A year‐long acoustic survey for critically endangered North Atlantic right whales was conducted at two sites on the central and western Scotian Shelf. Autonomous hydrophones recorded sound continuously from July 2004 to August 2005. Right whale contact calls (upcalls) were identified using automatic recognition software, and the resulting detections were checked manually. Substantial numbers of hours with upcalls were observed at both sites, with approximately four times as many hours with calls at the western site as the central one. Calls occurred mainly from August through October, with the earliest calls in late June and the latest at the end of December at both sites. In addition to this seasonal trend, there was a significant diel pattern in calling at the central site but not at the more westerly site. Results are analyzed in light of feeding ecology and broad‐scale movements of right whales.

We present multiple lines of evidence for years to decade-long changes in the location and character of volcanic activity at West Mata seamount in the NE Lau basin over a 16 year period, and a hiatus in summit eruptions from early 2011 to at least September 2012. Boninite lava and pyroclasts were observed erupting from its summit in 2009, and hydroacoustic data from a succession of hydrophones moored nearby show near-continuous eruptive activity from January 2009 to early 2011. Successive differencing of seven multibeam bathymetric surveys of the volcano made in the 1996-2012 period reveals a pattern of extended constructional volcanism on the summit and northwest flank punctuated by eruptions along the volcano's WSW rift zone (WSWRZ). Away from the summit, the volumetrically largest eruption during the observational period occurred between May 2010 and November 2011 at 2920 m depth near the base of the WSWRZ. The (nearly) equally long ENE rift zone did not experience any volcanic activity during the 1996-2012 period. The cessation of summit volcanism recorded on the moored hydrophone was accompanied or followed by the formation of a small summit crater and a landslide on the eastern flank. Water column sensors, analysis of gas samples in the overlying hydrothermal plume and dives with a remotely operated vehicle in September 2012 confirmed that the summit eruption had ceased. Based on the historical eruption rates calculated using the bathymetric differencing technique, the volcano could be as young as several thousand years.

Volcanoes at spreading centres on land often exhibit seismicity and ground inflation months to years before an eruption, caused by a gradual influx of magma to the source reservoir [1][2][3][4] . Deflation and seismicity can occur on time scales of hours to days, and result from the injection of magma into adjacent rift zones [5][6][7][8] . Volcanoes at submarine rift zones, such as Axial Seamount in the northeast Pacific Ocean, have exhibited similar behaviour [9][10][11][12] , but a direct link between seismicity, seafloor deformation and magma intrusion has never been demonstrated. Here we present recordings from ocean-bottom hydrophones and an established array of bottom-pressure recorders that reveal patterns of both microearthquakes and seafloor deformation at Axial Seamount on the Juan de Fuca Ridge, before it erupted in April 2011. Our observations show that the rate of seismicity increased steadily during a period of several years, leading up to an intrusion and eruption of magma that began on 6 April 2011. We also detected a sudden increase in seismo-acoustic energy about 2.6 h before the eruption began. Our data indicate that access to real-time seismic data, projected to be available in the near future, might facilitate short-term forecasting and provide sufficient leadtime to prepare in situ instrumentation before future intrusion and eruption events.

NW Rota-1 is a submarine volcano in the Mariana volcanic arc that is notable as the site where underwater explosive eruptions were fi rst witnessed in A.D. 2004. After years of continuous low-level eruptive activity, a major landslide occurred at NW Rota-1 in August 2009, triggered by an unusually large eruption that produced 10 times the acoustic energy of the background level of activity. An anomalous earthquake swarm preceded the eruption, suggesting that the sequence started with a magmatic intrusion and associated faulting beneath the volcano. We quantify the size and extent of the landslide using bathymetric resurveys and interpret the timing of events using data from an in situ hydrophone. This is the fi rst instrumental documentation of an earthquake-eruption-landslide sequence at a submarine volcano, and illustrates the close interaction between magmatic activity and mass wasting events in the growth of undersea arc volcanoes.