Tag Archives: Geoscience

Geoscientist’s Toolkit: SERC

Have you ever developed your own activities for doing outreach related to your research? Or wanted to find a way to teach a geoscience concept to a class?

There is a great resource available for this kind of thing: the Science Education Resource Center, at Carleton College [my alma mater].

From demos to lab ideas to tutorials on how certain types of equipment work, SERC has lots of great material. Of course, it doesn’t just appear out of nowhere. If you have taken the time to develop an interesting and useful activity, guide, or lab, you can submit the materials for others to use (under a Creative Commons license).

I have used SERC to get activities on dinosaurs (this one on calculating the speed of dinosaurs was awesome!), as well as to find good resources on mineralogy (my background as a chemist left me a bit behind mineralogy/petrology when I joined an Earth Science research group). There are activities and discussions around topographic maps, glaciers, climate change, groundwater, and the geologic timescale (my introduction to the geologic timescale, which isn’t on SERC, can be found here).

SERC is a great resource, and they hold workshops/webinars too!

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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.

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.

Where on Google Earth #492

For WOGE #491, Ole showed us a Jurassic/Cretaceous endorheic basin in Argentina, where little water-erosion has taken place since the deposition of the tephra and lavas.

While the forests in WOGE #491 were petrified, the forests of WOGE #492 are still very much alive.
woge_492

Find this place on Google Earth, then post the latitude and longitude in the comments, along with a description of the geology, geography, or other interesting -ologies of the place. The first commenter to correctly identify the place will host the next WOGE (guest-hosting can be arranged). A list of previous WOGE selections is available here (kmz) and here (twitter).

Geoscientist’s Toolkit: Radiosonde

Radiosonde launch.  Image credit: Laikolosse (CC-BY-NC).
Radiosonde launch. Image credit: Laikolosse (CC-BY-NC).

Last weekend, I had the opportunity to tour the National Weather Service‘s Weather Forecast Office in Chanhassen, MN. One of the highlights of the tour was the upper air sounding facility, which launches a radiosonde (weather balloon) twice daily (at 0000 UTC and 1200 UTC, which is 7:00 local time here in Minnesota during the summer).

Radiosondes provide crucial information about the state of the atmosphere by measuring pressure, temperature, relative humidity, wind speed, and wind direction. Wind speed and direction are determined by the movement of the balloon as measured by GPS. Observations are transmitted back to the launching station via radio, where they are merged with all the other observations around the world. The merged observations from the most recent soundings are fed into the numeric weather prediction models used by your local weather service office (and your local TV meteorologist) to create forecasts and evaluate severe weather threats.

Radiosonde instrument packages are fairly small—about the size of a thick book, like Anna Karenina, but mostly styrofoam. A wire protrudes from the instrument package which acts as the radio antenna and holds the temperature sensor away from the body of the radiosonde. The instruments are suspended on a line beneath a parachute, which is in turn held up by a large helium-filled balloon, perhaps 1.5 m in diameter (~5′). Upon release, the balloon will rise around 5-8 m/s (11-18~mph), and can reach a peak altitude of more than 38 km (23.5 miles), well into the stratosphere. At these altitudes, where pressure is less than .5% of the surface pressure, the balloon can expand to a diameter of 7.5 m (~25′).

Temperature and dewpoint profiles are often plotted as functions of pressure (closely related to altitude). In the lower part of the atmosphere, the troposphere, temperature gradually decreases as altitude increases. This is why mountains have a snowline. Beyond the troposphere lies the stratosphere. In the stratosphere, the temperature tends to increase with altitude, due to the absorption of UV light by ozone. Pictured below is a temperature profile from Chanhassen, MN, on a clear, warm day.

Temperature (right) and dewpoint (left) profile from Chanhassen, MN, on a clear, warm evening.  The x-axis is showing temperatures (°C), while the y-axis is showing pressure (in hPa; 1000 hPa is roughly surface pressure near sea level).  Image credit: University of Wyoming Department of Atmospheric Science.
Temperature (right-most dark trace) and dewpoint (left-most dark trace) profile from Chanhassen, MN, on a clear, warm evening. The x-axis is showing temperatures (°C), while the y-axis is showing pressure (in hPa; 1000 hPa is roughly surface pressure near sea level). For those curious about the purple and green lines, see here and here. Image credit: University of Wyoming Department of Atmospheric Science.

With a little training (e.g. this web course), a meteorologist can look at a temperature/dewpoint profile and identify whether it is sunny, cloudy, or if severe storms are likely.

