Glaciology is Mathematics

Glaciology is Mathematics: The perspective of a master of mathematics student

James Headen, Elizabeth City State University

Panorama of Camp 10. Photo by author

ʃ8xdx...2x²+2x²… 3a=12x², regardless of the equation, there exists an explicit solution (definition: a function expressing a solved relationship between variables). Although mathematics has its share of implicit solutions (definition: an unsolved relationship between variables), the solution still has a variation of some finite (definition: known value) equation. Glaciers on the other hand, have so many unknowns that solving or drawing near a conclusion can be overwhelming. And that is the exact reason I’m drawn to nature’s canvas. 

Sunset view looking westward from Camp 17. Photo by author.

My background is strictly mathematics and physics, therefore any knowledge gained about glaciers is extremely new. I am a novice with any activity associated with glaciers and even using glacier terminology is unfamiliar. Such subjects as basal sliding, surface velocity or even measurements of movement uses an amazing quantity of mathematics. For instance, flux quantities are a mathematical representation of glacier movement. I enjoy observing the effects a simple derivative can have on glacier factors. For instance, constructing a simple differential equation with parameters such as height, length, gravity, and variables that represent changes in position interval exponents, produces a surface velocity at a specific point. Together, a motivated group of individuals and I are using these equations to create a cross-section model of the Taku Glacier. My portion focuses on using differential equations, the Pythagorean Theorem and GPS coordinates to extract surface velocity for specific points. Every day is the perfect balance of lab time with your project team and field time to experience the JIRP tradition. 

Representation of velocity flow along a glacier surface

Originally, I felt my mathematics would be put in the back corner during the length of the program, but I have experienced quite the opposite. Consequently, I can honestly say JIRP has a little bit of something for everyone. Whether it’s the mathematics student, the biology student, the programmer or even the outdoor enthusiast, each interest has life here at JIRP. 

Mathematics is everywhere……even at camp 18. Photo by author.

But can math really answer the deep questions of the icefield? My honest answer is YES!!

To understand the icefield requires mathematics. Math helps us understand glacier behaviors. In understanding the movement of glaciers, we can track possible areas of crevasses and map the general topography. Knowing these characteristics will increase safety for future exploration.

Mathematics helps us understand how climate impacts glaciers and in turn helps us understand how glacier change influences downstream ecosystems. Nature is math. To understand nature, we create mathematical representations (also known as models) to describe and predict its cycles. Through this we can prepare for future changes in our environments.

So to the aspiring JIRPmaticians, math lives here on the icefield! 

Ruminations from a JIRP Faculty

Ruminations from a JIRP Faculty

Donald Voigt, Research Associate, Penn State University, College of Earth and Mineral Sciences

Students aren’t the only ones inspired, challenged and stretched at JIRP. As my second season on the Icefield draws to a close, I feel that I am starting to earn my FGER stripes and maybe it is time for my reflections.

I was inspired by the sight of Tadhg coming into Camp 18 on one ski after the failure of his binding on the traverse from Camp 10. Full pack. Big full pack. One ski. He was laughing.

I discovered that Spam is better with Siracha, lots of Siracha. And that oatmeal with Spam is a thing; for supper. Maybe a good vs. evil sort of thing. And I still don’t understand Pilot Bread, an Alaska thing made in Virginia. Like saltines with the nutrition removed.

I was inspired by the constant interruption of our class discussion by ice falls from the Vaughn Lewis Glacier behind me. The subject was the physical properties of ice; go figure. And I was challenged by having to draw the phase diagram of water upside-down on a white board; without a net. Way out of my comfort zone.

Don Voigt challenging himself to draw the phase diagram of water upside down. Photo by Kristin Timm.

I was dismayed to find out that the fancy new activity tracker I am wearing doesn’t care about the weight of my pack. Or that the 3000 steps I took were more vertical than horizontal. It also didn't seem to work while skiing. But that didn’t seem to matter at the end of the day when talking to friends about the trip and the glories of skiing in the ping pong ball.

I was challenged to keep up with a dozen student climbing up from Heather Camp in 45 minutes to make it back in time for dinner when it took us an hour to make the descent.

And I am always inspired when the student staring off into space, seemingly not paying any attention, comes up with insight that causes me to start making plans for next year’s season on the Icefield.

