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.
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.
Are you looking forward to our upcoming show? With only a few weeks to go, it’s coming up fast. This year’s show Chair, Rose Jackson, is working diligently to bring things together, but she’s going to need help.
You know, an important part of being a club member is participation. Our Operating Procedures state that two of the duties of members are;
To attend club functions and
Volunteer your time and expertise.
So in that spirit, I trust you will come forward and give Rose the help she needs. With everyone coming together to help, no one has to work too hard and everyone can enjoy the show, the camaraderie of friends and share in the attention a show like this brings to our club. Continue reading “February 2016 President’s Message”→
The event will feature Eric Lindquist demonstrating how to create holograms and their potential uses as a special presenter.
There will be demonstrations of jewelry making including wire-wrapping, cabbing, and wearable art. Other presentations include rock and gem identification with several gemstone and rock experts. There will also be auctions and more fun and entertainment for families and individuals. Continue reading “Roxy Ann Gem Show 2016”→
One of our sister clubs in the Portland, Oregon, area, Mt. Hood Rock Club will have their annual Rock and Gem Show Friday and Saturday from 10-5 and Sunday from 10-4 at the W.P. Jackson Armory, 6255 NE Cornfoot Road, Portland, Oregon, from April 22-24, 2016.
Admission to the annual event is free, with each child receiving a free rock.
The rock and gem show will feature a wide variety of local and international rocks, minerals, fossils, jewelry, beads, equipment, games, demonstrations, silent auctions, and excellent vendors and exhibitors. An oral auction will be held at 1PM on Sunday.
Mt. Hood’s members specialize in local rocks and minerals and lapidary.
This is a great event for families, and everyone. See you there.