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2 volcanoes at once is weird, right? Let’s talk volcanoes for #volcanomonday. Last Friday, we ran two posts about volcanic eruptions that started that day; one in Iceland and one around the world in Papua New Guinea. A question that came up both in press reports and even in our own comments is…is this unusual?The answer is no, it’s not unusual at all for many volcanoes to erupt at the same time. For example, this satellite image was taken last week and it shows the island Nishino-shima south of Japan. Last December, we covered the formation of a new island here, Niijima, a volcanic peak that emerged from beneath the waves (http://tinyurl.com/oe22xtl). Niijima has spent the last 9 months erupting, with no signs of slowing down, and has grown so large that it consumed the island it appeared next to.That’s one volcano that has erupted almost non-stop for nearly a year, and there’s nothing abnormal about that at all. When people were asking whether the two eruptions on Friday were unusual, the continuing eruption at this volcano was forgotten. That should help convey the point; volcanoes can stay active for years, even decades at a time. In fact, there are some volcanoes that almost never shut off.The most famous of those are probably Kilauea and Stromboli. Kilauea, on the big island of Hawaii, has been constantly pouring out lava since 1983. The volcano Stromboli off the coast of Italy has been in a state of eruption for about 2000 years. Other volcanoes, like Ol Doinyo Lengai and Erta Alae in Africa and Erebus in Atarctica are regularly erupting as well, sometimes even maintaining long-lived lava lakes.The real extreme of this effect, by the way, is the mid-ocean ridge system. Mid-Ocean ridges around the world are almost constantly erupting; if you counted up each location as a volcano, there would easily be hundreds of different eruptions at any given time. Around the world, volcanoes become active and shut down. Sometimes we notice and cover them, some times we don’t. There are usually well over 10 around the world erupting, sometimes several dozen, but most of them don’t get much coverage. The difference typically is whether or not they’re in urban or developed areas. In developed areas, we hear reports of them, and most importantly photographs are produced. When a volcano like Erebus, on the continent of Antarctica erupts, we typically don’t get good pictures of it. When a rift zone opens on Iceland, we get great coverage and images of every step because people are there to watch it.Volcanoes in one part of the world don’t impact another part of the world. So under the #volcanomonday tag today, just count this as a reminder that a couple volcanoes being on your news feed might be a cool thing to watch, it might produce some great images, but there’s no larger story other than the way plate tectonics works on an average day.-JBBImage credit: NASAhttp://earthobservatory.nasa.gov/IOTD/view.php?id=84232&eocn=image&eoci=moreiotdList of currently active volcanoes:http://www.volcanodiscovery.com/erupting_volcanoes.htmlPress report calling it weird:http://www.mtv.com/news/1916782/mount-tavurvur-volcanoes-erupting-bardarbunga/Stromboli: http://www.volcanodiscovery.com/stromboli.html

2 volcanoes at once is weird, right? 

Let’s talk volcanoes for #volcanomonday. Last Friday, we ran two posts about volcanic eruptions that started that day; one in Iceland and one around the world in Papua New Guinea. 

A question that came up both in press reports and even in our own comments is…is this unusual?

The answer is no, it’s not unusual at all for many volcanoes to erupt at the same time. For example, this satellite image was taken last week and it shows the island Nishino-shima south of Japan. Last December, we covered the formation of a new island here, Niijima, a volcanic peak that emerged from beneath the waves (http://tinyurl.com/oe22xtl). Niijima has spent the last 9 months erupting, with no signs of slowing down, and has grown so large that it consumed the island it appeared next to.

That’s one volcano that has erupted almost non-stop for nearly a year, and there’s nothing abnormal about that at all. When people were asking whether the two eruptions on Friday were unusual, the continuing eruption at this volcano was forgotten. That should help convey the point; volcanoes can stay active for years, even decades at a time. In fact, there are some volcanoes that almost never shut off.

