RedMew/locale/gen_shared/chunk_utils.lua

function removeChunk(event)
	local surface = event.surface
	local tiles = {}
	for x = event.area.left_top.x, event.area.right_bottom.x do
		for y = event.area.left_top.y, event.area.right_bottom.y do
			table.insert(tiles, {name = "out-of-map", position = {x,y}})
		end
	end
	surface.set_tiles(tiles)
end