While I prefer the traditional name to the hyped one currently doing the rounds of the internet, these relatively short lived flaming twisters are an interesting phenomenon, and they may become more common as wildfires get more frequent and intense due to global warming. They usually only last a few minutes, though during the 2003 wildfires near Canberra in Australia, one is known to have left a 25km swath of burnt snapped trees and overturned cars after a 250kph fiery twister formed in oil rich eucalypt forest.
They form, like all vortices in whatever medium, when two masses in different states meet at speed. With tornadoes, warm moist air is meeting cold dry air in the turbulent conditions of a supercell thunderstorm. During wildfires, the intense heat and turbulent contrast with the surrounding air can be enough to create these twisters, and sometimes sustain them for quite awhile. The vortex also sucks up combustible gases from the fire (such as evaporated tree resin), which ignites in the oxygen rich centre of the vortex, giving the twister another dose of energetic fuel. They can also spread the fire by whirling burning debris far and wide.
A similar phenomenon was responsible for the Hamburg firestorm in 1943, when several days of incendiary bombing ignited a self sustaining enormous conflagration that took weeks to burn itself out fully.
Should any of our readers ever see one of these, do NOT go closer in order to get a photo, they behave unpredictably, and discretion being the better part of valour, please run away as fast as is safe. Bushfires in general are best avoided at all times, unless you're a dedicated fire fighter.
Image credit, taken in Missouri: Janae Copelin/Barcroft USA
http://www.theguardian.com/world/shortcuts/2014/may/11/firenado-fire-tornado-firenadoes
Its summer solstice today, and as is my wont I present one of the prehistoric wonders of the world, the 10,000+ aligned standing stones of Karnac In Brittany (France, though some of them don't agree). These are the prototypical menhirs, as carved by Obelix, one of my heroes since childhood.They were carved from the tough granites and gneisses of the Armorican Massif, the roots of once tall mountains that have been remobilised (ie grew and were eroded again) a full three times. The first was the Cadomian half a billion years ago followed by a complex series of tectonic events as the supercontinent Pangaea assembled during the Devonian and Carboniferous between 400 and 280 million years ago. Armorica started off life as the northern shore of Gondwana, before rifting off and colliding with Laurussia during the Hercynian event. The assembly of Pangaea when Euramerica collided with Gondwana in the Variscan orogeny completes this continental dance of mountain creation.
Each event was accompanied by extensive metamorphism, melting of both sedimentary and volcanic rocks into granite as they were buried under the pressure and heat of rising mountains and subduction related volcanism as ancient oceans closed. Since then of course Pangaea has split up, and the once proud peaks have been ground down by erosion, so that the tallest rise in the region is a mere 480 metros.
Legend states that they are a Roman legion, transformed into stone by the wizard Merlin, though they date from the Neolithic period around 4,500-2,000 BCE, long before the Celtic peoples moved west from their probable heartland in the Danube. Dating their erection is difficult, since little organic matter was buried under them for C14 data but the peak is thought to have been around 3,300 BCE. They are the largest assemblage of menhirs in the world, spread out over a wide area.
There are three main alignments related to the solstice sunrise and sunsets at both ends of the year, known as Menec, Kermario and Kerlescan in the local Breton language, though they may have formed as single grouping as stones have been removed over the millennia for building and other purposes. All of them have taller stones to the west (the traditional direction of death) and shorter ones to the east (that of birth).
Previous posts in this series:
The geology of newgrange: http://tinyurl.com/qhj3e4v
The geology of Stonehenge 1&2:http://tinyurl.com/kec8tu3 andhttp://tinyurl.com/nbaq8v5
Image credit: Jim Brandenburg via wallpaper downloader
http://www.farnhamgeosoc.org.uk/archive/reports/brittany11.pdf
Thanks to Charles Darwin, the Galapagos Islands are known as a biological wonderland. After all, it was the relationships between its species which enabled Darwin to understand how different species could arise from a common ancestor.But from a different perspective; the Galapagos actually aren’t species-rich; visitors to the islands often are surprised at how limited the number of species there really are compared to the mainland. The islands are remote, nearly 1000 kilometers from the mainland, and only a handful of species could ever make that trip.
In that setup…it turns out that the Galapagos tortoises wound up playing the role of a keystone species, one which the entire ecosystem depended on.
