Tuesday, September 23, 2014

Magnificent Mayon


Held by some to be the most perfect stratovolcanic cone in the world, the Philippines' most active volcano last erupted just over a year ago (see our coverage of the latest of the 48 recorded eruptions in the last 400 years at http://tinyurl.com/mcporfd). Rising 2,462 metres high on the main island of Luzon, it has been a national park since 1938 and has played an important part in the history and culture of the island. It is named after a heroine in a local legend who eloped with her lover. The gods buried the furious father who was chasing them under a landslide.

The magma feeding this smoker is born deep below, as the Philippine oceanic crust subducts beneath the Philippine continental plate (formed of a belt of continental fragments). When the plate reached a certain depth, and set of pressure/temperature conditions, the water in the altered seafloor basalt is literally baked out of the minerals it was locked in, and lowers the melting point of the mantle wedge above, causing it to partially melt and the resulting less dense magma rises towards the surface through a line of weakness such as a fault in the overlying crust.

The cone is formed of layers of welded ash from pyroclastic flows alternating with layers of lava that oozed out of the volcano over the millennia of its geological history. Its products are classified as basaltic andesite, lavas being graded according to richness in silica.

Sitting above the city of Legaspi, the mountain has several associated hazards, ranging from lava and pyroclastic flows (clouds of very hot air and ash running down the ravines carved into the cone by tropical rains from typhoons) during eruption to subsequent lahars, flows of running mud that rush down river valleys when downpours mix with the fine ash, obliterating everything before them. The rain from Typhoon Durian killed over a thousand back in 2006. Its most powerful recorded outburst buried the town of Cagsawa in 1814.


Image credit: Dacel Yazon Andes

https://www.facebook.com/dacelyazonandes
http://www.phivolcs.dost.gov.ph/html/update_VMEPD/Volcano/VolcanoList/mayon.htm
http://volcano.oregonstate.edu/mayon
http://www.britannica.com/EBchecked/topic/371043/Mayon-Volcano

Kaieteur falls


This waterfall is Kaieteur Falls, found in the nation of Guyana within Kaieteur Falls National Park. 

This waterfall sits on the Potaro River, a tributary of the Essequibo River that drains a large portion of South America north of the Amazon Basin. 

The falls cascade over cliffs made of conglomerate and sandstone, dropping over 225 meters in the initial fall. These falls aren’t either the biggest or tallest in the world, but the drop is 4 times the height of the well-known Niagara Falls and twice the height of Victoria falls. These falls are therefore one of a few found globally that have both a very large drop, a high flow rate, and a narrow focus in its canyon, giving the waters pouring over the cliff immense power by the time they reach the base.


Image credit: Cody H (creative Commons):
https://www.flickr.com/photos/codiferous/362100114

Read more:
http://www.worldwaterfalldatabase.com/waterfall/Kaieteur-Falls-114/

Sunday, July 6, 2014

Mount Fuji - Japan


You cannot help but be calmed by this beautiful shot of Mount Fuji, looking over Lake Kawaguchi. 

Indeed such is the beauty of this volcano that TES has posted pictures and stories of it in almost every situation:

sunset: http://on.fb.me/1lgGLJM
moonlight: http://on.fb.me/1qecbs5
under a comet: http://on.fb.me/1yR3juK
from space: http://on.fb.me/1qydsaT
under a cloud: http://on.fb.me/1mhqAfn
and even the chance to climb it using Google Street View: http://on.fb.me/1qKNsLX

The Japanese football team’s dreams of rising majestically above the competition will have to wait until four years time, as they finished bottom of a tough Group C. They were tipped to perform well, but football is often unpredictable, just as volcanic activity can be.

Many factors are taken into account in trying to predict volcanism, which can be read about in relation to Mount Fuji’s individual situation here: http://on.fb.me/1nKVKNH and more generally here: http://on.fb.me/Tm3lKa .


