In three weeks I will be attending the American Geophysical Union (AGU) fall meeting, and on Thursday morning I will be presenting a poster about the Retreat of Stephenson Glacier, Heard Island, from Remote Sensing and Field Observations.1,2 I am very much looking forward to it, and if you will be at the meeting I hope you will stop by. There is likely to be a journal article forthcoming on this work, and the conference will be a great opportunity to discuss my project with glaciologists and get feedback on it—exactly what poster sessions at conferences are for, from what I understand.
Although my analysis is pretty much done, there is still quite a bit of work to go. Most importantly, the poster needs to be created. For that, I’ll start with a list of graphics and figures that will be needed for the poster:
Map of the world, showing the location of Heard Island
Map of Heard Island, showing the location of Stephenson Glacier
Satellite image(s) of Stephenson Glacier, showing the retreat
From that graphical outline will follow a minimal amount of text to guide a reader through the project with introduction, methods, results, and discussion sections. Once all that gets put together, it gets reviewed, sent to my co-author for further review, then changes are made until we’re satisfied and it’s sent off to the printer.
Following the conference, I hope to get a more detailed manuscript written. When it is ready for submission, I expect it will go to EarthArxiv, a new Earth science pre-print server, as well as an appropriate journal with open-access options.
Publication of that article would be the final step for this project, but there are quite a few new project ideas which have sprung up while I’ve been preparing this poster and article. One of the great things about using openly available data is that there are so many projects which could be done relatively simply and at little cost. Of course, a few other ideas have come to mind—and are perhaps more interesting—that would need further field studies.
Unless the affiliation is “Unaffiliated” for the lead author, it is incorrect. I have tried to get it corrected, but apparently the system can’t handle that.
During the Heard Island Expedition, although I was close to Stephenson Glacier I was unable to travel to that part of the island. Fortunately my co-author and several other expedition members did get there and took lots of photographs among other sampling and documentation efforts.
On July 21, 2017, the Landsat 8 satellite imaged a fresh landslide on Heard Island, seen in the picture above. The slide occurred in the northeast portion of the island, on top of Compton Glacier, and I have annotated it for clarity in the image below.
This landslide is quite easy to spot because of the relatively clear conditions over Heard Island and the very high contrast between the dark, presumably-basaltic rocks and the white snow of the glaciers. Given that it is presently austral winter and Heard Island is located south of the Antarctic Convergence, the rate of snow accumulation should be quite high. It will be interesting to see how long it takes to be covered by snow.
I am fairly convinced that this is a rock- or landslide rather than an eruption. The head of the flow is along the top of a steep ridge, and the infrared imagery shows no thermal anomaly in this part of the island.
What’s interesting to me is that this slide appears to have eroded some snow on top of the glacier which then caused a secondary avalanche from a north-facing slope. I’ve annotated this in the image below.
This landslide has a run-out of about 2.5 km, an elevation drop of ~750 m, and a total affected area of ~0.8 km2. Several flow tongues are evident in the close-up image, even though the satellite imagery resolution is a modest 15 m/pixel.
From this image, it looks like the rockfall mostly happened in the portion running west-to-east, then as it turned the corner to head northeast, transitioned to a surface flow. In many ways, this reminds me of the Mt. Dixon (New Zealand) rock avalanche in 2013 (coverage by Dave Petley here and here, among others). The video below is from the Mt. Dixon (NZ) rock avalanche, but is likely similar to what occurred on Heard Island.
A fly-over after the Mt. Dixon (NZ) rock avalanche provided more video of the rock avalanche scar.
I look forward to seeing more images of this slide as they come in. Heard Island is imaged roughly every 8 days by Landsat 8, which as far as I can tell is the only publicly available high-resolution imagery for the island now that EO-1 has been decommissioned.
One year ago, I was on Heard Island. Over the course of the expedition I took more than 6000 photos. Although I took three images with the Gigapan (Big Ben, the Azorella Peninsula, and—my favorite—Windy City), I also took photos for stitching together manually using my own camera.
I have been slow in stitching these pictures together, but with the one-year anniversary of their production coming around, I decided it was time to finish one or two of them. This is the first, and I hope I’ll find time to finish more. Putting it together, I was amazed that this is still a relatively wide-angle compared to what I had available: 70 mm on a 70–200 mm lens. The detail came out well, as is evident at full-size. The glaciers, moraines, and hills are all more than a kilometer distant over the “nullarbor”, a broad, flat, volcanic-sand plain.
