Alaska Time Zone to 03:00 LDT on the second Sunday in March and returns at 02:00 LDT to 01:00 LST on the first Sunday in November. Two time zones have been referred to as the "Alaska Time Zone": a zone based on UTC−10 that covered much of Central Alaska in the early 20th century, and a zone based on UTC−9 zone that has covered all of the state except the Aleutian Islands since 1983. The Standard Time Act of 1918 authorized the Interstate Commerce Commission to define each time zone. The United States Standard Alaska Time was designated as UTC−10. Some references prior
Aleutian subduction zone rocks, with trace amounts of Paleozoic rocks intruded by Mesozoic batholiths. Most of the Aleutian Islands are composed of sedimentary rocks from granitic and metamorphic rocks from Oligocene-Miocene. There are Quaternary volcanoes on the north of the Aleutian Islands structural axis, which is composed of andesite mostly, mixed with olivine basalt to rhyolite. The eastern Aleutian volcanoes have more silicic magma while the western Aleutian arcs lack the sial magma. The Aleutian Trench formation is associated with the subduction of the Pacific Plate beneath the North American plate. The horizontally-curved shape of the trench is due to the change in