Why are all Continents Gone from Earth 1 million years into the future?

I think the timeline we are presently on (or another one) creates this from Global Climate changes eventually.

This doesn't all happen at once by the way and many people from Earth will colonize other planets before this happens by the way.

However, this does appear to be Earth 1 million years into the future.

One of the clues is that Eridian(Meridian) live in an underground Crystalline city under Boone, North Carolina where Arcane arrives on earth having been banished there by Tech Noir of Isfahel (Mars) during the same era as Arcane's birth.

So, since Meridian is in an underground Crystalline city it might make sense why people are living underground then. However, it is also true that no humans in physical form are allowed on earth then because it is in a demilitarized zone at that time where no physical humans are allowed anymore.

So, Eridian (Meridian) has waited a long time for someone evolved like Arcane to show up to make him sort of like a Knight of Earth to send through time to help create a better earth in the past, present and future.

At the time ARcane Meets Meridian(Eridian) there are still wolves and trees on earth and continents. So, obviously something happens between 800,000 AD and 1 million AD to where all the continents have gone. 

I have speculated before that it is the winds and water slamming into the continents over time. However, it is also possible that all the continents are gone from some kind of space weapon which might make sense given the fact that Earth is a demilitarized zone in an interplanetary battle in 800,000 AD. 

So, technically speaking it is illegal for any human physical being to be on earth at all in 800,000 AD. However, it is also true that Meridian is the Time Lord of Earth just like His Oneness of Lemuria was the previous time lord of Earth Sanctioned by the Galactic Sentience who is the leader of the Galaxy. So, demilitarized zone or not anyone messing with a Oneness of Earth sanctioned by the Galactic Sentience is going to disappear maybe permanently if he interferes with a Oneness Sanctioned by the Galactic leader of the whole Galaxy. So, this is why Arcane is safe from any local Solar system rules because of this during this era.