It is now believed that the several moving plates of the Earth's crust are formed by volcanic activity at the oceanic ridges and destroyed in great seafloor trenches at the margins of the continents, accounting for the massive redefinition of the Earth's surface over millenia.
(the several moving plates of the Earth's crust; destroyed; L:in great seafloor trenches; L:at the margins of the continents)
the several moving plates of the Earth's crust
destroyed
L:in great seafloor trenches L:at the margins of the continents