In new research, Dr. Cynthia Froyd of Swansea University took samples of soils throughout the Galapagos and tested them for the types of environments recorded and the species present.
They found that, prior to 500 years ago; they found “dung-affiliated” fungi, suggesting a large, plant-eating organism dominated the area. Since there aren’t other options living in the Galapagos wetlands, the only option was the tortoises.
Prior to the arrival of man, tortoises roamed freely across the islands, but starting in the 16th century, their numbers declined from 250,000 to 14,000 by 1970, and 5 of the original 14 subspecies have gone extinct.
At the same time, wetlands began drying up, a change recorded by the soil samples. About 500 years ago, the tortoise feces vanish, and at the same time, the plants change. The freshwater wetlands that once populated large areas of the Galapagos dried and the plants supported by those wetlands began dying, disappearing, and even going extinct.
The plants which supported those wetlands relied on the tortoises in several ways, including fertilization and churning up the ground as they walked through. The tortoises were a keystone species; once they began dying, the entire ecosystem surrounding them died with them.
Today, efforts are underway to protect the remaining tortoises and to introduce them into their previous environments, but many of the areas where the tortoises used to live simply don’t exist anymore. Once the tortoises died or were killed, the wetlands died with them, and reestablishing the entire ecosystem will be a difficult, long-term task.
Image credit: Wikimedia commons
http://en.wikipedia.org/wiki/File:Galapagos_tortoise_bathing.jpg
Original paper:
http://onlinelibrary.wiley.com/doi/10.1111/ele.12203/abstract
This photo shows one of the many glaciers on Baffin Island, in the far northern reaches of Canada. New research from this island tells a stark story of how unstable these glaciers are becoming.Baffin Island is in the middle of the area strongly affected by Milankovitch cycles. As the Earth wobbles in its orbit, northern Canada is seeing particularly large swings in the amount of sunlight it receives, making it a key contributor to the expanding and melting of ice sheets.
Right now, we’re at a point where solar input to Canada is declining. About 11,700 years ago, the solar energy input to this area was about 9% greater than it is today; at about the same time, the large ice sheets covering Canada were collapsing.
Not every glacier in Canada collapsed, particularly here in Baffin Island, just the large ice sheet. But, since these glaciers aren’t linked to the large ice sheet, one would expect that Baffin Island is a place on Earth that should be cooling right now. It is getting less sunlight than it did 10,000 years ago, so if any place on Earth should be slowly cooling, it should be right here.
A new study led by Dr. Gifford Miller at CU Boulder found something remarkable. These glaciers are melting slowly at their edges, releasing some plants and rocks that have been trapped in the ice. These scientists sampled some of those plants, expecting that their radiocarbon ages would be a sign for how long the plants had been trapped in the ice. Using that information, they could estimate how much the glaciers of Baffin Island grew as the solar input decreased.
When they got a radiocarbon date on those formerly-frozen plants, they found that to their surprise the age was infinite. Radiocarbon dating doesn’t provide solid answers past about 40,000 years even in the best labs – beyond that the calculated age goes to infinity, so these plants must have been much older than 40,000 years – a time when all of Canada was covered by ice sheets.
Their conclusion is that these plants were trapped in ice during a previous time in-between the formation of ice sheets. The most recent inter-glacial time was about 125,000 years ago – a likely time for these plants to be trapped.
The presence of these plants means a couple things. First, ice that hasn’t melted in at least 125,000 years is melting today. Second, that ice is melting even though the amount of sun coming in to Baffin Island today is decreasing – the changing global climate is overwhelming the decreasing solar input.
Finally…125,000 years ago, the ice sheets on Greenland and Antarctica melted a lot more than they did in this inter-glacial period. If these plants are from that time…they come from a time when sea level was between 5 and 9 meters higher than it is today. To say that a different way, the last time the these plants were outside of a glacier, sea level was about twice the height of the hurricane Sandy storm surge in New York.
