The Earth Story

Is waiting for a volcano better than watching paint dry? The Reykjanes Peninsula in Iceland runs off to the southwest side of the island. It's the point at which the Mid-Atlantic Ridge comes onshore, and it is above the ocean surface because of the interaction between volcanism on that ridge and the nearby Iceland Plume. The rocks, therefore, are recent volcanic rocks, and the peninsula is resurfaced by volcanism every few thousand years.

Marie Tharp and the Mid-Atlantic Ridge

The ocean floor has always been a mysterious place and in the 1950’s it was even more so; most believed it was simply a flat, boring plain. After World War II, many feared the next warfront would be underwater, so the quest to gather more information about the ocean floor was in full force, which proved to be good for science.

Marie Tharp was working at the Lamont Geological Observatory when the funding for ocean research started pouring in. Many of her colleagues would go out to sea and come back with mounds of sonar data that could be used to determine the depth of the ocean floor. Back at the lab, Marie began piecing together the numbers and using them to make a map of the ocean floor.

Marie, and her colleague Bruce Heezen, began to notice something interesting about the map (which she made by hand, by the way)—the ocean floor was not flat. In fact, there were mountains! Underwater! Most notably, these mountains formed a very long chain, one that went right down the middle of the Atlantic Ocean. Marie thought it was a volcanic rift center, an idea that was initially dismissed as “girl talk”.

Marie and Bruce (who came around to the idea that it was a volcanic rift center) published their first map in 1957. At this time, most people still did not like the idea of a mid-ocean ridge because it was too closely linked with continental drift, which was considered geological nonsense at the time. A few years later, Harry Hess would use the Mid-Atlantic Ridge to support his theory of seafloor spreading, which ultimately led to the unifying theory of plate tectonics.

Marie devoted much of her life to mapping; she and Bruce released a map of the entire ocean floor in 1977. Our modern understanding of Earth processes and plate tectonics would not be possible without these maps. The discovery of mid-ocean ridges was a crucial piece to the puzzle of how continents move and ultimately why Earth works. So thank you Marie!

-CM

For more information: http://bit.ly/1BfCjWE http://huff.to/18oityd A brief autobiography: http://bit.ly/1mEqFR7 This book:http://amzn.to/1wMccZ0

Photo (Marie with Bruce Heezen) credit: Marie Tharp Maps http://bit.ly/1NqP5YX

Original caption:

Original caption:

Bridge over 2 continents, Þingvellir National Park, Iceland

The drone view of the icecap and tiny valley glaciers coming out of this is spectacular. Narrated Iceland trip tells you the geologic story of Iceland while simultaneously exploring the landscape. Original video caption:

Diving into the Silfra Fissure - open rift off the coast of Iceland formed by faulting related to the Mid-Atlantic Ridge

Drone flight along Þingvellir rift, Iceland - cracks are faults that are expressions of the mid-atlantic ridge running through Iceland.

Freezing waterfall, mist, and morning sun, Þingvellir - Thingvellir National Park, Iceland

The basalt columns of Reynisfjara beach

As basaltic lava cools, beautiful geometric hexagonal columns emerge. They often form steep cliffs and can be found all around the world. One exceptional example of these basalt columns can be found in Iceland. The island on the Mid-Atlantic Ridge is characterized by continuous volcanic activity and offers a variety of interesting landforms.

This particular example of basalt columns lies near the village Vík í Mýrdal on Iceland’s South Coast. On the impressive black sand and pebble beach a huge number of basalt columns hide under the mountain Reynisfjall. Out in the sea there are more spectacularly shaped sea stack called the Reynisdrangar.

The area has a rich bird life including puffins, fulmars and guillemots. The weather is very wet and rough but that doesn’t keep large numbers of tourists visiting this great geological site. The dangerous weather and wave conditions make it not completely safe to visit the place and safety precautions are being debated after a recent deadly incident at the columns.

Xandi

Image Credits: http://bit.ly/2fnx01Y http://bit.ly/2eN9Jbw Sources: http://bit.ly/1SMnpCr http://bit.ly/2fnx01Y

Birth of the Atlantic

This is a gorgeous computer rendering of the opening of the Atlantic Ocean and the breakup of the Supercontinent Pangaea.

