Twould knock the earth out of its orbit, to start...

I remember a question asked a while ago and it stated that a 8 foot giant could barely lift it's own weight. How does a continent sized dragon not crush itself? Not to mention the fact that (because of the square-cube law) if the height doubles, the blood need octuples.

That's a good question, and one that should probably be posed to the race which holds this religious belief. With that said, this colossal being is considered to be a god, if not the God - and once you consider that, in my opinion all bets are off.

A bird sitting on a phone line can make a mess of the roof of your car. A dragon the size of Asia would cover the world in dragon poop.

Most of the answers assume the dragon itself is the entirety of the continent, if the dragon isn't itself a continent and is instead a mountain range on a larger continent (therefore, has bedrock beneath it and most of the volume of the mountains is the dragon itself), the effects are lessened quite a bit. For comparison, the volume of the Andes is 2,880,000,000 m^3 (within an order of magnitude) and above sea level. Though, a less bad apocalypse is still an apocalypse. Perhaps, they could convince it to stay for tea for a few millennia: it wouldn't cause too much trouble moving around.

Stanslaw Lem examines the economic consequences of such a continent sized dragon in one of his short stories, The use of a Dragon

It sounds like the dragon is the environment - at least, it accounts for a majority of the globe's biomass and a significant proportion of its land area. Perhaps you could be more specific about what you consider "environment" to mean in the question?

I wonder how much the Earths gravity would change with such a loss of mass?

@PeterTaylor The idea for the religious story is that the land was literally built atop the dragon's body - as such, you're correct in presuming they're one and the same. The legend as written (though it's certainly open to altering, especially given some of the great responses here) goes that the earth is its flesh; the oceans, its tears; the air, its final breath... And so when it is resurrected, it will sunder the planet and bring fire and death to all who reside on it - save for the faithful, who will be carried upon its back to ascend to the stars to complete their holy mission.

I feel like this question would be a good answer to this question

"Ha ha, you fool! You fell victim to one of the classic blunders! The most famous of which is 'never get involved in an air war in Asia...'" oh bother.

Somebody already thought of that : Brian ALDISS, Heresies of the huge god

@nzaman it wouldn't, really - the whole earth crust is less than just 0.5% of its mass, so a single continent (a fraction of the crust) moving around wouldn't have a major impact on the orbit or gravity of the molten ball of rock that forms almost all of our planet.

@Peteris Less moving around and more of an impact of an asteroid the size of Asia pushing away the earth. The force required to move something that big to escape velocity should be more than enough to change the earth's orbit

This question reminds me of the game Xenoblade Chronicles and the way the world you're in is made up of two dead ancient giants

The impact would be bigger than any meteorstrike...

If it's already magical in nature, you could probably work a way in for it to stabilize those living on its back. I mean if they are going into outer space, there needs to be some magic to stabilize lifeforms on its back. Say a purple aurora borealis across all the sky signals the coming of judgment day, for believers to make a pilgrimage to their mecca. At this central city, they descend into the dragon, into a hospitable environment sheltered within. The earth is screwed, but it wouldn't be the first religion that believes their final salvation comes with the ending of the rest of the world.

Have you played Mother 3?

@ThisRandomGuy Did you mean 80 foot tall? There are people alive today who are 8' tall. The tallest person recorded was Robert Wadlow who was almost 9' tall and he could certainly walk. Could carry people up flights of stairs even.