Ringwoodite Holds the Majority of Earth’s Water Underground

Blue Ringwoodite - Wiki CommonsFollowing up on theories that ringwoodite minerals deep within the Earth’s mantle may contain water, a BBC News report says researchers have provided the first direct evidence of this theory.

Diamonds, brought to the Earth’s surface in violent eruptions of deep volcanic rocks called kimberlites, provide a tantalising window into the deep Earth.

A research team led by Prof Graham Pearson of the University of Alberta, Canada, studied a diamond from a 100-million-year-old kimberlite found in Juina, Brazil, as part of a wider project.

They noticed that it contained a mineral, ringwoodite, that is only thought to form between 410km and 660km beneath the Earth’s surface, showing just how deep some diamonds originate.

While ringwoodite has previously been found in meteorites, this is the first time a terrestrial ringwoodite has been seen. But more extraordinarily, the researchers found that the mineral contains about 1% water.

According to the news report, this discovery is important because it solves a 25-tyear-old controversy about deep Earth being wet, dry, or wet in patches. The finding implies that the interior of the planet may store several times the water in the oceans, and demonstrates how hydrogen plays a critical role in the interior processes of the planet, and possibly other planets including Mars.

For more information on ringwoodite:

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Cascadia Subduction Zone: Unprepared and Liquefaction

Call me paranoid, but when I see a 7.8 earthquake in Indonesia, and the news recalls the 8.9 magnitude earthquake that triggered the deadliest tsunami in history in 2004 killing more than 200,000 people, I’m reminded that we live in the shake zone of earthquakes and tsunamis, the Cascadia Subduction Zone. It doesn’t help when The New Yorker Magazine tells us that the “Really Big One” is coming and we’ll be able to surf to Idaho soon.

Last year, OPB-TV won awards for their “Unprepared” television series and documentary on the historical “big one” coming to the Pacific Northwest. It led to discussions around the state of Oregon involving geologists, seismologists, and area experts, all asking if we are prepared and what are we going to do or not do about it. They talked about the state of our bridges, schools, and the impact of liquefaction on our ports, home to fuel tanks, some almost 100 years old, that could rupture, dump into our precious waterways, and burn for ages. It was a wake-up call for all of us.

As a rock lover, I started questioning the ground under my feet. According to FEMA’s Earthquake Risk and Cascadia Region Earthquake Workgroup (CREW) and their educational Cascadia Subduction Zone Earthquakes 9.0 Magnitude Scenario (PDF), while I’m personally outside of the tsunami zone, besides being cut off from the rest of the world, the thing to fear most is: Liquefaction.

Tilted Victorian Home in San Francisco due to liquefaction - Photograph by G.K. Gilbert of the U.S. Geological Survey

Liquefaction is the process in which soil, often thought to be firm and solid, is “reduced” by earthquake shaking. While most commonly associated with saturated soils, liquefaction occurs in dry soils where there is space between the particles. Take a jar and fill it full of flour or grains. Tap it against the counter and you will see the level drop. Depending upon the space and shape of the grains, it might drop a little or a lot. That’s liquefaction in action. Continue reading “Cascadia Subduction Zone: Unprepared and Liquefaction”

Jade: Did You Know There are More Than Two Types?

The following is by Tualatin Valley Rock and Gem Club member Taylor Hunt. if you would like to contribute to our newsletter and website with articles on various rocks, minerals, and gems, please contact us.

The gemstone jadeite generally forms as a result of the plate tectonic process of subduction. Jade made from jadeite forms when supercritical fluids from subducting oceanic crust condense in the overlying man-tel wedge (the “wedge” is all the sediments swept up, piled and squeezed between the subducting oceanic plate and a continental mass), between 20 & 60 km deep in the Earth. Jadeite deposits thus mark the loca-tion of exhumed fossil subduction zones.

A new term PTG’s, plate tectonic gemstone, and jadeite is one PTG currently recognized. For various reasons most PTG’s are found in rocks or continental plates considered young to planet Earth. Most are no older than the formation of the supercontinent of Rodinia or 1,000 ma yr. Petrotectonic indicators that form deep in the Earth have the added advantage that their record is unlikely to be obliterated by erosion. Recognition of the PTG’s links modern concepts of plate tectonics to economic gemstones deposits and the ancient concepts of beauty, and may aid in exploration for new deposits.