Toward the left half of the image are some penguins for scale. They look like king penguins, putting their height around 1 meter. I count at least 31 penguins in the entire image.
I think I spot some of the relatively rare basement limestones cropping out at the very left edge of the image, and their appearance is consistent with a dip of 25–35° to the south. A closer view (200 mm focal length) shows them more clearly.
On February 4th, Landsat 8 captured a clear view of the summit of Big Ben volcano, at Heard Island. Heard Island is a very cloudy location, so clear views are uncommon (I don’t have numbers, but would estimate <20%). However, the February 4th images are even more spectacular: they capture an ongoing volcanic eruption.
In the sharpened true-color image (above), four or five different lava/rock/debris flows are visible emanating from the summit. Using a false-color infrared image (below), two hot regions are apparent (red/orange/yellow), and are separated by about 250 meters. The longest of the flows stretches nearly 2 km, and drops from an elevation of roughly 2740 m to 1480 m (using 2002 Radarsat elevation data with 20 m contours). All three of the large flows to the west or southwest of the summit drop below 2000 m elevation at the toe.
In the sharpened true-color imagery, I have identified five rock and debris flows originating at the summit, as well as one potential avalanche. Annotation of these observations is found on the pictures below.
The streaky, varying lightness of the flow areas, presence of snow and ice, and steep terrain lead me to believe that what is showing up here are mixed snow/rock/lava debris flows, rather than pure lava flows. A mix of rocky debris and snow would not be out of line for a supraglacial eruption on a steep mountain. The longest flow drops nearly 1300 m along its 2000 m horizontal path according to the 2002 Radarsat elevations. I’ll be the first to admit that I am distrustful of the specifics of the Radarsat contours due to the rapidly changing landscape and an intervening 15 years, but I think that it manges to get the general picture right.
Southwestern Heard Island is a high-precipitation area, so rocks exposed on the surface of the glaciers are likely quite fresh. It probably won’t be long before most of the deposits are covered in snow again.
Speaking of snow, it looks as though there is a faint outline of an avalanche scarp/deposit on the northeast side of the summit, which I annotated below in green.
The two hot spots provide an interesting challenge for interpretation. Two scenarios come to mind quickly: there are two vents from which lava is issuing, or there is a lava tunnel from a summit crater down to a flow front or breakout. Analyzing the Landsat 8 OLI/TIRS infrared imagery from January 26th (most recent previous high-resolution image), only one hot spot is present—in the same place as the eastern hot spot in the February 4th infrared image. For spatial correlation without doing the whole image processing and GIS thing, use the forked flow to the south-southeast of the hotspot as a reference.
Due to a different time of day for imaging, there are significant shadows in the January image on the southwest side of ridges. It’s tricky to figure out what is going on for the flows (even in visible imagery), but the hot spot from January 26th is right on top of the eastern hot spot from February 4th.
Another thing which becomes apparent in the January image is the topography at the summit. The clouds form a blanket at an atmospheric boundary (and roughly-constant elevation), which is conveniently just below the elevation of the summit. A roughly circular hole in the clouds is present, and a conical mountain summit pokes through with the hot spot right in the center. That suggests that the second hot spot seen in the February 4th image is at a lower elevation—a possible flow front or breakout.
Excitement in the Mundane
Finding this eruption was a bit of a surprise to me: the low-resolution preview image for the Landsat data on EarthExplorer was so coarse that there wasn’t anything striking or out of the ordinary visible at the summit. Clouds covered most of the rest of the island. However, when I opened up the full-resolution color images (30 m/pixel), it was immediately evident that this was a special day. Sharpening the true-color bands with the high-resolution panchromatic band using QGIS made it pop all the more!
Upon seeing both the lava/debris flows and the thermal anomaly, I checked the MODIS volcanism (MODVOLC) site to see if the Terra and Aqua MODIS instruments had picked up thermal anomalies as well over the preceding week. They had, as shown below. Both satellites had recorded thermal anomalies at Heard on February 2nd and 3rd.