The most famous of those are probably Kilauea and Stromboli. Kilauea, on the big island of Hawaii, has been constantly pouring out lava since 1983. The volcano Stromboli off the coast of Italy has been in a state of eruption for about 2000 years. Other volcanoes, like Ol Doinyo Lengai and Erta Alae in Africa and Erebus in Atarctica are regularly erupting as well, sometimes even maintaining long-lived lava lakes.

The real extreme of this effect, by the way, is the mid-ocean ridge system. Mid-Ocean ridges around the world are almost constantly erupting; if you counted up each location as a volcano, there would easily be hundreds of different eruptions at any given time. 

Around the world, volcanoes become active and shut down. Sometimes we notice and cover them, some times we don’t. There are usually well over 10 around the world erupting, sometimes several dozen, but most of them don’t get much coverage. The difference typically is whether or not they’re in urban or developed areas. In developed areas, we hear reports of them, and most importantly photographs are produced. When a volcano like Erebus, on the continent of Antarctica erupts, we typically don’t get good pictures of it. When a rift zone opens on Iceland, we get great coverage and images of every step because people are there to watch it.

Volcanoes in one part of the world don’t impact another part of the world. So under the #volcanomonday tag today, just count this as a reminder that a couple volcanoes being on your news feed might be a cool thing to watch, it might produce some great images, but there’s no larger story other than the way plate tectonics works on an average day.

-JBB

Image credit: NASA
http://earthobservatory.nasa.gov/IOTD/view.php?id=84232&eocn=image&eoci=moreiotd

List of currently active volcanoes:
http://www.volcanodiscovery.com/erupting_volcanoes.html

Press report calling it weird:
http://www.mtv.com/news/1916782/mount-tavurvur-volcanoes-erupting-bardarbunga/

Stromboli: http://www.volcanodiscovery.com/stromboli.html

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Subduction through the mantleA few days ago I described the “Wadati-Benioff zone” as one way of tracking the remnants of oceanic plates as they subduct into the Earth (http://tinyurl.com/mjcg7n7). A subducting oceanic plate is colder than the mantle around it, cold enough that it can produce earthquakes until it reaches 700 kilometers depth.Geophysicists have another tool that allows them to track subducting plates even deeper than that called seismic tomography. When an earthquake happens anywhere on Earth, it sends out seismic waves in all directions. Some of that energy passes through the entire planet and can be detected by seismometers on the opposite side of the planet.Those seismic waves travel through whatever rocks are in the mantle, and in the process they are slightly altered by the trip. Some rock types slow down seismic waves, some speed them up. From a single seismic station you can’t tell much about the mantle, but if hundreds of stations detect a single earthquake, that’s a setup where computers can help.In medical facilities today, computers are regularly used to reconstruct 3-D pictures inside the human body. To do this, data needs to be collected at a points surrounding the body, as in an MRI tube. Seismic tomography works the same way; with enough data points from hundreds of seismic stations and earthquakes, a computer can reconstruct a 3-D picture of where seismic waves slow down and where they speed up. The differences are tiny, less than 1% changes in the wave speed, but enough that modern equipment can detect it with accuracy.In addition to the composition of the rocks, the temperature of rocks also affects seismic waves; cold rocks transmit seismic energy faster. If oceanic plates are cold when they subduct, seismic tomography has the potential to track them most of the way down through the mantle, and here you see exactly that. The red and blue images are cross-section paths across subduction zones in seismic tomography. The blue blobs on their way down are cold objects in the mantle. They start at the surface at locations of subduction zones and the deepest ones reach depths of over 1700 kilometers into the mantle. Seismic tomography is precise enough to track slabs down almost the entire way through the mantle.Interestingly, one feature in many of those slabs stands out. When the slabs reach a depth of ~700 kilometers, several turn horizontal. That level is interesting as at about 660-670 kilometers deep, the main phase in the mantle changes. The upper mantle is dominated by a mixture of garnet and olivine-like minerals called Wadsleyite and Ringwoodite; at 670 kilometers depth, those minerals all change into Bridgmanite, the most abundant mineral inside the Earth. The fact that slabs appear to get hung up at this level means that there is some strength to that transition; it’s hard for things to get across. That means it is at least possible for that phase transition within the mantle to serve as a major dividing line, between partially isolated upper and lower mantle areas, over geologic time.-JBBImage credit: http://eesc.columbia.edu/courses/v1011/topic_4_2.htm

