Frost Earthquakes (Cryoseisms)

By Kristina Kassis (Fall 2012 GE 101 student)

Have you ever been jarred awake in the middle of a particularly cold night by what seemed to be a small earthquake? If you have, chances are that it was not an earthquake but rather a rare frost quake, also known as a Cryoseism.

Frost quakes are non-tectonic seismic events  that are caused when a sudden drop in temperature induces the freezing of groundwater, which expands and then cracks under pressure. This crack may be explosive, resulting in loud noises and movement of the earth, similar to what occurs during a small earthquake. However, unlike earthquakes, which have effects that can be very widespread, frost quakes have extremely localized effects: a family in a house might feel a frost quake, while a family merely one street away may not feel the ground move at all.

While frost quakes are a  rare phenomenon, there have been a number of  cases reported in the Northeastern United States in the last century in places such as Ohio, Wisconsin, Indiana, upstate New York, Vermont, Massachusetts, Connecticut, and Maine. In some of these cases, people were actually able to find a small fissure in the ground at the point where the Frost quake originated.

Frost quakes have been reported across New England as far back as the early 20^th century. In 1908 it was reported that a frost quake occurred at four different locations in New England on February 5. In Danbury, Connecticut, for example,  the headline of the local newspaper read Earth Tremors Due to the Extreme Cold. The article continued, “The event in Danbury left large fissures in several streets in the early morning hours. Other locations feeling a frost quake were Portland, Maine; Nashua, New Hampshire; Nyack, New York; and Brockton, Massachusetts. Several Portland residents reported their houses shaken by the event.”

On January 30, 1994, residents of West Berlin in Wisconsin were frightened by what they believed to be an earthquake. The startled residents reportedly experienced loud noises “like explosions” and violent ground tremors. Ron Friedel, the curator of the University of Wisconsin-Milwaukee’s seismograph station, attributed the event to a frost quake resulting from changing temperatures.  Again, no damages or injuries occurred as a result of the quake.

Another substantial frost quake occurred during the early morning hours of February 10, 2011. During the night, temperatures had fallen well below freezing  in some areas across Central and Eastern Indiana and into Western Ohio. These icy conditions were ideal for a widespread outbreak of frost quakes. Residents of  the area reported that they heard loud explosions reminiscent of thunder and felt tremors similar to an earthquake that supposedly persisted for over 8 hours. They were understandably frightened by this event  and  quickly reached out to local media and government agencies for an explanation. Their answer: a frost quake! Thankfully no damage or injuries occurred.

The large Frost quake felt in Indiana and Ohio in 2011 is only one example of many frost quakes documented all across New England and other parts of the Northeastern United States in the past century. Perhaps the best-documented frost quake in history occurred during the early afternoon of January 31, 2008 at Madison, Wisconsin.  This frost quake was especially surprising because they usually occur between midnight and dawn, during the coldest part of the night. At around 12:50 p.m. however, tremors around Lake Mendota that persisted several seconds registered on a  seismograph in the  University of Wisconsin-Madison Geology Department.

Seismologist Cliff Thurber, who saw the quake’s effect on the department’s seismograph, was struck by this event. Thurber hypothesized, after observing a large shift of ice on the surface of Lake Mendota, that a sudden drop in temperature was responsible for the tremors. Thurber later noticed a new large visible break in the lake’s surface ice, supporting his hypothesis that the icy conditions had caused a Cryoseism.

There is little scientific data pertaining to frost quakes. Michael Hansen, director of the Ohio Seismic Network, said the recipe for a frost quake requires “a sunny day that helps thaw ice and snow, followed by a quick freeze.”  Beyond that, he said, very little is known about what causes frost quakes to occur in some regions and not in others. “These things are really poorly understood,” he added.

While frost  quakes may be misunderstood, they are not dangerous. In no cases of frost quakes reported were any damages or injuries incurred.

So next time you find yourself  abruptly awoken in the middle of  a cold night by tremors in the earth, do not be alarmed: Mother Earth merely has a case of the shivers.

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[1] Heidorn, Keith C. PhD. “Weather Almanac for March 2012: Frost Quakes.” The Weather Doctor. N.p., 01 2012. Web. 1 Nov 2012. <http://www.islandnet.com/~see/weather//almanac/arc2012/alm12mar.htm&gt;.

[2] Hunt , Spencer, and Meredith Heagney. “Cyroseisms: a Case of Mother Earth’s Cold Shivers, and not and Earthquake: A Watchman’s Report.” . N.p., 12 2011. Web. 1 Nov 2012. <http://beforeitsnews.com/strange/2011/02/cryoseisms-a-case-of-mother-earths-cold-shivers-and-not-an-earhquake-a-watchmans-report-415211.html&gt;.

