Geoscientist’s Toolkit: Rock Hammer

Hammer for scale rests on a silicic dike in the Benton Range, near Bishop, CA.  Image credit: Bill Mitchell.
Hammer for scale rests on a silicic dike in the Benton Range, near Bishop, CA. Image credit: Bill Mitchell.

In the field, a rock hammer can be a very versatile and useful tool. One of its primary purposes is to give a sense of scale to photos which otherwise would lack one (see above). A related use is pointing to a specific feature in an outcrop photo, such as an interesting layer of sediment or a fossil.

Finally, and perhaps the use most people would think of, is to make big rocks into smaller rocks (while wearing appropriate eyewear and other protective clothing). Often rocks at the surface have been subject to weathering from sun, wind, and rain. To get to fresh, unweathered rocks, it is necessary to dig back into the rock face. Upon reaching fresh rock, the rock hammer can be used to break off smaller bits that can be analyzed back in the lab.


Where on Google Earth #474

For WOGE #473, we had a trip to the Diamantina River in western Queensland, Australia.

This being the first time I have hosted a WoGE, a short rules explanation:
A Google Earth image is posted with no coordinates. You find the spot in Google Earth, then post the lat/long in the comments here, along with a brief description of the geology of the area. Upon winning, it is your responsibility to host the next WoGE on your blog (or ask another player, e.g. me, to host for you), within a few days. More complete rules here, and hints on finding places here.

Without further ado, I present WoGE #474.


I will invoke the Schott rule: previous winners must wait 1 hour for each previous win. Published 2048 UTC Feb. 24

@Wogelix maintains a Twitter feed of links to the latest WoGE.

I am on Twitter, too: @i_rockhopper.

T -8.5 Months and Counting

A cold winter day in Minnesota.  The weather makes staying inside working on Heard Island expedition planning easier.  Image credit: Bill Mitchell.
A cold winter day in Minnesota. The weather makes staying inside working on Heard Island expedition planning easier. Image credit: Bill Mitchell.

We are more than eight months away from departing Fremantle bound for Heard Island, but there is a lot happening behind the scenes. Here is a sampling of what I have been up to for the last week or so.

I have been appointed the on-island IT czar for the expedition. Making sure the expedition computers run, and that the network interfaces properly to the satellite equipment for phone/data links to the rest of the world, fall under my responsibilities. Despite the satellite phones, we have to plan for having no or nearly no data connection with the outside world. Any software we need has to be installed before we go. Manuals need to be saved locally, because the standard “just ask Google” method of tech support will not work.

The amateur radio operations (VK0EK) will need some fairly complicated software and networking. Data needs to be saved redundantly, and shared across computers in near-real-time. We also intend to have custom software sending some of that data back to the outside world. So this week, I have been installing software on a laptop I will use for testing everything. I met with the software developer of our custom software via Skype to get an idea of how it works and what the trouble spots may be. Documentation is important, so I am taking notes on how the computer is being set up. Once it’s working, we may need to replicate it on another 10 computers.

Some of the programs I am installing are new to me, so I have also been learning how to use them. This weekend, I will have a chance to test my understanding of them more thoroughly. There are several different programs which all need to function in concert with each other, and we need for things to be very reliable.

One consideration that goes into the decisions on technology for Heard Island is that with the high winds, volcanic ash and dust tends to get picked up and blown about absolutely everywhere. This is not only a problem in terms of keeping the insides of the shelters clean, but can also do quite a number on moving parts such as motors, fans, and hard drives. In creating our technology plan, we need to plan for multiple hardware failures, and devise a resilient solution. With guidance from the many experienced team members (both on- and off-island folks), I think we will do well in creating a computer system to support the expedition. It looks to be coming together well so far.

In addition to the IT work, I have been working on my plans for scientific work on the island (mini-spoiler: I’m not ready to disclose details of the plans; the following will be abstract). Scientific activities this week have included trading a few emails with a potential collaborator, continuing to track down as much Heard Island research in the peer-reviewed literature as possible, and even reading some of that literature.

