I hope someone who actually knows their stuff can fill in the details but here's something amazing: it's possible the remains of a subducted plate (known as a "slab") to stick around as a distinct entity within the mantle for an extremely long time.
A diagram on that page shows a model of the "Farallon Slab" believed to lie beneath North America.
DisillusionedExLib t1_jb44z8w wrote
Reply to What happens at the end of a subduction zone? When the entire plate subducts? by kittens0423
I hope someone who actually knows their stuff can fill in the details but here's something amazing: it's possible the remains of a subducted plate (known as a "slab") to stick around as a distinct entity within the mantle for an extremely long time.
A diagram on that page shows a model of the "Farallon Slab" believed to lie beneath North America.