Mineral of the Week: Corundum

By Kristina Kassis (Fall 2012 GE 101 student)

Image source

Most people, when asked to name minerals, can easily recognize commonly known minerals such as Gold, Silver, Sulfur, Carbon, Iron, Zinc, Tin, Calcium, Potassium, Hydrogen and others.  However, how many of you reading this have heard of a mineral known as Corundum?  My guess would be very few. Corundum is an exceptionally hard and durable form of aluminum oxide (Al2O3).   With a hardness of 9 on Mohs Hardness Scale, Corundum is in fact the third hardest mineral, with only Diamond and Moissinite surpassing it in hardness. Corundum can be found in igneous rocks that are very high in Aluminum but are very low in Silicon, such as Pegmatite.  Corundum can also be found in metamorphic rocks that were formed through contact metamorphism. For example, marble, hornfels, Schist, and gneiss (both forms of metamorphosed shale) are often found to contain very small traces of corundum. Because Corundum is so durable and resistant to corrosive acids and chemicals, it is able to persist long after many other elements have been eroded, so it is commonly found in beach sands and in other similarly harsh environments.

In addition to its extraordinary hardness and durability, Corundum has many other distinguishing physical characteristics. In terms of color, Corundum is frequently gray, but can also be found in white, brown, red, blue, yellow, green, purple and a variety of other colors. When scratched across a streak plate, Corundum produces a distinct white streak. It has a shiny to almost glassy luster, but is not metallic. Corundum is not opaque, but rather typically transparent to translucent. The crystals in Corundum are fine and hexagonal in shape. These crystals are usually elongated and striated crosswise and often form in thin plates.  Corundum has no natural cleavage planes, but does have conchoidal fracture, mineral fracture in which the indentation is rounded and resembles the shell of a bivalve.  All together, these physical characteristics of Corundum in conjunction with chemical properties such as whether or not it reacts with acid (Corundum does not) make it a unique mineral and therefore help geologists to determine its identity in nature.

Clearly, Corundum is unique for its exceptional hardness and durability. One of the most notable facts about Corundum however, is that it can also form not one, but TWO types of precious gemstones: rubies and sapphires, the birthstones for the months of July and September, respectively.  In fact, the name “Corundum” is derived from the Tamil word kuruntam meaning “ruby”, and related to Sanskrit kuruvinda.  Rubies are formed when small traces of Chromium contaminate Corundum and stain it a deep red. Sapphires can be found in many colors, but are most commonly light to dark blue and are also formed by contamination of other minerals, specifically Titanium and Iron in Corundum. Corundum that contains very small amounts of Titanium is completely colorless. However if a similar amount of Iron is present instead in the corundum, it may appear pale yellow in color. In addition, if both Titanium and Iron impurities are present together within the Corundum, the result is a striking deep blue Sapphire. These sapphires are the most valuable.  Notable deposits of rubies and sapphires occur in Burma, Cambodia, Sri Lanka, India, Afghanistan, Myanmar, Thailand, Vietnam, Pakistan, China, Australia, Kenya, Tanzania, Nigeria, and Malawi.  In fact, much of Africa has recently become a significant producer of Corundum, especially in Madagascar. Even the United States has deposits of Corundum. For example, Montana has a large quantity of Ruby and Sapphire deposits. So despite its obscure name, Corundum can be found all over the world!

Due to its exceptional hardness, Corundum is most commonly used as an abrasive. It is crushed to a powder of varying size depending on how rough the grinding stone, cutting tools or sanding paper needs to be.  Emery, the most common form of natural corundum used to manufacture abrasives, is a granular metamorphic or igneous rock that is very rich in Corundum.  Emery is a conglomerate of many different oxide minerals, typically Corundum in conjunction with magnetite and hematite.  Apart from ornamental uses and abrasives, synthetic corundum is also used to produce mechanical parts as well as scratch-resistant glass and laser and spacecraft components because it is resistant to UV light. Clearly, Corundum is not only a durable, but also extremely versatile element.

Surprising right? It turns out that most people are actually familiar with Corundum, but few know it by its mineral name. So, July and September babies, next time someone asks you what your birthstone is, present them with a conundrum and tell them its corundum!

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[1] “The Mineral Corundum.” The Mineral and Gemstone Kingdom. Hershel Friedman and Minerals, n.d. Web. 30 Oct 2012. <http://www.minerals.net/mineral/corundum.asp&xgt;.