During the Triassic and Jurassic, North America began rifting from the part of Gondwana (today Africa) that it had collided with to build the Appalachian Mountains and later during the Jurassic, the huge block of South America and Africa that had been linked together for hundreds of millions of years also separated.

The breakup of a Supercontinent can have many causes. Plates far away can be pulled down into the mantle and a rigid plate could transmit stress to weak points far away, causing the plate to pull apart. Alternatively, something could wedge its way in-between the plates and force them apart; both of these breakups occur at the same time as huge outpourings of volcanic lava, maybe suggesting that a hot plume of mantle material rose up and pushed them apart. The arrows that appear and change on each plate show how the plate motion directions change as these different forces interact. The longer the arrow = the faster the plate is moving.

The plate motions of the past 200 million years or so are known extremely well because of magnetic anomalies. When new seafloor is created at a mid-ocean ridge, that seafloor records the direction of the Earth’s magnetic field at the time. As the rocks move away from the ridge, they preserve a record of where on the planet’s surface they formed. By mapping out magnetic anomalies across the planet’s ocean floors, we find a record of how the oceanic plates move.

That record only goes back about 200 million years because that’s the oldest oceanic crust on Earth. Almost all the oceanic crust older than that age has cooled off so much and become so dense that it has readily subducted, heading down into the mantle to start the cycle again. The age contours in this plot let you see how that age progression happens; new crust formed at mid-ocean ridges and then older crust vanishing beneath subduction zones like those on the western side of North and South America.

-JBB

Video Credit: NOAA http://sos.noaa.gov/Datasets/dataset.php?id=569

Marie Tharp and the Mid-Atlantic Ridge

In honor of International Women’s Day and the beginning of Women’s History Month, we thought some of our favorite female geologists deserved a shout out. One of my personal favorites is this girl, Marie Tharp, who did something very important for our modern understanding of geology—she discovered the Mid-Atlantic Ridge.<!-- more --.

The ocean floor has always been a mysterious place and in the 1950’s it was even more so; most believed it was simply a flat, boring plain. After World War II, many feared the next warfront would be underwater, so the quest to gather more information about the ocean floor was in full force, which proved to be good for science.

Marie was working at the Lamont Geological Observatory when the funding for ocean research started pouring in. Many of her colleagues would go out to sea and come back with mounds of sonar data that could be used to determine the depth of the ocean floor. Back at the lab, Marie began piecing together the numbers and using them to make a map of the ocean floor.

Marie, and her colleague Bruce Heezen, began to notice something interesting about the map (which she made by hand, by the way)—the ocean floor was not flat. In fact, there were mountains! Underwater! Most notably, these mountains formed a very long chain, one that went right down the middle of the Atlantic Ocean. Marie thought it was a volcanic rift center, an idea that was initially dismissed as “girl talk”.

Marie and Bruce (who came around to the idea that it was a volcanic rift center) published their first map in 1957. At this time, most people still did not like the idea of a mid-ocean ridge because it was too closely linked with continental drift, which was considered geological nonsense at the time. A few years later, Harry Hess would use the Mid-Atlantic Ridge to support his theory of seafloor spreading, which ultimately led to the unifying theory of plate tectonics.

Marie devoted much of her life to mapping; she and Bruce released a map of the entire ocean floor in 1977. Our modern understanding of Earth processes and plate tectonics would not be possible without these maps. The discovery of mid-ocean ridges was a crucial piece to the puzzle of how continents move and ultimately why Earth works. So thank you Marie!

-CM

For more information: http://bit.ly/1BfCjWE http://huff.to/18oityd A brief autobiography: http://bit.ly/1mEqFR7 This book:http://amzn.to/1wMccZ0

Photo (Marie with Bruce Heezen) credit: Marie Tharp Maps http://bit.ly/1NqP5YX

Fracture Zone quake

On Friday, a large earthquake occurred in a geologically interesting area of the mid-Atlantic ridge. The mid-ocean ridge system is a gigantic chain of mountains that stretches around the world on the ocean floor at the boundaries where plates are spreading apart.

The mid-ocean ridges aren’t just straight lines; they twist from side to side and are broken into segments that lock in the original shape of the plates. The oceanic rift zones themselves are dominated by normal faults, the kind that commonly occurs when two plates pull apart. To step sideways, a spreading center breaks into two segments with a strike-slip fault in-between, the type of fault that forms when one plate grinds past another.