Ogives: Glacial Masterpieces

Ogives:Glacial Masterpieces

Joel Wilner, Middlebury College

If you’ve made it to this website, chances are you’ve seen a picture of the dramatic Gilkey Glacier and its ogives – curving bands of ice on a glacier that alternate from dark to light.  Also known as band ogives or Forbes bands, ogives (pronounced oh-jives) are among the planet’s most extraordinary natural phenomena in terms of both aesthetic quality and scientific intrigue.

On yesterday’s long traverse to Camp 18 from Camp 10, my trail party was stuck in a whiteout for most of the trek. Today, though, the skies cleared and we were afforded an astonishing panoramic view of the Gilkey Trench, the Vaughan Lewis Icefall, and the Gilkey Glacier’s famous ogives. The sudden sight of the ogives is admittedly overwhelming, particularly after a “ping-pong ball day” in a whiteout. 

A close-up view of the arced bands of ogives below Camp 18. Photo by author

Scientists have proposed several different ideas about how ogives form. However, there are certain things about ogives that we know for sure: 1) all ogives form at the foot of icefalls (icefalls are jumbled, chaotic regions of a glacier in which ice moves much faster than elsewhere in the glacier, usually because of a steep slope), although not all icefalls create ogives; 2) the ogive bands begin as a series of bumps on the surface, sometimes five meters tall initially, but eventually flatten out; and 3) each pair of dark and light ice bands in an ogive system usually corresponds to one year of a glacier’s movement. An early idea proposed that the ogives are formed by pressure waves, just like pushing a spoon through a bowlful of thick honey. This idea theorized that as the icefall slides faster each summer than it does in winter, the speed increase causes the icefall to compress the ice below, gradually forming annual waves in the ice.

 The Vaughan Lewis Icefall (bottom left) and the ogives (right) it produces. Photo by author.

However, some scientists have seen holes in that theory, arguing that compression force alone cannot fully explain the bands, so a second theory was studied and proposed. This second theory contends that since ice speed is far greater in an icefall than elsewhere in the glacier, ice stretches as it enters the icefall, similar to water stretching as it flows over a cliff into a waterfall. As a result, the surface area of any ice that enters the icefall increases. This means that in summer as ice from the icefall melts, much more ice melts at a time than anywhere else on the glacier. More melt means that more debris and dust that was stuck inside of the ice is revealed, creating the dark troughs of the ogives. Ice that spends winter in the icefall is able to accumulate more snow and reveals less debris, emerging from the icefall as the light crests of the ogives. Glaciers flow faster in the middle, so the bands are shaped into arcs.

So, why do some icefalls produce ogives and others don’t? Scientists speculate that it again has to do with stretching at the beginning of the icefall. In order for the right amount of ice to be stretched, it needs to travel through the zone of rapid stretching in a short amount of time – six months or less. If it takes much longer for ice to move past the onset of the icefall, the stretching will be off and the icefall won’t generate ogives. Many different factors can affect this, including steepness and climate conditions.

 I feel incredibly fortunate to be able to observe these rare, unique natural wonders firsthand. Sometimes, we forget that nature isn’t all just random disorder. From the shattered shards and chaos of icefalls emerge these works of art, with remarkable regularity and precision. Nature is indeed an artist, and in her chaotic ways she paints masterpieces.

The Vaughan Lewis Icefall. Photo by author

Mass Balance Project 2015 Video

The 2015 Glacier Mass Balance project crew created this video blog to give readers a better sense of their efforts. Enjoy!

Peering Beneath the Ice

Peering beneath the Ice

Anna Clinger—University of Michigan

Word was out. A large crevasse near camp had opened up and soon, a group of us would be heading out to explore it.  Armed with our harnesses and prussiks, we skied out to the site and began setting up anchors to belay down the openings. From a distance, it was hard to tell the difference between the crevasse opening and the rest of the snowpack. But this can be the scary thing about crevasses—you really have to keep an eye out since you might not realize just how close you might be….

Ari tying her final safety knots with the crevasse opening several meters behind her. Photo by author.

Much of our traverse has been spent zig-zagging around crevasses. Cautionary tales of slips and falls have been ever-present. During safety week at C-17, we learned to self-arrest and maneuver pulley systems. Knots upon knots were taught and tested. And then as we roped up to travel over Nugget Ridge and the Norris Icefall and during pretty much most of our treks in and out of camp, we kick and glide past these unassuming windows into a hidden world below. 

