This is evidenced by the spatial and temporal correlation between the major continental flood basalts formed in the last 300 Myr and the different phases of fragmentation of Pangea, the youngest supercontinent in Earth’s history 26 (see also Table 1). In contrast, most Phanerozoic plume-related LIPs are known to be associated with the break-up of continents and the subsequent opening of large oceanic basins. Such small-scale anomalies in the upper mantle (also called “baby” plumes) 18 could originate from “primary” (super)plumes ponding at the 660 km phase change boundary 19 or be the result of deep dehydration of oceanic slabs stagnating in the lower part of the MTZ 20, 21, 22.Īlthough the formation of LIPs is by definition not causally linked to plate-tectonic processes, Precambrian records in southern Africa show that LIPs may occur during supercontinental assembly 23 through thermal blanketing beneath the growing continent 24 and without support from mantle plumes 25. Importantly, these upwelling structures are not limited to the classic (“primary”) Morgan-type plumes 15 that rise from the mantle–core boundary (~2900 km) throughout the entire mantle but also include so-called “secondary” plumes 16 rooted in the upper-lower mantle transition zone (MTZ: ~410–660 km) 17. Most commonly, both the transient dome-shaped surface uplift 6 and the subsequent intraplate magmatic activity 7 are attributed to mantle plumes 8, seismically detected thermal 9, 10 or thermal–chemical 11, 12 anomalies in the Earth’s mantle 13, 14. Within continents, such a sudden occurrence of continental flood volcanism is usually preceded by a rapid uplift of the surface topography of 0.5–2 km within a few Myr 4, 5. Large Igneous Provinces (LIPs) are defined as large volumes of predominantly mafic rocks characterized by a high rate of magma accumulation and unrelated to plate-tectonic processes, i.e., formed far away from plate boundaries within intraplate tectonic environments 1, 2, 3. The proposed new classification of LIPs may provide useful guidance for future research, particularly with respect to some inherent limitations of the common paradigm of purely passive continental break-up and the assumption of a direct link between internal mantle dynamics and the timing of near-surface magmatism. A special case is the North Atlantic Igneous Province (NAIP), formed due to the “re-awakening” of the Iceland plume by the lateral propagation of the spreading ridge and the simultaneous approach of the plume conduit to adjacent segments of the thinner overlying lithosphere. Here, we show that the role of the LIPs in rupture of the lithosphere ranges from initial dominance (e.g., Deccan LIP) to activation (e.g., Central Atlantic Magmatic Province, CAMP) or alignment (e.g., Afar LIP). Moreover, the classical model of purely active (plume-induced) rifting and continental break-up often fails to do justice to widely varying tectonic impacts of Phanerozoic LIPs. However, this does not always seem to be the case, as illustrated by, for example, the Siberian Traps, one of the most voluminous flood basalt events in Earth history, which was not followed by lithospheric rupture. I feel my “A” from CYA is well covered in that this building is typical for the era, and the area, as well.Traditionally, the emplacement of the Large Igneous Provinces (LIPs) is considered to have caused continental break-up. Combined with a context of an area with a recorded historic snowfall level of less than 1cm and a grand total of zero hurricanes, I see no reason to even raise the issue, and certainly not to refer to a SE or PE (beyond here on this forum, thanks Darren). In this case of this particular roof, on seeing the slope I immediately looked for signs of wall spreading. And, annoying the non-greedy professionals who get called out on the referrals.įor older buildings there’s an existence proof: if it’s been there X years, is there any evidence of a developing problem? Is it a home component that wears out? My advice is to reconsider that approach, especially in a home inspection report.Īs inspectors we risk either being ignored, or sending owners on wild goose chases of fixing things that don’t need fixing. It doesn’t matter then the structure was built, when I see a problem, a material defect, or unsafe condition I analyze it based on the current requirements.
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