Tag Archives: Glaciers

Nares Glacier to Mount Drygalski Panorama

Panorama from Nares Glacier (left) to Mt. Drygalski (right) from the Atlas Cove camp.  This view spans from ESE through SSW, and is roughly 85 megapixels at full size.  Image credit: Bill Mitchell (CC-BY, hosted on flickr).
Panorama from Nares Glacier (left) to Mt. Drygalski (right) from the Atlas Cove camp. This view spans from ESE through SSW, and is roughly 85 megapixels at full size (28 MB). Image credit: Bill Mitchell (CC-BY, hosted on flickr).

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.[1] A closer view (200 mm focal length) shows them more clearly.

Location of limestone, with annotation.  Image credit: Bill Mitchell (CC-BY).
Location of limestone, with annotation. Image credit: Bill Mitchell (CC-BY).
Full-zoom on the limestone outcrop.  Bedding is clearly visible, dipping south.  Image credit: Bill Mitchell (CC-BY).
Full-zoom on the limestone outcrop. Bedding is clearly visible, dipping south. Image credit: Bill Mitchell (CC-BY).

[1] Quilty, P. G. & Wheller, G. 2000; Heard Island and The McDonald Islands: a Window into the Kerguelen Plateau. Papers and Proceedings of the Royal Society of Tasmania. 133 (2), 1–12.

Big Ben Eruption, 2017-02-04

Lava and debris flows radiate away from Mawson Peak on Heard Island.   February 4, 2017.  Image credit: Bill Mitchell (CC-BY) using data from Landsat 8 OLI (NASA/USGS; public domain).
Lava and debris flows radiate away from Mawson Peak on Heard Island. February 4, 2017. Image credit: Bill Mitchell (CC-BY) using data from Landsat 8 OLI (NASA/USGS; public domain).

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.

Observations
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.

False-color infrared imagery of Mawson Peak, Heard Island.  Two vents are visible in red/orange/yellow, separated by 250 meters. Data source: Landsat 8 OLI/TIRS bands 7-6-5.  Image credit: Bill Mitchell (CC-BY), data from NASA/USGS (public domain).
False-color infrared imagery of Mawson Peak, Heard Island. Two vents are visible in red/orange/yellow, separated by 250 meters. Data source: Landsat 8 OLI/TIRS bands 7-6-5. Image credit: Bill Mitchell (CC-BY), data from NASA/USGS (public domain).

Interpretation
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.

Annotation of lava/rock/debris flows from Mawson Peak, Heard Island, February 4, 2017.  Image credit: Bill Mitchell (CC-BY).
Annotation of lava/rock/debris flows from Mawson Peak, Heard Island, February 4, 2017. Image credit: Bill Mitchell (CC-BY).

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.

Annotation of avalanche scarp and deposit, Mawson Peak, Heard Island, February 4, 2017.  Image credit: Bill Mitchell (CC-BY)
Annotation of avalanche scarp and deposit, Mawson Peak, Heard Island, February 4, 2017. Image credit: Bill Mitchell (CC-BY)

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.

False-color infrared image of Mawson Peak, January 26, 2017.  Landsat 8 OLI/TIRS bands 7-6-5.  Image credit: Bill Mitchell (CC-BY) using NASA/USGS data (public domain).
False-color infrared image of Mawson Peak, January 26, 2017. Landsat 8 OLI/TIRS bands 7-6-5. Image credit: Bill Mitchell (CC-BY) using NASA/USGS data (public domain).

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.

MODIS thermal events at Heard Island, in the week preceding February 6, 2017.  Image credit: MODVOLC.
MODIS thermal events at Heard Island, in the week preceding February 6, 2017. Image credit: MODVOLC.

Update:: Follow-up from February 27, 2017.

Big Ben Gigapan

Processing the Big Ben gigapan.  Screenshot by Bill Mitchell.
Processing the Big Ben gigapan. Screenshot by Bill Mitchell.

