Dead Sea Models Salt Deposition

A correspondent sent me THIS LINK. The article is based on THIS ACADEMIC PAPER. The Dead Sea is, at the moment, the only water body sufficiently deep enough and salty enough to model the conditions which produced the vast salt deposits which are found in many places and times in the geological record.

The academic paper, in particular, examines, in great detail, all the things which determine the salt deposition. These include temperature, which varies with the seasons, salt concentration which varies with depth, temperature and the season, evaporation which depends on temperature and wind, wind which affects mixing, sizes of the deposited halite crystals and beach deposits.

Reading the reports makes me realise that it is very complicated! And that I am ill equipped to explain it all to you! So read the papers, and hope that you can begin to understand what is going on. 

 Is the Core Separate from the Mantle - Maybe Not

A correspondent sent me THIS LINK which looks at new evidence suggesting that material from the core is getting into the mantle and, eventually, to the Earths surface.

We have long been taught that the lighter mantle floats above the denser metallic core and that there cannot be movement between the two (except for earthquake waves).

But work on helium isotopes casts doubt about the separation. Helium-3 was formed just after the Big Bang and was confined to deep in the Earth, some believed it was confined to the core. Helium-4 is formed from the decay of uranium and thorium and is confined the mantle and the Earths surface. But then Helium-3 was found in volcanic lavas from mid-ocean ridges.

Ruthenium is an element with an affinity for iron and thus is concentrated in the iron-rich core. This applies particularly to Ruthenium-100. Other ruthenium isotopes came to Earth later via meteorites but Ruthenium-100 should be confined to the core. But it is now found at the surface.

So how is the core stuff getting into the mantle? Debate rages with a lot of attention being paid to two huge "blobs" - one under the Pacific and the other under Africa. These are believed to be hot but dense and supplying plumes leading to the surface. Are they "mining" the core or are they a bridge from the core to the surface.

Expect to hear more about this in the future.

 Down to Earth Extra August 2025

The August 2025 edition of Down to Earth Extra has been published. You can download it HERE or you can read it below.

 The Grand Canyon - Then and (Almost) Now

My attention has been drawn in the last week to two articles both concerning the Grand Canyon. THIS ARTICLE was sent to me by a correspondent - thank you - and concerns well preserved fossils from the middle Cambrian (Bright Angel Formation) 505 million years old, found in the Grand Canyon, and THIS ARTICLE which suggest that the meteor impact which created Meteor Crater, 100 miles from the Grand Canyon, caused landslides which dammed the canyon. This happened 56,000 years ago - almost yesterday!

The Cambrian fossils found are slightly younger (3 million years only!) than those of the Burgess shale and are mainly priapulid worms with some crustaceans and molluscs. They show that life was innovating new forms. The source paper can be found HERE and has some wonderful pictures of the beautifully preserved (but tiny) fossils.

Crustacean sternal elements from the Bright Angel biota.

Paragnath-bearing triangles are indicated by 1 s, and the successive posterior triangles by 2 s. (A) Posterior end of paragnath-bearing triangle and anterior section of successive triangle. (B) Complete triangle with laterally splayed paragnaths (black arrows). (C) Detail of scaly ornament of median cuticular strip in (B). (D) Detail of anterior setose surface in (B). (E) Complete paragnath-bearing triangle, with articulated anterior section of successive triangle. (F) Detail of boxed area in (E) showing scale-bearing cuticular strip and marginal setal fringes. (G) Articulated paragnath-bearing and partial posterior triangles defining median food groove. (H) Detail of boxed area in (G) showing sphaeromorphic acritarch adpressed onto the food groove cuticle. (I) Subtriangular cuticular lobe, representing possible setulose labrum. (J) Complete paragnath-bearing triangle and articulated, semi-complete posterior triangle. (K) Detail of boxed area in (J) showing spheroidal acritarch adpressed onto the food groove cuticle. Slide numbers and England Finder coordinates listed in data S1. Scale bars, 50 μm except in (C) and (H) (5 μm) and (D), (F), and (K) (25 μm).

The evidence for the damming of the Grand Canyon is not controversial. There are caves 45m above the river which have driftwood logs in them. In the last few years improved dating techniques have been used and they show that the ages of the damming and the meteor impact are about the same. Whether one caused the other is rather more difficult to prove.