u/Geoscopy

About 200 km beneath New England, seismic waves slow down inside a roughly 350 to 400 km wide zone of unusually hot mantle known as the Northern Appalachian Anomaly.

A 2025 paper argues that this “heat blob”suggests a migrating mantle instability triggered when Greenland and North America split apart near the Labrador Sea around 80–90 million years ago.

If the model is right, the Appalachians may still be partly supported from below by deep mantle buoyancy.

I wrote a long-form explainer on Tuzo and Jason, the two continent-sized Large Low Shear-Wave Velocity Provinces sitting at the base of Earth’s mantle, one beneath Africa and one beneath the Pacific.

The article covers how seismologists found them through tomography, why their margins are often linked to mantle plumes, how they may relate to hotspots and flood-basalt provinces like Hawaii, Réunion/Deccan, and Siberia, and what the current origin debate looks like.

The most interesting part to me is that we still do not know what they are made of. Some models treat them as ancient piles of subducted oceanic crust. A newer 2025 Nature Geoscience paper argues they may instead be primordial residues formed when material exsolved from Earth’s cooling core into a basal magma ocean. The Theia-impact idea is also still in play.

I tried to keep the article readable while still being careful about the uncertainties, especially around plume reconstructions, LLSVP stability, ULVZs, and the “graveyard of slabs” vs primordial-origin debate.

Would be very interested to hear what people here think, especially from anyone working on mantle geophysics, geochemistry, tomography, or plume modelling.

Natural hydrogen, the kind generated underground by water reacting with iron-rich rocks, has gone from a Malian curiosity to a multi-billion-dollar exploration category in a decade. The geology, the discoveries in Mali, Albania, Kansas and Lorraine, and where the skeptics are right.

5.3 million years ago, the Mediterranean nearly stopped being a sea.

Cut off from the Atlantic, it became a vast evaporating basin of salt. Then the ocean broke back in.

The story of the Messinian Salinity Crisis and the Zanclean megaflood:

https://geoscopy.com/when-the-mediterranean-vanished-the-600000-year-drought-and-the-megaflood-that-ended-it/

At Pozzuoli, near Naples, three Roman marble columns carry a strange dark band: holes bored by marine molluscs.

They are a biological watermark from the centuries when the ground sank below the Mediterranean, and later rose again.

That slow rise and fall is called bradyseism. At Campi Flegrei, it is the visible pulse of a restless volcanic caldera beneath one of Europe’s densest coastal regions. INGV says the current bradyseismic phase began in 2005 and had produced about 144 cm of uplift by April 2025.

The full story, from a Roman market to modern earthquake swarms, is now on geoscopy.com.

Image source: “Macellum - 161010.jpg,” described on Wikimedia Commons as the ruins of the Macellum in October 2017. Photo by Rolf Cosar / Wikimedia Commons, CC BY-SA 4.0.

#Geoscopy #CampiFlegrei #Volcanoes #Geology #EarthScience