Southeast Asia has had both volcanic tsunamis and possesses some of the most densely populated, economically important and rapidly developing coastlines in the world. This contribution provides a review of volcanic tsunami hazard in Southeast Asia. Source mechanisms of tsunami related to eruptive and gravitational processes are presented, together with a history of past events in the region. A review of available data shows that many volcanoes are potentially tsunamigenic and present often neglected hazard to the rapidly developing coasts of the region. We highlight crucial volcanic provinces in Indonesia, the Philippines and Papua New Guinea and propose strategies for facing future events.
6The thermal evolution of planets during their accretionary growth is strongly 7 influenced by impact heating. The temperature increase following a collision 8 takes place mostly below the impact location in a volume a few times larger 9 than that of the impactor. Impact heating depends essentially on the radius of 10 the impacted planet. When this radius exceeds ∼ 1000 km, the metal phase 11 melts and forms a shallow and dense pool that penetrates the deep mantle 12 as a diapir. To study the evolution of a metal diapir we propose a model 13 of thermo-chemical readjustment that we compare to numerical simulations in 14 axisymmetric spherical geometry and with variable viscosity. We show that the 15 metallic phase sinks with a velocity of order of a Stokes velocity. The thermal 16 energy released by the segregation of metal is smaller but comparable to the 17 thermal energy buried during the impact. However as the latter is distributed 18 in a large undifferentiated volume and the former potentially liberated into a 19 much smaller volume (the diapir and its close surroundings) a significant heating 20 of the metal can occur raising its temperature excess by at most a factor 2 or 3. 21When the viscosity of the hot differentiated material decreases, the proportion 22 of thermal energy transferred to the undifferentiated material increases and a 23 protocore is formed at a temperature close to that of the impact zone. 24 3 planets, a local differentiation may occur between heavy metal and light silicates 54 in the heated anomaly (Tonks and Melosh, 1992). Hence, a thermo-chemical 55 readjustment follows, associated with the sinking of the metallic component 56 toward the center of the impacted protoplanet ( Fig. 1). 57For large planets, gravitational energy release due to core formation can 58 induce melting of the whole planet (Stevenson, 1989; Ricard et al., 2009). This 59 subsequent melting depends on the mechanisms of the metal descent (Samuel 60 and Tackley, 2008; Golabek et al., 2008). The aim of this study is to determine 61 the thermal evolution of metal during descent and the thermal state of the core. 62First, we propose analytical and numerical isoviscous models of segregation 63 of a purely spherical iron diapir. As the viscosity contrast between molten metal 64 and undifferentiated cold material can reach several orders of magnitude, we 65 then focus on more realistic models of segregation of metal after a large impact 66 with temperature dependent rheologies. We show that the size of impactors and 67 viscosities involved largely determine the inner thermal state of a young planet. 68 2. Thermo-chemical state after large impact 69 2.1. Thermal state 70 After a meteoritical impact, heating is localized in a spherical region called 71 the isobaric core just beneath the impact site. The radius of the isobaric core 72 R ic is comparable to the radius of the impactor R imp and depends on en-73 ergy conversion during the shock. With a minimal set of assumptions, we get 74 R ic = 3 1/3 R imp following Senshu et...
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