Field of crevasses near our Camp 18 nunatak. Photo by author.

While maneuvering the cracks has become a part of our daily life, it’s sometimes difficult to wrap our minds around the size and depth of a crevasse.  In lecture, we’ve talked about their formation in terms of glacier movement. The glacier is constantly moving, evolving, and deforming.  As the glacier flows down the valley slope due to its own weight, it travels over underlying rocks, between mountains, and around nunataks (exposed rock at the surface of the ice). The shape of the surrounding environment helps dictate the flow of the glacier and creates a path down the valley towards lower elevations. Each of these obstacles can provide resistance to glacial movement.

We can then characterize the movement by whether or not the flow is accelerating (extensional flow) or decelerating (compressional flow) which often depends on the thickness of the ice and the direction the rock under the glacier is sloping. During extensional flow, the bedrock slope underneath the glacier is getting steeper so the ice moves faster.  This process can cause the ice to break or fracture at the surface as the ice gets pulled apart. Inversely, if the bedrock slope is less steep down-glacier, compressional flow can occur, which essentially pushes the ice together and causes the surface ice to break apart. These fractures are the formations we’ve come to know as crevasses.

One by one, we took turns exploring down into the crevasse. I was one of the last to go and it was really strange to watch them slowly disappear into the snowpack for 15 to 30 minutes at a time but soon they’d lunge back over the snowpack lip and rejoin the group.

Looking up, out of the crevasse. Photo by Lara Hughes

Soon, my turn came around and, after a final double and triple check of my knots, I began to lower myself down into the hole. I didn’t realize how nervous I was until I noticed my arms shaking as I let more rope out.  I slowly made my way down and was soon hanging in mid-air, occasionally testing my weight on a sketchy snowbridge and scanning this new, unfamiliar world around me.   

Drew all the way at the bottom of the crevasse. Photo by Lara Hughes

The most incredible thing was how illuminated the crevasse was. Light danced off the walls down onto the icy spires extending from below. The towers were twisted, interwoven, and warned me against testing my luck too far. As I tied my leg prussik, I attempted to balance between two drop-offs. Water was dripping everywhere. I zipped my rainjacket tightly and repositioned my rope which had become slightly forgotten in my state of awe. The crevasse extended much deeper than this year’s snowpits--I could see the layers of previous years’ snow, firn, and ice. They were lodged like history books hidden in the glacial walls. Books that help us better understand our icefield home which can seem so steady at the surface. But as our traverse continues, I’m learning more and more that we’re only just beginning to unfold its mysteries.

Lara in a crevasse. Photo by Drew Higgins

And as I slowly began my ascent up, I couldn’t help but feel lucky to have this chance to explore the icy cavern but incredibly thankful to have helpful guidance (and a few strong pulls) from up above to carefully return back to solid ground.  

How White is Snow?

How white is snow?

About the concepts of snow reflectance

23th of July 2015

Adrian PETER, University of Berne, BE, Switzerland

Katherine POPYACK, Hartwick College, NY, USA

Elizabeth PERERA, DePaul University, IL, USA

In everyday life we experience different surfaces reflecting light. Whether it be by the sun shining into the sea during a nice boat ride or a skyscraper’s window reflecting the sun’s rays, we all know how it feels to be momentarily blinded by the sun. This is because the light from the sun travels to the earth whereupon it bounces off the surface and shoots directly into your eye (if the angle is correct).

A second observation we probably all make is that, compared to light colors, darker colors get warmer under the sun. That’s why in summer, wearing a white shirt rather than a black t-shirt in is often preferred, which scientifically is due to the relative amount of reflected sun rays to the absorbed sun rays. The darker a surface is, the more light it absorbs and the warmer it becomes.

So we’ve just stated two major processes. First, light is likely to be passed onwards by bouncing off a surface. Second, not all the incoming light will be reflected – a portion will be changed into heat and therefore absorbed by the surface. This all depends on the features of the surface.

This relation between incoming and outgoing light is referred to as reflectance. The higher the reflectance, the brighter the surface.

But why does this matter? Snow is white, right? Although most snow appears white to the human eye, there are in fact many different shades of white. Moreover, snow may also be covered by dust, soot, organisms or other debris. Individually, every single impurity reduces the mirroring ability of snow and leads to more surface melt. Additionally there are also light spectra we humans cannot see which also impacts the reflective properties of a surface. Such spectra are near infrared or ultraviolet.

