Author Archives: Steve Drury

Earth-pages has closed

Dear Earth-pages readers,

It is almost two decades since I was invited to write a regular series of articles on developments in the geosciences at Earth-pages. The site’s archives comprise more than 1200 of my commentaries, covering over 1500 publications. Since 2011 its annual readership has been between 40,000 to 80,000. Sadly, Earth-pages closed on August 1 2019 and no new posts will be added to it. Instead, activity has been transferred to a new site called Earth-logs. Titles of new additions to Earth-logs will continue to be posted here with links to the full text.

Given its wide and loyal readership, I believe that the Earth-pages archives will continue to remain useful, especially for students, teachers and those hoping to begin geoscientific research. So, with the permission of Wiley-Blackwell, they too have been transferred to the new Earth-logs site .

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The format is different: the early posts (2000 to 2018) are logged annually under 12 broad themes: GeohazardsGeomorphologyHuman evolution and migrationsMagmatismMiscellaneous CommentaryPalaeoclimatologyPalaeobioloy; Physical ResourcesPlanetary ScienceRemote SensingSedimentology and Stratigraphy, and Tectonics. Each of these pages indexes the research topics covered during each year, along with links to PDFs of the annual logs.

New posts are added regularly to the Earth-logs Home Page. I intend to continue writing these commentaries in the same style as I have adopted at Earth-pages, for as long as I can. An important addition is direct web access to most of the papers on which the posts and the entries in annual logs are based, so that readers can download them as PDFs for their own use.

Thanks for reading my stuff here. Hopefully you will continue to do so at Earth-logs

Steve Drury

More on the Younger Dryas causal mechanism

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Colour-coded subglacial topography from radar sounding over the Hiawatha Glacier of NW Greenland (Credit: Kjaer et al. 2018; Fig. 1D)

Read about new data from lake-bed sediments, which suggest that a major impact around 12.8 thousand years ago may have triggered a return to glacial conditions at the start of the Younger Dryas.

 

How does plate tectonics work?

Read about a new computer model that charts the co-evolution of the mantle and lithosphere, i.e. the linkages between deep convection and plate tectonics.

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Still from a movie of simulated breakup of a supercontinent, in bland blue-grey, showing what happens at the surface (left) and, at the same time, in the mantle (right): note the influence of rising plumes (credit: Nicolas Coltice)

What followed the K-Pg extinction event?

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Reconstruction of the 35 kg early Palaeocene mammal Taeniolabis (credit: Wikipedia)

Read about processes connected with the Chicxulub impact that may have influenced the K-Pg mass extinction and the evolution of mammalian survivors during the first million years of the Palaeocene, as revealed by a unique sedimentary sequence near Denver, Colorado, USA.

Chaos and the Palaeocene-Eocene thermal maximum

Read how chaotic behaviour in the Solar System may have affected Milankovich cycles in the late Palaeocene

Life with the Neanderthals

Hundred of 80 thousand-years old footprints – which could only have been made by Neanderthals, have been found in a dune sand depost at Le Rozel on the Cherbourg Peninsula in Normandy, France. Their abundance and diversity has presented an opportunity to to analyse the social structure of the Neanderthal group that produced them.

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The Le Rozel excavation, with weighted plastic sheets to protect the site from erosion between visits (credit: Dominique Cliquet)

To learn more about this unique discovery visit Earth-logs

Ediacaran glaciated surface in China

Read about a unique confirmation of Snowball Earth conditions during the Ediacaran Period at Earth-logs.

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29 Ma old striated pavement beneath the Carboniferous Dwyka Tillite in South Africa (credit: M.J Hambrey)

Ecological hazards of ocean-floor mining

Read about the threat posed by deep-ocean mining of polymetallic nodules at Earth-logs

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The distribution of potential ocean-floor metal-rich resources (Credit: Hefferman 2019)

 

A dinosaur nesting colony

Read about a new discovery in Mongolia at Earth-logs

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Clutch of near-spherical dinosaur eggs from Mongolia: scale bar = 10 cm. (Credit: Kanaka et al. 2019; Fig. 2A)

Out of Africa: The earliest modern human to leave

The 2017 discovery in Morocco of fossilised, anatomically modern humans (AMH) dated at 286 ka (see: Origin of anatomically modern humans, June 2017) pushed back the origin of our species by at least 100 ka. Indeed, the same site yielded flint tools around 315 ka old. Aside from indicating our antiquity, the Jebel Irhoud discovery expanded the time span during which AMH might have wandered into Eurasia, as a whole variety of earlier hominins had managed since about 1.8 Ma ago. Sure enough, the widely accepted earliest modern human migrants from Skhul and Qafzeh caves in Israel (90 to 120 ka) were superseded in 2018 by AMH fossils at Misliya Cave, also in Israel, in association with 177 ka stone artefacts (see Earliest departure of modern humans from Africa, January 2018). Such early dates helped make more sense of very old ages for unaccompanied stone tools in the Arabian Peninsula as tracers for early migration routes. Unlike today, Arabia was a fertile place during a series of monsoon-related cycles extending back to about 160 ka (see: Arabia : staging post for human migrations? September 2014; Wet spells in Arabia and human migration, March 2015). The ‘record’ has now shifted to Greece.

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Key ages of early H. sapiens, Neanderthals and Denisovans (credit: Delson, 2019; Fig. 1)

Fossil human remains unearthed decades ago often undergo revised assessment as more precise dating methods and anatomical ideas become available. Such is the case for two partial human skulls found in the Apidima Cave complex of southern Greece during the late 1970s. Now, using the uranium-series method, one has been dated at 170 ka, the other being at least 210 ka old (Harvati, K. and 11 others 2019. Apidima Cave fossils provide earliest evidence of Homo sapiens in Eurasia. Nature, v. 571 online; DOI: 10.1038/s41586-019-1376-z). These are well within the age range of European Neanderthals. Indeed, the younger one does have the characteristic Neanderthal brow ridges and elongated shape. Albeit damaged, the older skull is more rounded and lacks the Neanderthals’ ‘bun’-like bulge at the back; it is an early member of Homo sapiens. In fact 170 ka older than any other early European AMH, and a clear contemporary of the long-lived Neanderthal population of Eurasia; in fact the age relations could indicate that Neanderthals replaced these early AMH migrants.

Given suitable climatic conditions in the Levant and Arabia, those areas are the closest to Africa to which they are linked by an ‘easy’, overland route. To reach Greece is not only a longer haul from the Red Sea isthmus but involves the significant barrier of the Dardanelles strait, or it requires navigation across the Mediterranean Sea. Such is the ‘specky’ occurrence of hominin fossils in both space and time that a new geographic outlier such as Apidima doesn’t help much in understanding how migration happened. Until – and if – DNA can be extracted it is impossible to tell if AMH-Neanderthal hybridisation occurred at such an early date and if the 210 ka population in Greece vanished without a trace or left a sign in the genomics of living humans. Yet, both time and place being so unexpected, the discovery raises optimism of further discoveries to come