The Earth Story

Sorted Garnets This is kinda neat. This is a pile of sand-sized grains of garnets, originally from New Mexico. The grains started out in one of several large areas of precambrian-aged metamorphic rocks exposed in the area; these rocks originally were metamorphosed as the continent Laurentia – today forming the bulk of North America – was growing by collisions with other continents and island arcs. Those ancient rocks are now exposed at the surface today, where they are eroding and shedding sediments into nearby lowlands. This sand was first sorted and kicked up by ants, while they were building hills out of sand grains.

The Earth - not a perfect bar magnet

Do you carry around a smartphone? If you do, you’re carrying a map like this one with you.

Have you ever adjusted a compass for “Declination”? You’ve also dealt with this map.

Smartphones have a compass built into them able to detect Earth’s magnetic field. The magnetic field is generated deep within our planet’s outer core, created by flowing, super-heated, liquid iron that carries electrical currents and charges. The magnetic field of Earth mostly points north south, showing that the Earth’s rotation affects the motion in the core, but it isn’t quite perfect. There are lots of subtle variations in the magnetic field, such that magnets at most spots on the Earth don’t point directly at the North Pole. 

We don’t understand what is happening in the core well enough to predict exactly how the magnetic field is going to change over time, but we can predict that areas that are currently weakening or strengthening will keep doing that. Those predictions usually work for several years but lose accuracy farther out.

This magnetic declination map was released earlier this year - delayed in part by the US Government Shutdown. It shows the separation between the north pole as pointed to by a compass, and true north - the axis the planet rotates around. It combines the fact that the magnetic and true north poles don’t line up with the small-scale features on the Earth’s surface and allows phones and compasses to correct for these variations.

The lines marked in green are the only places on the globe where a compass with no calibration will point directly to the North Pole. Everywhere else on the Earth, compasses and smartphones need corrected to one side or the other.

A map like this for 2019  is now on your smartphone whether you know it or not. Every app that uses the compass to determine direction makes use of it. You’re carrying around the work of the World Magnetic Model in your pocket.

-JBB

Image credit: WMM https://www.ngdc.noaa.gov/geomag/WMM/DoDWMM.shtml

Tenerife black sand on a Fitbit

Assembly of that trilobite art I featured last week (apparently held together with Nd magnets)

Gadolinium - a magnetized rare earth metal

Discovered in 1880 by Swiss chemist Jean Charles Galissard de Marignac, this malleable and ductile element resides in the 64th square of the periodic table, sitting right in the middle of the Lanthanide series. It was named after mineralogist Johan Gadolin. However, this was discovered in its pure, unnatural form embedded in samarskite, a radioactive rare earth metal. It was not produced in its pure (~99.3%) form until 1935. Enough with history, let's talk chemical petrology. Of all the stable elements on the periodic table, gadolinium has the highest thermal neutron capture cross-section. That's a mouthful - essentially, gadolinium has the highest probability of absorbing thermal neutrons in a nuclear reaction of all stable elements.

Gadolinium was also the first element to be considered magnetized other than the traditional elements of Fe, Ni, and Co. In fact, Gadolinium can be even more magnetic than Iron, but only in certain cold conditions. This is because Gadolinium has a dual nature to its magnetism. The element transitions from paramagnetic (generally weak attraction to a magnetic field) at high temperatures to ferromagnetic (strong magnetic attraction) at low temperatures.

This magnetic nature provides the platform for one of its key industrial uses. Gadolinium provides the contrast in MRIs. Additionally, it is one of the elements that expresses a strong magnetocaloric effect, making it useful in magnetic refrigeration. This means that when gadolinium leaves an magnetic field, its temperature will decrease. Apart from magnetism, it is also a material in the production of industrial garnets.

In the earth's crust, Gadolinium has a concentration 5.2 parts per million (weight). It is not found alone in nature but is contained within minerals like bastnaesite.

--Sam J.

Image Credit: Accelerating Future

References:

http://www.chemicool.com/elements/gadolinium.html

http://www.ias.ac.in/jarch/currsci/4/114-117.pdf

http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Paramagnetism.html

http://www.che.cemr.wvu.edu/publications/projects/prod_design/magnetic_refrigerator.pdf

So much beauty in dirt

This hand is holding a magnet that was dipped into the sand at Piha black sand beach, North Island, New Zealand. Although there are exposed dark, igneous rocks at that beach, much of the sediment at that site apparently comes from farther inland in the Taupo Volcanic Zone. The rocks erupted by the Taupo Caldera contain the mineral titanomagnetite, which is a dark, dense crystal. As the volcanic rocks are eroding, the denser minerals are progressively separating out as the water flows downstream in the Waikato River. By the time it gets to this beach, the sediment is dark and enriched enough in the magnetic grains that a magnet stuck into the beach will come out covered in those grains.