[2] “Corundum Mineral Data.” Mineral News: The Mineral Collector’s Newsletter. N.p Web. 30 Oct 2012. <http://www.webmineral.com/data/Corundum.shtml

[3] “Blue Sapphire.” Causes of Color. N.p Web. 30 Oct 2012. <http://www.webexhibits.org/causesofcolor/8.html&gt;.

[4] “Corundum.” Geology.com: News and Information about Geology. Geology.com, n.d. Web. 30 Oct 2012. <http://geology.com/minerals/corundum.shtml&gt;.

[5] “Corundum Uses.” Gemstone Advisor: Your Advisor on Gemstones and Gemstone Jewelry. N.p n.d. Web. 30 Oct 2012. <http://www.gemstonesadvisor.com/corundum-uses/&gt;.

Acid Lakes: Kawah Ijen

By Kristina Kassis (Fall 2012 GE 101 student)

 

A famous scene in the 1997 drama Dante’s Peak features the protagonists, played by Pierce Brosnan and Linda Hamilton, attempting to navigate their way across a lake that Brosnan’s character Harry Dalton, a volcanologist, claims has been transformed into corrosive acid by volcanic activity. Upon first watching this scene, I was unsure if this phenomenon was real or merely included in the film for dramatic effect. However, upon further research, I was amazed, excited, and frankly a little frightened to learn that volcanic activity can and actually has transformed many lakes into corrosive acid.  Largest and perhaps most well-known of these acid lakes is located near the Indonesian volcano Kawah Ijen. This lake consists of 36 million cubic meters of acid and has a maximum depth of 760 feet, making it by far the largest acid lake on Earth. At the edge of the lake, volcanic gas eruptions, known scientifically as fumaroles, spew out nearly 4 tons of sulfur daily. In addition to pure sulfur, the lake contains 600,000 tons of hydrogen chloride, 550,000 tons of sulfuric acid, 200,000 tons of aluminum sulfate and 170,000 tons of iron sulfate.  These acids are the most powerful acids on earth and could quite easily burn through human flesh, similar to what happened to Ruth in Dante’s Peak. Perhaps as a testament to this power, an enormous bubble of sulfuric dioxide killed 11 people in 1976 after rising out of the surface of the lake. The local people, perhaps seeking justification for the tragedy, claimed it was the sacrifice asked by the volcano for offering its riches.

Despite the obvious danger of coming within close proximity of such corrosive acids, scientists have made concerted efforts to explore and conduct scientific research on the acid lake located in Kawah Ijen. For instance, in 2008, explorer George Kourounis took a small rubber boat out onto the acid lake to measure its acidity. This was a bold and undoubtedly frightening exploration by Kourounis, and it led to an even more frightening discovery: The pH of the water in the crater was measured to be 0.5 due to sulfuric acid.  It is through daring exploration such as Kouronis’ journey onto the acid lake at Kawah Ijen that scientists are able to learn more and more about these acid lakes and how they form.

In addition to using the lake at Kawah Ijen for scientific purposes, humans have used this natural phenomenon to their economic advantage. The lake is the site of a labor-intensive sulfur mining operation, in which sulfur-laden baskets are carried by hand from the crater floor.  In addition, people from the neighboring area extract sulfur from the crater manually, which is extremely laborious and dangerous work. According to one account:

“To increase efficiency, the workers construct tunnels made out of stone and undulated plates to channel the sulfur-rich fumaroles. The sulfur then leaks, cools down and solidifies inside these improvised channels, which are subsequently broken using metal piles. The recovered stuff contains 99 % sulfur. The sulfur is cut up, loaded into baskets and transported manually out of the crater. The sulfur is then transported to local towns and used for vulcanizing rubber and refining sugar.”

Industrial exploitation of the lake has not been planned so far because Kawah Ijen is active and therefore erupts from time to time, projecting acid to the height of up to 2000 feet and splashing the neighboring areas with an extremely corrosive rain.  Despite the dangerous nature of the lake at Kawah Ijen, humans continue to use the lake to gain profit.

The acid lake at Kawah Ijen has also been featured extensively in the media. For instance, Ijen and its sulfur mining was featured as a topic on the 5th episode of the famous BBC television documentary Human Planet. Additionally, in the controversial documentary film War Photographer, journalist James Nachtwey visits the volcano and risks his own health and well-being while trying to photograph workers as they transported sulfur from the crater. Finally, Michael Glawogger film Workingman’s Death is also about the plight of sulfur workers at Kawah Ijen, Seeing as humans are drawn to anything that they can profit from even at the risk of their lives, I believe won’t be long before Kawah Ijen is a tourist attraction.