Image credit:
http://commons.wikimedia.org/wiki/File:Glacier,_Glacial_Lake,_and_Terminal_Moraine,_Baffin_Island_-a.jpg
Original paper:
http://dx.doi.org/10.1002/2013GL057188
Press report:
http://instaar.colorado.edu/news-events/instaar-news/instaar-study-shows-unprecedented-warmth-in-arctic/
Soaring over 60 m (≈200 ft) high in Colombia’s Cocora Valley is the giant wax palm: the tallest palm tree in the world. Growing at elevations as upward as 3150 m (>10,300 ft) above sea level, the wax palm trees live in seclusion in Colombia’s Andes Mountains, where they grow alongside coffee plants and other exotic vegetation. If a daring soul were to climb to the top (surely with a harness I’d hope), they may also be lucky enough to witness an endangered Yellow-eared parrot. The parrots are known to nest in the hollowed out trunks and leaf beds of the wax palms but they are extremely hard to find.
The wax palms get their name from a natural wax that covers their trunks which was also used for candles until the Colombian government passed a law that now protects the vulnerable trees. In addition to their waxy coating, the palm trees have also in the past been hunted for the Catholic holiday, Palm Sunday, as well as for architectural purposes.
The trees are now protected though, and it is not uncommon for Cocora Valley to be covered in fog, which gives the valley somewhat of a “Jack and the bean stalk” sort of feel to it. Standing below the palm trees and losing their green caps in a heavy fog can be almost as impressive as the sight of the palm trees on a clear day. However, there is nothing more humbling than standing directly beneath the palm tree that makes the mountains look small.
Photo Credit:
Alex Treadway, National Geographic
http://on.natgeo.com/1bEDG2b
References:
1.http://www.academia.edu/1865247/Colombia_national_tree_the_wax_palm_Ceroxylon_quindiuense_and_its_relative
2. http://www.colombiaexplorer.com/destinations/coffee-triangle/cocora-valley/
3. http://www.bbc.com/travel/feature/20130219-colombias-valley-of-the-palms
If
you’ve ever watched geology-related television shows, one favorite
story to tell is the idea of a mega-tsunami in the Atlantic Ocean caused
when of one of the Canary Islands collapses.
The Canary
Islands are islands off the coast of northwest Africa built by
volcanoes. These volcanoes grow when magma, generated in the Earth’s
mantle, forces its way upwards through the above rocks, fracturing them and pushing them apart.
Volcanoes like these literally break themselves in half. On several of
these islands, most notably the island of La Palma, there are a series
of faults (A good chance one of them is seen in the foreground here, the
sharp break in the slope) where parts of the island are sliding into
the sea. Every time magma comes up it pushes on faults like this,
forcing part of the island outwards.
Surrounding all of the
Canary Islands (and others in places like Hawaii) there are large debris
fields made of up rocks that broke off the islands and slid into the
sea. If you total up the size of these debris fields, they would have
been massive – so massive that if all that material fell into the ocean
at once, it would generate an enormous tsunami wave, one that could
still be 50 meters high when it reached New York.
It’s a great
story for TV; it’s plausible, you can go to the place where such a
breakaway would happen and put your finger on it, and then you can
animate that wave hitting New York, Boston, and Washington D.C.
The good news for most people is that the threat of such a
mega-landslide is almost certainly overstated for one reason; the
islands usually don’t collapse like that.
A paper published
last year by Dr. J.E. Hunt and colleagues at the University of
Southampton, UK, performed a detailed mapping study of the landslides
over the last 1.5 million years. When they looked carefully at the
largest landslide deposits, they found that instead of being one large
landslide, they were each composed of several smaller units with large
time breaks in-between.
In other words, these big landslides
didn’t come down all at once, they came down slowly. The largest slide
they found was about ¼ the volume of the full debris area on the side of
an island.
Tsunami heights don’t scale directly with landslide
volume, but it takes a really enormous landslide in the Canaries to do
major damage to the U.S. East Coast. The largest slide they found would
still cause a tsunami that would damage the islands themselves and
possibly the coasts of Africa and Spain, but it wouldn’t be a major
threat to far-flung population centers.
This research, of
course, does not mean that such a giant collapse is impossible. Unique
things do happen, and just because the previous collapses were small
doesn’t 100% guarantee that any future ones will be also.
But,
if you hear someone say “this island will collapse in the next few
thousand years and cause a tsunami” or any version of that…that’s not
how things have happened for the last 1.5 million years, and if we’re
planning for the future, it’s not something we need to fear happening
any time soon.