The sand deposits concentrated near these beaches have been developed as ironsand, an iron resource used as feedstock for steel making. The same process that concentrated the iron here also created New Zealand’s richest iron ore resources.

-JBB

Image credit: https://flic.kr/p/8LozJf

References: https://www.volcanodiscovery.com/taupo.html http://www.piha.co.nz/volcanic-past-of-piha/ http://www.piha.co.nz/piha-beach/ http://www.tandfonline.com/doi/pdf/10.1080/00288306.1985.10421203 http://www.nzsteel.co.nz/new-zealand-steel/the-story-of-steel/the-history-of-ironsand/

Japanese overcome against China’s stranglehold over rare earth elements!

Since the 1990s, China had a near monopoly over rare Earth metals. These rare Earth metals, such as europium (http://on.fb.me/14VqvLo), dysprosium, ytterbium, and terbium, are important in use for raw materials in hi-technologies & advanced weapon systems. Controlling nearly 97% of the global supply, China started restricting exports in 2009.

Japan, as the third largest consumer of these minerals, found the restriction of the exports as a call for urgency on finding their own source of these elements. They took immediate actions by dispatching their own team of marine scientists to explore the seabed of the Pacific Ocean for their own source of metals. Two years later in 2011, Japan hit the jackpot as they discovered a large quantity of the metals near Hawaii and Tahiti. Then again, last month near the same region of the first findings. The latest find is located in the deep-sea mud around the island of Minami-Torishima. It sits at 5.7 km below sea level.

Leading the team is Professor Yasuhiro Kato of Tokyo University. Professor Kato claims the extraction of the minerals to be a low costly venture. With just the use of pressurized air and a minimal disturbance of the seafloor, he believes that they can extract enough minerals to force China to lift their restrictions. Professor Kato will continue his research for the next two years.

Other countries such as the U.S. and parts of Europe are also building a case against China while also opening up their own mining explorations. The use of these metals can also extend out to green technology, health care, etc.

~era

Sources: [Japanese found metals in 2011] http://www.telegraph.co.uk/finance/commodities/8616623/Rare-earth-minerals-find-in-Pacific-could-spark-Japan-Hawaii-stand-off.html [Japanese Finds metal in March 2013] http://www.telegraph.co.uk/finance/comment/ambroseevans_pritchard/9951299/Japan-breaks-Chinas-stranglehold-on-rare-metals-with-sea-mud-bonanza.html [China’s announced restriction on exports] http://www.telegraph.co.uk/finance/china-business/8022484/China-blocked-exports-of-rare-earth-metals-to-Japan-traders-claim.html [Overall information] http://www.eaglespeak.us/2013/03/breaking-chinas-monopoly-japan-says-its.html

More info on the minerals from our page: http://on.fb.me/14VqvLo [Europium] http://on.fb.me/10HLPwB [Industrial mining]

The search for the unicorn’s other horn ….

In the dim and distant past, the days when I was a young scientist, I had a theoretical physicist friend who was trying to predict the behaviour of magnetic monopoles. He likened his project to the quest for the unicorn’s second horn. No one expected to see it any time soon.

With the passage of time it seems that the quest has moved from theoreticians to experimentalists. In 2013, a group of scientists reported the first results of their search for magnetic monopoles, which they suggest, should be concentrated in rocks derived from Earth’s deep mantle. Needless to say (sorry, my cynical side is coming out here), they have not yet found one. But they still think they might.

So, why the interest in magnetic monopoles? Well, we know that electric dipoles (a positive and negative charge separated from each other) exist – materials rich in these dipoles are used in your camera flash, in passive infrared burglar detectors, and even in the memory card of your Sony PlayStation. Electric monopoles also exist – as isolated positive or negative electric charge (giving rise to static electricity, for example). But their magnetic equivalents seem different. A magnetic north pole seems always to be accompanied by a magnetic south pole, to form a magnetic dipole (like a bar magnet or a compass needle). Can norths or souths exist in isolation, in the same way that positive or negative electric charges do? Well, experience says no.