But why do we care? By measuring the reflectance of snow we try to determine the impact of several parameters on the ability of snow to reflect light. Elizabeth wants to determine how much the grain size of snow crystals matters, Katherine is focusing on a particular species of reddish algae that is able to live in cold/harsh conditions, and Adrian is asking how much black carbon and dust are affecting the brightness of the snow. Although there are more surface properties that affect Icefield reflectivity, up here we are limited to only one instrument to measures spectral radiation (called a spectroradiometer).  On a maritime glacier such as the Taku in Southeast Alaska, surface processes are playing a major role in mass loss. 

JIRP students Katherine, Lara and Elizabeth (from left to right) taking reflectance measurements. Photo: Allen Pope

Here at Camp 10 on the Juneau Icefield, we have the opportunity to take reflectance measurements with our boots in the snow (in-situ). Our normal routine involves grabbing the scientific gear, our skis, some snacks, and skiing over to field locations to collect data. In order to take reflectance measurements  we point the sensor above spots which have the specific features of interest, save the readings, and add notes manually (e.g. coordinates and description of what we measured and observed).  Back in camp we process the data we’ve collected on the computer (over a hot cup of coffee) and compare it to our notes. Afterwards we analyze our processed data by comparing it to what we understand snow reflectance should look like. If we are able to find some patterns in the shape of the reflectance curve (e.g. same depression at same locations for every measurement of dirty snow) we may be able to link it to specific features and therefore gain an answer to our questions.

At the moment we are focusing on plotting and then comparing our first few measurements. Hopefully we will be able to provide you with answers in the next weeks. Stay tuned!

If you’re keen to know more, check out this video, too: 

Science is Complicated

Science is Complicated

Austin Carter, University of Michigan

I’ve always thought of science as a simple, routine-like discipline: sample data, analyze data, and report data. However, there are a multitude of obstacles that make it more difficult, and I’ve come to understand this through my experience with JIRP.  For my individual research project, I’ve decided to collect rainwater samples, measure the isotopic concentration of those samples, and compare this to the temperature at which the rain fell. The idea is to create a relationship specific to the Juneau Icefield between stable water isotopes and temperature (for more information about isotopes see Jutta Hopkins-LeCheminant’s blog entry). My project originally sounded like a piece of cake because all I had to do was collect rainwater and measure temperature. How hard could that be? However, it became much more involved than I expected and although I’ve hit many “speed bumps” during my research, I’ve learned from each experience and grown as a young earth scientist. Here are a few skills I’ve learned so far:

Author collecting rainwater samples at Camp-10. Photo by Blaire Slavin.

Slow Down and Think First. When I first decided what I wanted to research, I became extremely excited and wanted to start immediately. During the first rainfall, I quickly threw on my rain jacket and rain pants, found a nice spot outside, and set out my first sample bottle around a pile of rocks. I waited hours, checking on it regularly, to see how much water I’d gathered. To my surprise, I had collected very little water; that is to say not enough to be considered a “sample.” Because I rushed into my project without thinking first, I didn’t consider using something with a bigger surface area to collect more water to pour into my small sample bottles. Having learned from this mistake, I now use a big silver bowl to capture a greater amount of water and have more appreciation for thinking ideas through before executing them.

Be Creative. The “teeth” on the zipper of my $300 waterproof Arc’teryx rain jacket fell off, rendering it useless because I couldn’t zip it together. Considering that my project meant I needed to be outside every time it rained in order to collect samples, I would get really wet without a proper rain jacket. When it did rain, I got creative and wore a fashionable black garbage bag over my body to keep me dry and, unexpectedly, it kept me rather insulated too.  Even if a substantial amount of planning is made on selecting quality equipment, I now know that problems can still arise and it’s always a great decision to try to think outside the box to solve any issue that occurs. Luckily, my mother shipped a replacement jacket to me that arrived by helicopter fairly quickly so I retired the garbage bag for good.