Image credit: Wikimedia commons
http://commons.wikimedia.org/wiki/File:Plantation_banana_La_Palma.jpg
Original paper (Subscription):
http://onlinelibrary.wiley.com/doi/10.1002/ggge.20138/abstract
Article:
http://blogs.agu.org/landslideblog/2013/12/13/canary-islands-tsunami/
We’ve
covered the ongoing eruption at Sinabung volcano on the western side of
the Indonesian island of Sumatra several times here at the Earth Story.
The volcano erupted in 2010 following several centuries of inactivity
and then entered a much more active phase in September of 2013. This
weekend saw yet another phase of extreme activity from the volcano and
an enlargement of the evacuation zone again, moving an additional 5000 people from their homes.
The volcano had about 30 separate explosions reported during the day on
Saturday, with some of the largest outpourings of lava seen in the
years of this eruption. The largest ash plumes reportedly went over 4000
meters into the sky.
The total evacuations associated with this eruption now exceed 20,000.
Previous posts: http://tinyurl.com/k8uv35j, http://tinyurl.com/ov6swbw, http://tinyurl.com/nevogf9 and http://tinyurl.com/lctx9tg
Image credit: Binsar Bakkara/AP
http://blogs.ft.com/photo-diary/tag/eruption/
There aren’t many places in California where one can find snow on Christmas. California Christmases are, for obvious reasons, typically spent trying to avoid bragging to relatives about the weather.However, there’s one place in California legendary for its snowfall: Mammoth Mountain.
Mammoth is one of the most popular ski areas in the country. People flock to its slopes during the winter; many without pondering the unique geology that creates the snowcapped peak lost in the clouds in this photo.
Mammoth sits in a very unusual place within the Sierra Nevada mountain range. There’s a gaping hole in the middle of the Sierras known as the “Long Valley Caldera”. You can see it reflected in the flatland in the foreground of this image.
The entire flatland in the foreground of this photo is a giant volcano. It erupted over 700,000 years ago, spitting out almost as much lava as the Yellowstone eruptions. When the eruption was finished, the ground collapsed downwards into the now-empty magma chamber, forming the caldera and leaving a giant gaping hole in the center of the mountain range.
The Sierra Nevada range runs parallel to the Pacific Ocean coastline. When moisture from the Pacific tries to enter the continent, it runs into this huge mountain range and typically is dumped as snow. That is, except for one place where moisture is able to penetrate deep into the mountains…because there’s a giant, gaping hole in the center of the range.
Moisture from the Pacific is able to penetrate into the mountains near Long Valley because the highest part of the range at that point was totally blown away. But, there is one mountain sitting in the way, sitting in the path of all that moisture – Mammoth Mountain.
Why is this one mountain sitting in that path, right next to the gaping hole? Well, it’s a volcano too.
Mammoth Mountain is made up of a couple million years worth of lava flows and eruptions, piled on top of one another to build the mountain. It sits just outside of Long Valley caldera, stuck at the perfect place to create massive snowpacks. It exists because of the caldera and it receives its snow because of the caldera.
It’s still active too. In the late 1980’s, there was a series of earthquakes recorded beneath Mammoth due to movement of magma within the crust, and a large number of trees in one area near Mammoth were killed due to venting volcanic gases.
That seems appropriate for a California Christmas. A snowcapped ski course on the slopes of a volcano, sitting along the edge of a giant volcano that blew a massive hole in a mountain range.
Image credit:
http://www.flickr.com/photos/21051229@N06/5605360066 (Creative Commons license)
Africa's most active stratovolcano culminates at 3,470 metres over lake Kivu and the city of Goma on the Albertine branch of the great East African rift, where a new ocean may be in its early birth throes. Located in the Virunga volcanic field and national park (seehttp://tinyurl.com/ntwhof8) in the Democratic Republic of Congo, it is one of 8 active smokers in the field. The mountain sits at the intersection of several major faults, which allow the magma to rise from the mantle below. The extensional tectonics of the rift part the plate allowing the magma through.
