June 23, 2015
(Photos by Summer and Kerry)
After getting the camp house set up yesterday, today was the first day of field operations. There was still a bit of equipment preparation left to do and both the seismic and the MT teams got busy early.
Here’s the view out of the garage door at the camp house from the previous evening. On the right hand side Georgie is putting our electrodes into cloth bags of wet bentonite mud, which helps increase the electrical contact with the ground for high quality MT recordings.
Here’s Paul putting ropes around our induction coil magnetometers. We bury these sensors about 1 foot in the ground to stabilize them from shaking by the wind, and the ropes are useful for pulling them back out at the end of the deployment:
The night before, we fired up the four Zonge Zen MT data loggers and made some dummy recordings to make sure they were still working after being shipped up from Scripps. Note the black case holding the field laptop as later it played a helpful role during our journey in the caldera.
The seismic team had to set up 13 broadband seismometers for year long deployments around Okmok. Tim Parker from the Portable Array Seismic Studies of the Continental Lithosphere (PASSCAL) Instrument Center came out to help out with the seismometer installation and was a lot of fun to be around. Here’s Tim checking out the Quanterra Q330 data logging systems:
Here’s a few of the Nanometric broadband seismometers being tested. In the field they are carefully installed so that the stone sensor pad couples well with the ground and the seismometer is leveled on top of it:
Here’s a charging station we set up in the back of the camp house. Matt Haney from AVO/USGS brought along several of their radios as well as a hefty repeater box (orange case on the ground) which ended up being super helpful for communications between the field teams, the helicopter pilot and the field coordinator at the camp house.
The weather was looking decent that morning so the first thing was to take the repeater up to the caldera rim and set it up. Here’s the helicopter heading up to the caldera rim just to the east of Tulik:
By lunch time the radio repeater had been installed and the weather was still looking good so the MT ream decided to head straight into the caldera. We knew the weather was going to be challenging on Umnak, and since we had most of our planned stations inside the caldera, it made sense to get in there and start getting some stations installed whenever the weather was good. Here’s the view from the helicopter just after taking off from the ranch and bee-lining for the caldera rim to the north-west near Tulik:
The helicopter could only fit two field crew members when taking a full load of the MT gear, so Georgie and Paul flew in first and then Sam came pack to pick me up. Here’s a video showing the approach to the caldera rim:
And here’s another showing us passing over the caldera rim:
In the video clip, the small cones sticking up from the caldera floor are some of the vents of recent eruptions. Cone A is the one on the left side and the one in the distance near the end of the clip is Cone D. On the back side of Cone D is Ahmanilix, which is the new vent that formed during the 2008 eruption (we will get to know this vent better in a future post).
This was the first time I had ever flown in a helicopter; I was surprised at how smooth the flight was, and obviously I was stoked by the amazing view of the caldera. The helicopter dropped me off at station P07, where Paul and Georgie had been dropped off earlier. Sam then flew back to the ranch to pick up the seismic team and take them on a site survey for one of their stations outside the caldera.
MT station P07 is on a flat part of the caldera floor near the southeastern rim wall, which is about 500-800 m high, as shown in this photo:
Paul and Georgie had already surveyed in the station geometry and were digging three holes for the north, east and vertical magnetometers, so I helped bury the electrodes in the ground. Here’s the view from one of the electrode holes, looking across the caldera floor towards Cone D:
The wire leading up to me connects the electrode back to the data logger, which records the electric potential between two electrodes. We then divide the potential by the distance between the electrodes to form an approximation of the electric field (which has units of V/m). The electrodes are configured in a giant cross, two of them separated by 100 m in the north-south direction and two separated by 100 m in the east-west direction.
