The triangle is formed by lines of equal age in the ocean floor derived from bands of alternating magnetism as the earth’s pole flipped. It is one of the great mysteries discussed previously. The ocean floor gets progressively older from all three sides towards a small triangle in the middle. If this were the remains a hot spot where ocean floor was emerging and spreading out, it would be progressively younger toward the center.
How could such a feature form? One possibility is that it is the signature of a sink hole, the tectonic opposite of a hot spot. Another possibility is that the tiny center triangle marks a place where three ridges arose at the same time and spread away. Interesting regarding either possibility is that the signature of the Mendocino Fracture Zone (visible extending to the right all the way to the Juan De Fuca Ridge) telegraphs back to the 170mya chron. The Murray and Molokai Fracture Zones further south seem to bottom out at 150mya.
Here is an image of a map by Christopher Scotese showing the isochrons for the whole world. The age is RGB, with red the youngest and blue the oldest. You can see that ocean floor emerges at the spreading ridges and spreads in both directions. Bilateral spreading.
Here is Scotese at the beginning of ocean floor time 180mya. There is actually some 250mya ocean floor north and east of Africa discussed previously, but it is of little importance here. Contemplate the sheer mass of ocean floor showen white here that all gets subducted one way or another to make room for what we see today.
Unfortunately the Pacific Triangle gets divided between the lower right and left in this projection, but there it is, starting out rather too large at 170mya, but infilling properly with older material at 160 and 150mya. What Scotese is saying here is that he believes it was ridges propagating from the tiny triangle. Notice that the Triangle is the only place ocean floor is formed away from a continent, and that continental rifting seems unilateral (one sided). We see no bilateral spreading before 150mya.
Interesting. If this is correct, the Juan de Fuca Ridge is a remnant of the original troika and its signature can be traced back to the 170mya isochron.