Tag Archives: Geology

Azorella Peninsula Gigapan

Processing the Azorella Peninsula gigapan.  Image credit: Bill Mitchell (CC-BY).
Processing the Azorella Peninsula gigapan. Image credit: Bill Mitchell (CC-BY).

This is the second in a series of three posts about the gigapan images taken on Heard Island (1: Big Ben, 3: Windy City), with more information about the Azorella Peninsula gigapan.

The Azorella Peninsula is on the northern edge of the main part of Heard Island, east of the Laurens Peninsula. It forms the eastern boundary of Atlas Cove (Laurens Peninsula forms the western boundary; see map below). At the west end of the Azorella Peninsula’s southern margin is the heritage zone around the ANARE campsite, two water-tank shelters, a green “apple” shelter, and the area where our expedition made camp. That many of the camps are all in the same area is no accident: Atlas Cove is probably the best harbor on the island (though still not sheltered from a northerly swell), there is a convenient beach for boat landings, and a small step up of elevation from the lava flows of the Azorella Peninsula provides higher ground than the sometimes-inundated Nullarbor.

Heard Island Map, 1985. Image credit: excerpt from the Division of National Mapping.
Heard Island Map, 1985. Image credit: excerpt from the Division of National Mapping.

Getting a gigapan here was not as straightforward as I had hoped. Although there were plenty of pahoehoe flow tops, cracks where a flow had deflated and collapsed in on itself, and other lava flow features, few of them were of a scale and in a location which enabled them to be nicely gigapanned with the tripod I had. With another 3–5 m of elevation, the gigapan would be spectacular.

As it was, there were some additional features besides the lava flows which I wanted to include. For one, the landscape has significant erosional processes happening, and there are sandy areas which get washed when it rains. Even more than the rain, though, the wind creates eolian features. Many of the small rocks have a little dune in their lee, and often the Kerguelen cabbage and Azorella moss grow on the leeward side of rock barriers as well. Some of this organization is visible in the gigapan.

At the top right of the Gigapan image, and lost to the fog and overexposure of the image, is a strongly layered prominence: Corinth Head. Although I would have liked to go see this outcrop up close, our permit did not allow that—the area is a major nesting site for burrowing seabirds, and in places there are lava tubes with thin ceilings which may give way underfoot.

Corinth Head, Heard Island, viewed from the south (further east than the Gigapan was taken).  Layering is clearly visible, and is likely of igneous origin.  Image credit: Bill Mitchell (CC-BY).
Corinth Head, Heard Island, viewed from the south (further east than the Gigapan was taken). Layering is clearly visible, and is likely of igneous origin. Image credit: Bill Mitchell (CC-BY).

Where the Azorella Peninsula lava flow field meets the Nullarbor, there was a little flow which caught my eye. There, one flow clearly traveled through an older channel or tube. Weathering has removed some of the older flow, giving a cross-sectional view of the dark vesicular rock.

Lava flows of the Azorella Peninsula meet the Nullarbor.  An older, grey unit is visible with a redder unit in the middle.  Notebook is 19 cm wide.  Image credit: Bill Mitchell (CC-BY).
Lava flows of the Azorella Peninsula meet the Nullarbor. An older, grey unit is visible with a redder unit in the middle. Notebook is 19 cm wide. Image credit: Bill Mitchell (CC-BY).

Some lava tubes showed obvious signs of deflation or lava tube collapse. The one seen below had eolian features nearby, and the Kerguelen cabbage and Azorella moss can be seen growing on the leeward side of the rocks. An elephant seal is also present.

Deflated lava flow beside the Nullarbor on the Azorella Peninsula, Heard Island.  Some eolian features are present.  Note the Azorella moss and Kerguelen cabbage at right, in the lee of the solid rocks.  The tan mass at right is an elephant seal.  Notebook is 12x19 cm.  Image credit: Bill Mitchell (CC-BY).
Deflated lava flow beside the Nullarbor on the Azorella Peninsula, Heard Island. Some eolian features are present. Note the Azorella moss and Kerguelen cabbage at right, in the lee of the solid rocks. The tan mass at right is an elephant seal. Notebook is 12×19 cm. Image credit: Bill Mitchell (CC-BY).

Finally, here is another example of a collapsed lava tube, which shows off a cross-section of the top of the lava tube as well as some pahoehoe flow tops.