Pretty soon we had all the sensors buried and their cables plugged into the data logger, so we set it up to start recording using the user interface software that runs on our rugged field laptop; once started, the data logger records all on its own and is time synchronized to GPS time. We then put a tote box upside down over the logger and battery boxes to provide a little more weather protection (we later added some piles of dirt on top to keep the tote from blowing away). That’s when we started thinking it’s getting quite a bit foggy out:
Meanwhile Sam picked up the seismic team at the camp and they went to survey a seismic site location. Here’s Summer looking happy to be riding in the helicopter:
And here’s Ninfa and Matt checking out the seismic station location. While the inside of the caldera is mostly devoid of plant life, the grassy slopes outside the caldera are chock full of blossoming wildflowers including lupines, orchids, chocolate lilies, bluebells, wild geraniums, mayflower anemones, paintbrushes, irises, yellow monkey flowers, rhododendrons and a few others I don’t yet know the names of:
Back in the caldera, we were discussing what to do. The helicopter needs to maintain ground visibility during flight and so the increasingly thick fog ruled out having the helicopter return over the caldera rim to pick us up. We radioed Sam and he said he would try to enter the caldera through the Gates, which is the entry portal on the northeastern side where the caldera rim wall is missing and Caldera Creek flows out. There was a bit of wind pushing the fog around, so Paul, Georgie and I hunkered down in the lee of a ridge to stay warm. After about 20 minutes or so Sam told us over the radio that the fog was too thick to enter the Gates and that he would try again later. Since the wind was blowing a bit, we figured the fog was likely to clear up, even if only temporarily; not wanting to sit around getting cold, we decided to hike over to the next station, P08, with our shovels and start digging the holes for its magnetometers. We put on our high-visibility gear so that it would be easier for Sam to spot us should he be able pick his way in through the fog:
P08 is at a slightly lower elevation than P07 and Paul found lots of oozing mud when using the post-hole digger to make a deep hole for the vertical magnetometer:
Paul radioed Sam, who said it was still too foggy to enter the caldera through the Gates. Since the short walk from station P07 to P08 wasn’t bad, and our handheld GPS unit said it was only about 3 miles to the Gates (as the crow flies that is), we decided we would try hiking out to meet the helicopter outside the Gates where the fog wasn’t as thick. Hiking sounded more interesting (and warmer) than waiting around for the fog to clear.
When planning the project earlier this spring, both Max Kaufman and Jeff Freymueller from AVO, who have worked in the caldera before, warned us that there’s a good chance the fog and other bad weather could trap us in the caldera overnight or for up to a few days and we should be prepared. So we had personal survival bags that contained sleeping and bivy bags, thermal blankets, rain gear, a water filter, a jetboil stove, 2 fuel canisters, tarps, headlamps, first aid kit, gerber tool, satellite phone, GPS unit, etc. We also packed a small amount of survival food, along with the water bottles and field snacks we replenished each day. So we were prepared to spend the night, but hiking out and going back to a warm dinner (and cold beer) sounded better, so off we went on a walk toward the Gates.
Cone D was directly to the north of us and beyond that the Gates, and the flat valley floor soon transitioned into thick tephra badlands that blocked our desired walking direction. We looked for the path of least resistance that was also pointing somewhat towards the gates. Here’s what a section of it looked like:
This was basically a melting mud of tephra badlands. That rain and runoff were clearly effective at carving away at this massive pile of tephra which was probably ejected during the 2008 eruption, since it wasn’t shown on the topography map on our GPS (which uses older topography). In some places dirty snow and ice were visible beneath the surface and it was clearly melting fast, leading to collapse induced cracks as shown in the section Paul is standing on above. In other places the tephra looked like it was slowly sliding down the hillsides, in super ultra slow motion over the course of days to weeks or even months. We slowly walked in the slot canyons, from one to another, for about an hour. It wasn’t terribly hard walking, but it also wasn’t easy since we had to avoid the thick oozing muds in the bottom, and it didn’t exactly seem safe, especially in the deeper slot canyons where the fragile looking tephra walls towered steeply over us. It was also lightly raining and so we were carefully watching the runoff in the canyon bottoms, hoping it would stay at a trickle. Eventually we reached this wide flat watershed that led down to a big lake on the west side of Cone D:
