New Zealand scientists have figured out how tectonic plates move by blowing up dynamite beneath the earth's surface in the North Island.
The research, by Victoria University, has uncovered information about what happens underneath tectonic plates and how that affects the way they move around.
By detonating dynamite underground to generate seismic waves across the bottom half of the North Island, the scientists were able to see how the waves changed as they passed through different layers in the earth.
It provided geologists with the most detailed image to date of what the bottom of the Pacific Plate - which is 100km below the surface - looks like.
The study has helped scientists address the question of what actually moves plates around, something which the theory of plate tectonics - that the earth's surface consists of a mosaic of moving rigid plates - did not make clear when it was first proposed in the 1960s.
There are two possible explanations behind their movement.
The plates can be pulled or pushed along their edges; or they can be dragged along at their base by convection in the deeper parts of Earth's mantle.
If they're dragged, that would require the base of the plates to be more closely coupled to this underlying flow, say scientists.
The new images obtained by detonating dynamite underground show the tectonic plates gliding on a distinct layer of rock only 10km thick.
The layer's properties indicate it contains slippery molten rock that makes it much easier for the plates to slide on.
This means tectonic plates are mainly driven from the sides without strong resistance from the base, much like a ski sliding smoothly over snow.
The discovery of a weak, slippery base underneath plates also helps explain why tectonic plates can sometimes abruptly change the direction in which they are slipping.
The New Zealand-led study with contributions from GNS Science and universities in the United States and Japan was published in the international journal Nature.
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