A collapsed lava tube on the Azorella Peninsula, Heard Island, gives a cross-sectional view of the roof of the lava tube.  Kerguelen cabbage plants in foreground are roughly 25 cm across.  Several pahoehoe flow tops are visible: small-scale in the foreground, and large-scale in the center toward the top of the image.  Image credit: Bill Mitchell (CC-BY).
A collapsed lava tube on the Azorella Peninsula, Heard Island, gives a cross-sectional view of the roof of the lava tube. Kerguelen cabbage plants in foreground are roughly 25 cm across. Several pahoehoe flow tops are visible: small-scale in the foreground, and large-scale in the center toward the top of the image. Image credit: Bill Mitchell (CC-BY).
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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.

Farewell, Cape Town!

HDT Airbeam tent being loaded onto the Braveheart.  The tent is also blocking a nice view of Table Mountain.  Image credit: VK0EK team.

We are in the final breakfast and boarding process for departing Cape Town. Above is a picture from yesterday, where all the inspected expedition gear was loaded onto the Braveheart.

Cape Town has been very nice. Our hotel is within an easy walk of the ship, and there are many shops nearby where we have acquired food, groceries, clothing, outdoor gear, and souvenirs. Weather has been quite warm (26 °C, 79 °F) with a breeze. The local Cape Town team has been extremely helpful and have made much of the project move more smoothly. Crew from the Braveheart have also been wonderful to work with, and I’m looking forward to getting to know them more in the next six weeks. As the ships were loading, a seal was playing in the harbor, gulls were flying around, and even a few terns were spotted.

As can be seen in the photo above, there is some interesting geology around Cape Town. Most noticeable is Table Mountain, which is primarily made up of the Table Mountain Sandstone. Closer to the hotel is Signal Hill, which has slates that have been tilted nearly vertical. We were able to see these up close yesterday evening after the ship was loaded and things were under control. It’s quite a view from up there (sorry, haven’t had time to process pics). For more on the geology of Cape Town, take a look at this post by Dr. Evelyn Mervine, who writes one of the AGU blogs.

Internet connectivity on the ship is likely to be minimal, but with luck I’ll be able to get a post or two up from Heard Island! More frequent news updates can be found at vk0ek.org.

A One-Stop Heard Island Expedition Primer

North-up view of Heard Island seen from the International Space Station, Nov. 24, 2011.   Image credit: NASA (public domain)

North-up view of Heard Island seen from the International Space Station, Nov. 24, 2011. Image credit: NASA (public domain)

Heard Island, the southernmost surface exposure of the Kerguelen Plateau, is an uninhabited Australian territory situated in the southern Indian Ocean, roughly 450 km SE of the Kerguelen Islands. It is classified as a UNESCO World Heritage Site both for its geologic significance as well as its relatively undisturbed ecosystem. Heard Island is unique among sub-Antarctic islands for having no known human-introduced species.

Physically, Heard Island is roughly circular, with a diameter of 20 km. In the center is Big Ben, a volcano which reaches to 2700 m and was observed erupting within the last 10 days. To the southeast is Elephant Spit, a long sandy spit which protrudes 10 km past the circular shape of the island. In the northwest is the Laurens Peninsula, where volcanoes have added another 10 km to the windward side of the island, against the erosive power of the heavy Southern Ocean seas.

On March 10th, an expedition team of 14 scientists and a ship’s crew of five will depart Cape Town, South Africa, aboard the Braveheart and begin the roughly (and rough) 10-day voyage southeast to the island. Upon arrival at Heard Island, our team will wait for sufficiently calm surf to safely land boats on the beach. About three weeks will be spent on the island before a 10-day voyage to Fremantle, Australia.

For accommodations, two HDT Global air-beam shelters (20’x21′) will be erected at Atlas Cove, in the northwestern part of the island and in the lee of the Laurens Peninsula. A covered walkway, also from HDT Global, will allow travel between tents without full exposure to the elements. Nearby is an emergency refuge (condition unknown) from previous Australian Antarctic Division expeditions, as well as the potentially asbestos-containing ruins of the Australian research base from the 1947-1955 expedition. The ruined base is in a restricted area on account of the asbestos, and expedition members will not enter that area. Restrooms will be in the form of a portable toilet, and portable generators will provide electricity for the site.

Airbeam tent set up at HDT Global headquarters.  This is one of two which will be set up on Heard Island.  Image credit: Cordell Expeditions.
Airbeam tent set up at HDT Global headquarters. This is one of two which will be set up on Heard Island. Image credit: Cordell Expeditions.

Although featuring a large, vegetation-free sand and gravel plain, Atlas Cove is not devoid of life. Our neighbors will include elephant seals, fur seals, four species of penguin—gentoo, king, macaroni, and rockhopper—and many other types of seabirds. Leopard seals have been seen at Atlas Cove as well. To the northeast on the Azorella Peninsula, a colony of the endemic Heard Island cormorants nests atop a moss-covered lava field (access is forbidden due to the sensitive mosses and potential for lava tube collapse).

