Why are there small islands far away from continents?

Question

Per my understanding, the ocean is largely very deep.

I can understand why there might be small, not-mountainous islands near the coasts of major landmasses, as it would only take a marginal elevation anomaly to create one there, but: How do places like Polynesia exist?

In: Other

Answer 1

Often they over volcanic hotspots so they are huge mountains if you measure from the seafloor. Hawaii the hot spot is moving (or the crust is) resulting in a chain of islands.