Acid lakes like the lake in Kawah Ijen result from a mix of rainfall water with gases coming in from the depths of the volcano, and are also found on the volcanoes Kusatsu-Shirane in Japan and Poas in Costa Rica, demonstrating that this phenomenon is not as rare as one may think. Still, the existence of these lakes, specifically the lake in Kawah Ijen, is an example of a geological phenomenon that is as fascinating as it is terrifying. Each day, I become increasingly aware of nature’s tremendous power. From acid lakes to volcanic lightning, Mother Nature is certainly a force to be reckoned with.

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[1] Anetei, Stefan. “The Largest Lake of Acid on Earth.” . Softpedia, 21 2008. Web. 30 Oct 2012. <http://news.softpedia.com/news/The-Largest-Acid-Lake-on-Earth-81388.shtml&gt;.

[2]  http://www.stormchaser.ca/Volcanoes/Kawah_Ijen/Kawah_Ijen.html Measuring the acidity of Kawah Ijen crater lake.

[3] Indra Harsaputra, Kawah Ijen: Between potential and threat’, The Jakarta Post, 19 December 2011.

Volcanic Lightning: Beautiful but Deadly

By Kristina Kassis (Fall 2012 GE 101 student)

Image source

On June 5, 2011, Chile’s Puyehue volcano, located in the Andes Mountains of Southern Chile about 575 miles South of the Capital, Santiago, erupted explosively, demonstrating the dramatic power of nature by sending its plume of ash six miles high all over Chile, over Argentina and out toward the Atlantic Ocean. The Puyehue volcano has not been active since 1960, when it erupted after a massive magnitude 9.5 earthquake.  On June 5, however, tens of thousands of people were evacuated from 22 surrounding rural communities in Chile as a blanket of grey ash rained down like a deadly snow. Perhaps most striking about the Puyehue eruption, however, was the spectacular display of lightning that illuminated the sky above the volcano during the eruption.

Volcanic thunderstorms or “dirty thunderstorms” are rare and not fully understood by scientists, but it is widely believed that friction between particles and gases is largely responsible for the lightning displays that occur in conjunction with volcanic eruptions.[1] A study in the journal Science indicated that electrical charges are generated when rock fragments, ash, and ice particles in a volcanic plume collide and produce static charges, just as ice particles collide in regular thunderstorms. The large amounts of water present in magma may also help to fuel volcanic thunderstorms. Earle Williams of MIT and Stephen McNutt at the University of Alaska hypothesize that “dirty thunderstorms” might simply be caused by a build up of ice. Because thunder and lightning in conventional storms are essentially caused by a buildup of ice and water, Williams and McNutt claim that large volcanic eruptions are similarly a result of the abundance of water present in magma.

“There’s just so much water in magma, that’s the main issue,” Williams says. When magma explodes during eruptions, this water escapes.  But, Williams notes, the presence of water alone is not enough to spark lightning. First, he says, the particles must bang into each other enough times to promote a build-up of static charge, like a balloon rubbed repeatedly back and forth across someone’s head. Second, the positive and negative particles must separate because lightning is just a spark between these two differently charged regions. In a smaller thundercloud, positively charged particles generally gather above larger, negatively charged clumps of faster falling ice; if the cloud grows high enough, the two regions are dragged far enough apart to trigger lightning.[2] This is exactly what Williams and McNutt claim happens above a volcano.

Reports from eruptions seem to agree with Williams and McNutt’s hypothesis. For example, analysis of the Mount St Helen’s plume in 1980 found negatively charged particles at lower altitudes and positively charged particles higher up. Similarly, when the Sakurajima volcano erupted in Japan 1996, scientists recorded that positive charges dominate at the top of the plume and negative charges dominate at the base,[3] again supporting Williams and McNutt’s hypothesis.

Williams and McNutt are not the only scientists who have studied and analyzed “dirty thunderstorms.” For example, researchers with The Scientific American hypothesized that the amount of lightning correlated with the height of the plume: the taller the plume, the more spectacular the lightning show during eruption. This hypothesis is supported by Alaska’s Mt. Redoubt. Redoubt had a series of more than 20 eruptions over 13 days in March of 2009, all of which were accompanied by lighting flashes.[4]

“In general, the higher the plume went, the more lightning we got,” said Ronald Thomas, a physicist and electrical engineer at the New Mexico Institute of Mining and Technology. This information may tell us little about why volcanic lightning occurs, but it is undoubtedly a fascinating correlation and could be beneficial to scientific inquiry in the future.