Image credit (non commercial): Masaru Minoya (http://bit.ly/1lgDKsU)



Sunrise over Lake Malawi


Lake Malawi sits near the southern end of the East African Rift Zone and borders the nations of Malawi, Mozambique and Tanzania. Some of the bordering countries refer to the lake as Lake Nyasa, using the name that predated the founding of Malawi as a country.

The lake sits in a tectonic basin being formed as the eastern side of Africa pulls apart. The East African Rift Zone is a feature formed over the last several million years as tectonic forces are splitting the very continent apart. On land, these forces result in the formation of rift valleys; deep, linear valleys surrounded by steep cliffs and normal faults. Some of those steep cliffs can be seen in the far distance in this photo.

Lake Malawi National Park sits at the southern end of this lake in Malawi and has been declared a UNESCO world heritage site due to the setting, surrounded by the scarps of the Great African Rift Valley, and due to the variety of fish and other wildlife sustained by its waters.


Image credit: http://www.fotopedia.com/items/flickr-2368169377
(Creative commons)

Tuesday, June 24, 2014

Klyuchevskaya Sopka


Hell yeah, that’s a volcanic eruption as seen from space.

To be more precise, it is the eruption of Klyuchevskaya Sopka taken by the Space Shuttle Endeavour on the 30th of September 1994.

Impressive, isn’t it eh?

This particular eruption expelled ash and gases upwards of 18,300 metres above sea level and the winds carried the ash as far as 1,030 km. Looking at this image and reading just how enormous the eruption was, it is easy to understand why some people link current climate change with events like volcanic eruptions. But, what role do volcanoes actually play?

As we can see, during major volcanic eruptions huge amounts of volcanic gas, aerosols and ash are injected into the stratosphere. The ash tends to fall fairly rapidly from the stratosphere; a matter of days or weeks and has little implication on the climate. However, volcanic gases like sulphur dioxide can cause global cooling and volcanic carbon dioxide, the infamous greenhouse gas, has the potential to promote global warming.

Perhaps contrary to belief, the most significant climate impacts of volcanic activity are as a result of sulphur dioxide. Sulphur dioxide gas is converted to droplets of sulphuric acid in the stratosphere over the course of a week to several months after the eruption. Winds in the stratosphere spread the aerosols until they practically cover the globe. As the droplets have a high albedo, they reflect sunlight reducing the amount of energy reaching the lower atmosphere and the Earth's surface; cooling them. (NASA,1996)

Once formed, these aerosols stay in the stratosphere for around 2 years, although data from NASA’s stratospheric Aerosol and Gas Experiment (SAGE II) showed the effects of the eruption of Mt. Pinatubo in 1991 lingered for up to 10 years.

As mentioned previously, carbon dioxide is also emitted during volcanic eruption and a question that has commonly been asked is “Don’t volcanoes contribute much more CO2 emissions than human activities?

Unfortunately the answer to that question is a clear and unequivocal “No”.

Published reviews of the scientific literature by Kerrick et al (2001) report a minimum-maximum range of emission of 65 to 319 million tonnes of CO2 per year from subaerial and submarine volcanoes.

This seems like a huge amount, and it is. That is, until we compare it to anthropogenic emissions.

According to an International Energy Agency some 30. 6 billion tonnes of carbon dioxide were released into the atmosphere as a result of human activity in 2010.To say that another way, assuming the highest estimates of volcanic CO2 emissions (319 million tonnes), human-emitted carbon dioxide levels were more than 95 times higher.

The Mount Pinatubo eruption in 1991 emitted 42 million tonnes of CO2 (Gerlach et al 1996). Now, compare this to human emissions in 1991 which were a total of 23 billion tonnes of CO2 (CDIAC). The strongest eruption over the last half-century amounted to 0.2% of human CO2 emissions in that year. 0.2%.