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]

[1] Quilty, P. G.; Wheller, G. (2000) Heard Island and The McDonald Islands: a Window into the Kerguelen Plateau. Papers and Proceedings of the Royal Society of Tasmania. 133 (2), 1–12.

[2] 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.

[3] 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.

[4] 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.

Eruption on Heard Island

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.

Lava flow on Heard Island, April 20, 2013. Image credit: NASA Earth Observatory image by Jesse Allen and Robert Simmon, using EO-1 ALI data from the NASA EO-1 team.
Lava flow on Heard Island, April 20, 2013. Image credit: NASA Earth Observatory image by Jesse Allen and Robert Simmon, using EO-1 ALI data from the NASA EO-1 team.

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).[1] 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.

Finally, if you’re wondering what happens when a basaltic lava flows out onto ice and snow, know that experimental volcanologists at Syracuse University have asked that question and made a video.

***

[1] 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.

Glacial Erratics

Glacial erratics on a prairie in South Dakota.  Image credit: laikolosse (CC-BY).
Glacial erratics on a prairie in South Dakota. Image credit: laikolosse (CC-BY).

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.

Geoscientist’s Toolkit: QGIS

QGIS screenshot, showing Heard Island.  Brown is land/rock, blue are lagoons, and the dotted white is glacier.
QGIS screenshot, showing Heard Island. Brown is land/rock, blue are lagoons, and the dotted white is glacier.

One of a geoscientist’s most useful tools is a geographic information system, or GIS. This is a computer program which allows the creation and analysis of maps and spatial data. Perhaps the most widely used in academia is ArcGIS, from ESRI. However, as a student and hobbyist who likes to support the open-source software ecosystem, I use the free/open-source QGIS.

QGIS can be used to make geologic maps of an area, chart streams, and note where certain geologic features (e.g. volcanic cones) are present. For instance, at the top of this post is a map of Heard Island that I’ve been playing with, from the Australian Antarctic Division. It is composed of three different layers, each published in 2009: an island layer (base, brown), a lagoon layer (middle, blue), and a glacier layer (top, dotted bluish-white).

I believe I have mentioned here previously that one interesting thing about working with Heard Island is that with major surface changes underway (glacial retreat, erosion, minor volcanic activity), the maps become obsolete fairly quickly. This week I have been learning about creating polygons in a layer, so that I can recreate a geologic map from Barling et al. 1994.[1] One issue I’ve come up against, though, is that the 1994 paper has some areas covered in glacier (from 1986/7 field work), whereas my 2009 glacier extent map shows them to be presently uncovered. In fact, even the 2009 map shows a tongue of glacier protruding into Stephenson Lagoon (in the southeast corner), while recent satellite imagery shows no such tongue.

During the Heard Island Expedition in March and April, 2016, I hope that we will have time to go do a little geologic mapping. Creating some datasets showing the extent of glaciation (particularly along the eastern half of the island) and vegetation, as well as updating the geologic map to include portions which were glaciated in 1986/7, would be a worthwhile and seemingly straightforward project.

QGIS itself is much more than a mapping tool (not that I know how to use it), and can analyze numeric data which is spatially distributed, like the concentration of chromium in soil or water samples from different places on a study site. QGIS provides a free way to get your hands dirty with spatial data and mapping, and is powerful enough to use professionally. Users around the globe share information on how to use it, and contribute to its development.

For those looking to go into geoscience as a career, I would strongly recommend learning how to use it. I didn’t learn GIS in college (chemists don’t use it much), and somehow avoided it in grad school. But I regret not having put time in to learn it sooner. There’s all kinds of interesting spatial data, and a good job market for people with a GIS skillset (or so I hear). I have only scratched the surface of QGIS’s capabilities with my use of it, but I definitely intend to keep learning. You can probably follow the day-to-day frustrations and victories on my Twitter account (@i_rockhopper).