In a paper entitled “Search for Magnetic Monopoles in Polar Volcanic Rocks” a team assembled from Sweden, Switzerland, Iceland, Denmark, USA and the UK explain that magnetic monopoles formed in the very early Universe, and predicted by grand-unification theories, may persist by attaching themselves to magnetic nuclei. It has been suggested that they would be present in cosmic rays, so material subjected to cosmic ray bombardment – Moon rocks, rocks from Earth’s crust, and meteorite samples, have been the focus of earlier (fruitless) searches. Bendt and co-workers point out that (heavy) monopoles in Earth’s interior would accumulate towards the core, but would end up trapped at the core-mantle boundary where Earth’s geodynamo forces them to the magnetic axis in the polar regions. Mantle convection then brings them back toward the surface, eventually (over a time scale of around half a billion years) appearing in igneous rocks generated from mantle hot spots.

This thesis has been the reasoning behind the group’s quest for magnetic monopoles in igneous rocks from high latitudes. They have, for example, analysed rocks from Antarctic and Arctic flood basalts and intrusions, such as the Skaergaard intrusion shown here. More than 20 kg of rock have yet to yield any sign of a monopole. While this negative result may seem unremarkable to many, it does set limits on the likely mass of the elusive magnetic monopole.

~SATR

Image: Sødalen scientific camp, near the Sgaergaard intrusion, Eastern Greenland (credit: “submanant”, Flickr).

Links: http://arxiv.org/abs/1301.6530

http://physics.aps.org/articles/v6/34

http://www.spacedaily.com/reports/Searching_for_magnetic_monopoles_in_polar_rocks_999.html

Delightful combination with the wispy aurora dancing in the foreground and the terminator appearing in the background

Meteorite magnetism reveals secrets of early solar system

Pallasites are the most attractive meteorites, with their green to brown crystals of olivine embedded in a shiny matrix of metallic iron and nickel. Long thought to be the core mantle boundaries of ancient planetismals (the building blocks of our solar system), they may be due instead to collisions between them but the issue is still in doubt. They are thought to be the remnants of the first bodies in the solar system, many of which amalgamated together to form the planets. High levels of radioactivity back in those days melted and differentiated them into metallic and silicate layers.

New research has captured the last moments of an asteroid's magnetic field, giving insights into the process of our solar system's growth and hints as to the future of the Earth's own core when it finally freezes. The metal in the pallasites contained a magnetic memory some 4.5 billion years old (just as iron minerals do in the Earth's rocks, used amongst other things to infer palaeo latitude of sedimentation or eruption).

The research team from Cambridge University used beamed x-rays to image nanoscale patterns in the magnetic memory at the highest resolution ever and captured the entire story of asteroid core freezing up to the precise moment when it ended (marking the death of the body's field). No one had done this before since it was wrongly assumed that pallasites had poor magnetic memories, and would have been over written many times during their journeying around the solar system.

The data was squeezed out of 100nm particles of a rare and very stable magnetic mineral called tetrataenite, which chronicled the changes in the strength and direction of the field over time. It revealed that the asteroid's field lived for longer than previously thought, up to hundreds of millions of years, and resulted from a similar mechanism of swirling liquid metal with compositional gradients that expels sulphur from the freezing inner core as Earth's. The shorter life span of asteroid cores is being used as an analogy for our own.

The meteorites used both fell in Latin America, one at Esquel in 1951 and the other at Imilac in 1822. Of course, after the core froze, at some point the magnetically dead asteroid suffered a collision that shattered it, and sent the meteorites on their long spinning journey to the Earth's surface.

Loz

Image credit: Slice of Esquel pallasite in hand: Doug Bowman, sliced Brahin pallasite Steve Jurvetson.

http://www.skyandtelescope.com/astronomy-news/long-lived-meteorite-magnetic-fields/ http://www.sci-news.com/space/science-meteorites-magnetic-messages-early-solar-system-02425.html http://www.geologypage.com/2015/01/death-of-dynamo-hard-drive-from-space.html http://www.nature.com/nature/journal/v517/n7535/full/nature14114.html