Image courtesy of NASA

References:

Carbon Dioxide Information Analysis Centre:http://cdiac.ornl.gov/trends/emis/overview_2006.html

Kerrick, D. M. (2001). "Present and past nonanthropogenic CO2 degassing from the solid earth." Rev. Geophys. 39(4): 565-585.

NASA,1996; “Atmospheric Aerosols: What Are They, and Why Are They So Important?”

Terrence M. Gerlach(1996) Pre-Eruption Vapor in Magma of the Climactic Mount Pinatubo Eruption: Source of the Giant Stratospheric Sulfur Dioxide Cloud . http://vulcan.wr.usgs.gov/Projects/Emissions/Reports/Pinatubo/pinatubo.html

Annular Eclipse


Almost 14 days ago, there was a lunar eclipse visible in the Western Hemisphere. A lunar eclipse takes place when the Earth is directly between the Moon and the Sun. It takes the Moon 28 days to orbit around the Earth, so 14 days after a lunar eclipse, the Moon is on the opposite side of the Earth, between the Earth and the sun.

If the angles line up correctly, that’s the day when a solar eclipse is possible, and on April 29th, there will be an annular eclipse of the sun. Unfortunately the eclipse will be best viewed from remote areas in Western Australia, the southern Indian Ocean, and Antarctica, but populated areas in Eastern Australia may be able to see up to about 60% coverage just before sunset on Tuesday.

An annular eclipse occurs when the Moon blocks out most, but not all, of the sun’s disk. The moon’s orbit around the Earth is not circular, so at some times it’s closer to the planet and other times it’s farther away. An annular eclipse happens when the moon is at a point in its orbit far from earth, making the moon’s disk small enough to allow this “ring of fire” around the edge.

As with most eclipses, it is not safe to view this eclipse with the naked eye; you will cause eye damage if you look. Standard sunglasses also do not provide enough protection. Instead, eclipse-viewing glasses, welding shields, cameras, or other viewing devices will be required for save viewing.


Image credit: t-mizo (creative commons license): previous annular eclipse viewed from Japan
https://www.flickr.com/photos/tmizo/7241286428/

Read more:
http://www.space.com/25639-first-solar-eclipse-2014-tuesday.html
http://www.huffingtonpost.com/2014/04/24/solar-eclipse-2014-ring-of-fire_n_5204928.html?utm_hp_ref=science

Eye safety:
http://eclipse.gsfc.nasa.gov/SEhelp/safety.html

Nohkalikai Falls


During the monsoon season, this area of the north eastern Indian state of Meghalaya near Cherrapunji has been named the wettest place on Earth. All that water has to go somewhere, and several of the Subcontinent's tallest falls are located in the area. The monsoon gathers during the spring as the land bakes, causing a column of rising air that pulls moist sea air behind it, bringing the annual rains on which Indian civilisation has depended since pre Vedic times.

Nohkalikai is supposedly the tallest plummet in India, at around 340 metres, and at the right time of year one of the most powerful. The crashing waters have carved out a deep rock pool at the bottom of the plateau that changes colour from blue to green depending on the season. The rocks are a Cretaceous-Paleogene sedimentary stack made of limestone and sandstone.

The name (jump of Ka Lilai) is associated with a tragic legend of a woman who went mad after a family tragedy and threw herself off the cliff. During the dry season thee falls slow to a trickle. They sadly often hide in cloud during the monsoon season when at their most spectacular.


Image credit: Sunanda
http://www.world-of-waterfalls.com/asia-nohkalikai-falls.html
http://www.wondermondo.com/Countries/As/India/Meghalaya/Cherrapunji.htm

Fire Whirls


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

The geology of Carnac


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

Sunday, February 16, 2014

Tortoise poop


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

Baffin Island melting unprecedented


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/

Reach for the Skies: Colombia’s Giant Wax Palm Trees


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

Sunday, February 2, 2014

Will the Canaries Collapse?


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/

Sinabung explodes…again and again.


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/

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