continental borderland is the region beyond the continental margin.
continental borderland is the region beyond the continental margin.
what is the region beyond the continental margin?
continental borderland
continental margin









































the continental margin is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. the continental margin is the shallow water area found in proximity to continent. the continental margin consists of three different features: the continental rise, the continental slope, and the continental shelf. continental margins constitute about 28% of the oceanic area.
continental margin
the first event began 130 million years ago when a group of active volcanic islands approached a pre-existing continental margin and coastline of north america. these volcanic islands, known as the insular islands by geoscientists, were formed on a pre-existing tectonic plate called the insular plate by subduction of the former farallon plate to the west during the early paleozoic era. this subduction zone records another subduction zone to the east under an ancient ocean basin between the insular islands and the former continental margin of north america called the bridge river ocean. this arrangement of two parallel subduction zones is unusual in that very few twin subduction zones exist on earth; the philippine mobile belt off the southeastern coast of asia is an example of a modern twin subduction zone. as the insular plate drew closer to the pre-existing continental margin by ongoing subduction under the bridge river ocean, the insular islands drew closer to the former continental margin and coastline of western north america, supporting a pre-existing volcanic arc on the former continental margin of north america called the omineca arc. as the north american plate drifted west and the insular plate drifted east to the old continental margin of western north america, the bridge river ocean eventually closed by ongoing subduction under the bridge river ocean. this subduction zone eventually jammed and shut down completely 115 million years ago, ending the omineca arc and the insular islands collided, forming the insular belt. compression resulting from this collision crushed, fractured and folded rocks along the old continental margin. the insular belt then welded onto the pre-existing continental margin by magma that eventually cooled to create a large mass of igneous rock, creating a new continental margin. this large mass of igneous rock is the largest granite outcropping in north america.
coast mountains