She had not noticed that the books themselves formed a geological model—or if she had, it had been pushed aside in the interest of her current project.  The high plains of the floor slowly rose into a broken upslope of books, finally topping out—unsurprisingly—at the weighty peaks of Mt. Agriculture.  Passage across the range would be best accomplished through Xenobiology valley: it was only one book tall.  Twilight resolved to fix this oversight the next time she put in an order for more books from Canterlot.