Be Patient. I’m probably one of the few students on this program who gets incredibly thrilled when it rains. Most people dislike it because it means they’re going to be both wet and cold, but for me a storm means I get to collect more rainwater and ultimately acquire more data. However, weather can be unpredictable, especially when you’re on top of a mountain. Most days I find myself waiting for the gloomy weather to flow in before I can continue with my project; it’s unfortunate but that’s necessary for my project. Data collection isn’t always instantaneous and sometimes waiting for the right moment is all that one can do.

Analyzing rainwater samples using a water isotope analyzer. Photo by Blaire Slavin.

Since getting to the Juneau Icefield, I’ve learned an incredible amount about remote field work and how to be a better earth science researcher. Because of JIRP, I’ve gained and will continue to gain valuable scientific skills that I will utilize on future research projects. For now however, I can’t wait to put what I’ve learned into practice as I continue to figure out the results of my rainwater analysis.

Stable Water Isotope Science on the Juneau Icefield

Stable Water Isotope Science on the Juneau Icefield

Jutta Hopkins-LeCheminant, Yukon College

Here at Camp 10 we are now frantically working on group and personal science projects.  I am a member of the group studying the stable isotopic composition of the water, snow and ice here on the Juneau Icefield.

 Sampling at various depths in snow pit on the Taku Glacier.  (photo credit Jutta Hopkins-LeCheminant)

We have collected and will continue to collect samples from various locations as we traverse from Juneau, Alaska to Atlin, British Columbia.  Some of the samples we have collected will be bottled, sealed and sent by helicopter to be analyzed at various labs at a later date, while we will analyze other samples right here at Camp 10 with the Los Gatos laser water isotope analyzer fondly known as “Steve, the Isotopolizer”.

At this point some readers may be asking “what is a stable water isotope and why are you studying them?”  I am happy to share a little bit of what I have learned so far…

Water, which is composed of hydrogen and oxygen, contains two stable oxygen isotopes- 18O and 16O.  Isotopes are variations of the same element that are of a slightly different mass, with 18O having two more neutrons than 16O.  18O is often referred to as the “heavy isotope” and 16O as the “light isotope”. 

Once the isotopic composition of a sample is determined, the ratio of heavy and light oxygen isotopes in the collected sample is compared to the ratio of a “known standard sample”, one being Vienna-Standard Mean Ocean Water or VSMOW.  The manner in which the samples differ from VSMOW can be used to determine the source(s) of the water, the temperature at which it fell as precipitation, and even how long the water has separated from the atmosphere.

While isotopic science has been used in many fields, only recently has the science been heavily applied to glaciology.  In his often cited 1953 paper, W. Dansgaard observed that precipitation in mid- and high latitude regions has a stable isotopic composition that relates to the air temperature at the site of precipitation (Dansgaard 1953).  In a 1970 paper T. Dincer et al. expanded on this by using the stable isotopes in water to observe water flowpaths and water age.  Fast forward to the present and glaciologists are now using stable water isotopes as an “isotopic thermometer” to calculate past temperatures based on the isotopic composition of snow and ice.

Austin C. with ice core samples from snow pit on the Taku Glacier. (photo credit Jutta Hopkins-LeCheminant)

One of the interesting processes that JIRP students will be studying is how stable water isotopes are related to local hydrologic patterns. The timing and amount of precipitation in the Icefield environment are responsible for the presence of glaciers on the Juneau Icefield.  The cycle begins with the clouds that form over the Pacific Ocean off the Alaskan Coast, as water evaporates from the ocean and forms clouds that contain more light isotopes than heavy isotopes relative to the ocean water.  The latitude and location at which the Alaskan Coast clouds form impart a unique isotopic composition to the water vapor within the clouds when compared to those formed at lower latitudes or over inland water bodies.

Same Icefield, Different Memories

Same Icefield, Different Memories

Blaire Slavin, The Benjamin School

I’ve been thinking a lot about following in the footsteps of others. This concept is meaningful to me because I would not be here if I didn’t follow the footsteps of my father (’73), brother (’11) and sister (’12) who all went to JIRP when they turned seventeen. Growing up I would always listen to all of their incredible JIRP stories hoping that when I turned seventeen I would be able to do the exact same. Finally, my turn has arrived. Wearing my sister’s hat and my brother’s jacket (which is way too big for me but I still love it), I perched myself on a rock overlooking the breathtaking Taku Towers just as they did. 

