Abstract Charles Darwin's research during the second voyage of HMS Beagle is examined within the context of Charles Lyell's ideas on crustal movement. Darwin's pre-voyage training is summarized and the impact on his own subsequent theorizing of his commitment early in the voyage to a Lyellian theoretical framework is analysed. Two sites studied by Darwin which he interpreted as strong support for Lyell's theory of vertical crustal mobility are examined: the first is Signal Post Hill in the Cape Verdes, visited in 1832; the second is Agua de la Zorra in Argentina, visited in 1835. Darwin's work at both sites was key to his first theory of globally-balanced elevation and subsidence as an explanation for the structure and distribution of coral reefs. The case is made that both sites are of international geoheritage importance and that their protection should be assured with enhanced access and interpretation.

Abstract Some significant geological sites are inaccessible. Among the most inaccessible sites are the hydrothermal vents and their associated biological communities located deep in the ocean. These prime geoheritage sites, hosting what may be the most primordial life on Earth, are vulnerable to mineral and fishing exploitation. Many lie in international waters, protected only by non-binding agreements with no clearly defined means of enforcement. The discovery of these vents in 1977 fundamentally altered scientists’ view of basic Earth processes and the extreme conditions under which life can exist. The discovery of the vents was a group effort and required technological accomplishments not available to previous generations of researchers. Often overlooked in the credits for this discovery was the persistence and determination of Kathleen Crane, a graduate student at Scripps Institution of Oceanography. Many women of her era faced significant challenges as they attempted to break into an often-unwelcoming field, marine geology. The challenges were not unique to geology; women were not welcomed in many other disciplines, both scientific and non-scientific. In spite of the obstacles, few people have made as remarkable a geoscience discovery as Dr Crane.

Abstract Mass transport deposits have long been known on the Exmouth Plateau, offshore NW Australia, identified in 2D and 3D industry seismic lines. The expedition SO257 in 2017 collected 30 high-resolution, shallow seismic lines along targeted transects on the northern Australian margin. Many of these imaged mass transport deposits, with the top 700–800 m of the section captured in detail not available with industry seismic data. We present nine new high-resolution seismic lines from three separate areas of the North West Shelf. Slides in the Roebuck Basin show complex anastomosing ductile extensional mechanisms, with multiple slip surfaces and no headscarps or adjacent faults. Slides on the Exmouth Plateau have fault control, with surface fault offsets of up to 300 m, indicating seismicity as a likely triggering mechanism. Slumps along the western margin of Western Australia are more limited in extent, associated with surface notches, with indications of previous activity at depth. All areas show a repeated history of mass transport deposits. The area of the active landslide province offshore of NW Australia is far larger than the individual slides recognized on the Exmouth Plateau.

Abstract The IGUANES cruise took place in May 2013 on the R/V L’Atalante along the Demerara passive transform margin off French Guiana and Surinam. Seismic, multibeam and chirp acquisitions were made. Piston cores were collected for pore geochemistry and sedimentology. A mooring was deployed on the sea-bottom for 10 months (temperature, salinity, turbidity and current measurements). This new dataset highlights the lateral variability of the 350 km-long Guiana–Surinam transform margin due to the presence of a releasing bend between two transform segments. The adjacent Demerara Plateau is affected by a 350 km-long giant slide complex. This complex initiated in Cretaceous times and was regularly reactivated until recent times. Since the Miocene, contourite processes seem to be active due to the onset of the North Atlantic Deep Water (NADW) bottom current. A main NADW water vein flows towards SE, eroding slide headscarps and allowing the deposition of contourite drifts. Numerous depressions looking like comet tails or comet scours record this flow. Some of those were interpreted before the cruise as active pockmarks. Pore geochemistry and core analysis do not show any evidence of present-day gas seepage.