It was a big relief to get out of the badlands and we were all happy that we were back on flat ground and soon would be making faster progress toward the Gates. We followed this drainage down toward the lake, and then turned to the east to walk along an alluvial fan on its southeastern shore. As we traversed the fan we neared a steep cliff on the side of Cone D; at the base of the cliff was a thirty foot wide stream with what looked to be a foot or so of deep water quickly flowing downstream. Both Paul and Georgie were wearing rubber boots, Paul’s were the Alaskan favorite Xtratuf boots and Georgie’s were from our marine foul weather gear kits. I was naively wearing my ankle high Keen hiking boots based on the good weather we saw earlier in the day. Paul and Georgie waded across the stream easily while I headed downstream towards where it spread out widely near the lake shore thinking that the shallower water there could be easily crossed without dunking my shoes too deeply. So far the ground had been really solid, other than the obviously very muddy sections at the bottom of the badlands, so I was cautiously avoiding the deep water and entirely trusting what looked like solid ground. That’s when it gave way and I sunk in to just below both knee caps. Yikes quicksand! Luckily I was carrying that watertight black computer case shown in a previous photo above, so I pushed it into the quicksand and used it to push off, pulling one foot out at a time, gingerly stepping back toward more solid ground.
Now my feet were wet and shoes filled with tephra grit, and the few miles left to hike to the Gates wasn’t sounding so fun anymore. I doubled back upstream to where Paul and Georgie had safely crossed and decided to wade through, no harm now that my shoes were already soaked. After I made it across we decided we would avoid going close to the lake shore since the shallow water table there meant more quicksand was likely. So we began traversing the next alluvial fan too the right, at quite a distance from the lake. This fan was covered by a myriad of braided streams coming out of the badlands of Cone D, but all had very thin veneers of water, so it looked safe to cross that region and so on we went.
The tephra quicksand is really unexpected as one step is on solid but damp looking ground and the next step the saturated tephra bubbles away as your boot sinks in quickly and easily. I can’t remember who went in first, but both Paul and Georgie went in to their knees at about the same time; I was on solid ground but completely panicked at watching my companions stuck in the mud. Georgie was further out and in deeper quicksand; she struggled to get out and was sinking in deeper and her instincts led her to turn and go into an army crawl back the way she came; I rushed over as close as I could without sinking in and threw her the computer case, which she used to push off of and get back to solid ground. Paul’s boots were stuck badly and so we threw him the computer case and he was able to push out as well. (Pro tip: bring a waterproof case for flotation when hiking near quicksand)
We now all had boots that were wet and gritty inside. Amazingly, Georgie’s army crawl across the quicksand managed to only soak her outer shell layers and she said she was dry underneath. Despite being shaken by the experience, we were all still in pretty good spirits and Georgie was able to make light of her first swim in quicksand:
After regrouping and a mostly useless attempt at cleaning off the tephra grit, we continued hiking, now cold from being wet and now far above the lake shore. We crossed another alluvial fan and found ourselves cornered in. To the left a steep badlands cliff met the lake shore blocking the passage, and a small valley straight ahead dead ended in badlands, with the fog obscuring the top and not offering any sign of an easy passage forward. We decided to take a short break to clean out more of the grit from our boots and to change wet clothes; Paul went exploring the badlands, looking for a high point where he could radio Sam. I climbed up a nearby ridge and captured this photo looking back on where we came across the edge of the lake. You can see the stream coming down to the lake near the right side of the encircled area and the braided stream quicksand region to the left of that:
Mentally we were all preparing to spend the night there, which didn’t sound so good now that we were wet. But alas, Sam answered Paul’s call on the radio and said he was just picking his way through the fog at the Gates. Pretty soon we could hear the helicopter approaching, and soon it landed nearby. Hurray!
After about 15 minutes we were back at the camp enjoying the warm dinner the rest of the team had made and telling stories about Georgie’s swim in the quicksand. Tomorrow we would start off with much easier field work on the grassy slopes outside the caldera.