Though volcanic lightning does not occur with every volcanic eruption, there have been many instances throughout the years. There are now more than 150 recorded cases of electrical storms breaking out directly above craters of erupting volcanoes, dating back several centuries.[5] For example, the 1980 eruption of Mount St Helens in Washington state, one of the most studied eruptions in recent times, produced a lightning bolt every second.[6]  In addition, a famous image of the phenomenon was photographed by Carlos Gutierrez and occurred in Chile above the Chaiten Volcano in 2008.[7] Other instances of volcanic lightning have been reported above Alaska’s Mount St. Augustine volcano when it erupted in 2006 and Mount Redoubt in 1989 and 1990.  Yet another spectacular of example of volcanic lightning occurred with the eruption of the Sakurajima Volcano in 1914, the most powerful eruption in Japan in the 20^th Century. Iceland’s Eyjafjallajokull Volcano on March 24^th, 2010 and Grimsvotn Volcano in November of 2004 both produced spectacular displays of volcanic lightning as well, so it is clear that volcanic lightning, though a rare and misunderstood phenomenon, is not unheard of.

So what does this all mean? It is clear that volcanic lightning is a phenomenon that may never be fully explained by scientists. There are hundreds of possible hypotheses. However, if Williams and McNutt are correct in their hypothesis that water is largely responsible for generating electric lightning, it has important implications:  the water could trigger devastating mudslides known as Lahars, merely adding to the threat posed by volcanic eruptions. All in all, volcanic lightning may be fascinating to watch and learn about, but it proves beyond a reasonable doubt the tremendous force of nature, and the capacity for something beautiful and awe-inspiring to rapidly become deadly. A picture may be worth a thousand words, but a photograph of volcanic lightning says only two: “WATCH OUT!”

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[1] Fischer, Richard V “Volcanic Lightning.” 1997, n.d. Web. 29 Oct 2012. <http://volcanology.geol.ucsb.edu/lightnin.htm&gt;.

[2] Adam, David. “Volcanic Lightning: Very, Very Frightening.” The Guardian. Guardian News and Media, 08 2004. Web. 29 Oct 2012. <http://www.guardian.co.uk/science/2004/dec/09/science.research&gt;.

[3]  “The Chilean Volcano Puyehue.” Esoteric Online: Social Networks for Sacred Science. N.p 19 2011. Web. 29 Oct 2012. <http://www.esotericonline.net/profiles/blogs/the-chilean-volcano-puyehue&gt;.

[4] Klotz, Irene. “Volcano Sparks New Type of Lightning.”DiscoveryNews. Discovery Communications, LLC, 2012, 05 2010. Web. 29 Oct 2012. <http://news.discovery.com/earth/volcano-eruption-lightning.html&gt;.

[5]  “The Chilean Volcano Puyehue.” Esoteric Online: Social Networks for Sacred Science. N.p 19 2011. Web. 29 Oct 2012. <http://www.esotericonline.net/profiles/blogs/the-chilean-volcano-puyehue&gt;.

[6] Adam, David.

[7] “Chile Volcano Erupts with Ash and Lightning”. National Geographic. May 6, 2008. October 29, 2012.

Baumgartner’s Big Jump

Austrian daredevil Felix Baumgartner’s jump from a space-bound platform on October 14 set several human records despite challenging atmospheric conditions. Baumgartner achieved the highest human freefall to Earth ever: 38.6 km, from his pedestal to the New Mexican desert. In addition, he broke the sound barrier—another human-freefall feat—reaching speeds of 1,342 km/h, or Mach 1.24. The daredevil’s descent may have been all the more impressive in light of the varied atmospheric circumstances that he encountered. To that end, Baumgartner passed through two zones of Earth’s atmosphere and experienced potential perils throughout his transit.

Source: http://www.wired.com/playbook/wp-content/uploads/2012/10/felix-baumgartner-red-bull-stratos-01.jpg

Earth’s atmosphere consists of approximately four vertically layered zones with varied sizes and properties. The troposphere extends 0 – 20 km vertically from sea level, and is the region where Earth’s weather patterns form—where air convection and circulation shape distinct climates over time. The stratosphere, Baumgartner’s launch point, extends ~20 km – 50 km above Earth. The upper stratosphere hosts Earth’s ozone layer, which absorbs ultraviolet sunlight. Above the stratosphere, the mesosphere (~50 – 85 km) and thermosphere (~85 – 690 km) can experience phenomena as diverse as meteor activity and aurora formation from ionized atoms, respectively. While Baumgartner did not quite make it to meteor country, therefore, he had quite a ride through the stratosphere and troposphere.