Here are some of the questions I’m wrestling with:

  • Where are the best places to sample?
  • What equipment will best balance scientific value of samples with cost, size, and the number of personnel needed to operate it?
  • What are the likely difficulties I will encounter?
  • What am I likely to find?
  • In what ways will the simple model I have in my head differ from the more complicated reality on Heard Island?
  • How close are the sampling locations to the base camp?
  • Would any of the work I intend to do be replicating what has already been done?
  • Are there ways to make my work help guide interpretation of previous research or other research being done on this expedition?
  • How much time is needed for carrying out the scientific work, and in what size blocks?

Many of these questions are interconnected. Sampling locations need to be close enough to the base camps that I can reach them easily, no multi-day hiking trips will work for me, and water transportation is unreliable due to the weather. They need to be in a location which has the kind of rocks/other stuff I want to study. I need to have the tools to sample or measure well, but they can’t be so large or bulky that they require a 4-person team to haul and operate. All of the equipment has to be landed by zodiac, after all. The overall budget for my research is not very large, so equipment choice will need to bear that in mind.

But the biggest thing is figuring out what to expect. Will the sample of rock I get be a few years old? A few decades? Tens of thousands of years old? More? Will vegetation, ice, or fauna block access to the sampling location? If I were to sample sedimentary rocks, would processes such as mass wasting (e.g. landslides), glacial movement, or animal burrowing have disrupted the even bedding of my ideal sediment? The equipment which is best suited for the work, and the amount of interest from collaborators, could vary greatly depending on what the expected results are.

So in the mean time, I read all that I can, talk with other scientists, and prepare a plan of action. Decisions need to be made soon, because equipment needs to be acquired either in Australia by some of the local team there, or here in the US in time for the Bay Area team to load it into the container to be shipped in the early (northern hemisphere) fall.

Back to work!

Geoscientist’s Toolkit: Camera

Columns of the Giants.  Image credit: Bill Mitchell
This is not a camera. It is a picture of Columns of the Giants, taken with a camera under less-than-ideal lighting conditions. Image credit: Bill Mitchell

A good camera is handy to have in the field. You can capture in a picture more details than you can sketch in a reasonable time. Additionally, if you sketch like I do, the picture will be far more accurate in its recording of what you are seeing. For instance, the above photo shows Columns of the Giants, from well up into the Sierra Nevada range in California. From this picture, you could estimate cliff height, the height of the columns (at the base of the cliff), the typical size of the columns, and so forth.

One or two lenses are generally sufficient: a wide-angle lens to get big features (choose this if there can be only one), and a macro lens for close-ups.

When taking pictures, it is important to include a scale of some sort. It can be a finger, shoe, pen, hammer, person, truck, whatever. Just make sure there is some context for the size of the image. I was reassured when, in my quest for a scale-less picture for last week’s post, I had difficulty finding one. For many places, you might get by if you forget. However, on Heard Island, the barren and alien landscape will not be so forgiving.

Peer-Reviewed Research: Terrestrial Vegetation and Environments on Heard Island

Kerguelen cabbage (Pringlea antiscorbutica).  Image credit: B.navez, CC-BY-SA, via Wikimedia commons.
Kerguelen cabbage (Pringlea antiscorbutica). Image credit: B.navez, CC-BY-SA, via Wikimedia commons.

Previously I’ve mentioned rocks, glaciers, a volcano, penguins, and elephant seals, but what about plants on Heard Island? That has been well-covered (pardon the pun) by Bergstrom and Selkirk (2000), who published their findings in an open-access journal.[1]*

Vegetation on Heard Island is generally categorized into six groups (“communities”), which reflect the general microhabitats and species makeups of the area. Here are a couple of brief descriptions:

Poa cookii maritime grassland” is characteristic of nutrient-enriched, animal influenced environments (Hughes 1987, Scott 1988). This community is dominated by the small tussock grass Poa cookii (Hughes 1987), with the nitrophiles Callitriche antarctica and Montia fontana also common.

“Feldmark communities” are characterised by less than 50% vegetation cover. Hughes (1987) described feldmark as having high relative vasular plant diversity but low species abundance, with predominant plants being Azorella selago, Poa kerguelensis, Colobanthus kerguelensis, Pringlea antiscorbutica, bryophytes and lichens. Scott (1988) recorded feldmark on well-drained areas of high altitude/high wind exposure, areas of recent glacial retreat, flat valleys likely to be subject to cold air drainage, and geologically recent lava flows.

