A large number of volcanoes with distinct origions are developed on the tectonic boundaries and interior of the Pacific plate, thus the Pacific Ocean is an excellent laboratory to study volcanism on Earth. This review finds out that, scientists have conducted systematic researches of volcanism at mid-ocean ridges, subduction zone island arcs, and intraplate mantle plumes, proposing classical models of decompression melting, slab dehydration-induced mantle melting, and plume-related high temperature mantle melting. However, the deep origins and shallow channels of non-plume intra-plate volcanoes are still poorly understood. To address these important scientific issues, comprehensive multi-disciplinary joint observations must be conducted in the future.

The greatest flexural bending of the oceanic lithosphere and major earthquakes occur at subduction zones. When the bending stresses exceed the rock yield strength, pervasive normal faulting and extensional earthquakes would be generated within subducting plates. Normal faulting provides conduits for fluids to reach the upper mantle and facilitates serpentinization. Extensional earthquakes could also trigger tsunamis. Thus, better understanding flexural bending, stress distribution, and brittle failure of the subducting plate is essential to study the mechanism of earthquake and Earth's water cycle. Based on summary of geophysical observations and geodynamic simulations of the most representative Japan, Izu-Bonin, Mariana and Yap subduction zone and Tonga-Kermadec subduction zone in the western Pacific Ocean, this paper presents overview of characteristics of plate bending, bending-related normal faulting and corresponding brittle yield zone. The distribution characteristics of bending-related normal faults in different subduction zones were analyzed, and the correlations between plate deformation and earthquakes were discussed. It reveals the potential plate hydration characteristics of bending plates with normal faults. This study provides a basis for the future research on the plate deformation mechanism of subduction zones.

In 2022, the Tonga volcanic eruption triggered a global tsunami. The widely observed volcanic tsunami attracts wide attention to such an atypical tsunami source in the academic world. In this paper, we review the historical records of volcanic tsunamis and summarize the triggering mechanisms into five categories:volcanic earthquake, volcanic structure instability, underwater explosion, pyroclastic flow and atmospheric pressure wave. We also briefly discuss the triggering mechanism of the 2022 Tonga volcanic tsunami event. It is pointed out that the future research directions of volcanic tsunamis are as follows:analyzing the temporal and spatial distribution of potential volcanic tsunamis from tectonics; Developing and perfecting the mechanism and propagation theory of potential volcanic tsunami with the emphasis on meteorological tsunami and underwater explosion; Solving the volcanic tsunami warning problems from the technical point.

The Hunga Tonga-Hunga Ha'apai (HTHH, 175.39°W, 20.55°S) volcano, which locates in the region of the volcanic chain of the southern Pacific Tonga subduction region, erupted on 15 January 2022, at 04:14 UTC. In this study, we review the state-of-the-art observations of the volcanic eruption and the triggered tsunami waves associated with the 2022 HTHH event, including submarine sensors, barograms, atmospheric wave observation from varies of satellites, and ionospheric disturbance. Together with the local geological setting and volcanic eruption history, we analyze the characteristics of the volcanic eruption and tsunamis feature of the HTHH event. Finally, we specify the prospects and direction of future research in marine geological hazards of global subduction zones, which includes detailed marine geophysical survey and comprehensive quantitative study of the potential impact of large-scale submarine volcanic eruption on global climate based on the latest observations.

The improvement of seismic monitoring in subduction zone remains a challenge, especially for densely populated areas. The eruption of the Hunga Tonga-Hunga Ha'apai volcano in January 2022 and subsequent earthquakes highlighted such urgency. This paper exhibits comprehensive seismological observations in Tonga, implying ongoing hazards in the short future in terms of small-scale volcanic eruptions. There is an urgent need to keep close watch on this very active volcano. Based on ocean bottom seismometer network data between 2009 and 2010 in Tonga, this paper applies novel machine learning algorithms to earthquake detections. The obtained high-resolution earthquake catalog is fundamentally important for a better understanding of the volcano structures and associated magmatic activities.

On January 15, 2022, an explosive and violent eruption occurred on the undersea volcano of Hunga Haapai Island in the southwest Pacific Ocean, attracting global attention. The Hunga Haapai Island is located in the Tonga-Kermadec subduction zone. Based on the previous research results, this paper makes a preliminary analysis of the geological structures, seismic and volcanic distribution of the Tonga-Kermadec subduction zone, and finds that (1) The forearc area of the Tonga-Kermadec subduction zone mainly develops large-scale normal faults; (2) The subduction of the Louisville Ridge Seamount Chain divides the Tonga-Kermadec subduction zone into the Tonga subduction zone in the north and the Kermadec subduction zone in the south. The plate aggregation rate along the Tonga subduction zone is 67-84 mm/a, and the plate aggregation rate along the Kermadec subduction zone is 41~58 mm/a. The difference in plate aggregation speed cause differences in the current subduction depth between the Tonga subduction zone and the Kermadec subduction zone; (3) North of the Louisville Ridge Seamount Chain, the thickness of the overburden sediment in the Pacific Plate is less than 0.4 km, and it reaches about 1 km on the south side. Differences in sediment thickness cause differences in earthquake generating capacity in the Tonga subduction zone and the Kermadec subduction zone. These understandings are of great significance for studying the volcanic eruption mechanism, the cause mechanism of major earthquakes and disaster risk in the subduction zone.

Oceanic plateaus are the most remarkable large igneous provinces in deep sea basins. They document massive magmatism in the oceans, and are important for better understanding crustal structure, plate tectonics, mantle geodynamics and Earth's evolution history. Oceanic plateaus are most developed in west Pacific Ocean, providing the optimal place to study their internal structure and formation. This paper selects six representative oceanic plateaus within west Pacific Ocean:Shatsky Rise, Hess Rise, Magellan Rise, Ontong Java Plateau, Manihiki Plateau and Hikurangi Plateau. We present brief geologic overview of each plateau and summarize major geophysical and geochemical observations. Based on the common characteristics of these plateaus, including massive topographic uplift, abnormally thick crust, negative mantle gravity anomaly, and formation on or near the mid-ocean ridge; the formation mechanisms are discussed, and the future investigations are suggested, i. e., interaction between mantle plume and mid-ocean ridge may be the main origin of oceanic plateaus.

The short-term surface carbon cycle on the Earth's surface affects global climate change and the Earth's livable environment. More than 90% of the carbon content is stored in the deep Earth. The long-term deep carbon cycle in the Earth's interior has an important impact on the surface carbon cycle. Studying the deep carbon cycle has an important indicator significance for the surface carbon cycle. The carbon cycle is one of the most cutting-edge issues in the interdisciplinary field of geoscience. This paper presented a brief overview of deep carbon cycle in different tectonic backgrounds, such as convergent plate boundary, discrete plate boundary, intraplate environment and new type seamount, and expounds the scientific problems that need to be studied in depth in the future, which may cause the peer to pay more attention to the relevant research of deep carbon cycle, such as decarbonization mechanism and efficiency of subduction zone, and the existing form of carbon in mantle, et al.