Any mineral or stone beautiful enough to be sought, mined and sold for its beauty alone is a gemstone. The subclass of rocks and minerals that comprise gemstones—whether precious or semi-precious—has mostly been established since antiquity. Humans have sought and prized gemstones since thousands of years be-fore the science of geology was established. Because gemstones are rare by definition, the geological conditions that produce them must have been exceptional. Thus, there is a confluence of economic, aesthetic and academic interest in gemstones. Jade — specifically the variety jadeite — is the characteristic beautiful product of normal oceanic lithosphere subduction.

The following images are from Wiki Commons and Flickr contributors, used under copyright and public domain free image licenses.

Jade is a term ascribed to two different materials with similar properties, toughness, and beauty that evolved in usage and significance from toolstones for axes, choppers and hammers to one of the most highly revered gemstones in the world. As a tool, jade was employed during the Paleolithic (stone age, before 3500 BCE) but was raised to high symbolic stature as a gemstone in proto—Chinese Hongshan and Liangzhu cultures by 3500 BCE, and in the Jom’on culture of Japan by 3000 BCE, and in Central America by the Olmec of the Early Formative period by at least 1500 BCE and later in the Mayan civilization. Hard jade (jadeitite) or “ying yu” in Chinese consists predominately of pyroxene minerals, jadeite (Na,Al,Si2,O8), while soft jade (nephrite jade) “ruan yu” come from amphibole minerals of tremolite-actinolite [Ca2(Mg,Fe)5,Si8O22(OH)2]. The term jade was derived from the Spanish “piedra de yjada” (loin stone) for talismans worn by the Aztec to ease abdominal pain, but was mistranslated to the word jade. In New Zealand, nephrite jade is sometimes called greenstone and was a favorite of the Maoris. Continue reading “Jade: Did You Know There are More Than Two Types?”

Adopt-a-Mineral at the Rice Northwest Museum – Fluorite

The Rice has a great program called Adopt-a-Mineral, allowing the public to donate to the museum by adopting a rock and mineral. The following article is about one of those minerals, fluorite, available for adoption now.

Fluorite (AM 29, AM 30)

Carlo Galeani Napione named the mineral fluorite in the late 1700s. The name derives from the Latin “fleure”, meaning flow, because it is commonly used as a flux. Fluorite is a halide, in which a metal is bonded to one of the halogen elements (fluorine, chlorine, bromine, iodine).

The following images are used courtesy of Wiki Commons.

Fluorite is commonly translucent and found with a vitreous (glassy) luster. It has many colors including, green, purple, yellow, pink, brown and colorless. Its streak (color of the powdered mineral) is white. Fluorite has a hardness of ~4 and is the hardness reference species on Mohs’ scale. It is a brittle mineral, and it will fracture and break along perfect cubic and octahedral cleavage planes. Fluorite usually occurs as cubes, although it can also be found as octahedra (8-faced crystals), and rarely as dodecahedra (12-faced crystals). Sometimes these forms can be found combined in single crystals. When not seen as large crystalline specimens, fluorite is usu-ally massive, or an aggregate of very small cubes. Continue reading “Adopt-a-Mineral at the Rice Northwest Museum – Fluorite”

Mount Saint Helen’s Crystals Predict the Past

Scientific American reports that a team in England and Germany are using crystallized minerals formed in the volcano just before eruption to determine a timeline of volcanic activity, and possibly predication from a study in the May 25 issue of Science.

…the researchers report that crystals of the silicate mineral orthopyroxene from 1980 and from subsequent eruptions trace various injections of magma, as well as other chemical changes, within the bowels of the volcano.

The crystals contain concentric rings of differing chemical composition. Some orthopyroxene crystals, for instance, have a magnesium-rich core surrounded by an iron-rich rim; others have an iron-rich core and a magnesium-rich rim. Each type of crystal zonation can record the conditions of the magma reservoir from which it emerged.

“We chemically fingerprint each of those zones to determine how they formed,” says lead study author Kate Saunders, a volcanologist of the University of Bristol in England. The outer rim of an orthopyroxene crystal, she says, represents the most recent stage of crystal formation and typically grew just months before the crystal’s emergence in volcanic ejecta. That allowed the researchers to make precise estimates of when, and how, the crystals acquired their chemical forms. “Mount Saint Helens is really good—because the samples, we know exactly when they erupted,” Saunders says.

They hope that the study of these crystals will corroborate and offer insight into the historical timeline of erruptions, something researchers today can only guesstimate.

For more information, see “What’s the Point of Volcano Monitoring?” from Scientific American and “Linking Petrology and Seismology at an Active Volcano” from Science.