How were the magnetic patterns on the seafloor discovered?

With sensitive scientific instuments

Explanation:

"Scientists found that stripes of rocks that formed when Earth's magnetic field pointed north alternate with stripes of rock that formed when the magnetic field pointed south." - Phschool.com

for e2020. the answer would be some directions from the mountain range so we can find mt. whitney. to locate which direction is north, you should use a   compass. this would not only find mt. whitney, but also becuase of this long paragraph you would get points because it's not like anyone actually reads your work becuase once they read the first sentence it sounds dumb enough to not read becuase i'm not good at answering this but the answer is compass for your benefit.

for e2020 ; -;