***

[1] 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, p. 1017–1053. doi: 10.1093/petrology/35.4.1017

Compton Glacier Calving Seen from Space

Heard Island on a clear morning, seen by the MODIS instrument on NASA's Terra satellite.  July 31, 2015.  Image credit: NASA GSFC (Terra/MODIS).
Heard Island on a clear morning, seen by the MODIS instrument on NASA’s Terra satellite. July 31, 2015. Image credit: NASA GSFC (Terra/MODIS).

July 31st was a remarkable day on Heard Island, for several reasons. First, the weather was clear—a rare event in itself. Second, both NASA’s Terra and Aqua satellites had Heard Island reasonably near the center of their swath images. That’s not super-rare, but it’s probably <25%. Third, not only was the weather clear, but it was clear for both satellite overpasses, so both Terra and Aqua had good views of the island.

Many days, as I check the satellite images to see if Heard Island is visible, I end up playing “where in this image is Heard Island”. Imagine my surprise when I saw the Terra MODIS preview image from the morning pass, and there was a nice, bright white spot with some swirling grey vortices pointing toward it. The full-resolution image is shown above (cropped). It’s exactly the charismatic image I watch for, even though the resolution is moderate.*

I scrolled down the page to the Aqua MODIS images, which come from the early afternoon. Although Heard Island was a little off to the side of the image, leading to some artifacts, it was still free of the usual obscuring clouds. What a day! Two great images from when the island was within the usable part of the MODIS swaths.

Heard Island, standing in stark contrast to the dark blue waters of the Indian Ocean, July 31, 2015.  Image credit: NASA GSFC (Aqua/MODIS).
Heard Island, standing in stark contrast to the dark blue waters of the Indian Ocean, on the afternoon of July 31, 2015 as seen by NASA’s Aqua satellite. Image credit: NASA GSFC (Aqua/MODIS).

As I looked more closely, I noticed something odd about the afternoon image: Compton Lagoon, in the northeast corner of the island, had a very odd shape. Usually it looks rather like it does in this map from the Australian Antarctic Division:

Topographic map of Heard Island, published July, 1999.  Compton Lagoon is prominent in the northeast.  Image Credit: Australian Antarctic Division.
Topographic map of Heard Island, published July, 1999. Compton Lagoon is prominent in the northeast. Image Credit: Australian Antarctic Division.

Let’s look more closely at the satellite images.

Heard Island, morning of July 31, 2015. (Terra MODIS, as above; annotations mine).
Heard Island, morning of July 31, 2015. (Terra MODIS, as above; annotations mine).
Heard Island, afternoon of July 31, 2015.  (Image from Aqua MODIS, as above; annotations mine).
Heard Island, afternoon of July 31, 2015. (Image from Aqua MODIS, as above; annotations mine).

Some of the difference between images comes from the North Barrier ridge, which runs from high up the volcano down to the west of Compton Lagoon, bounding the Compton Glacier to the northwest. With the sun in the northeast in the morning and northwest in the afternoon, the ridge stands out much more in the afternoon when it casts a shadow on the light glacier.

The lagoon, however, is quite different. Much of what was blue lagoon in the morning is grey in the afternoon, and the glacier seems to be a bit darker grey near its toe. I interpret that as evidence for a significant calving event, where ice, snow, and rocks from the glacier break off and slide/fall into the lagoon. A wind from the northeast (evidenced by the clouds) helps to keep the floating ice toward the west end of the lagoon.

Of course, it would be nice to have a second image showing the ice floating around in the lagoon, or a higher resolution image of the glacier. Unfortunately, since these images were taken, the images have been cloudy and/or off to the side of the field where distortion and artifacts are at their worst. I was hoping that the EO-1 satellite or Landsat 8 would get a good image with their 30 m resolution, but that doesn’t seem to be the case. That just goes to highlight how incredible these images are!

***

* That’s the MOD in MODIS, the MODerate resolution Imaging Spectroradiometer; at its best (directly beneath the satellite) the resolution is 250 m/pixel.