Subduction through the mantle

A few days ago I described the “Wadati-Benioff zone” as one way of tracking the remnants of oceanic plates as they subduct into the Earth (http://tinyurl.com/mjcg7n7). A subducting oceanic plate is colder than the mantle around it, cold enough that it can produce earthquakes until it reaches 700 kilometers depth.

Geophysicists have another tool that allows them to track subducting plates even deeper than that called seismic tomography. When an earthquake happens anywhere on Earth, it sends out seismic waves in all directions. Some of that energy passes through the entire planet and can be detected by seismometers on the opposite side of the planet.

Those seismic waves travel through whatever rocks are in the mantle, and in the process they are slightly altered by the trip. Some rock types slow down seismic waves, some speed them up. From a single seismic station you can’t tell much about the mantle, but if hundreds of stations detect a single earthquake, that’s a setup where computers can help.

In medical facilities today, computers are regularly used to reconstruct 3-D pictures inside the human body. To do this, data needs to be collected at a points surrounding the body, as in an MRI tube. Seismic tomography works the same way; with enough data points from hundreds of seismic stations and earthquakes, a computer can reconstruct a 3-D picture of where seismic waves slow down and where they speed up. The differences are tiny, less than 1% changes in the wave speed, but enough that modern equipment can detect it with accuracy.

In addition to the composition of the rocks, the temperature of rocks also affects seismic waves; cold rocks transmit seismic energy faster. If oceanic plates are cold when they subduct, seismic tomography has the potential to track them most of the way down through the mantle, and here you see exactly that. The red and blue images are cross-section paths across subduction zones in seismic tomography. 

The blue blobs on their way down are cold objects in the mantle. They start at the surface at locations of subduction zones and the deepest ones reach depths of over 1700 kilometers into the mantle. Seismic tomography is precise enough to track slabs down almost the entire way through the mantle.

Interestingly, one feature in many of those slabs stands out. When the slabs reach a depth of ~700 kilometers, several turn horizontal. That level is interesting as at about 660-670 kilometers deep, the main phase in the mantle changes. The upper mantle is dominated by a mixture of garnet and olivine-like minerals called Wadsleyite and Ringwoodite; at 670 kilometers depth, those minerals all change into Bridgmanite, the most abundant mineral inside the Earth. 

The fact that slabs appear to get hung up at this level means that there is some strength to that transition; it’s hard for things to get across. That means it is at least possible for that phase transition within the mantle to serve as a major dividing line, between partially isolated upper and lower mantle areas, over geologic time.

-JBB

Image credit: http://eesc.columbia.edu/courses/v1011/topic_4_2.htm

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Castellana CavesThe weirdly-shaped features you see on the floor of this cave are quite unusual. This photo comes from Grotto di Castellana or the Castellana Caves in southern Italy.Like most caves, the rocks are limestones. These were deposited about 90 million years ago in the Tethys Ocean; the great seaway that once separated Africa and India from the rest of Asia. The closure of the Tethys seaway has driven faulting and mountain building from Spain to China and in this place brought the limestones to the surface.Erosion of limestone often leads to cave formation. Limestone dissolves easily when exposed to water, formation of a small pool of water on exposed limestone can start the long process of erosion that eventually leads to a cave. One of several distinguishing features of this cave is the shape of the stalagmites (or speleothems – a more general term for any structures created by dripping water in a cave setting). Normally, dripping water builds stalagmites as vertical pillars, but here, these have grown in many directions. It’s not quite clear why these pillars have grown this way, but it probably involves variable wind flows in the cave that push water droplets around and changing water levels over time, which combined to prevent the formation of the classic vertical structures and cause the stalagmites to grow outwards instead of upwards.-JBBImage credit: EGU Open Access, Deaa Alwannyhttp://imaggeo.egu.eu/view/2153/Read more:http://www.triposo.com/poi/T__32494a37325ahttp://www.grottedicastellana.it/en/the-caves/lorigine/

Castellana Caves

The weirdly-shaped features you see on the floor of this cave are quite unusual. This photo comes from Grotto di Castellana or the Castellana Caves in southern Italy.

