Saturday 24 June 2023

Does Banded Iron Formation Cause Mantle Plumes?

 Does Banded Iron Formation Cause Mantle Plumes?

It seems a stretch to connect a sedimentary rock, which needs life to form, is connected with things happening at the core/mantle boundary. Surface life affecting the very deep Earth.

The cause, if it exists, is the density of BIF (Banded Iron Formation). BIF density is about 3.5t m⁻³, which is rather heavy for the rocks found at the Earths surface.

What would happen if BIFs were subducted? They would sink and keep on sinking and eventually reach the Core/Mantle Boundary. Their high iron content and the associated high conductivity might encourage heat transfer from the core causing mantle plumes and Large Igneous Provinces.

You can read an introduction to this scenario HERE. It is inspired by THIS ARTICLE in Nature.

Banded Iron Formation

Saturday 17 June 2023

How Did Dinosaurs Grow?

 How Did Dinosaurs Grow?

A correspondent sent me links to three articles which he found interesting. This blog post concerns THIS ONE. The others, which are beyond my skill to write about, but certainly look interesting, are HERE and HERE.

Do dinosaurs (or other animals) grow quicker and faster or slower and longer - the answer is both. Fast growers can out-compete other species but they need lots of food. Slow growers face more risks but they can get through hard times.

But how do you study this? By looking at their bones! (As that is, for the most part, all that you have got, it is the obvious answer.) Theropod bones were sliced and polished down to wafers the researchers could see through. And then the growth rings could be studied - similar to tree rings.

It was found that some species grew larger over time, while others grew smaller, but there was no consistency - except in the case of the species which led to birds. Presumably being smaller makes flying easier.

The speed of growth does not determine eventual size - slow growers can be as large as fast growers, it just takes longer.