The summit has a 2 kilometre wide caldera, that has had periods (including the present) of containing a long lived seething lava lake. Since the mountain's product is very fluid alkaline basalt, the convection patterns and overturns in the lake make for an ever shifting pattern of cooling black rocky crust and molten red lava. The lake existed continuously between 1894 and 1977, when it emptied in less than an hour as the crater walls fractured, engulfing several villages downstream. The lava is so fluid due to its low silica content that it can race down the steep conical sides of the mountain at up to 100kph. The flanks are littered with cinder cones. It was famously explored and studied by Belgian/French vulcanologist Haroun Tazieff in the early 70's (seehttp://tinyurl.com/m3b9oob)
It presents a serious hazard to Goma, and the 2002 eruption lava flows carved through parts of the city, including the airport runway, whose population was swollen with refugees from the endemic war that has raged in the Kivus since the 1990's. This led to serious disruption, as aid could not arrive by air until the runway was cleared. Lava flows also reached lake Kivu, prompting fears that it might cause its higly stratified waters to overturn, potentially releasing the CO2 in the saturated deeper layer and axphyxiating people and livestock, as happened at Lake Nyos (Cameroon) in 1982 (see http://tinyurl.com/qxnsx34)
It has erupted at least 34 times since 1882, sometimes continuously for years. The dense population in the area and the exceptional lava flow risk led to it being nominated a Decade volcano, and extensively studied and mapped from a hazards perspective. Ongoing conflict has made the required amount of study difficult.
Image credit: Matin Rietze
http://www.volcanolive.com/nyiragongo.html
http://www.atlasobscura.com/places/lava-lake-nyiragongo-volcano
http://www.photovolcanica.com/VolcanoInfo/Nyiragongo/Nyiragongo.html
http://www.volcanodiscovery.com/nyiragongo.html
http://ngm.nationalgeographic.com/2011/04/nyiragongo-volcano/finkel-text
On the morning of December 22, 2008, a rumbling began along the Emory River in East Tennessee. Moments later, walls of water and ash washed around the streets, bridges, and houses of the surrounding community. A disaster few had considered possible was underway.This image shows the end result of the Kingston coal ash spill. The smokestacks in the distance are coal-fired power plant. When coal is burnt for electricity, there is always something left over, material known as fly ash. These leftover products of coal burning contain a variety of contaminants including heavy metals and chemicals that can irritate respiratory systems.
At this plant, ash was being dumped into a retaining pond and used to build a dam. 5 years ago today, that dam gave way, and 5.4 million cubic yards of material dumped into the Emory river.
Today, the cleanup of the area is well underway, but the disaster has created a number of longstanding environmental and legal problems.
The Tennessee Valley Authority which operates the plant has spent over a billion dollars on cleanup. They paid to remove the houses of the people who lived in the affected areas, spent tens of millions of dollars building new parks and bridges for the cities that lost land, and dredged a majority of the ash out of the river.
About 10% of the ash volume is going to remain in the Emory River. Rivers are really good at dispersing sediment, so once the dam collapsed recovering every bit was never going to be possible. Some of that sediment has washed downstream while some has been trapped in isolated areas of the river. A variety of monitoring efforts are underway from the TVA and local universities to track these contaminants as they migrate towards the Gulf of Mexico.
The plant itself continues operating and construction of new holding facilities is underway.
This disaster created a variety of national and legal issues that have still not been resolved. Prior to this spill, the Environmental Protection Agency generally ignored coal fly ash and power plants dealt with it on their own. This disaster showed that setup was simply inadequate and the director of the EPA promised to issue rules by the end of 2009 for ash storage, but the EPA has yet to issue those rules. Ash like this is stored in hundreds of facilities nationwide, and at those facilities, groundwater contamination and smaller spills are commonplace.
There are also lawsuits directly relating to the Kingston ash. That ash was taken by train for disposal at a landfill in Alabama, and the local community (with a mostly African American population) has filed a civil rights lawsuit asking why the material was too dangerous to store in Tennessee but safe enough to store in their communities.
The Kingston fossil plant ash spill left a substantial mark on the surrounding ecosystems, and the ramifications continue to be felt to this day.
Image credit: Knoxville News Sentinel
http://media.knoxnews.com/media/img/photos/2009/12/19/122009flood1_t607.jpg
http://www.knoxnews.com/news/2013/dec/22/five-years-later-reviews-mixed-on-kingston-coal/
http://www.knoxnews.com/news/2013/dec/22/ulla-reeves-five-years-after-coal-ash-spill-epa/