After establishing some terminology about what types of communities are there, the authors move into the environmental factors that influence the plants on Heard Island.

Animal-derived nutrients are one factor. “A nutrient gradient is apparent, diminishing away from coastal seal and bird-breeding, resting, and hauling-out areas. Areas affected by direct manuring by seals, penguins, cormorants and giant petrels are generally devoid of vegetation, reflecting toxic nutrient levels and physical damage to plants.”

The types of rocks present, and the geochemistry of those rocks, could control what plants will thrive there. However, that has not been studied in detail on Heard Island (yet! [as of 2000]).

Salt spray from the ocean can make life difficult for plants, as can debris blowing in the wind. The depth to which roots can be sunk varies greatly, from almost nothing on the lava flows to more than 50 cm on moraines and other areas of loose sediment. Water availability also is important; some areas with poor drainage form pools, while other areas of loose rocky material drain very quickly. Snowmelt provides water throughout the summer, although precipitation is frequent throughout the year.

Movement of the rock/soil surface, such as through landslides, frost-heaving, and sediment accumulation can disrupt plant activity. Animals can trample (and eat!) plants, in addition to “adding nutrients”. Of course, the general climate influences, such as temperature (warmer toward sea level) and sunlight (more clouds on west side, more sun on east side) also play a role.

Bergstrom surveyed the plant diversity and abundance quantitatively during the 1986/1987 Australian National Antarctic Research Expedition to Heard Island. Almost 500 quadrats (1×1 m squares) were surveyed, and included three main vegetated areas of the island: Laurens Peninsula (northwest), Spit Bay (southeast), and Long Beach (south-southwest). By placing these quadrats on random (or as random as practical) ice-free locations, representative population statistics can be tabulated. Some species occur primarily clustered with certain other species, and others (e.g. Azorella selago) are widespread.

This survey of terrestrial flora provides an excellent baseline from which to study the changes in populations as the climate warms and glaciers recede on Heard Island. Through this kind of work, scientists can find how the plants are responding to changing conditions and new areas to colonize.

Beyond this research are some big questions: how did plants first arrive on Heard Island? Where did they come from? Which species were first to arrive? When did they arrive, and how long had Heard Island been above the ocean when they came?

[1] Bergstrom, DM and Selkirk, PM (2000) Terrestrial vegetation and environments on Heard Island. Papers and Proceedings of the Royal Society of Tasmania, 133 (2). pp. 33-46. ISSN 0080-4703

* Open access journals are a great way to ensure that research is widely accessible. I am considering outlining my views on academic publishing in a later post (this footnote is only so large).

Geoscientist’s Toolkit: Scale Bars

Zircon grains, without scale bar.  Image credit: Bill Mitchell
Zircon grains, without scale bar. Image credit: Bill Mitchell

Scales are useful. Many times a picture alone may not give adequate information about the scale, particularly absent recognisable objects or vegetation. For instance, the zircon crystals above have no scale: how long do you think they are? (answer below!)

Similarly, this outcrop photo does not have a scale either. How large are the beds in the fold?

Fold in outcrop, without scale.  Image credit: Bill Mitchell
Fold in outcrop, without scale. Image credit: Bill Mitchell

In the geosciences, a sense of scale is particularly important. Without it, these images lose context which may be important to their interpretation.

Let’s see how you did.

The zircons are around 100-150 microns long. For context, a standard piece of copier paper is around 100 microns thick.

Zircon grains, with scale bar.  Image credit: Bill Mitchell
Zircon grains, with scale bar. Image credit: Bill Mitchell

How about the outcrop? Here’s another picture, with a pen in the lower left for scale.

Fold in outcrop, with scale.  Image credit: Bill Mitchell
Fold in outcrop, with scale. Image credit: Bill Mitchell

Those are two examples of ways to put scale bars in. The first is by calibration of the relation between pixels and size for a microscope. The second is by the addition of a common object.

Another way to be particularly quantitative about the scale bar is to include a scale in the photo itself, as below. Off to the left you can see the edge of a small whiteboard, which is used to write the sample name and latitude/longitude coordinates for future reference. It’s the old-fashioned way to embed metadata, and is great for when you get back from your field work and are wondering what the heck your picture is actually of.

