I've often thought: "What if I bought a nice big piece of land somewhere, along with a digging machine and spent the rest of my days making a hole in the earth. That is my current thought on how to make the biggest, lasting impact on this earth.
Of course, without looking it up, I couldn't tell you who they were, even though some of these "big holes" are right here in "my backyard" down in southern Arizona (about the best I can tell you is that they were mostly for copper mining and...yep).
Or - take this big hole; without looking it up, do you know who made it?
http://www.nationmultimedia.com/img/news/2017/08/06/30322996...
...got the owners a lot of diamonds, though.
Even so - they'll be just as forgotten.
Nature will rapidly disappear and or anonymize your earth hole, or someone will simply fill it in (just one person digging with industrial equipment will make a surprisingly modest dent in the earth in a lifetime). You need to make it obnoxiously unreasonable to bother getting rid of it.