pork carnitas and reveled in a refreshing swim at Kangaroo Lake.

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Day 3: Kangaroo Lake Mapping (Katrina Zamudio)

Several of us have been in bed by 8:30pm for the past couple of nights. That is one of my favorite parts of field camp: going to bed with the sun and rising with the sun. Last night was way colder than the first night. The morning was no different. We headed up the slope from camp at about 8:40 expecting the day to warm up but it never really did. There was a strong cold wind all day.

We started out looking at a tonalite dike cutting through some gabbro. Near that there were gabbro pieces coated with a blue-green mineral. The best guess so far is that it is chrysocolla but Nick took a piece to check back at Stanford. We then moved upslope. Team Trilobite and Team Ammonite split up with the Trilobites mapping in gabbro “pods” in the peridotite. These patches of gabbro are common on the peridotite on this slope. The gabbro probably formed a sill in the peridotite and the peridotite covering the gabbro and some of the gabbro got eroded away so now we just see patches of gabbro on the peridotite.


After lunch at the top of the ridge behind some rocks that provided a wind break, we headed to the eastern Side of the map to pick up where we left off yesterday. The manzanita bushes thrive on gabbro derived soils so we were able to infer a contact between peridotite and gabbro where we couldn’t see it. We finished mapping in the main peridotite/gabbro contact and then headed back to the west.

We also discovered that we had missed a section of dunite within the peridotite (harzburgite due to the lack of clinopyroxene) we mapped yesterday. It is very serpentinized so it has a blue-green color. There are also some large, beautiful hornblende crystals in the gabbro around the contact which we have been finding. Our best guess is that they are a reaction rim around the contact between the peridotite and gabbro that formed when the gabbro intruded.

At around 2:30/3:00 we noticed that the smoke from the fires nearby had dramatically increased into a mushroom cloud. The wind thankfully didn’t blow the smoke to us like yesterday.


We spent the rest of the day mapping in tonalite and diabase dikes on the western part of the map. We also mapped in part of the peridotite/gabbro contact based on the presence of carnivorous pitcher plants which love to grow on serpentine soils which we infer to be where the peridotite is.

Our goal back at camp was to come to agreement on our tonalite/diabase identifications. Team Ammonite cooked pasta for dinner. Verizon users still have impeccable phone service at camp. I still can’t decide whether this is a good or a bad thing because sometimes it’s nice to go completely off the grid. Even so, we can’t keep our phones charged.

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