Volcanic ash, with scale bar for scale.   Image credit: Bill Mitchell.
Volcanic ash, with scale bar for scale. Image credit: Bill Mitchell.

Such emphasis on scale may seem pedantic for many field or lab photos. However, in environments where there is little available to give a sense of scale, such as the polar regions, or deserts, scale is an important thing.[1] This is a key consideration to keep in mind when travelling to places like Heard Island, where the scale will not necessarily be apparent without additional effort to include it within the pictures.

[1] Gould, L. M. Cold: The Record of an Antarctic Sledge Journey. New York, Brewer, Warren & Putnam, 1931.

Topographic Map(s) of Heard Island, and a Big Landslide

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.

A few days ago, I posted about topographic maps, including a discussion of how a small army of small surveyors made one of my local park. At Heard Island, surveying isn’t a walk in the park.

Many maps have been made of Heard Island, showing the topography and general geographic features of the island, and sometimes including the locations of major macrofauna (penguins, elephant seals, etc.).[1] An excerpt I made from one produced in 1985 is shown above. Although there are more recent maps available, including maps with higher topographic resolution, this one is more visually illustrative of the landforms.

Maps of Heard Island are difficult to produce, in part because there is a dearth of high-resolution, high-quality data. In most parts of the developed world, detailed topographic maps are made not through boots-on-the-ground surveying but by airborne LiDAR. For instance, aerial imagery and LiDAR provided very useful data for understanding the Oso landslide in Washington state. However, aerial flights over Heard Island are much less frequent, and mapping efforts there come without the obvious benefits to the local populace.

LiDAR map near the Oso landslide (red region at right), and a larger landslide complex (red region at center).  Image credit: Dan McShane.
LiDAR map near the Oso landslide (red region at right), and a larger landslide complex (red region at center). Image credit: Dan McShane.

Surveying the whole island by foot at high detail is untenable, because the area is quite large, the terrain difficult, and the weather inclement, even in the summer. However, portions have been mapped by hand (and theodolite).

But perhaps the biggest challenge Heard Island presents to cartographers is the rapidity of its changes. Volcanic eruptions can add new land to the island, or make parts higher. Glaciers can carve out the rocks and leave them as till, sometimes in the ocean, sometimes in the lagoons, and sometimes as moraines on the land. Not only can the glaciers carve out the rocks, but as less snow accumulates on the glaciers than is lost to melting, the glaciers will retreat. This opens up new land which before had been covered in ice. Stephenson Glacier, on the southeast corner of Heard Island, has retreated significantly in the last 60-70 years, revealing a great deal of new terrain.

Steep slopes and the very wet environment (lots of snow and rain) lead to very high rates of erosion. Outwash channels from the glaciers can carve into the rock and transport sediment into lagoons and near-shore areas.

Finally, there’s another agent of change: landslides. Take a look at the LiDAR image above, showing the landslide region. Now take a look at the southwest portion of the Heard Island shown at the top of the post. The curving crest along the north and east sides of the volcano, as well as the ridge extending to the south-southwest are interpreted to be the boundary (technical term: scarp) of a debris avalanche (a landslide-like process).[2]

Taken as a whole, these processes change the landscape significantly on a decade-to-century timescale, if not even more rapidly. This is why making maps and keeping them current is so valuable: it give us a way to see how the landscape is changing over time. Perhaps the upcoming Heard Island Expedition will do some mapping and be able to provide updates which reflect the latest changes at Heard Island.

[1], accessed Feb. 6, 2015. Free registration required for map download.

[2] 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.

Geoscientist’s Toolkit: Hand Lens

Vivianite (blue) in a lake sediment core, seen through a hand lens.  Image credit: Bill Mitchell
Vivianite (blue) in a lake sediment core, seen through a hand lens. Image credit: Bill Mitchell

A good hand lens is a fundamental part of a geoscientist’s toolkit. It is small enough to be carried around anywhere, and makes it easy to see details of the rock.

What aspects of the rock are important that might be missed without a hand lens?

Sometimes the minerals (grains of a certain chemical composition) are too small to see clearly with the naked eye. With a hand lens, these minerals can be identified, leading to clues about the chemical composition—and thus potential origins—of the rock. In the case of the photo above, the identification of vivianite gives clues about what conditions were present in the lake when it was deposited (lots of iron and phosphorous available; what scenarios would produce these kinds of conditions?).

