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Earth Matters


Congratulations to Dillion and Eric J.F. Kelijssen for solving the January Puzzler the fastest.  The answer is Oobloyah Valley on Canada’s Ellesmere Island. The image features four glaciersNukapingwa, Arklio, Perkeo, and Midgetflowing into the valley from the Krieger mountains to the north. At the end of each glacier, all of which are retreating, there are heaps of rock, gravel, and sand known as terminal moraines. As we explained in our Image of the Day on January 18, 2014, the moraines are of interest to ecologists because they offer an ideal natural laboratory for studying how plant species colonize recently exposed terrain.

One team of researchers led by Yokohama National University’s Akira S. Mori focused their search for Arctic plants on the moraine created by Arklio Glacier, the second to the left in the image above. (The Advanced Land Imager acquired this image of the glacier on June 19, 2012.) The moraine, which formed during the Little Ice Age, appears as a lobe-shaped bulge around the end of glacier. The light brown feature south of the moraine is a stream bed. The scientists found two dominant pioneer species living on the rocky, virtually soil-free moraine. The first is Epilobium latifolium, a flowering plant in the evening primrose family known as Dwarf fireweed. The second is Salix arctic, a type of creeping willow.

See Arklio’s terminal moraine and Epilobium latifolium (right) and Salix arctic (left) in the photographs below.


The snout of Arklio Glacier with its terminal moraine visible at the center of the image.  An earlier study of the area’s vegetation occurred at Moraine D. Image courtesy of Akiro Mori, Yokohama National University.


The dominant vascular pioneer plants that grow on Arklio Glacier’s moraine: Epilobium latifolium (right) and Salix arctica (left). Image courtesy of Akiro Mori, Yokohama National University.

Best of the Archives: Dunes of the Great Bahama Bank

January 16th, 2014 by Adam Voiland


Thirteen years ago, a satellite acquired this beautiful image (above) of light and sand playing off a portion of the ocean floor in the Bahamas. The caption that accompanied the image didn’t include many details, only noting that the image was acquired by the Enhanced Thematic Mapper Plus (ETM+) sensor on Landsat 7 and that, “tides and ocean currents in the Bahamas sculpted the sand and seaweed beds into these multicolored, fluted patterns in much the same way that winds sculpted the vast sand dunes in the Sahara Desert.”

An image as beautiful as this seemed like it deserved a bit more explanation, so I  grabbed a recent (January 9, 2014) scene of the same area captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite. That image (below) shows a much broader view of the area. You can still see some details of the intricate network of dunes, but the MODIS image offers a much better sense of the regional geology.  For instance, the section of dunes shown in the first image (the white box in the lower image) appear to be shoals made up small spherical grains of calcium carbonate known as ooids that sit on a larger limestone platform called the Great Bahama Bank. Limestone is a sedimentary rock formed by the skeletal fragments of sea creatures, including corals and foraminifera, and this particular limestone platform has been accumulating since at least the Cretaceous Period. 

You can also see a sharp division between the shallow (turquoise) waters of the Great Bahama Bank and the much deeper (dark blue) parts of the ocean. The submarine canyon that separates Andros Island from Great Exuma Island is nearly cut off entirely from the ocean by the Great Bahama Bank, but not quite.  A connection to deep waters to the north gives the trench the shape of a tongue, earning the feature the name “Tongue of the Ocean.” At its lowest point, the floor of the Tongue of the Ocean is about 14,060 feet (4,285 meters) lower than Great Bahama Bank. The shallowest (lightest) parts of the the feature, in contrast, are just a few feet deep.


January Puzzler

January 13th, 2014 by Adam Voiland

Every month we offer a puzzling satellite image here on Earth Matters. The January 2014 puzzler is above. Your challenge is to use the comments section to tell us what the image shows, what part of the world we are looking at, when the image was acquired, and why the scene is interesting.

How to answer. Your answer can be a few words or several paragraphs. (Try to keep it shorter than 200 words). You might simply tell us what part of the world an image shows. Or you can dig deeper and explain what satellite and instrument produced the image, what spectral bands were used to create it, or what is compelling about some obscure speck in the far corner of an image. If you think something is interesting or noteworthy, tell us about it.

The prize. We can’t offer prize money, but, we can promise you credit and glory (well, maybe just credit). Roughly one week after a puzzler image appears on this blog, we will post an annotated and captioned version as our Image of the Day. In the credits, we’ll acknowledge the person who was first to correctly ID the image. We’ll also recognize people who offer the most interesting tidbits of information. Please include your preferred name or alias with your comment. If you work for an institution that you want us to recognize, please mention that as well.

Recent winners. If you’ve won the puzzler in the last few months or work in geospatial imaging, please sit on your hands for at least a few days to give others a chance to play.

Releasing Comments. Savvy readers have solved many of our puzzlers after only a few minutes or hours. To give more people a chance to play, we’re going to wait between 24-48 hours before posting the answers we receive in the comment thread.