The Yakutat Block is a
terrane in the process of
accreting to the North American continent along the south central coast of
Alaska. It has been displaced about northward since the
Cenozoic
The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...
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 and
St. Elias Mountains
The Saint Elias Mountains (french: Chaîne Saint-Élie) are a subgroup of the Pacific Coast Ranges, located in southeastern Alaska in the United States, Southwestern Yukon and the very far northwestern part of British Columbia in Canada. The range ...
. 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
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate.
The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and Iza ...
and the
North American Plate. 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 and the
Eurasian Plate which is lifting the
Himalayas.
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