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| Yakutat microplate | |
|---|---|
| Name | Yakutat microplate |
| Type | Terrane / Microplate |
| Location | Gulf of Alaska, Alaska, Canada |
| Coordinates | 59°N, 143°W |
| Area km2 | ~150000 |
| Plate boundaries | Pacific Plate, North American Plate, Explorer Plate |
| Notable features | Yakutat Block, St. Elias Mountains, Fairweather Fault, Queen Charlotte Fault |
Yakutat microplate is a small, independently moving oceanic terrane and microplate located along the northern Gulf of Alaska margin adjacent to southern Alaska and northwestern Canada. It is bounded by major features such as the Alaska Range, St. Elias Mountains, Fairweather Fault, and the Aleutian Trench, and it plays a central role in shaping the geology of the Yukon coast, British Columbia panhandle, and Alaska's southern margin. The microplate has been the focus of studies by institutions including the U.S. Geological Survey, Geological Survey of Canada, University of Alaska Fairbanks, and international collaborations involving researchers from Scripps Institution of Oceanography and Lamont–Doherty Earth Observatory.
The microplate occupies a region that links the continental margin near Yakutat Bay and the Copper River delta to offshore basins like the Gulf of Alaska and the Alaskan Shelf. Its extent includes exposures of the Yakutat Block terrane along the coastal strip between Icy Bay and the Klukwan area, and offshore bathymetric highs mapped by expeditions associated with the NOAA and the Canadian Hydrographic Service. Coastal towns and settlements such as Yakutat, Alaska, Glacier Bay National Park and Preserve, and communities in the Yakutat Borough, Alaska lie within the influence of its uplift and sediment dispersal. The microplate's boundaries intersect with seismic and volcanic provinces linked to the Aleutian Arc, the Queen Charlotte-Fairweather transform system, and the continental margin adjacent to the Yukon–Alaska border.
The Yakutat region lies at the complex junction of the Pacific Plate, the North American Plate, and the smaller Explorer Plate and Juan de Fuca Plate systems, with the picritic Yakutat microplate acting as an indenter against the continental margin. Along its eastern and southeastern flank it is juxtaposed against the Pacific Plate at the Aleutian Trench and the Wrangell subduction zone where oblique convergence generates the Fairweather Fault transform. To the west the plate interacts with the Queen Charlotte Fault transform system and the plate boundary near the Gulf of Alaska fracture zones; to the north it underlies parts of the uplifted St. Elias orogen. Mapping campaigns by the United States Geological Survey, Geological Survey of Canada, and academic teams have used GPS networks including stations from UNAVCO to better constrain slip partitioning and relative motion on these boundaries.
The terrane now referred to as the Yakutat microplate accreted to the North American margin during Neogene time after a long history of oceanic plateau and sedimentary deposition associated with the Pacific Ocean basin. Its provenance has been traced through lithologic correlations that involve comparisons to the Wrangellia Terrane, Chugach Terrane, and displaced fragments linked to Paleogene and Miocene plate reorganizations following events like the Closure of the Bering Strait and reconfiguration of the Aleutian Trench system. Paleomagnetic studies, stratigraphic correlations, and radiometric dating by teams at University of Washington and Memorial University of Newfoundland indicate episodic underthrusting and translation during the Pliocene and Pleistocene, contributing to rapid uplift of the St. Elias Mountains and widespread glacial erosion recorded in the Cordilleran Ice Sheet stratigraphy.
The Yakutat microplate region is a locus of frequent seismicity including megathrust, thrust, and strike-slip events that implicate hazards for communities and infrastructure in Alaska and British Columbia. Historical earthquakes recorded by the Alaska Earthquake Center and global networks include large events near the 1958 Lituya Bay tsunami source area and ruptures linked to the 1964 Alaska earthquake stress field. Geohazards such as tsunamis affecting the Gulf of Alaska coast, landslides in fjord systems like Disenchantment Bay, and glacier-related outburst floods involve interactions among the microplate, regional glaciers in Glacier Bay National Park and Preserve, and human settlements such as Yakutat, Alaska. Monitoring is performed by collaborations including Pacific Tsunami Warning Center and research initiatives funded by the National Science Foundation.
Convergence between the microplate and the North American Plate is accommodated by underthrusting beneath southern Alaska, strike-slip translation along the Fairweather Fault, and distributed shortening within the St. Elias orogen. The plate acts as an indenter, transferring compressive stress into the Alaska Range and contributing to uplift and seismic deformation across the Yukon margin. Offshore, interactions with the Pacific Plate influence sediment transport to the Gulf of Alaska and the formation of accretionary prisms studied by expeditions from the Woods Hole Oceanographic Institution and Fugro. Slip rates and coupling have been constrained using GPS campaigns led by Scripps Institution of Oceanography and modeling efforts by researchers at Caltech and the University of Alaska Fairbanks.
Surface expressions of the Yakutat microplate include the dramatic topography of the St. Elias Mountains, glacial fjords such as Yakutat Bay, and coastal forelands blanketed by glaciofluvial and marine sediments. Rock types exposed along the coastal strip and in the orogen comprise mélange, turbidites, basalts, and sedimentary successions correlated with the Chugach accretionary complex and elements of the Wrangellia Terrane. Erosional processes driven by outlet glaciers from the Bagley Icefield and the Brabazon Range interact with rapid tectonic uplift to create high rates of sediment flux documented in studies by USGS Coastal and Marine Geology Program and university research teams at University of British Columbia and Simon Fraser University.
Category:Tectonics Category:Geology of Alaska Category:Microplates