How did the discovery about seafloor spreading modify the theory of Continental drift?

Answer 1

Seafloor spreading explained WHY and how Continental Drift occurs. How can lands be 'moving' without a catastrophic or even noticeable change--- seafloor spreading accounts for these small changes. It identifies where the actual changes take place (even if we cannot identify the exact spots where spreading occurs). We can better estimate how much the "spreading" equates to observable/measurable changes of continents, specifically how fast (slowly) continents are moving closer or further apart. Seafloor spreading explains other phenomena, too, like the expulsion of methane gas pockets at the ocean floor which are suspected to interfere with flotation of ships and possibly the downing of airplanes that pass over where methane is released when methane gas disrupts the air above the water. Seafloor spreading also gives clues as to how mountains and valleys form underwater and on land.