| North Bismarck plate | |
|---|---|
 | |
| Type | Minor |
| Movement1 | north-west |
| Speed1 | nil independent of Pacific plate which has 96 mm/year |
| Features | Pacific Ocean |
| 1Relative to theAfrican plate | |
TheNorth Bismarck plate is a smalltectonic plate located in theBismarck Sea off the northeast coast ofNew Guinea. It is currently regarded as a relic or inactive plate by most.[3][2] At one time it was called the Manus plate, but this term was later used for a modelled microplate at the south east boundary of the North Bismarck plate.[1]: 22
The plate contains most of the Melanesian arc volcanoes, related to current and historic arc volcanism, except those ofNew Britain which are on the activeSouth Bismarck plate.[2]
To the north it has collided with thePacific plate and theCaroline plate, part of the western part is subducting under other active plates inNew Guinea, and it is separated from the South Bismarck plate by adivergent boundary called theBismarck Seismic Sea Lineation (BSSL).[4] The BSSL is a very seismically active area but the assigned shallow earthquakes tend to be less than magnitude 7.[5] The plate is moving westerly along with thePacific plate.[2] Between the plate and theCaroline plate is theWest Melanesian Trench and between the plate and the Pacific plate is theKilinailau Trench.[2] Neither trench has good evidence for current subduction activity but were certainly historically active.[2]: 68 There are a few shallow low intensity earthquakes to the south/south west of these trenches on a line of the old arc that extends from the smaller northern Admiralty Islands in the west through toMussau Island and beyond.[6]