Inside your smartphone Do you carry around a smartphone? If you do, you’re carrying a map like this from the British Geological Survey with you. Smartphones have a compass built into them able to detect Earth’s magnetic field. The magnetic field is generated deep within our planet’s outer core, created by flowing, super-heated, liquid iron that carries electrical currents and charges. The magnetic field of Earth mostly points north south, showing that the Earth’s rotation affects the motion in the core, but it isn’t quite perfect.  The Earth’s magnetic north pole doesn’t match up perfectly with the north-south axis that the planet rotates around. On top of that, there are small-scale changes in the magnetic field around the world created by complex flows and features in the core, 10 to 100 times weaker than the main north-south field but enough to be a small error in pointing to the North Pole. We don’t understand what is happening in the core well enough to predict exactly how the magnetic field is going to change over time, but we can predict that areas that are currently weakening or strengthening will keep doing that. Those predictions usually work for several years but lose accuracy farther out. The British Geological Survey in December released the 2015 World Magnetic Model, this map of the differences between magnetic north, pointed to by a compass, and true north. It combines the fact that the magnetic and true north poles don’t line up with the small-scale features on the Earth’s surface and allows phones and compasses to correct for these variations.  The lines marked in green are the only places on the globe where a compass with no calibration will point directly to the North Pole. Everywhere else on the Earth, compasses and smartphones need corrected to one side or the other. A map like this for 2015 and beyond is now on your smartphone whether you know it or not. Every app that uses the compass to determine direction makes use of it. You’re carrying around the work of the World Magnetic Model in your pocket. -JBB Image credit: BGS http://www.bgs.ac.uk/news/docs/WMM2015_FINAL.pdf

STONES FROM ANCIENT HANGI PITS MIGHT REVEAL EARTH'S PAST MAGNETIC FIELD Dr Gillian Turner from Victoria University, Wellington, New Zealand is studying the Earth's magnetic field using the stones that line Māori pit ovens, known as hāngi (sometimes called umu). Scientists have good palaeomagnetic data from around the world, recording field strength and direction, particularly from the Northern Hemisphere. There is a gap in detail however in the southwest Pacific; Dr Turner’s research hopes to fill that gap. Dr Turner’s project aims to retrieve information about changes in the Earth’s magnetic field over the past 10,000 years. Normally pottery would be used for data on the last few centuries. Pottery is used for such research as when the clay is fired in the kiln the minerals within the clay are heated above the Curie temperature and are demagnetised. As the clay objects cool down to become pottery, the minerals become magnetised again in the direction of the prevalent field; the strength of the magnetisation is directly related to the strength of that field. Māori did not use pottery, so an alternative source for data on the Earth’s magnetic field needed to be found. That alternative was the hāngi. Hāngi is the traditional Māori method of cooking food using heated rocks buried in a pit oven; Pacific Island nations use the same method. This method of cooking was and still is used in Chile, the Balkans, and certain parts of North Africa and the Middle East. To ‘put down a hāngi’ a pit is dug into the ground, stones are heated in the pit with a large fire and baskets of food are placed on top of the stones. Everything is then covered with Hessian bags, sheets, or flax mats and then covered with earth and leaves for several hours, before the hāngi is uncovered. For economical reasons, the traditional hāngi cooking principals are now mainly used for special occasions. Dr Turner, who has received funding from the Marsden Grant for this work, is undertaking an archaeological search in New Zealand to find ancient hāngi sites. The cooking stones used in these hāngi could give insight into Earth’s magnetic behaviour going back hundreds of years. Dating for these stones will be achieved through radiocarbon analysis of the charcoal left from the firewood used to light the pit oven. Dr Turner and her colleagues experimented with a modern-day hāngi to see if the stones at the base of the pit could reach over the Curie temperature and be re-magnetised, to prove hangi stones could be used as an alternative to pottery for their study. In Māori legend, the stones become ‘white hot’ with heat. Red hot heat is about 700ºC; Turner and her team put some thermocouples in the stones and were able to show they got as high as 1,100ºC. At such a high temperature, rock-forming minerals start to become plastic. Dr Turner’s team was able to show that a re-magnetisation had taken place by placing a compass on top of the cooled hāngi stones. Hāngi stones were carefully chosen; one of the most popular types used was an andesite boulder found in Central North Island. These volcanic boulders were preferred as they don’t crack or shatter in the fire. For the team of researchers, the volcanic boulders are the best because magnetically they behave better as they form with a high concentration of magnetite. Stones from hāngi sites will only provide data for the last 700-800 years. Dr Turner will also be studying volcanic rocks as well as lake and marine sediments in New Zealand. The outcome will be a detailed history of the southwest Pacific’s magnetic field over the last 10,000 years. For those interested: How to cook a hangi http://bit.ly/VM8qLH Guide on how to prepare a hangi http://bit.ly/ht49MP -TEL http://www.royalsociety.org.nz/2011/10/06/turner/ http://www.genuinemaoricuisine.com/Folders/Hangi.html http://www.bbc.co.uk/news/science-environment-20520454 http://www.livescience.com/25328-maori-stones-magnetic-field.html Image: http://www.hangiunderground.co.nz/gallery

