Question

how did research about the sea floor in the second half of 1900 affect scientific thought about continental drift

Answer 1

Scientists now think that the continents are not actually drifting, but are parts of giant, moving plates. This evidence is from mapping the sea floor and discovering patterns.

Answer 2

Afred Wegener found that large bodies of earth that were previously considered "stuck together" were actually drifting and moving apart. This inspired and largely produced new research into continental drift wherein the continents previously had all fit together perfectly. This inspired the idea for the ancient super-continent "Pangea".