Communications is an important part of this project. Already we have done a major outreach effort in person, via the internet, and on social media. Many different levels of communications need to be covered: ship-to-civilization, ship-to-island, on-island, island-to-civilization, and amateur radio from the island. We will have several different satellite phone/data systems, marine radios for ship-to-island contacts, and amateur radios for both on-island and worldwide communications. Being able to talk with field teams, the ship, and the outside world is a important for a safe expedition.

Soon after the tents and generators are set up, the antennas used to make contacts around the world will be erected. Amateur radio operators have given generously to support this expedition, and are often curious about science. Making contacts with these amateur stations helps to bring visibility to Heard Island, its unique geology and ecology, and the science being done to better understand and protect the World Heritage Site. Large numbers of amateur radio contacts will also provide an interesting dataset, because the locations one can reach will vary depending on conditions in the upper atmosphere (ionosphere). During the expedition, near-real-time maps of contacts can be found here.

At the camp, an automated weather station will be set up. Being far from human civilization and in the middle of the ocean, a record of weather at Heard Island would be valuable for assessing climate change in an under-sampled region of the globe.

Automated weather station for temperature, pressure, relative humidity, and wind measurements.  Our station will be similar but not identical to this one.  Image credit: US Marine Corps (public domain)
Automated weather station for temperature, pressure, relative humidity, and wind measurements. Our station will be similar but not identical to this one. Image credit: US Marine Corps (public domain)

When weather permits, a small field party will venture out to collect rock samples from the Laurens Peninsula. These samples will be used to answer questions like the environmental conditions when the rock was deposited, the processes that produced the unit (glacial, marine, volcanic, etc.), the duration of deposition, and the age (via biostratigraphy or radioisotopic dating). It is unknown when volcanism began on Heard Island, and whether the volcanism has been relatively continuous or more episodic. There have been no geologic research parties on the island since 1987, so this is an opportunity to collect important samples—especially because glacial retreat has exposed areas which were previously inaccessible. Field parties will not only collect samples, but will map the extent of glaciation and vegetation using GPS.

I will be taking the lead on a different geology project: capturing high-resolution panoramic pictures. Through collaboration with Prof. Callan Bentley and the GEODE project supported by the National Science Foundation (NSF DUE 1323419), we will have a Gigapan system on Heard Island. Using a robotic camera mount and a telephoto lens, a series of images are taken from one location. Upon return to camp, the images are transferred to a computer, where they are automatically stitched together with specialized software. The resulting images, which can be several gigapixels large, can be viewed using a web browser and offer pan-and-zoom capabilities (example from Axel Heiberg Island, Nunavut, Canada). We will use these high-resolution images to provide context for geologic sampling, to document the extent of glaciers and the appearance of landforms, and potentially to estimate populations of seabirds or marine mammals. Because the images will be very large, they may not be available online until after we return to the developed world.

Another project I have in mind, which may or may not be feasible, is to do at least some basic population counts for eBird. There have been four eBird checklists submitted for Heard Island, but none in March or April. I feel fairly confident on my ability to distinguish different types of penguins (at least at close range). Other seabirds, such as albatrosses, petrels, and prions, will be more difficult for me. Perhaps another team member will be able to help out.

Rockhopper penguins in the Falkland Islands.  Image credit: David Stanley (CC-BY)
Rockhopper penguins in the Falkland Islands. Image credit: David Stanley (CC-BY)

Along the shoreline, our team will record the concentrations of anthropogenic marine debris (plastic bits, fishing gear, etc.). The amount of debris and extent to which it is interfering with seabirds and marine mammals at Heard Island is unknown, and we are particularly interested in documenting cases where skeletal remains have associated debris.

There are a few more projects, and more detailed project descriptions can be found on the expedition website project page. If the winds are calm enough a few quadcopters may even be deployed to take pictures in areas too dangerous for us to reach on foot.

Heard Island is home to virtually pristine ecosystems, and our expedition will take care to keep it that way. Rodents are a particularly high concern, so before the ship sails from Cape Town, it needs to be certified free of rodents and must follow several rat prevention protocols. All gear has to be thoroughly cleaned and sanitized before being brought onto the island. On the island, when we move between ice-free areas (Atlas Cove and Spit Bay), we have to clean everything again. Even the food we eat must be in line with ecosystem preservation: no fresh fruit or vegetables, no poultry or eggs (except egg powder kept in sealed containers opened only indoors), and no brassicas (broccoli, cabbages, turnips). This expedition isn’t just an extra-large camping trip.

After three weeks of science, radio, documentation, and outreach, we will pack everything back up onto the Braveheart and embark on a 10-day voyage to Fremantle, Western Australia. On the ship, to the extent we are functioning on what could well be very rough seas, we will probably get started on data analysis, further documentation, and the task of identifying the most compelling photographs.

