GL102 Lecture Notes - Lecture 16: North American Plate, Seafloor Spreading, Unconformity
Document Summary
Sometimes an island arc collides with a continent. As the arc and continent converge, the intervening ocean floor is destroyed by subduction. When collision occurs, the arc, like a continent, is too buoyant to be subducted. Continued convergence of the two plates may cause the remaining seafloor to break away from the arc and create a new site of subduction and a new trench seaward of the arc. Note that the direction of the new subduction is opposite the direction of the original subduction (this is sometimes called a flipping subduction zone), but it still may supply the arc with magma. The arc has now become welded to the continent, increasing the size of the continent. Some mountain belts form when an ocean basin closes and continents collide along a suture zone. Mountain belts that we find within continents (with cratons on either side) are believed to be products of continent-continent convergence. Our highest mountains are in the himalayan belt.
