Buried Fe-Mn nodules on the World ocean floor

Ocean floor Fe-Mn nodule sequence is a product of Mesozoic-Cenozoic global epoch of Fe-Mn oxide ore accumulation. Buried nodules formed in Late Paleocene-Eocene, Late Cretaceous, Cenomanian.

The Age and Paleomagnetism of Jurassic dykes, western Dronning Maud Land: implications for Gondwana breakup

New 40Ar/39Ar data from dykes intruded into Sverdrupfjella and Ahlmanryggen, Dronning Maud Land, Antarctica, indicate that dyke emplacement commenced at ca. 207 Ma and lasted until ca. 178 Ma. Whereas the ages ascribed to the Karoo-age magmatism contributing to Gondwana breakup are typically inferred as being ca. 182 Ma, the data indicate that ages older than ca.192 Ma in the broader Karoo Province are restricted to western Dronning Maud Land, Antarctica, indicating the locality where break-up was initiated. Limited palaeomagnetic data from ca. 178-185 Ma dykes combined with published palaeomagnetic data from similar aged dykes in Vestfjella and the Ferrar Province, suggest that Antarctica had already drifted/rifted significantly away from southern Africa from ca. 207 Ma to ca. 180 Ma, earlier than previously thought. The data, if correct, require a re-evaluation of the ages ascribed to ocean-floor anomalies used to constrain reconstructions of Gondwana and may provide insight into the history of microcontinental blocks including the Falkland Islands, Haag nunataks, Ellsworth-Whitmore block and Maurice Ewing Bank.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5612838

Atmospheric Visions: Mirages, methane seeps and ‘clam-monsters’ in the Yellow Sea

Mirages seen at sea have a long history of being interpreted as distant islands and mythological realms. Hot and cool pockets of air refracting light can make boats and islands appear as if floating in air. These atmospheric visions can be studied as physical phenomena and as cultural imaginaries, an extension of what Philip Hayward has called the aquapelagic imaginary. In alliance with Donna Haraway’s mythology-inspired Chthulucene, this article will use the Chinese folklore of the shen (蜃) (‘clam-monster’) to consider ecological issues around deep sea mining. In the ancient etiology of the shen, its breath was thought responsible for visions of Penglai, the fabled island home to the Eight Immortals believed to lie somewhere in the Yellow Sea. The search for Penglai and its rumored elixir of life has now been supplanted by exploration for methane, a largely untapped fossil fuel seeping up from the ocean floor. The clams and multi-species communities that cluster around these emissions, alongside mythological sea creatures, give shape to changing affects and atmospheres on the horizon.

Plate Tectonics

This chapter illustrates the most significant revolution in the understanding of the Earth discovered in the last 75 years, plate tectonics. The theory of plate tectonics is the second overarching precept of the field of geology (after the geologic time scale). Plate tectonics and its history as a theory are traced in this chapter. Early explorers and others had noticed the apparent fit in the shapes of the continents, but these ideas were not explicitly stated until Alfred Wegener detailed his evidence for the drift of the continents, though he had no viable mechanism on how the drift would have occurred. World War II technology, including sonar and radar, allowed scientists to understand the ocean floor. Rather than a flat, featureless plain, they found a vast undersea mountain range known as the mid-oceanic ridge that wraps around the world like seams on a baseball. Harry Hess proposed a new mechanism for continental drift through mantle convection cells, causing seafloor spreading. These ideas were confirmed by magnetic surveys and subsequent research, leading to the theory of plate tectonics. A final section looks at the maturation of the theory as geologists continue to learn more details about the movement and intricacies of the tectonic plates.

PREDICTING BOTTOM CURRENT DEPOSITION AND EROSION ON THE OCEAN FLOOR

Three types of oceanographic data are integrated in this study to predict thermohaline geostrophic bottom current deposition and erosion on the ocean floor. These data types are, 1) high-resolution bathymetry, 2) numerical model data of bottom current shear stress and 3) model data of the distribution and amount of sediment on the ocean floor. Intervals of thermohaline geostrophic bottom current deposition and erosion can be quantified from this information, which are then be extrapolated across the ocean floor in 4.5 x 9.3 km grid-size resolution. The results of this analysis are displayed on a map that shows the distribution of zones of bottom current erosion and deposition. This map is then cross-referenced for accuracy using documented examples of mapped erosional and depositional bottom current systems, which demonstrates this study’s approach has strong predictive capabilities. The model developed herein is used to derive boundaries for depositional bottom current regimes and formulate generalized patterns that contribute to bottom current erosion and deposition, and then discuss the importance of these interpretations for resource extraction and ocean floor mapping.

Getting to the Bottom of Trawling’s Carbon Emissions

A new model shows that bottom trawling, which stirs up marine sediments as weighted nets scrape the ocean floor, may be releasing more than a billion metric tons of carbon every year.