The thing I have difficulty on this question is that... Earth is big as a setting.
There's numerous cultures, both historical and current. Do you mean magic has always been here, so it has to make sense in a historical context, too?
Or does magic change with the times?
Or does magic change with the environs?
In Swift's world, there's a stark difference between magic of nature and magic of cities, for example. Swift is an urban sorcerer. He draws on the magic of cities. The flow of traffic. The meaning of zoning laws. The boundaries of urban life (ie, as I gave example before: you don't get on the subway without a ticket. It says so on a ticket. People, more or less, believe this. Magic monster is coming up at you-- get a ticket, get past the boundary, hold the ticket up! You've now effectively cast a ward against the monster crossing a line that has meaning because people believe it). All these things are utterly mundane, but because people live them, they have a supernatural force.
Now, go into nature. Go into a rural space. Magic is different. The rules are different. There's still magic there, but it follows the patterns and structures of rural life. Druids thrive there.
The idea is that there is no inherent 'earth magic', there's people-magic. Back in Egypt, magic was about words. What you say: what you write. Repetition. These are the essence of spells. People believe them. That creates a ripple through reality and gives truth to the act of casting a spell.
The world moved on: Egyptian magic stopped working because people stopped believing in it, it stopped being part of the rules that people just assumed were true.
But off in Sumeria, maybe they had magic too, that worked different. Because people and life and the order of life was different there.
This is the issue I have with the question, and why I ask for context: Earth is big. Diverse. There's almost nothing universal about it. Magic is life and life is magic, but the life I live in Los Angeles doesn't relate to the life someone might live in New Delhi.
If I were to try to make a general 'Earth' magic, one that had meaning in both the past and the present, in rural and urban contexts.. I am suddenly blank.