The Yakutat Block is a fragment of oceanic crust and overlying sedimentary rocks that has been accreted onto the southern margin of Alaska. This block is significant in tectonics and seismology for its role in the active deformation and seismicity of southern Alaska, the uplift of the St. Elias Mountains, and the ongoing collision between the Pacific Plate and North America.
Reference: Plafker, G., & Berg, H. C. (1994). “The Geology of Alaska.” Geological Society of America.