Source: http://destinationofmarvel.blogspot.com/2011/01/atmosphere.html

By beginning his ascent high in the stratosphere, Baumgartner faced several dangerous factors that could have harmed him considerably. Aside from potential equipment malfunctions and skydiving’s inherent physical instability, he encountered numerous atmospheric hazards. For starters, pressure above ~19 km is sufficiently low to boil an exposed human’s blood and bodily fluids (again, the jump began 38.6 km above sea level).  In addition, temperatures lower than -50°F characterize some stratospheric areas that Baumgartner crossed. UV radiation—100,000 times stronger at 36 km than at Earth’s surface—also could have been problematic for him; however, Baumgartner’s quick descent probably reduced radiation’s relevance. Once in the troposphere, nonetheless, he also would have faced Earth’s unpredictable weather systems: wind and precipitation, namely, could have injured him or sent him off course. A plethora of physical conditions—not to mention the dangers of breaking the sound barrier—thus greeted Baumgartner during his descent from the heavens.

While Felix Baumgartner broke a number of astonishing human records, therefore, the environment in which he broke those records added gravity (knee slapper) to his achievements. The stratosphere is no place for humans, but Baumgartner found his way through it, and through the troposphere, without major complications or setbacks.

 

 

Sources and further information:

http://www.cnn.com/2012/10/14/us/skydiver-record-attempt/index.html

http://www.cnn.com/2012/10/15/tech/innovation/space-jump-tech/index.html?hpt=hp_bn5

http://csep10.phys.utk.edu/astr161/lect/earth/atmosphere.html

http://www.forbes.com/sites/quora/2012/10/16/what-were-the-risks-of-felix-baumgartners-jump/

Atmospheric Layers

Fractals

                                                     Fractals are awesome
Figure 1. Fractal courteous of http://www.fractalforums.com/images-showcase-%28rate-my-fractal%29/mandelbrot-safari/

A fractal is a function that when you graph it appears the same at all scales,infinitely. You can zoom in forever on the tiniest detail and find yourself amid geometry that closely if not exactly mirrors the scale you started at. Check out the below video for an amazing example of this!
http://vimeo.com/12185093

        A French-American by the name of Benoit Mandelbrot first described fractals lucidly (others had noted the presence of them before but hadn’t realized the mathematics or meaning behind them).

Figure 2. Benoit Mandelbrot, the man himself. Image courtesy of http://en.wikipedia.org/wiki/Beno%C3%AEt_Mandelbrot

This a geoblog though, not a math blog and I can’t justify showing you fractals just because they are beautiful.  However, I can show you fractals because they are beautiful and fundamental parts of geomorphology!

Figure 3. Malaysian river system with a fractal form. Courtesy of http://www.mymodernmet.com/profiles/blogs/paul-bourke-google-earth-fractals

Figure 4. River system showing fractal form in Mexico. Courtesy of http://photography.nationalgeographic.com/photography/photo-of-the-day/baja-california-rivers/

Figure 5. Greenland coastline showing fractal form. Courtesy of http://artsonearth.com/2008/08/11-phenomenal-images-of-earth.html

Fractals aren’t just a cool thing we can observe qualitatively in landscapes around us either.  An important question is, at what scale are these fractal landforms most variable? If you wanted to measure the length of Britain’s coast line, what length ruler would you use? Is most of the erosional work in a river system done by a few big, wide rivers or by the net effect of many smaller tributary streams? Quite a few papers have been published around the quantification of fractals in landforms. One of the more particular interesting ones called “Fractal properties of landforms in the Ordos Block and surrounding areas, China” takes a series of cross sections through topography in such a way that the ground surface is represented as a wave on a graph (figure 6a).
Figure 6. a represents the cross-section through topography. b represents the complex topographical wave broken down into a set of sine waves.  c is the wavelengths of these sine waves graphed with respect to amplitude. This process is called taking a fourier transform.

A mathematical function called a Fourier transform converts the topographical wave (figure 6a) into a set of sine waves (figure 6b) that added together recreate the topographical wave. The sine wave with the biggest vertical distance between the peak and trough (known as the amplitude) is the dominant scale at which that stretch of topography changes over. A flat desert with lots of dunes would have a dominant wave on the scale of the dunes whereas a mountainous area with smooth exposed bedrock would have a dominant wave on the scale of the mountains. These results might seem to be something that you could just easily observe by looking at the landscape, but they provide a quantified representation that would be difficult to obtain otherwise. This allows scientists to define fundamental aspects about landscapes in a way that could allow a deeper understanding of erosion, geomorphology and geology as a whole.