Radiosondes are a great way to get detailed data about the state of the atmosphere. Within the US, there are roughly 90 balloon sounding stations, and there are many more stations around the globe. If I had more time and the funding to do it, I would love to send radiosondes up from Heard Island—it certainly is an under-sampled area of the globe.

Geoscientist’s Toolkit: Frantz Magnetic Separator

Frantz magnetic separator.  Image credit: Bill Mitchell (CC-BY).
Frantz magnetic separator. Image credit: Bill Mitchell (CC-BY).

When a sample for geochemical analysis gets in to the lab, often one of the first priorities is to separate the mineral(s) of interest in the rock (e.g. zircon, potassium feldspar, or quartz) from the other minerals. Once a rock has been crushed and milled to single-grain size, the sample is ready for separation.

One of the first methods employed is magnetic separation, which will separate the more magnetic (paramagnetic) minerals from the less magnetic (diamagnetic).

For magnetic separation, a Frantz magnetic separator is used (see figures). It has a chute which is tilted both down its long axis (right to left in the picture) and its short axis (far to near in the picture). With the chute alone, the samples would end up in the non-magnetic (near, pink) bucket from gravity. However, a strong electromagnet is used (big black things above and below chute) which holds the paramagnetic materials up against the force of gravity, directing them into the far chute.

Annotated Frantz magnetic separator, including the plan view (blue) and left-to-right along-chute view (maroon).  Image credit: Bill Mitchell (CC-BY).
Annotated Frantz magnetic separator, including the plan view (blue) and left-to-right along-chute view (maroon). Image credit: Bill Mitchell (CC-BY).

Both the feed chute and the main chute have vibrating motors attached, so that the grains get slowly bounced around and move gradually down. The electromagnet provides enough force to keep the paramagnetic minerals in the upper (far) part of the main chute. By adjusting the current running through the electromagnet, the threshold for magnetic/non-magnetic can be controlled.

Geoscientist’s Toolkit: Science on a Sphere

An educator from the Denver Museum of Nature and Science presents about sea floor spreading at the Science on a Sphere network meeting in Long Beach, CA (2012).  Image credit: Bill Mitchell.
An educator from the Denver Museum of Nature and Science presents about sea floor spreading at the Science on a Sphere network meeting hosted by the Aquarium of the Pacific in Long Beach, CA (2012). Image credit: Bill Mitchell.

One of the coolest tools I’ve had an opportunity to work with in the course of my research, outreach, and explorations of science centers, is the Science on a Sphere (SOS), which can be found at any of more than a hundred museums, educational institutions, and science centers worldwide.

Developed by NOAA, Science on a Sphere is a 1.7-meter diameter globe, surrounded by four projectors, which can display animated digital maps of the globe. Because the display is actually spherical, the maps do not have edges or strongly distorted projections, which can make looking at rectangular maps confusing.* On this display, it makes perfect sense why a flight from Los Angeles to Beijing would go near or over the Aleutian Islands of Alaska.

Many, many maps are available, covering a variety of topics including biology, geology, meteorology, planetary science, oceanography, and geography. There are maps of temperature changes going forward a hundred years, generated for each of the scenarios in the IPCC’s latest report. There are near-real-time maps of clouds seen (in infrared) by NOAA’s GOES and POES weather satellites. A near-real-time feed of earthquakes, coded by size and depth, is provided by the USGS. Following a tsunami, NOAA provides computer model output showing the wave heights as the waves travel across the ocean.

You can see the paths of commercial airplanes, the Earth at night, agricultural regions and their productivity, and the locations of volcanoes worldwide. Even the Moon, other planets (particularly Mars), and the Sun have their own visualizations.

Through the marvels of modern technology, these datasets can be overlain on top of each other, paused, backtracked, and even marked up like a sportscaster.

I spent many hours with the SOS at the Lawrence Hall of Science while I was living in Berkeley. Not only did I have fun talking with visitors about science, but I brought my favorite dataset to Science on a Sphere: near-real-time true-color imagery from the MODIS instrument aboard NASA’s Aqua satellite.

Aqua/MODIS image of Earth, March 30, 2015.  Can you spot Heard Island peeking out from the clouds?  Image credit: NASA.
Aqua/MODIS image of Earth, March 30, 2015. Can you spot Heard Island peeking out from the clouds? Image credit: NASA.

You should see if your local science center has a Science on a Sphere exhibit. The Science Museum of Minnesota does!

* For the curious, SOS maps are stored in an equirectangular (i.e. lat-long) format.