Like most caves, the rocks are limestones. These were deposited about 90 million years ago in the Tethys Ocean; the great seaway that once separated Africa and India from the rest of Asia. The closure of the Tethys seaway has driven faulting and mountain building from Spain to China and in this place brought the limestones to the surface.

Erosion of limestone often leads to cave formation. Limestone dissolves easily when exposed to water, formation of a small pool of water on exposed limestone can start the long process of erosion that eventually leads to a cave. 

One of several distinguishing features of this cave is the shape of the stalagmites (or speleothems – a more general term for any structures created by dripping water in a cave setting). Normally, dripping water builds stalagmites as vertical pillars, but here, these have grown in many directions. It’s not quite clear why these pillars have grown this way, but it probably involves variable wind flows in the cave that push water droplets around and changing water levels over time, which combined to prevent the formation of the classic vertical structures and cause the stalagmites to grow outwards instead of upwards.

-JBB

Image credit: EGU Open Access, Deaa Alwanny
http://imaggeo.egu.eu/view/2153/

Read more:
http://www.triposo.com/poi/T__32494a37325a
http://www.grottedicastellana.it/en/the-caves/lorigine/

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A city grows in the desertOne of the amazing properties of the series of images collected by the Landsat satellites is its ability to watch as humans shape the world through time.The image on the left shows the city of Riyadh, Saudi Arabia, in 1972. On the right is Riyadh as captured last year by the Landsat 8 satellite.-JBBImage credit: USGS/NASAhttp://earthshots.usgs.gov/earthshots/Riyadh#ad-image-3

A city grows in the desert

One of the amazing properties of the series of images collected by the Landsat satellites is its ability to watch as humans shape the world through time.

The image on the left shows the city of Riyadh, Saudi Arabia, in 1972. On the right is Riyadh as captured last year by the Landsat 8 satellite.

-JBB

Image credit: USGS/NASA
http://earthshots.usgs.gov/earthshots/Riyadh#ad-image-3

Photoset

Komodo Island

This peak rising from the waters of the eastern Indian Ocean is Komodo Island, an island near the eastern edge of the Indonesian island arc.

The island owes its existence to a combination of volcanic and tectonic forces. It sits above the Sunda subduction zone, where the oceanic crust of the Indo-Australian plate is sliding beneath the Eurasian plate. The subduction creates stresses that have forced sedimentary rocks deposited in the ocean up to the surface, so the islands contain a mix of shales, carbonates, corals, and even some sandstones.

Inter-mixed with those rocks are all sorts of volcanic rocks that hold up the high peaks on the island. The volcanoes are produced by subduction as well; all over the world, volcanic arcs sit above subduction zones. In this case, the volcanoes have not been active recently, but instead played a large role in building the island tens of millions of years ago.

Of course, from the name of the island you might have already guessed that its most interesting feature is actually its biology. This island hosts part of Komodo National Park, a UNESCO world heritage site and the home of the Komodo monitor lizard, aka the Komodo dragon.
The island sits at an interesting place oceanographically. The waters around it are a location of significant upwelling in the ocean. Upwelling waters from deep within the ocean often carry a variety of minerals and nutrients dissolved in them, so upwelling waters often are highly productive biologically. The island is ringed with coral reefs that use these nutrients and take advantage of the clear waters, but many of the reefs are now damaged or dying due to human activities according to UNESCO.