Pretty sweet I say! -TB

If you would like to see more of these fractals yourself, or you don’t believe me check out this link that includes kmz files that bring you to places in google earth that have fractals!

References:

Fractal Patterns in Nature Found on Google Earth

Lisi Bi, Honglin He, Zhanyu Wei, Feng Shi, Fractal properties of landforms in the Ordos Block and surrounding areas, China, Geomorphology, Volumes 175–176, 15 November 2012, Pages 151-162, ISSN 0169-555X, 10.1016/j.geomorph.2012.07.006.
(http://www.sciencedirect.com/science/article/pii/S0169555X12003303)

What Kind of Rock Lies Beneath the Northwoods?

As the young scholar wanders Skidmore’s northern woodlands, he or she may come across any number of rock outcrops. In all likelihood, those outcrops, when unweathered by Earth’s climate, will have a medium to dark–gray color and a fairly coarse crystalline structure. Such rock, known as dolostone (CaMg(CO3)2), spans Skidmore’s Northwoods land. Very sporadic outcrops of sandstone and limestone (CaCO3), a close relative to dolostone, also appear on the property. Moreover, erratic boulders, vestiges of the last ice age, are also sparsely present, and a sedimentary rock known as chert appears intermittently; nonetheless, dolostone’s frequency in Northwoods is unmatched.

The question thus arises: how did all of this dolostone end up in our backyard? During the Ordovician Period of Earth’s history, from approximately 488 million years ago (Ma) to 444 Ma, Saratoga Springs (and North America) was much nearer to the equator than it is today; by virtue of plate tectonics, the future New York State occupied a tropical location in a world climatically warmer than today’s Earth. Sea levels were higher, and shallow seas covered Saratoga Springs. Consequently, tropical organisms with CaCO3 shells abounded and settled on our seafloors, ultimately lithifying as limestones. Later, briny fluids related to such a tropical environment probably flowed through those limestones, gradually replacing much of the limestone’s calcium with magnesium—forming dolostone. In later (millions of) years, other materials covered the dolostone; however, Earth’s climate, by the present, has largely eroded any layer(s) that used to overlay the Northwoods. And, hence, we have dolostone.

So, the next time you find yourself tripping over inconspicuous outcrops in Northwoods, keep in mind that you’ve fallen upon the closet thing to a tropical beach that Skidmore may ever enjoy (I can already hear the Environmental Studies Department’s exclamations of rising sea levels… What about the polar bears?). In all seriousness, you will be walking across history—not human history; but, perhaps, history bigger than humans, history representative of a world long before us.

To many people Geology may seem like its about rocks, and only rocks. Geologists look at rocks that tell them something about other rocks, for the purpose of understanding things about rocks. Geologists know otherwise, of course. Not only is a rock a springboard for immense spatial and temporal leaps of imagination, but the lithosphere (rocks) is tied to every other aspect of earth in intimate and complex ways. In so many words, rocks aren’t just interesting because they are the marks left behind from environments long gone, but they actively interact with the biosphere, atmosphere, and oceans as well. The subject of this week’s blog is on a particularly fascinating connection between rocks and the biosphere.

Sessile Benthic organisms are oceanic organisms that affix themselves to a surface and live a life stationary life. Mussels, corals and barnacles are some examples of organisms that adopt this lifestyle. How does an animal adapt to become a stationary organism like a plant? That itself could be the subject of countless blog posts as there is an amazing diversity in strategies, but it all has to do with growing up. The organism modifies its life cycle to include a free floating (benthic) stage and a stationary (sessile) stage. Organisms in the phylum Cnidaria, such as corals, go through a larvae stage. The organism is called a planula in this stage and lives a free floating life largely subject to the currents of the ocean. Ideally, the ocean carries the planula to a prime location to settle down.

Life cycle of a coral. Courtesy of http://www.icriforum.org/about-coral-reefs/what-are-corals

This stage only lasts several weeks or months though before the larvae must settle down and begin its polyp stage. This places a limit on how far away sessile benthic organisms can colonize, especially when there is a large expanse of uninhabitable habitat to cross for the organism.

Here’s where rocks come to the rescue. It turns out pumice created from explosive eruptions near or under the ocean can serve as perfect vehicles of transport for sessile benthic organisms. A quick aside for anyone not familiar with pumice, it is a rock created in explosive, usually dacitic (felsic) eruptions that cools and hardens in mid air. It contains such a high percentage of open spaces created by gases contained in the lava that it floats.