Aurora from Space Seeing the Northern Lights from Earth is on countless peoples' bucket lists. However, seeing it from space is something few can dream of. This photo depicts the aurora borealis as seen from the ISS. This phenomena occurs when charged particles from the Sun's solar wind collide with other gas particles in the Earth's magenetosphere. The seemingly random shape of the lights is actually due to the lines of the Earth's magnetic fields repelling the charged particles into certain areas. On average, the Sun undergoes a cycle lasting 11 years (give or take a couple) in which the amount of radiation admitted fluctuates. The Sun achieved its last solar maximum in 2013, making it a great year to view the Northern Lights. In 2010, the Canadian Space Agency, in collaboration with three other partners, launched AuroraMAX, a web portal and public initiative dedicated to engaging the public further in science. The portal broadcasts each night's aurora and also serves to explain the science behind the phenomena. -CS Image Credit: NASA.  Read more: http://www.spacefellowship.com/

GEMS FROM SPACE CREATED BY CELESTIAL COLLISION Only a small fraction of all meteorites found on Earth are pallasites: translucent, olivine crystals embedded in an iron-nickel matrix. Pallasites were first identified as originating from outer space more than 200 years ago. New research from a team of geophysicists using a carbon dioxide laser, a magnetic field, and a sophisticated recording device has shown the likely formation of the pallasites as a collision between an asteroid and a planetary body.  It was previously assumed that pallasites formed at the boundary between the iron core and the rocky mantle in a planetary body. However a team of geophysicists, led by John Tarduno at the University of Rochester, discovered that they most likely formed when a smaller asteroid crashed into a planetoid about 30 times smaller than Earth. This would have resulted in the materials mixing before solidifying to produce the distinctive meteorites. Tarduno and his team discovered that the tiny metal grains within the olivine were magnetised to a particular direction; previous work had theorised that the iron intruded from the core into the olivine in the mantle.  The scientists used a carbon dioxide laser at the University of Rochester to heat the metal grains past their Curie temperatures (the point at which a metal loses its magnetisation). The metal grains were then cooled in the presence of a magnetic field to re-magnetise them; at the same time a measuring instrument known as SQUID (superconducting quantum interference device) was used to record the data. The team was able to calculate the strength of the past magnetic field and then the rate of cooling. The measurements from the experiment, combined with a computer model, indicated the parent body had a radius of about 200 km, qualifying it as a proto-planet. For the metal grains within the olivine to be magnetised, the planetary body in which they formed must have had a molten iron core, to create a magnetic field. Temperatures at the core-mantle boundary would have been close to 930°C and too hot for magnetisation to take place. Pallasites therefore would have formed at somewhat shallow depths in the much cooler mantle of the proto-planet. This research also provides further evidence that small celestial bodies can have dynamo activity; a rotating liquid iron core that can create a magnetic field. The iron-nickel in the pallasites is believed to have originated from the collision with the asteroid, where molten iron from the core of the smaller of the two asteroids was injected into the mantle of the larger body, creating the textures observed in the pallasites.  The image is a piece measuring 210 mm by 190 mm by 5 mm of the Esquel meteorite, which contains the pallasites. The meteorite was discovered in Chubut, Argentina in 1951 as a single mass weighing more than 700 kilograms.  -TEL http://www.rochester.edu/news/show.php?id=4972 John A. Tarduno, Rory D. Cottrell, Francis Nimmo, Julianna Hopkins, Julia Voronov, Austen Erickson, Eric Blackman, Edward R.D. Scott, Robert Mckinley. Evidence for a Dynamo in the Main Group Pallasite Parent Body. Science, 2012 DOI: 10.1126/science.1223932 http://www.sciencemag.org/content/338/6109/939 Image: http://www.meteoriteguy.com/collection/esquel.htm