The Lizard - Origin and Emplacement

I came across THIS ARTICLE just this morning and have not had a chance to study it in any depth. As I will not be writing in the blog  for several weeks, and the article will be of interest to many of you, here is a short summary written by Google Gemini:-  

This article details the formation, subduction, and obduction of the Mid-Devonian Lizard ophiolite within the Variscan orogenic belt of Cornwall, SW England.

Key Findings and Geological History:

Ophiolite Structure and Origin: The Lizard ophiolite represents a nearly intact thrust slice of oceanic crust (dated via U-Pb zircon to ~386.8 Ma, Givetian) and upper mantle. It originally formed above a south-dipping subduction zone within the Rheic Ocean.

Metamorphic Sole: Situated at the base of the ophiolite is an amphibolite-to-greenschist facies metamorphic sole (~395 Ma, late Emsian). This sole is intruded by the Kennack Igneous Complex, a suite of granitoids reflecting the partial melting of diverse protoliths during subduction and subsequent obduction.

Underlying Thrust Sheets: Mechanically underlying the ophiolite is a complex mélange unit alongside the heavily folded and faulted Middle Devonian to Carboniferous sedimentary rocks of the Dodman, Veryan, and Carrick thrust sheets.

Tectonic Progression: Tectonic shortening propagated from the south-southeast (SSE) to the north-northwest (NNW). This structural push progressively emplaced distal Gramscatho Group rocks onto the passive continental margin of Avalonia (Laurussia).

Post-Collisional Activity: Following initial crustal shortening, the region experienced Late Carboniferous to Early Permian extensional reactivation and subsequent crustal melting, culminatng in the widespread intrusion of the Cornubian granites between 295 and 275 Ma.

The paper highlights that the overall tectono-stratigraphy, metamorphic sole development, and underlying thrust architectures of the Lizard ophiolite share distinct geological parallels with the iconic Semail ophiolite in Oman.

 Down to Earth Extra June 2026

The June 2026 edition of Down to Earth Extra has been published. You can download it HERE or you can read it below.

 The Earth's Core Changes Direction

But Does it Matter? THIS ARTICLE caught the attention of a correspondent who forwarded the link to me (Thank You!). It concerns the flow of the molten iron which forms the outer core of the Earth. The outer core starts at a depth of 2,890km and is 2,260km thick. It is thought to be 80 to 85% iron, about 5% nickel and the rest is a mix of lighter elements like sulphur, oxygen, silicon and carbon.

It is the outer core which generates the Earth's magnetic field and this keeps cosmic radiation out. This is a good thing! And it is the study of the magnetic field which tells us the direction the core is moving. For a long time it was thought that a gentle western drift of 10 to 40 km per year (1mm per second) was normal. 

But in 2010, the bit under the Pacific, started moving eastwards. This continues but has slowed since 2020. What caused this is unknown and the change was unexpected. Perhaps there is more happening in the core than we know about!

Does it matter? Probably not - the Earth's magnetic field is still doing its job and shows no sign of turning off. 

The academic paper on which the article is based will be found HERE

The End of the Dinosaurs

THIS ARTICLE in The Conversation gives a minute by minute account of what happened when the asteroid struck. And it tells how the impact led to the death of the dinosaurs and the rise of the mammals. And it is co-written by Mike Benton and Monica Grady, so it is most probably correct! (At least at the time of writing.)

The article is well worth reading. If you are content with a summary, below is Google Gemini's.

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The Immediate Aftermath (T+0 to 5 Minutes)

The asteroid, traveling faster than the speed of sound, hit the Yucatán Peninsula with the force of billions of Hiroshima bombs. If you were within 1,000 miles, you didn't hear the impact; you were vaporized by the thermal radiation before the sound waves could even reach you.

Within minutes, supersonic winds—stronger than any Category 5 hurricane—flattened entire forests. The atmosphere briefly turned into an oven, reaching temperatures of over 200°C (400°F).

