The Yakutat Block is a

terrane In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust (geology), crust fragment formed on a tectonic plate (or broken off from it) and Accretion (geology), accreted or "Suture (geology), sutured" to crust lying on another pla ...

in the process of accreting to the North American continent along the south central coast of

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S. ...

. It has been displaced about northward since the Cenozoic along the Queen Charlotte-Fairweather fault system. The Yakutat Block is bounded on the northeast by the Fairweather Fault, and on the north by a system of thrust and possibly strike-slip faults in the

Chugach Mountains The Chugach Mountains of southern Alaska are the northernmost of the several mountain ranges that make up the Pacific Coast Ranges of the western edge of North America. The range is about long and wide, and extends from the Knik and Turnagai ...

and St. Elias Mountains. The Yakutat Block is bounded on its southwest side by an as yet undefined underwater geologic feature known as the Transition Zone.

Global Positioning System The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...

(GPS) measurements indicate that the Yakutat block has a distinctive velocity relative to both the Pacific Plate and the

North American Plate The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Pacif ...

. Thus it appears to be a terrane in the process of accreting rather than a block already sutured on to the Pacific or North American plate. Relative to North America, the Yakutat Block moves at a rate of about to the north northwest, along the Fairweather fault. There is about of contraction between the Yakutat block and the Pacific plate, which is probably accommodated on an offshore structure. South of Yakutat Bay, the boundary between the Yakutat block and the North American plate is once again along the Fairweather Fault. North of Yakutat Bay, between Yakutat Bay and the Copper River/Wrangell Mountains region, about of contraction is taken up by compression, accommodated by faults within the continental crust. The convergence rate is among the highest in the world within continental crust, surpassing even that which is occurring between the

Indo-Australian Plate The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and the surrounding ocean and extends northwest to include the Indian subcontinent and the adjacent waters. It was formed by the fusion of the Indian an ...

and the

Eurasian Plate The Eurasian Plate is a tectonic plate that includes most of the continent of Eurasia (a landmass consisting of the traditional continents of Europe and Asia), with the notable exceptions of the Indian subcontinent, the Arabian subcontinent and ...

which is lifting the

Himalayas The Himalayas, or Himalaya (; ; ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the planet's highest peaks, including the very highest, Mount Everest. Over 10 ...

References

* Active Accretion of the Yakutat Block to North America, by Freymueller, J. T.; Larsen, C. F.; Fletcher, H. J.; Echelmeyer, K.; Motyka, R. J. Published 2002 by the American Geophysical Union

Terranes Geology of Alaska {{US-geology-stub