A 20 dollar bill with a pumice hat. Courtesy of http://en.wikipedia.org/wiki/File:Pumice_on_20_dollars.jpg

In a recent study called “Rapid, Long-Distance Dispersal by Pumice Rafting” a pumice raft created from a volcanic vent to the northeast of New Zealand was tracked. The pumice raft created from the eruption was on the order of >440 square kilometers. This mass of pumice was found to travel >5000 km away reaching the eastern coast of Australia up to 3 ½ years later.

Computer model of the trajectory of the pumice raft. 

For several weeks after the eruption the pumice remained sterile, with no colonization by sessile benthic organisms.  As time went on however, coral planula and other sessile benthic larvae looking to settle down attached to the pumice and began to colonize it.

16 months after the eruption, more the 3/4ths of most pumice surfaces were covered in organisms. For Goose Barnacles alone, the study finds a conservative estimate of the organisms transported to be 10 billion individuals. These pumice colonizers weren’t just passive passengers either. The colonization of the pumice by organisms reinforced the buoyancy of the pumice in several ways, of which two I will mention. First organisms that grew on the surface of the pumice created a shell that locked out water from seeping into the air pockets in the pumice. Second, algal and cyanobacterial respiration released gas into the poor spaces of the rock, increasing buoyancy.

        This isn’t a rare occurrence either. In the last 200 years, pumice rafts have occurred in all the major oceans. In the south west of the Pacific a pumice raft occurs about every 10 years! This all suggests that pumice rafts play a very significant role in the spread of sessile benthic/corals.

What more eloquent connection between rocks and the biosphere could there be? -TB

References:

1. http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=78863

2. http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0040583

Condit Dam

        The history of earth is a story full of the massive, brief events. Most of the time, we only catch a glimpse of the mark they left behind such as a turbidite from an underwater avalanche, or a ignimbrite deposit from an immense volcanic eruption. The geologist is left to imagine the power and sheer awesomeness of these processes that only once in a great while manifest themselves. However, with the rise of the internet and dissemination of technology more and more moments of amazing natural phenomena are being captured and shared. In this case of this blog post, its’ the removal of the largest dam ever in the United States.

       The Condit Dam is located on the White Salmon River in Washington state. It was dismantled on October 26th, 2011. Fortunately, a man by the name of Andy Maser captured this process with time lapse photography.

http://vimeo.com/31305629

       While the impressive torrent of water released downstream is cool to watch, the more interesting thing to me is what happens upstream of the dam. If you watch carefully, in the last 30 seconds or so there are three periods where the entire surface of the river bed appears to move. If you missed them, I made three gifs showcasing the movements.           https://docs.google.com/open?id=0B8sTdzWGqSNLQWN5b0NiUXl6Ujg          https://docs.google.com/open?id=0B8sTdzWGqSNLa3dKeUUwOUxwYlE          https://docs.google.com/open?id=0B8sTdzWGqSNLOTktMWNrLWxiMkk

         What is triggering the mass wasting? What interrelated factors are changing such that the river bed is oscillating from a stationary state to a state of motion? I am unsure of the real answer to this as the makeup of the stream bank is unknown to me, and even if it was the mechanics are complex. However, if I were to make an educated guess I would say that a high angle of incision may have caused the mass wasting of the river bed.

figure 1. the dam before the removal

figure 2. Steep incisions, or drops in river beds are transmitted upstream through river erosion. Before the introduced hole into the dam, this process was stuck in limbo due to the structural integrity of the dam. Once the dam was bypassed, the steep incision was free to migrate upstream. This figure simplifies the reality of the situation by assuming the vertical drop created by the dam is accommodated by one large incision when in reality several probably occurred, each migrating upstream independently. This could explain the multiple mass wasting events.

figure 3. At some point the incision migrating upstream reached a point where the hanging wall of the incision was structurally weak, or an influx of water from upstream pulsed. Either way, a large block of sediment detached from the ground and slid downstream. It is interesting to note that when the mass wasting occurs the block of loose sediment acts essentially as a solid and the internal geometry is mostly preserved. That is, the whole thing moves, but it still looks the same afterwards.

        Again the process going on here is probably much more complicated than I am presenting it as. For example, the first gif/movement appears to fit my model and the third gif/movement appears to be a rotational variation of it. However, the second gif/movement may have something to do with a wave from upstream dislodging the sediment (notice how the sediment rises before it moves).  Watch the videos and gifs for yourself and see what you think!

Until next time -TB

Student Blog: Logan B

Check out Logan B’s blog as she spends the spring 2011 semester in Turks and Caicos!

http://loganintci.blogspot.com/

We all wish we were somewhere tropical too.