Tag Archives: Gear

Geoscientist’s Toolkit: Secchi Disk

Secchi disk being lowered into the water to measure water clarity.  Image credit: J. Albert Bowden II (CC-BY).
Secchi disk being lowered into the water to measure water clarity. Image credit: J. Albert Bowden II (CC-BY).

Some lakes and rivers are very clear, while others are very murky with sediment or organic material. Water clarity can yield information about what kind of environment is present around the water body (in its watershed). My local lake is fairly murky, due to significant nitrogen and phosphorous in the run-off from the many well-tended lawns in the area.

Secchi disks, are 20-30 cm diameter disks, generally white (freshwater disks generally have two black quadrants on them as well). These disks have a line attached to their center, and are lowered down into the water until they are just barely visible. That depth is the Secchi depth, and would be recorded.

In the Boundary Waters of northern Minnesota, scientists are interested in how the water quality of the lakes are changing. If you’re headed up there on a canoe trip, you can volunteer to take secchi depth measurements.

Getting secchi depth measurements in the lagoons and near-shore waters of Heard Island could be an interesting project, too.

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Geoscientist’s Toolkit: Dilute Acid

Folded outcrop of marine sediments in Berkeley, CA.  Image credit: Laikolosse (CC-BY-NC).
Folded outcrop of marine sediments in Berkeley, CA. Image credit: Laikolosse (CC-BY-NC)

When looking at sedimentary rocks in the field, one of the questions which may come up is whether or not a rock is a carbonate, such as in the outcrop pictured above. Although it is easy to determine that with an electron microprobe in the lab, there is a faster field test method: using dilute hydrochloric acid.

Sedimentary geologists will often carry a bottle of 0.1 M HCl and a watchglass with them in the field. A chip of the rock in question can be broken up and placed on the watchglass. When the acid is added, a carbonate will fizz as the acid releases carbon dioxide. This is the same process which makes a baking soda volcano erupt.

In some of my field work in the Texas Panhandle, I encountered a white layer among the redbeds. This bed was not gypsum, as many of the other white beds were. Because I was looking for volcanic ash deposits, not carbonates, an acid test was performed in the field. Unfortunately for me, the ground up sample started fizzing, so I knew it wasn’t the volcanic ash I wanted to find.

T -7 Months and Counting

Fair weather at Atlas Cove and on the Laurens Peninsula, Heard Island, taken April 10, 2015.  Nominal resolution is 250 m/pixel.  Image credit: NASA Terra/MODIS.
Fair weather at Atlas Cove and on the Laurens Peninsula, Heard Island, taken April 10, 2015. Nominal resolution is 250 m/pixel. Image credit: NASA Terra/MODIS.

We are now just under seven months from departure from Fremantle, Australia, to Heard Island. Preparations continue for the expedition; seven months may seem like a long time, but many projects need to be accomplished by then.

With plans for operations coming together nicely, there is a new focus on selecting, acquiring, and testing the equipment and supplies to be used on the expedition. Here are a few examples of choices which will need to be made:

  • What kind of shelter will we use?
  • What will we do to keep the shelter from blowing away?
  • How will we keep the shelter warm?
  • On what will people sleep?
  • What food will be brought on the expedition?
  • What kitchen equipment do we bring?
  • How will we network the computers, including shelters 200–300 m away?

Of course, as we make these choices, we are also considering what sort of backup plans we have. This expedition, like any other, is a delicate balance between redundancy, robustness, and minimalism (weight, cost, and labor).

One factor in choosing gear which is often overlooked in temperate climes is that of its poor-weather field-usability. With the precipitation, high winds (blowing snow, rain, and volcanic sand and dust), and cold temperatures, small pieces or anything requiring manual dexterity should be avoided. Choosing glove-appropriate tools and equipment can make the difference between a good day of efficient field work, and a very uncomfortable, miserable day in the cold, wet wind. Without glove-appropriate gear, the gloves have to come off, which in turn drastically reduces their [the gloves’] effectiveness.

Fortunately, on this expedition we will not have to deal with the temperatures found in the coldest regions of the world. In those extremely cold regions, eating utensils (at least fork and spoon) must not be made from metal—they will act as a heat sink and conduct heat away from your mouth very efficiently. I may bring wooden utensils just in case.

Procuring the gear we need presents its own logistical problems. The expedition leader and many of the support team are based in the US, but anything bought in the US has to be shipped to Australia. Buying things in Australia saves shipping, but larger items can’t be tested by the US team. There are further differences in things like electrical power distribution; generators will need to match the plugs and voltage required by the equipment, and the VK0EK amateur radio team need to be confident that the electrical devices we bring won’t interfere with their operations.

For my proposed research project, I have been wrestling with a the questions I posed in my previous post on expedition preparation. Some of the questions have been resolved. Not all of my lines of inquiry were successful. A number of locations I thought would be good to sample have, upon further reflection and study, turned out to be unlikely to yield results which would add meaningful data to my research. Further discussion with other scientists is planned, and I expect will help further clarify a plan of action—though it may be to scrap the project altogether and pursue a related research question.

This weekend, I finally got my hands on a book I have been looking forward to reading: Heard Island: Southern Ocean Sentinel. I took a brief glance through it, and there is a lot of good information there. Although I had planned to write today about glaciers, specifically the glaciers on Heard Island, I have deferred that for the time being so I can read more before writing that post. Maybe next time!

Geoscientist’s Toolkit: Sample Bags

Sample bag and purple volcanic ash.  Yellow tag is 5 cm by 7 cm.  Image credit: Bill Mitchell
Sample bag and purple volcanic ash. Yellow tag is 5 cm by 7 cm. Image credit: Bill Mitchell

Often when in the field, it is useful to bring back samples of rock. To keep samples labeled and contained, each sample is put into its own sample bag, which is then labeled and securely tied shut.

I have used both cotton and synthetic sample bags (the one shown above is synthetic), and generally prefer the cotton. The bags are a bit sturdier, and with some of the rocks I sample being fairly pointed, they hold up more nicely in shipping. Sturdy cotton sample bags are also a bit heavier, so on expeditions where every ounce matters, the synthetic may be the bag of choice. My samples are also generally dry, but in wet environments the cotton sample bags may not be appropriate as they may degrade during shipping.

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.

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.

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.