The Charlie Gibbs fracture zone is an oceanic transform fault, a strike-slip fault on the ocean floor. On Friday, that fault broke, producing a magnitude 7 earthquake.

Because the rocks just were sliding past each other, side to side, there was no tsunami generated and since the quake occurred far out to sea there was no major damage, just a geologically interesting place for a strong earthquake. This fracture zone has produced several earthquakes of this size in the past 60+ years since humans have been actively monitoring seismic signals.

-JBB

Image credit: USGS http://on.doi.gov/1KTMeFx

The Most Isolated Island in the World – Bouvet Island  Go to Iceland, turn south on the Mid-Atlantic Ridge and follow it all the way to the triple junction where the ridge intersects the Antarctic Plate, and there you will find… an island. At 2260 kilometers from the nearest inhabited island (Tristan de Cunha with a population of 271, if this counts), smack dab between Africa, South America and Antarctica, Bouvet island is not a very big island, less than fifty square kilometers in size with nearly all of it covered by a glacier, but is considered as the most isolated land mass on earth. Nevertheless, it turns out to be – an island of mystery! Discovered in 1739 by the French (hence the name), claimed by the British in 1825, and annexed by Norway in 1928, there has never been a war or disagreement about the sovereignty of the island – apparently no one loves it enough to argue over it, and it is, today, a nature reserve (apparently seals and penguins do like the place). The Norwegians take responsibility for it, with the island’s administration managed by their Polar Department of the Ministry of Justice and the Oslo Police. Since the island is uninhabited, the police have little to do there one supposes. Perhaps in hopes that someday someone would like to take up residence, an internet domain has been set up under its name (.bv), but as yet no takers. The average high temperature on Bouvet Island is just above 1C, and average low temperature is -2.3C – we know this because there is an automated weather station on this desolate locale. Nor is the island forgotten by the seismographs of the USGS who keep track of all earthquakes in the world, even those in Norwegian territories in the South Atlantic, and spotted a 5R earthquake near there (well, “near” as distances go for the most isolated spot in the world, about 348km west of the island) in 2009. Since geologists never forget about any island, no matter how great or how small, there are geologic papers on Bouvet Island that describe its volcanic composition (sitting on the Mid-Atlantic Ridge, not surprisingly these include Mid-Atlantic Ridge Basalts – “MORB”.) The island is as close to the site of a plate tectonic triple-junction as can be: it’s just on the edge of the African Plate next to the South American plate border (the Mid-Atlantic Ridge marking this), intersecting with the Antarctic plate. The island’s volcano has been hypothesized to be a “hot spot” where material is coming directly from the mantle. This tectonic environment is “way cool” for a geologist, and perhaps were there not so many glaciers occluding the island, some poor lost PhD student would have a great time in the frigid field. Some mysteries surround the island: an abandoned boat stocked with supplies (but no passengers) was found there in 1964; in 1979, a US satellite saw an extremely bright light flash from the uninhabited area near the island that is speculated to have been a nuclear bomb test by the Israelis and South Africa (come on, conspiracy theorists! You can do better than this!); AND there’s a disappearing island nearby!  Unlike Sandy Island in the Pacific that probably never existed in the first place (as recently reported by The Earth Story), Thomson Island was “discovered” to the northeast of Bouvet Island and seemed to exist in 1825 and 1893 (including very convincing sketches), but hasn’t been sighted since at least 1927. Possibly Thomson Island, also theoretically on the Mid-Atlantic ridge, could have been destroyed in an eruption or some caldera collapse, but in the 1960’s sonar failed to locate any sort of submerged shoal – since the original coordinates of the island’s position were done with the cutting-edge technology of 1825, possibly the sonar was looking in the wrong place.  Since the Norwegians haven’t yet sent out the Oslo Police to figure out who may have stolen the island, all theories are still open.  Annie R. Photo credit: We delightfully note that Google Panoramio has even made it to the most desolate island on earth and this photo is by: Franco Cain on Google Panoramio http://wikitravel.org/en/Bouvet_Island https://www.cia.gov/library/publications/the-world-factbook/geos/bv.html http://www.atlasobscura.com/places/bouvet-island http://www.antarctic.ac.uk/documents/bas_bulletins/bulletin13_06.pdf http://on.fb.me/1Ceod9v http://link.springer.com/article/10.1007%2FBF00451868?LI=true