-JBB

Image credits: Jonathan Shaw, Stephen Bugno, creative commons licensed
https://www.flickr.com/photos/johnnyshaw/4348840532
https://www.flickr.com/photos/52442953@N05/8090264476/

Read more:
http://whc.unesco.org/en/list/609/
http://www.komodoisland-tours.com/?module=news&news=Komodo+National+Park&news_id=10&news_title=Komodo+National+Park
http://www.flores-different.com/Komodo%20National%20Park.html

Photoset

Uku, the volcano, just wants someone to lava. (x)

(Source: movieclipsdotcom)

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KinkyThese rocks have had an interesting life. This photo shows layers of chert from the Franciscan complex in California, and there are a few blades of grass growing in them to give some scale.These rocks have been tightly folded into kinks, in a pattern known as Chevron folding. These alternating V-shaped folds tend to form in layered sedimentary rocks where there is a difference in strength between the two layers; the layers slide past each other until and the weaker layer flows until the structure locks, producing a very tight fold hinge.Layered cherts like this are a good rock to produce this structure in. Chert is a silica-rich rock, typically produced within the ocean by chemical precipitation. Silica-rich layers are strong and hard to bend, and here they are inter-mixed with weaker layers of fine-grained sediment.The layers of sediments were originally deposited in the Pacific Ocean. The Franciscan complex in California is a highly folded and faulted mass of sediments left over from when the Farallon plate was subducting beneath North America. When an oceanic plate subducts, the sediments on top of it are often scraped off, as though the continent was sliding a spatula over the oceanic plate. Those sediments will then be compressed, folded, and faulted, just as happened to these rocks of the Franciscan.-JBBImage credit: Copyright © Michael Collier, shared for non-commercial purposes through http://www.earthscienceworld.org/

Kinky

These rocks have had an interesting life. This photo shows layers of chert from the Franciscan complex in California, and there are a few blades of grass growing in them to give some scale.

These rocks have been tightly folded into kinks, in a pattern known as Chevron folding. These alternating V-shaped folds tend to form in layered sedimentary rocks where there is a difference in strength between the two layers; the layers slide past each other until and the weaker layer flows until the structure locks, producing a very tight fold hinge.

Layered cherts like this are a good rock to produce this structure in. Chert is a silica-rich rock, typically produced within the ocean by chemical precipitation. Silica-rich layers are strong and hard to bend, and here they are inter-mixed with weaker layers of fine-grained sediment.

The layers of sediments were originally deposited in the Pacific Ocean. The Franciscan complex in California is a highly folded and faulted mass of sediments left over from when the Farallon plate was subducting beneath North America. When an oceanic plate subducts, the sediments on top of it are often scraped off, as though the continent was sliding a spatula over the oceanic plate. Those sediments will then be compressed, folded, and faulted, just as happened to these rocks of the Franciscan.

-JBB

Image credit: Copyright © Michael Collier, shared for non-commercial purposes through http://www.earthscienceworld.org/

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This terrifies me.

This terrifies me.

(Source: yuskylyes, via yuskylyes)