Me, finally completing the Slavin family JIRP wall. Happy belated Birthday Dad! (Photo by Aaron Chesler)

However, following in people’s footsteps doesn’t just pertain to me, but to every JIRPer…both literally and figuratively. In the literal sense, on traverses from one camp to the next, trail parties follow the tracks of the teams that traversed just days before them. The procedures required to record annual mass balance were established in the early 50s and are still used today. The shelf I sleep on is covered in signatures of JIRPers ranging from the 60s to just last year. The snow machine and sled that Seth, Tadhg and I used to drag our GPR (ground- penetrating radar) equipment up and down the Taku glacier was from 1995. Even some of the outhouses we use, as gross as it is to think about, were built in the late 40s and have been there for almost every JIRPer since. These examples, among many others, serve as constant reminders that we owe all that JIRP is today to the contributions of all JIRPers who came before us.  

Seth, Tadhg, and I having a blast dragging our GPR equipment in the old sled. (Photo by author)

Although I’ve been focusing on the idea of following other people’s footsteps, every JIRPer creates their own unique path. When I go home and show my family pictures of Camp 17 or Camp 10, they will bring back memories that are entirely different for each of us.

Ultimately, all JIRPers have been to the same camps, skied the same terrain, and eaten the same tasty cans of SPAM, but the Icefield has changed each individual in a slightly different way. What JIRP has done for me might not be what it has done for others. For example Annika, a former student and current staff member says JIRP has “inspired [her] to pursue connections between people, place, and climate change—in the hope of creating ripples of positive change. Also [she] has never laughed more in her life.” Jeff, a current student, says JIRP has “changed [his] perception of science from something that is done in a lab or read in a textbook to something that applies to the real world”. Alf who first started coming in 67’ says “[he] married JIRP first”. What I’ve learned from the JIRPers around me, both past and present, is that JIRP doesn’t end when we step off the ice. The calluses, blisters, and inner nostril sunburns that we’ve earned will remind us of the many places we’ve been, knowledge we’ve gained and wonderful people we’ve met. 

A Brief Introduction to Igneous Petrology

A Brief Introduction to Igneous Petrology

Mickey MacKie, Harvard University

I study geology because I need to know Earth’s past in order to understand my place in the universe. I love being able to walk around and use clues from rock formations to read their past. The world is an open history book, or so I thought.

As it turns out, my understanding of geology was limited to sedimentary rock. There are also igneous and metamorphic rocks, which are formed by varying conditions of heat and pressure. These unfamiliar rock types have surrounded me since I arrived in Juneau. I was reminded of my ignorance every single day. It drove me nuts. I couldn’t read this landscape. Juneau Icefield, what was your history?

Then came Jen Witter, an igneous petrologist from Alaska Pacific University. Here was my chance at enlightenment. The rain stopped, the clouds cleared, and a few other students and I accompanied Jen on a hike up Taku B, the peak above Camp 10. We scrambled over beautiful, glorious igneous and metamorphic rock that I couldn’t understand.  Jen explained some of the formations and minerals, and I began to grasp the events that had created the terrain. We saw amphibolite, granodiorite, and various intrusions of molten rock.

Mafic inclusions in a felsic melt (photo: Mickey MacKie)

We worked our way to the top. The weather was happy enough to make up for its previous rage. I stood on top of the world and looked down. The Taku Glacier was sprawled far beneath our feet. I could see the gleam of sunshine on metal from camp down below. To our left lay the dirty depression of a drained glacial lake. Jen collected samples. Seth found a bottle of Tums with a pencil and notebook inside. It held the signatures of JIRPers before us. We added our own and lorded over our kingdom for a while before heading down.

View of the drained lake next to Camp 10 (photo: Mickey MacKie)

Mickey on top of Taku B (photo: Katie Popyack)

The crew on top of Taku B (photo: Aaron Chesler)

Jen told me that over 100 million years ago, the Pacific plate was pushed, or subducted under another plate. This created melting in the subduction zone and caused a plume of magma to form and rise within Earth’s crust. This plate was simultaneously subducting under the North American plate and caused melt to occur there as well. Eventually, that plate became almost entirely subducted so that the Pacific and North American Plates began to collide. This caused a thickening in the crust and an increase in temperature at depth, generating a melt that mixed with and altered rocks on the surface. These are some of the rocks seen south of Camp 10. Thanks to Jen’s sampling, the rocks on Taku B will soon be analyzed to determine their place in Juneau Icefield’s history.