How will the tectonic regime in the Philippines evolve?
On this website, we attempted to create a synthesized view of the many complex interactions between the plates in the Philippine region. On this page, we will use that information, in addition to estimated plate velocities from the Plate Motion Calculator to qualitatively estimate what the evolution of this region could look like.
When using this calculator, we chose to fix the African Plate in order to determine the relative velocities of the plates.
When using this calculator, we chose to fix the African Plate in order to determine the relative velocities of the plates.
The South China Sea & The Sunda Plate
Since the Sunda Plate is being subducted beneath the Philippine Accreted Terrane, we hypothesize that, just as with Taiwan in the north, the Sunda plate will eventually be entirely subducted causing a transition to continental-arc collision. In this scenario, the Philippine Archipelago will be accreted onto the margin of Eurasia in a fashion analagous to the cordillera of North America.
The geometry of the subducted slabs beneath the Philippine Accreted Terrane is not clear in this scenario, since it is not certain if the "space problem" (see the section in General Tectonics) will force a change in the tectonic configuration. However, it is speculated that if Sunda is indeed fully subducted and the Philippines are accreted to the margin of Eurasia, the Philippine Sea Plate will be subducted beneath Eurasia, as it is comprised of relatively young, dense oceanic lithosphere, where as continental Eurasia is much more buoyant. We suggest that the Manila Trench will change configuration drastically, allowing the subduction of the PSP (i.e. its orientation becomes similar to that of the Ryukyu Trench). To do this, it is likely that complicated slab tear mechanisms would need to be invoked.
Since the Sunda Plate is being subducted beneath the Philippine Accreted Terrane, we hypothesize that, just as with Taiwan in the north, the Sunda plate will eventually be entirely subducted causing a transition to continental-arc collision. In this scenario, the Philippine Archipelago will be accreted onto the margin of Eurasia in a fashion analagous to the cordillera of North America.
The geometry of the subducted slabs beneath the Philippine Accreted Terrane is not clear in this scenario, since it is not certain if the "space problem" (see the section in General Tectonics) will force a change in the tectonic configuration. However, it is speculated that if Sunda is indeed fully subducted and the Philippines are accreted to the margin of Eurasia, the Philippine Sea Plate will be subducted beneath Eurasia, as it is comprised of relatively young, dense oceanic lithosphere, where as continental Eurasia is much more buoyant. We suggest that the Manila Trench will change configuration drastically, allowing the subduction of the PSP (i.e. its orientation becomes similar to that of the Ryukyu Trench). To do this, it is likely that complicated slab tear mechanisms would need to be invoked.
The "Mariana Segment", the Pacific Plate, and the Relationship to the PSP
From the Plate Motion Calculator, the current plate velocity for the PSP (holding Africa fixed, using the NUVEL-1A model) is approximately 7 cm/year in a northwest direction. This is consistent with the values determined in the literature. Assuming this rate does not change substantially, the evolution of the PSP and the Pacific Plate depends heavily on the nature of the Mariana Trough.
If the Mariana Trough produces new oceanic crust at a rate much slower than the rate of the PSP's hypothesized subduction beneath Eurasia, it is likely the PSP will shrink over geologic time. However, if the rate of seafloor spreading exceeds the subduction rate, it is likely the PSP will grow, and continue to override the Pacific Plate. This scenario would be very likely in the case that oceanic crust production is unbalanced, with more crust being produced on the east side of the spreading center than the west. It is not clear if an elevated spreading rate would simply lead to a greater ridge-push force, and thus greater subduction rate beneath the Eurasian continent. If, as suggested, the Mariana sliver grows, eventually it could become a significant plate overriding the Pacific Plate, still related to the PSP by the seafloor spreading center.
From the Plate Motion Calculator, the current plate velocity for the PSP (holding Africa fixed, using the NUVEL-1A model) is approximately 7 cm/year in a northwest direction. This is consistent with the values determined in the literature. Assuming this rate does not change substantially, the evolution of the PSP and the Pacific Plate depends heavily on the nature of the Mariana Trough.
If the Mariana Trough produces new oceanic crust at a rate much slower than the rate of the PSP's hypothesized subduction beneath Eurasia, it is likely the PSP will shrink over geologic time. However, if the rate of seafloor spreading exceeds the subduction rate, it is likely the PSP will grow, and continue to override the Pacific Plate. This scenario would be very likely in the case that oceanic crust production is unbalanced, with more crust being produced on the east side of the spreading center than the west. It is not clear if an elevated spreading rate would simply lead to a greater ridge-push force, and thus greater subduction rate beneath the Eurasian continent. If, as suggested, the Mariana sliver grows, eventually it could become a significant plate overriding the Pacific Plate, still related to the PSP by the seafloor spreading center.
The Wild South
The literature is not conclusive as to the relative motions and evolution of the complicated arc terrane between the Indo-Australian plate, the Caroline Plate, the PSP, and the Sunda Plate. The future of the T-T-F triple junction in the region is not clear. Perhaps the sinistral Sorong Fault (the 'Fault' in the TTF triple junction) will displace the landmass of New Guinea westward, toward the Sunda Plate, which, in the context of our above speculation, might suggest it will eventually get accreted onto Eurasia's continental margin. According to the Plate Motion Calculator (keeping the same conditions as before), Australia migrating in a dominantly northward direction (consistent with it being coupled with India) at a rate of approximately 7 cm/year. If this rate is maintained, we speculate that the Australian Plate will continue to override the Caroline and Sunda plates.
The literature is not conclusive as to the relative motions and evolution of the complicated arc terrane between the Indo-Australian plate, the Caroline Plate, the PSP, and the Sunda Plate. The future of the T-T-F triple junction in the region is not clear. Perhaps the sinistral Sorong Fault (the 'Fault' in the TTF triple junction) will displace the landmass of New Guinea westward, toward the Sunda Plate, which, in the context of our above speculation, might suggest it will eventually get accreted onto Eurasia's continental margin. According to the Plate Motion Calculator (keeping the same conditions as before), Australia migrating in a dominantly northward direction (consistent with it being coupled with India) at a rate of approximately 7 cm/year. If this rate is maintained, we speculate that the Australian Plate will continue to override the Caroline and Sunda plates.
The (Immensely) Speculative Diagram for the Evolution of the Philippine Region: