I showed up to the interview dressed to the nines, post double shot latte, and mentally prepped only to be ushered to a hallway lined with chairs and a dozen other potential applicants already waiting their turn. I knew I needed something to make me stand out if I had any chance of securing the job.
Answer 1: At plate boundaries where sea-floor spreading occurs, magma wells up to fill the space created by the plates that are moving apart. Check out this United States Geologic Survey (USGS) educational animation to see visually how it works:
Plate Tectonics. Vine and Matthew's discovery of the magnetic striping on the sea floor showed that Hess' idea of sea-floor spreading was correct; oceans and continents moved together and the mid ocean ridges actually are areas where new ocean floor is created.