Wow. An actual geology question I know the answer to (you have NO idea how rare that is). Pick me! Pick me!
There are three different reasons for intraplate islands: hot spots (weak areas of the crust where stationary thermal plumes in the upper mantle create volcanos which then drift away as the plate moves on - ex. Hawaiian chain); tectonic control clusters (rather than plate boundaries, these clusters lie along shorter lines of crustal weakness - ex. Canary Islands and Cape Verde Islands); and isolates (former ridge islands that broke off from the ridge and went sailing out on their own carried by the newly formed plate fragment - ex. Asencion and St. Helena). In addition, some intraplate islands may actually be fomer continental fragments that went off on their own (the Seychelles is an example - there's good bathymetry to show a continuous basement associated with the Madagascar-India part of old Gondwanaland).
So coach, did I pass?
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