Doc Socks Junior Posted March 23, 2018 #1 Share Posted March 23, 2018 (edited) Ostensibly, it is a great article. Imaging a lower-mantle plume! A herculean task by any stretch of the seismological imagination. And in such an exciting area, too. A clear candidate for publication in Nature. Quote The Yellowstone hotspot, located in North America, is an intraplate source of magmatism the cause of which is hotly debated. Some argue that a deep mantle plume sourced at the base of the mantle supplies the heat beneath Yellowstone, whereas others claim shallower subduction or lithospheric-related processes can explain the anomalous magmatism. Here we present a shear wave tomography model for the deep mantle beneath the western United States that was made using the travel times of core waves recorded by the dense USArray seismic network. The model reveals a single narrow, cylindrically shaped slow anomaly, approximately 350 km in diameter that we interpret as a whole-mantle plume. The anomaly is tilted to the northeast and extends from the core–mantle boundary to the surficial position of the Yellowstone hotspot. The structure gradually decreases in strength from the deepest mantle towards the surface and if it is purely a thermal anomaly this implies an initial excess temperature of 650 to 850 °C. Our results strongly support a deep origin for the Yellowstone hotspot, and also provide evidence for the existence of thin thermal mantle plumes that are currently beyond the resolution of global tomography models. However, "Lower-mantle plume beneath the Yellowstone hotspot revealed by core waves", although an interesting paper, has some issues. Namely, their choice of methodology (SKS waves, i.e. shear waves hit the core, travel through as compressional waves, come back as shear waves) is prone to vertical smearing. Intuitive? Not to most people. And they even address it in their paper, at least so they claim. Quote The tests (Fig. 4) indicate the feature we imaged under Yellowstone is laterally well resolved and is unlikely to be caused by vertical smearing. However, looking at Figure 4 (see attached image), their tests wouldn't actually resolve vertical smearing!! Their input into the test is insensitive to it! Just goes to show. Stay woke, people. Trust no one. https://www.nature.com/articles/s41561-018-0075-y.pdf Edited March 23, 2018 by Socks Junior 3 Link to comment Share on other sites More sharing options...
Doc Socks Junior Posted March 24, 2018 Author #2 Share Posted March 24, 2018 See, the thing about this is, there is an anomaly below Yellowstone. No doubt. So much volcanic activity, beautiful age progression, the Snake River Plain is a clear testament that fits the plume paradigm well. But vertical smearing could make even a shallow (relatively) anomaly look like, well, a long narrow plume-like conduit. Hard to be convinced with this one. I'd say. The search for deep plume imaging continues. Also, these thoughts were clarified thanks to a good friend in seismo, who helps me make sense of the finer points of seismological witchcraft. 1 Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now