This post is the first in a series of three on the gigapans I took on Heard Island. (Part 2, Part 3)
My first gigapan on Heard Island, this one of Big Ben, came unexpectedly. As I was out hiking one afternoon, my hiking partner, Arliss, noticed that we had a clear view of the summit of Big Ben. Clearings like this can be relatively short and infrequent, so we took a few pictures immediately. We headed back to base camp just east of Atlas Cove, arriving under an hour before sunset. The mountain was still visible, so I moved quickly to set everything up and get the gigapan taken before the light faded.
From camp, Big Ben is situated to the southeast, rising up beyond the flat sandy plain of the nullarbor. In this view, the moraines and glaciers begin about 2 km from the camera. To the right of the image is the eastern slope of Mt. Drygalski. The edge of the Azorella Peninsula lava flow is in the bottom left corner.
Glacial features dominate the landscape, including a prominent moraine now covered in vegetation (lower right). Coming toward the camera are the Schmidt and Baudissin glaciers. I think this view covers from the Allison and Vahsel glaciers (at right) to the Ealey glacier (at left).
On the Nullarbor, there are a few king penguins and elephant seals, primarily to the left of center.
Big Ben itself has a range of rock types, including basanites, alkali basalts, and trachybasalts, overlying limestones and volcanic/glacial deposits.[1-4]
 Barling, J.; Goldstein, S. L. (1990) Extreme isotopic variations in Heard Island lavas and the nature of mantle reservoirs. Nature 348:59–62, doi 10.1038/348059a0.
 Barling, J.; Goldstein, S. L.; Nicholls, I. A. (1994) Geochemistry of Heard Island (Southern Indian Ocean): Characterization of an Enriched Mantle Component and Implications for Enrichment of the Sub-Indian Ocean Mantle. Journal of Petrology 35:1017–1053, doi 10.1093/petrology/35.4.1017.
 Stephenson, J.; Barling, J.; Wheller, G.; Clarke, I. “The geology and volcanic geomorphology of Heard Island”, in Heard Island: Southern Ocean Sentinel (Eds K. Green and E. Woehler) Surrey Beatey & Sons, 2006, p. 10–27.
Today there is a new video out from scientists aboard the R/V Investigator which shows a volcanic eruption occurring from Mawson Peak, Heard Island. This is an exciting video not because it is unusual for an eruption to happen on Heard Island—the Global Volcanism Program shows activity on about an annual basis for the last few years—but because it is unusual for someone to be there to see it!
In the video above, a small plume can be seen over Mawson Peak, and a few lava flows. Given the terrain near the summit and the imagery below from lava flows in 2013, I think it is safe to say that the flows are heading down the southwest flank. As someone going to this island in less than two months, the direction of lava flows is important: it is away from the campsites which we intend to use.
From the video above, this appears to be an effusive eruption, where lavas gently flow out of the volcano. That eruptive style is consistent with a hot (~1100 °C), basaltic (low-SiO2) melt—eruptions with a high SiO2 content tend to have cooler lava and are more often explosive in nature. Basalts or other lavas (trachybasalts and basanites) with low SiO2 (48–52%) are typical of the Big Ben series of lavas (Big Ben being the volcano upon which Mawson Peak is located). Predicting that the lavas from this eruption would be generally low-SiO2 seems fairly safe, although our expedition is not equipped to undertake the sampling required to test that prediction.
 Barling, J.; Goldstein, S. L.; Nicholls, I. A. (1994) Geochemistry of Heard Island (Southern Indian Ocean): Characterization of an Enriched Mantle Component and Implications for Enrichment of the Sub-Indian Ocean Mantle. Journal of Petrology 35:1017-1053, doi 10.1093/petrology/35.4.1017.
When glaciers flow down across the ground, they can break off rocks and pick them up in the ice. As the ice moves and eventually melts, those rocks are deposited. When the large rocks are exposed on the surface, they are termed glacial erratics. Much of Minnesota and the eastern Dakotas are covered under these glacial deposits, and these glacial erratics are relatively common.
Glacial deposits are also interesting because they will have grains or rocks of all sizes, from very fine silt and mud up through large boulders. This can make identifying glacial deposits in the field straightforward in some cases, because there will be many grain sizes all together. When grains settle out of the air or from water, the coarse ones deposit first, and the grains end up becoming finer as you go up the stratigraphic column.