My top 10 picks for geology research of the year. The lines between pure geology, historical geology, and palaeontology are somewhat blurry, so you may also find geology papers in those listings. The stuff here cannot be put in any other category: it’s all about the Earth. The master list has 19 papers. [OA] indicates open access papers.
This paper uses deep seismic surveys that can show long-subducted slabs and evidence from ancient volcanic arcs to reconstruct the tectonics of the Panthalassan Ocean 200 Ma, seen in B above. The Panthalassa Ocean is the one that surrounded Pangea, by the way.
First and foremost, this paper presents a massive compilation of the geochemistry of lithospheric rocks through Earth’s history. For that alone it deserves a spot on here. They find several specific trends with mafic and felsic rock types, but the more interesting correlation they find is pictured above: a sudden change in rock geochemistries coincident with the Great Oxidation Event. This is a seemingly baffling correlation with no causation – what does the atmosphere have to do with the deep Earth? But it hints at something that has long been hypothesised, that the Great Oxidation Event wasn’t just the result of the evolution of photosynthesis, but was also greatly helped or even enabled by geological changes.
Open any geology textbook and go to the section describing subduction. You’ll see a diagram where one plate slides below another in a curved line. This is highly simplistic: the slab that goes under will not just slide, it will crumple up and buckle. This paper’s insight is to confirm that buckling really is a universal feature, and uses a mathematical model to describe how the buckling will evolve under various conditions.
If you do a deep seismic survey to map out the area beneath an oceanic plate, you will encounter a distinct zone where your seismic waves travel much slower, 50-100 km beneath the ocean surface. This low-velocity zone is called the Gutenberg Discontinuity (G Discontinuity), after its discoverer, Beno Gutenberg. It can also be colloquially referred to as the boundary between the lithosphere and the asthenosphere. This paper enhances our conception of this area by finding that the G Discontinuity is not at a constant depth across a plate. Schmerr examines it across the Pacific Plate, and finds that its depth varies: where there is more melting, the disconinuity is shallower. So where there is plume, or water intruding into the asthenosphere, or just magma upwelling, we can expect a shallower G discontinuity.
One of the targets in earthquake research nowadays is to document earthquake interactions with hydrology. This paper finds that after the 1999 Chi Chi earthquake, the temperature of groundwater nearby decreased. The explanation by Wang et al. is that the earthquake increases permeability, allowing water to flow deeper into the mountain. The importance of this is that such deep and pressurised water flows could be causes of aftershocks, or even of earthquakes, hence why monitoring such changes is important.
This paper uses computer models to reconstruct observed CO2 levels during the Ice Ages. By doing do, we can look at what parameters are needed to reproduce those levels, and thus know what caused them to fluctuate. As expected, it turns out there is no single answer that fits all. While orbital changes, greenhouse gases, and atmospheric dust are universal modifiers, specifric CO2 fluctuations in the Ice Ages have been variably caused by oceanic temperature changes or oceanic geochemistry.
This paper uses a more reliable model to recostruct the conductivity of the Earth’s core and the exchange of heat between the core and mantle, and the difference to previous estimates is staggering: it’s 2-3 times more conductive, and the heat flux is also higher.
In palaeontology, we often say that “every specimen tells a story”. It’s the same in geology, where the minerals in a rock can tell us all we need to know about the journey that single rock took from its formation to its presence in the lab. This is exactly what this paper does, using a pieve of rock that comes from the very depths of the Earth: a volcanic rock from Iceland containing gas bubbles from the mantle, basically telling us what the air is like almost 3000 km beneath the Earth. Besides telling a cool story, the findings are also pretty significant: the neon isotopes in the gas were found to have come from the solar nebula – meaning these gases have been trapped there since Earth’s formation! This provides some exceptional insight into the Earth’s early formation, pointing at the existence of a large gas reservoir around which the rest of the planet accreted. Astronomers should also be interested in this paper. There are other important points in this paper, and it will certainly serve as a basis for many others in the future.
Some more stories from very deep rocks: this paper reports the isotopic composition of 2.8 Ga komatites, a rock type from the deep mantle, found in the Baltic Shield, Russia. It finds that the tungsten isotope levels are abnormally high compared to modern rocks; other old (3.5 Ga) rocks from Greenland show similar levels, so there seems to have been some special process operating back then, although interpretations are strictly at the hypotheses-to-be-tested stage at the moment. The only thing that’s relatively certain is that it means that the Earth was not completely molten at some point of its history, or else such isotopic signatures would have been erased.
Listen to enough New Age hippy quackery, and you’ll inevitably hear someone say that Mother Earth is angry at us, hence so many large earthquakes lately. This is a prime example of confirmation bias (as well as stupidity) – there has not been an abnormal increase in earthquakes. This paper shows that, for whatever it’s worth. Any increase is due to regular stochasticity, not ue to any procedural clustering. So, please, while some regions are always at risk of earthquake (you know, Japan, Chile, Turkey), there has been no unexpected increase in global rates. The Earth isn’t conscious and isn’t trying to destroy us if it were. What we’ve seen in the past couple of years is nothing more than a couple of large earthquakes releasing friction around their faults, leading to several large aftershocks. Plate tectonics as normal.