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Bubblegum Coral- The Coral that gets around!Considering that bubblegum coral is a resident of the deep sea, it is unusually common worldwide. There are multiple species of this coral type, but there is one species in particular that can be found all over the world. The species is Paragorgia arborea and is found in in the northern and southern Pacific and Atlantic, the Indian, the Arctic and the Southern oceans.A new genetic study published in the Journal of Molecular Ecology not only indicates these widespread populations belong to Paragorgia arborea, but it also offers a glimpse at how and when this coral was spread around the world. The science:The study involved the analysis of the genetic code of 130 pieces of the Paragorgia arborea species of bubblegum coral from around the world. The research was focused on the mitochondria and nucleus regions of the coral and by analysing the DNA it was concluded that all the samples shared a common ancestor. In other words, they were members of a single species.By further analysing the genetic makeup of the different samples, the researchers were able to ascertain that the genetic composition differed depending on where the sample was found, such as the North Atlantic or the South Pacific. Furthermore, by comparing the relative abundance of genetic differences among them researchers were able to track their movements through time. It is shown that the corals appear to have originated in the Northern Pacific more than 10 million years ago and then headed south. Millions of years later they headed towards the Atlantic and other areas. You might be wondering how they got here? While colonies of corals are attached to the seabed, their eggs and sperm are dispersed into open water for fertilisation and reproduction. It is highly probable that ocean currents carried the larvae and young polyps to different areas, inevitably letting them explore the sea!It’s a sad day when a coral has traveled further than you! -Jean For those with journal access, it can be found here: http://onlinelibrary.wiley.com/doi/10.1111/mec.12074/pdfFor those who don’t, the next best thing: http://www.whoi.edu/main/news-releases?tid=3622&cid=153889Photo courtesy of NOAA/Monterey Bay Aquarium Research Institute

Bubblegum Coral- The Coral that gets around!

Considering that bubblegum coral is a resident of the deep sea, it is unusually common worldwide. There are multiple species of this coral type, but there is one species in particular that can be found all over the world. The species is Paragorgia arborea and is found in in the northern and southern Pacific and Atlantic, the Indian, the Arctic and the Southern oceans.

A new genetic study published in the Journal of Molecular Ecology not only indicates these widespread populations belong to Paragorgia arborea, but it also offers a glimpse at how and when this coral was spread around the world. 

Read More

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Carolina BaysCarolina Bays are elliptical/oval shaped wetlands located mostly in North and South Carolina, though a few can be found in Georgia and as far north as Virginia and Delaware. The Native Americans called them ‘pocosin’ or ‘swamp on a hill’. They can range in size from one to several thousand acres in size. There are about 500,000 in the Atlantic Coastal Plain. All of the bays are oriented in the same general direction, northwest to southeast. Bays are some of the most ecologically diverse areas in the southeast US, being home to many endangered or threatened species. They are even home to carnivorous plants, like the pitcher plant and venus fly trap.The origins of the bays have sparked debate in the past. There are two main theories as to the origins; one being that prevailing winds scoured the depressions and left a depositional dune on the southeast side. The other theory is extraterrestrial in origin, a meteor storm or low-density comet caused the bays, and they are the impact crater remnants. Though this theory is the coolest, it has fallen by the way side due to lack of evidence.In the image you can see many bays clustered together, with the same general orientation, and with the dune on the southeast side.AWReferences/ Extra Readinghttp://www.srel.edu/outreach/factsheet/carolinabays.htmlhttp://www.dnr.sc.gov/wildlife/wetlands/carolinabays.htmlImage Credit: North Carolina Department of Transportation

Carolina Bays

Carolina Bays are elliptical/oval shaped wetlands located mostly in North and South Carolina, though a few can be found in Georgia and as far north as Virginia and Delaware. The Native Americans called them ‘pocosin’ or ‘swamp on a hill’. 

They can range in size from one to several thousand acres in size. There are about 500,000 in the Atlantic Coastal Plain. All of the bays are oriented in the same general direction, northwest to southeast. Bays are some of the most ecologically diverse areas in the southeast US, being home to many endangered or threatened species. They are even home to carnivorous plants, like the pitcher plant and venus fly trap.

The origins of the bays have sparked debate in the past. There are two main theories as to the origins; one being that prevailing winds scoured the depressions and left a depositional dune on the southeast side. The other theory is extraterrestrial in origin, a meteor storm or low-density comet caused the bays, and they are the impact crater remnants. Though this theory is the coolest, it has fallen by the way side due to lack of evidence.

In the image you can see many bays clustered together, with the same general orientation, and with the dune on the southeast side.

AW

References/ Extra Reading

http://www.srel.edu/outreach/factsheet/carolinabays.html

http://www.dnr.sc.gov/wildlife/wetlands/carolinabays.html

Image Credit: North Carolina Department of Transportation