Educational group representing rock, gem, and mineral enthusiasts on the west side Portland, Oregon.
Category: Earth Sciences
The Tualatin Valley Rock and Gem Club of Oregon is made up of hobbyists, enthusiasts, and experts in geology and earth sciences. Part of our responsibility as a rock club is to provide educational material as well as the latest news and information on earth sciences to our members and the general public, and that is what we do here in this category.
If you are a member of our club, please let us know at our regular meetings or contact us to discuss submitting content to our site.
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.
In a article on Phys, they report scientists have found clues in Alaska that has them rethinking how to continental crust forms based upon research published in Nature Geoscience.
A new study appearing in this week’s Nature Geoscience raises questions about one popular theory and provides new support for another, in which arc lava from the surface and shallow “plutons” – magma that solidified without erupting – are pulled down into the Earth at subduction zones and then rise up to accumulate at the bottom of the arc crust like steam on a kitchen ceiling. Scientists have found compelling evidence to suggest that this could have produced the vast majority of lower continental crust through Earth history.
The process, called relamination, starts at the edge of a continental plate, where an oceanic plate is diving under the continental plate and magma is rising to form a volcanic arc. As the oceanic plate dives, it drags down sediment, lava and plutonic rock from the edge of the arc. As arc material descends, minerals within it become unstable with the rising pressure and heat, and they undergo chemical changes. New minerals form, and chunks of the rock and sediment can break off. When those chunks are denser than the mantle rock around them, they continue to sink. But when they are less dense, such as those that form silica-rich granulites, they become buoyant and float upward until they reach the bottom of the arc crust and accumulate there.
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.
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”→
Recently, we have been able to provide some answers to the questions of how diverse through time has life been, based on the building of large fossil occurrence databases and new methods of analysing them. One such development has been the Paleobiology Database, a professional crowd-sourced archive of fossil history, where the context of fossils is provided in both space and time, and largely based on the published record of fossil discoveries.
…By applying SQS with our development of large fossil occurrence datasets, voila, we are able to gain renewed insight into the diversity of life through history in a way that accounts for the inherent biases of the fossil record!
And that’s just what a new study in PLOS Biology set out to do. Led by Roger Benson of the University of Oxford, an international team of researchers applied SQS to one of the largest tetrapod fossil occurrence databases ever assembled (if not the largest!), comprising more than 27,000 individual fossil occurrences! This represented almost 5000 fossil species, and the data were restricted to just those fossils that dwelled on land – so this excludes groups like ichthyosaurs and plesiosaurs, for example. They also excluded flying tetrapods, so birds, bats and mammals, as these are known to have very different preservational histories in the fossil record. For palaeontology though, this is definitely ‘big data’.
The team restricted their analyses to just the Mesozoic to early Paleogene, a time span of around 190 million years (a fairly long time, even by geological standards!). If you think about it, that’s 5000 species over about 190 million years, which compared to 30,000 around today is pretty weird even in itself.
The app is free and runs “silently” in the background. The app has the ability to distinguish between natural body and transportation movements and ground disturbances. The goal of the app is to collect enough data to help track earthquakes in a way that may lead to a global early warning system.
The app offers four key features in addition to collecting and transmitting earth movement data to Berkeley.
Recent: The Recent tab displays earthquake data globally with a magnitude of 2.5 or more within the past 7 days. Using a Google Map, the user may zoom around the globe to observer recent earthquake activity.
Safety: Simple steps to ensure the user is familiar with how to take cover before, during, and after an earthquake.
Senor: While mostly for fun, shake the phone around and you will see the phone’s senor record the movement.
Past: This is another Google Map highlighting the most powerful and noteworthy earthquakes throughout known history, some dating back hundreds of years.
BBC News Science and Environment column reported that scientists have catalogued the largest list ever of rare minerals. The list, published in American Mineralogist, was authored by Dr Robert Hazen, from the Carnegie Institution in Washington DC, and Prof Jesse Ausubel of The Rockefeller University, in New York, and includes more than 5,000 mineral species.
“Scientists have so far tracked down 5,000 mineral species and it turns out that fewer than a 100 constitute almost all of Earth’s crust. The rest of them are rare, but the rarest of the rare – that’s about 2,500 minerals – are only found at five places on Earth or fewer,” Dr Hazen told BBC News.
“And you ask: why study them; they seem so insignificant? But they are the key to the diversity of the Earth’s near-surface environments.
“It’s the rare minerals that tell us so much about how Earth differs from the Moon, from Mars, from Mercury, where the same common minerals exist, but it’s the rare minerals that make Earth special.”
The list includes rare examples including cobaltominite, abelsonite, fingerite, edoylerite, and the extremely rare “vampire-like minerals” that fall apart immediate when wet or the sun shines on them: edoylerite, metasideronatrite, and sideronatrite.
Oregon Field Guide is part of OPB-TV and is a long-time program for naturalists. Among its many award-winning programs and segments are some outstanding sessions on geology in Oregon and the Pacific Northwest.
For example, the Building the MAX-Line Tunnel episode takes you into the geology uncovered during the building of the Highway 26 Tunnel between Portland and Beaverton. On display in the tunnel station for the Children’s Discovery Museum and Oregon Zoo are core samples removed from that excavation, detailing the geological history of the area.
Most of these are featured on the Oregon Field Guide website for free viewing, and I highly recommend it if you are worn out watching Breaking Bad and Downtown Abbey reruns.
If you are heading north into Washington State, way far north towards the Canadian border, take time to drop by Western Washington University in Bellingham for their free and open to the public exhibit of the minerals, fossils of Washington state, reports the Bellingham Herald. The exhibit is on the ground floor and part of the first and second floors of the Environmental Studies Building.
It’s like a mini-museum, with displays that include mineral crystals, mammoth teeth and fossilized plant leaves, along with interpretive exhibits that highlight coal mining in Whatcom County and show some of the tools and equipment that scientists use to study the Earth. There’s even a seismograph and seismometer.
…Possibly the most fascinating display is a four-foot slab of sedimentary rock containing the three-toed footprint of a diatryma, a giant flightless bird from the Eocene Period, some 34 million to 56 million years ago. It was discovered in sedimentary rock that shook loose in a landslide several years ago near Racehorse Creek in the Mount Baker foothills. The slab was airlifted by helicopter to WWU.
As our members know well, Washington (as well as Oregon) is one of the most geologically dynamic areas in the world. This exhibit is designed to showcase what they are calling “Northwest Origins” going back more than 1 billion years old.
If you head up there, please let us know and consider writing a report about the exhibit for the website and newsletter.