The Environmental Collapse (T+1 Hour to 1 Week)

As the crust rebounded from the impact, it formed a crater 30 kilometres deep, launching molten rock into space. This material rained back down as "impact spherules," igniting global wildfires.

Then came the "stinky" phase. The asteroid hit a region rich in sulphur, blasting massive amounts of it into the sky. Combined with the smoke from burning forests and decaying carcasses, the entire planet likely smelled like rotting vegetables and acrid smoke.

The Long Winter

The soot and sulphur created a global shroud, blocking the sun for years. Photosynthesis stopped. The oceans became acidic from nitrogen oxides, and the planet plunged into a deep freeze.

It is a humbling reminder of our planet’s fragility. While this Armageddon wiped out the giants, it left a tiny opening for small, burrowing mammals—our ancestors—to survive. Without that terrible Tuesday, humans might never have had the chance to walk the Earth.

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A Visualisation by Google Gemini

This visualization focuses on the global environmental shift. The sky is no longer blue but choked with thick, black soot and sulphate aerosols. This dense layer blocks the sun, plunging the planet into darkness. The illustration visualizes the "smell" described in the research by depicting the air itself as a visual fog of acid rain, illuminated by the low, dim, hellish glow of widespread global wildfires.

 Volcanic Items of Interest

Various items have come to my notice lately so here they are in no particular order.

• Can volcanic eruptions be forecast, like the weather? The origin of this was THIS ARTICLE and the answer is no but we are getting better at it. What controls volcanism is not easily visible and is not active all the time, unlike weather which is visible and happening constantly. The article covers many aspects of volcanism and has some spectacular photographs.
  
  
• Is the Campi Flegrei in Naples going to erupt? The Campi Flegrei to the west of downtown Naples is used to low grade volcanic activity - earthquake swarms, ground uplift and subsidence - there is a state of emergency but not yet at a level which would trigger mass evacuation. 
  
  
  Earthquakes detected in Campi Flegrei area, Italy from February 15 - 18, 2025. Credit: INGV
  
  
  
  
  
  
• Are Extinct Volcanoes actually Dormant? This comes from THIS ARTICLE. And the evidence for this comes from the "extinct" Methana volcano not far from Athens. It seems that zircon crystals formed throughout the volcanoes history, including during long periods of quiescence. Are they still forming now?
  
  

  

  
  

  The Southern Aegean Volcanic Arc, showing Methana on the left and Santorini at the bottom. (Giorgostr/Wikimedia Commons)
  
  

  
  
• Lots of magma under Tuscany. Tuscany is not known for volcanism but recent seismological studies have indicate that Yellowstone volumes of magma lie 10km under the surface. The academic paper detailing this is HERE. 

 Would You be Scared of this Giant Octopus?

Generally octopuses don't fossilise - they are essentially bags of water. But their beaks are preserved and someone has found some big ones in Cretaceous rocks. And using present day beak sizes and octopus sizes has come to the conclusion that their beaks belonged to an octopus 7 to 19 metres in length!

Cretaceous marine predators (at maximum estimated size) with a scuba diver for scale. Credit: After Ikegami et al. Fig. 4, and Jacobs 2026.

Was the octopus a top predator or was it an extra large food source for a Mosasaurus? It is certainly a very good focus for speculation. Proving anything might be a difficult task.

You can read all about it HERE, based on THIS PAPER

 Some New (but Old) Cambrian Fossils

A correspondent sent me THIS LINK (but I had spotted it my self!). It concerns a recently discovered Lagerstätte in Southern China, called the Huayuan biota.

It has an added importance as being just after the first mass extinction of the Phanerozoic. It contains some old favourites from the Burgess Shale but many new species have been identified.

The find is of importance for many reasons but for me it is important for the wonderful photographs of the beasties. The source academic paper is HERE

non-bilaterian metazoans and deuterostomes from the Huayuan biota