Another thing to look for, in sedimentary rocks, is the degree of rounding of the grains. Angular grains have not been smoothed much by wind or water, so they would have come from nearby. More rounded grains would have had more tumbling and pounding from transport by wind and water, so are likely of more distant origin. Sediments can also contain small fossils, which can be seen with a good hand lens. Identification of these fossils may enable a rough estimate of the age of the sediment.

For metamorphic rocks, a hand lens may reveal foliation, reaction rims, and even compositional banding in gneisses.

I use a 10x hand lens, and it works well for me. It’s small, light, and I have it on a nice lanyard.

Heard Island Rocks: A Primer

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. Full size image (same source).

Heard Island is covered in interesting geology, with windows into the past, the present, and the Earth’s interior. In the coming weeks, I expect this will be a recurring topic, so if there are parts you’d like me to elaborate on, please leave a comment!

There are three main rock types on Heard Island: volcanic rocks, marine sediments, and increasingly, glacial sediments. We will focus primarily on the first two, as the glacial sediments are quite recent and not yet lithified, and less has been written about them.

At the base of the stratigraphic sequence accessible above sea level are marine sediments, specifically limestone.[1] These sediments are composed of the carbonaceous shells of micro-organisms, and were deposited when the water was very shallow, but in an open-ocean setting. From the types of shells found, these limestones were deposited between about 60–30 million years ago (Ma).[1 and references therein] (Refresher on the geologic timescale)

Overlying the limestone is the Drygalski Formation, which is of volcanic origin, and begins around 10 Ma. The Drygalski formation includes pillows, which are small (<1 m diameter) blobs of rock which form when lava is erupted underwater, which rapidly cools the outsides.* Other rocks in this formation include hyaloclastite, which is also characteristic of submarine volcanism. Glacial sediments in the form of tillite (wide range of sizes of sediment with clasts (rock chunks) supported by much finer grain sizes) are also present in this formation, indicating the presence of glaciers in the area.

Volcanism has begun again more recently, no later than about 1 Ma (based on K-Ar dating), and created the modern volcanic structures on the Laurens Peninsula and Big Ben itself.[2] This volcanism continues in the present-day, and eruptions have been observed by satellite in 2013 (see picture above). Not only are there the volcanoes of the Laurens Peninsula and Mawson Peak atop Big Ben, but there are numerous small volcanic cones along the perimeter of the island. The age of these cones is unknown, but their small size and fresh appearance suggest they are quite recent (100-5000 years?).

On the subject of volcanism, Sand Atlas had a good post recently explaining the different types of lava flows. Heard has pahoehoe, a’a,[3] and pillows, and I expect there may be some columns as well.

Dr. Will Powell of Macquarie University has a number of good field photos from a trip to Heard Island in 2000, as well as a bit of commentary to go along with them. One of the pictures is of a basaltic dike intruding rocks on the north end of the Laurens Peninsula. That dike is where magma squeezed up from below, possibly to a surface eruption above which may have been subsequently eroded away.

Finally, Heard Island has glacial sediments (till). This is being deposited in the lagoons and on the land as the glaciers retreat. I expect to find medial and terminal moraines when I am there, and some of the moraines are presently visible in the satellite imagery. There is a terminal moraine (or is it a ground moraine?) at the end of the glacier in the upper right of the picture above, at around the 2:00 position in relation to Big Ben. It is manifested as a brown patch between the glacier and the lagoon.

So, that’s the brief overview of the rocks of Heard Island. All the rocks are from the Cenozoic (<66 Ma), with the oldest being limestones, then some much younger volcanics and glacial sediments on top, with both the volcanics and glacial sediments depositing presently. I can’t wait to get there and see them in person!

[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] Clarke, I., McDougall, I. & Whitford, D.J., 1983: Volcanic evolution of Heard and McDonald Islands, southern
Indian Ocean. In Oliver, R.L., James, P.R. & Jago, J.B. (Eds): ANTARCTIC EARTH SCIENCE. Australian Academy of Science, Canberra: 631-635.

[3] Arthur Scholes, Fourteen Men, E. P. Dutton, 1952.

* For more on pillow lavas, with some great pictures, check out this post at Magma Cum Laude.