We can work this out in reverse.

The Atlantic widens about 1cm per year. Words contain about 6 characters on average. At 12 points, or 4mm tall, that comes to about 2x6=12mm for an average word, make it 15mm for ease and spaces,

If the ocean gains 15x100=1500mm (150cm) of word-width per second, thats 150x60x60x24x365 ~ 4.7 billion centimeters of word-space per year.

Given that it only moves about 1cm, that's a quick and dirty 4.7 billion lines of text.

At 5mm tall (4mm of text, 1mm whitespace between lines), that comes to 23 million meters. Since the earth is about 40.000km or 40 million meters in circumference, and adding in rounding numbers and suffering tectonic drift numbers, 4.7 billion lines seems about the right order of magnitude.

Edit: nope, it works out!

Companion trivia: Can the whole of text of the internet cover the entire Atlantic in 12 point type, and if not yet, when based on how fast it grows?

Secondary question: What font would be best, besides Papyrus?

Depends on the projection.