Polar projection map of the route to and from Heard Island.  Image credit: Bob Schmieder/Cordell Expeditions
Polar projection map of the route to and from Heard Island. Image credit: Bob Schmieder/Cordell Expeditions

When possible, I will try to maintain my presence on Twitter (@i_rockhopper) and here on this blog during the expedition. However, I do not expect to have much time or bandwidth for such things when there is a lot of important field work to do. My hope is that I will get some posts queued up and scheduled for release during the expedition. However, failing that, the best place to find news will be the expedition website and the radio-focused website.

I’m very excited about these projects, and look forward to being on Heard Island in about six weeks!

Update Feb. 11, 2016: There has been a correction on the project collaboration for the Gigapans. The first version wrongly credited the NSF support to the MAGIC project, rather than its umbrella project, GEODE.

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.

This Year in Uranium Decay

Pumice from the Bishop Tuff (~767 ka).  Zircons in this pumice are rich (relatively) in uranium, with up to 0.5% U.[1,2]  Image credit: Bill Mitchell (CC-BY).
Pumice from the Bishop Tuff (~767 ka). Zircons in this pumice are rich (relatively) in uranium, with up to 0.5% U.[1,2] Image credit: Bill Mitchell (CC-BY).

With 2016 now upon us, I felt it would be appropriate to think about what a new year means for uranium geochronology. What can we expect from the year ahead? Without getting into any of the active research going on, I felt it would be useful to address simply what is physically happening.

On Earth, there is roughly 1×1017 kg of uranium.[3] The ratio of 238U:235U is about 137.8:1, and 238U has a mass of roughly 238 g/mol (=0.238 kg/mol). Looking only at 238U, that gives us
1x1017[kg]x(137.8/138.8)/0.238[kg/mol] = 4.17x1017 mol [238U]

Radioactive decay is exponential, with the surviving proportion given by e-λt where λ is the decay constant (in units of 1/time) and t is time, or alternatively, e-ln(2)/T1/2*t, where T1/2 is the half-life and t is time.

To find the proportion that decays, we subtract the surviving proportion from 1: (1-e-λt)

Multiplying this proportion by the number of moles of 238U will give us the moles of decay, and multiplying by the molar mass will give the mass lost to decay:

(1-e-λt)*molU

Plugging in numbers, with λ238 = 1.54*10-10 y-1, t = 1 y and the moles of 238U from above, we get:

(1-e-1.54*10-10)*4.17*1017 mol [238U] = 6.4*107 mol

That yields (with proper use of metric prefixes) roughly 64 Mmol U decay, or 15 Gg of U on Earth that will decay over the next year.

Although those numbers sound very large, they are much smaller than even the increase in US CO2 emissions from 2013 to 2014 (50 Tg, or 50,000 Gg); total US CO2 emissions in 2014 were estimated at 5.4 Pg (=5.4 million Gg).[US EIA]

As for what’s in store for geochronology as a field, I think there will be a lot of discussion and consideration regarding yet another analysis of the Bishop Tuff.[4] Dating samples which are <1 Ma (refresher on geologic time and conventions) using U/Pb can be tricky, and Ickert et al. get into some of the issues when trying to get extremely high-precision dates from zircons. The paper is not open access, but the authors can be contacted for a copy (@cwmagee and @srmulcahy are active on Twitter, too!).

***
[1] J. L. Crowley, B. Schoene, S. A. Bowring. “U-Pb dating of zircon in the Bishop Tuff at the millennial scale” Geology 2007, 35, p. 1123-1126. DOI: 10.1130/G24017A.1
[2] K. J. Chamberlain, C. J. N. Wilson, J. L. Wooden, B. L. A. Charlier, T. R. Ireland. “New Perspectives on the Bishop Tuff from Zircon Textures, Ages, and Trace Elements” Journal of Petrology 2014, 55, p. 395-426. DOI: 10.1093/petrology/egt072
[3] G. Fiorentini, M. Lissia, F. Mantovani, R. Vannucci. “Geo-Neutrinos: a short review” Arxiv 2004. arXiv:hep-ph/0409152 and final DOI: 10.1016/j.nuclphysbps.2005.01.087
[4] R. B. Ickert, R. Mundil, C. W. Magee, Jr., S. R. Mulcahy. “The U-Th-Pb systematics of zircon from the Bishop Tuff: A case study in challenges to high-precision Pb/U geochronology at the millennial scale” Geochimica et Cosmochimica Acta 2015, 168, p. 88-110. DOI: 10.1016/j.gca.2015.07.018

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.