Crustal structure of the Kermadec arc from MANGO seismic refraction profiles

Three active-source seismic refraction profiles are integrated with morphological and potential field data to place the first regional constraints on the structure of the Kermadec subduction zone. These observations are used to test contrasting tectonic models for an along-strike transition in margin structure previously known as the 32°S boundary. We use residual bathymetry to constrain the geometry of this boundary and propose the name Central Kermadec Discontinuity (CKD). North of the CKD, the buried Tonga Ridge occupies the forearc with VP 6.5–7.3 km s-1 and residual free-air gravity anomalies constrain its latitudinal extent (north of 30.5°S), width (110 ± 20 km) and strike (~005° south of 25°S). South of the CKD the forearc is structurally homogeneous down-dip with VP 5.7–7.3 km s-1. In the Havre Trough backarc, crustal thickness south of the CKD is 8-9 km, which is up-to 4 km thinner than the northern Havre Trough and at least 1 km thinner than the southern Havre Trough. We suggest that the Eocene arc did not extend along the current length of the Tonga-Kermadec trench. The Eocene arc was originally connected to the Three Kings Ridge and the CKD was likely formed during separation and easterly translation of an Eocene arc substrate during the early Oligocene. We suggest that the first-order crustal thickness variations along the Kermadec arc were inherited from before the Neogene and reflect Mesozoic crustal structure, the Cenozoic evolution of the Tonga-Kermadec-Hikurangi margin and along-strike variations in the duration of arc volcanism

Reconstructing subducted oceanic lithosphere by "reverse-engineering" slab geometries: The northern Philippine Sea Plate

Peer reviewe

Mantle flow in regions of complex tectonics: insights from Indonesia

Indonesia is arguably one of the tectonically most complex regions on Earth today due to its location at the junction of several major tectonic plates and its long history of collision and accretion. It is thus an ideal location to study the interaction between subducting plates and mantle convection. Seismic anisotropy can serve as a diagnostic tool for identifying various subsurface deformational processes, such as mantle flow, for example. Here, we present novel shear wave splitting results across the Indonesian region. Using three different shear phases (local S, SKS, and downgoing S) to improve spatial resolution of anisotropic fabrics allows us to distinguish several deformational features. For example, the block rotation history of Borneo is reflected in coast-parallel fast directions, which we attribute to fossil anisotropy. Furthermore, we are able to unravel the mantle flow pattern in the Sulawesi and Banda region: We detect toroidal flow around the Celebes Sea slab, oblique corner flow in the Banda wedge, and sub-slab mantle flow around the arcuate Banda slab. We present evidence for deep, sub-520 km anisotropy at the Java subduction zone. In the Sumatran backarc, we measure trench-perpendicular fast orientations, which we assume to be due to mantle flow beneath the overriding Eurasian plate. These observations will allow to test ideas of, for example, slab–mantle coupling in subduction regions

Tectonic evolution of the southwest Pacific using constraints from backarc basins

We present a revised model for the formation of southwest Pacific backarc basins from 120 Ma to the present day. Our aim is to improve our understanding of the tectonic regime operating in the region and its consequences for global plate motions. Such an understanding helps explain present-day structures observed on the continental and oceanic lithosphere and the underlying mantle. Regional plate reconstructions were created using gravity and magnetic data from backarc basins, plate-circuit closure, global tomography and existing geological data. Our model predicts convergence between the Australian and Pacific Plates along the Norfolk Ridge from 120 to 100 Ma, followed by the fragmentation of East Gondwana. East-dipping subduction east of Australia was initiated at ca 90 Ma along the Loyalty-Three Kings Ridge and may have trapped Cretaceous quiet-zone crust In the Norfolk Basin. The inception of this subduction system may have provided a driving mechanism for the opening of the Tasman Sea by means of slab pull. A jump in subduction to the east was subsequently initiated along a west-dipping subduction system at ca 45 Ma driven by the collision of the Loyalty Arc with New Caledonia. Consequently, spreading in the North Loyalty Basin occurred by anticlockwise rotation of the subduction hinge between chrons 20 and 16 (43.8–35.3 Ma). This was concurrent to Norfolk Basin opening and formation of the Cook Fracture Zone. Backarc-basin formation then transferred to the South Fiji Basin where magnetic anomalles from chron 12 to 7N (30.9–25.2 Ma) have been identified as two contemporaneous triple junctions. The complex spreading regime witnessed in the South Fiji Basin appears analogous to the North Fiji Basin and may represent the surface expression of a hot, shallow mantle consistent in character to a superswell. The South Fiji Basin ceased forming at ca 25 Ma in response to a major plate reorganisation coinciding with the inception of the Alpine Fault, docking of the Ontong Java Plateau with the Melaneslan Arc and transpressional obduction of the Northland ophiollte. A lull in basin formation throughout most of the Miocene was followed by the reinitiation of backarc basin formation in the Lau Basin (during the past ∼7 million years) and North Fiji Basin (during the past ∼10 million years). All these apparent episodes of backarc-basin formation during the past 45 million years are possibly related to mantle-slab interaction at the 670 km discontinuity

Ethical Tourism: The Theory Vs. The Hedonistic Reality in Popular Greek Tourism Resorts

Tourism has many uses and benefits for local societies, but in many cases a number of negative impacts too. The most important is the environmental impact that mass tourism may create. The tourists sometimes do not respect the cultural and the environmental profile of the country, creating a lot of problems. This is more frequent amongst young people that have not received sufficient education to recognise the importance of culture and traditions outside their own countries. Another serious problem that may arise is that only few people may benefit from tourism and money leaks outside the local community. Besides this, there is also a dark side of the lucrative business of mass tourism: violence by, and between, tourists and sex crimes such as rape. This is mainly attributed to large numbers of young tourists aiming at the consumption of large amounts of cheap alcohol. Drunken male tourists may end up fighting with each other or even harassing female tourists, or even raping them. The aim of this paper is to fill in this gap in the literature regarding this type of tourist behaviour in the Greek resorts: Faliraki and Kavos, by emphasizing actions taken as to prevent these kind of incidents and by focusing on the ethical issues surrounding them. This is a literature review which aims on initiating a discussion, which will lead the way for future research in the area. © 2019, Springer Nature Switzerland AG

Response to comment on "Major Australian-antarctic plate reorganization at Hawaiian-emperor bend time"

Accurately locating boundaries between continental and oceanic crust is topical in view of locating offshore boundaries relevant to margin formation models, plate kinematics, and frontier resource exploration. Although we disagree with Tikku and Direen's interpretations, the associated controversies reflect an absence of agreed-upon geophysical criteria for distinguishing stretched continental from oceanic crust, and a lack of samples from nonvolcanic margins.</p