If they had just let them sit there for 4 and a half billion years they would be half gone :-). If you hike around the Grand Canyon you are going to be exposed

If they had just let them sit there for 4 and a half billion years they would be half gone :-). If you hike around the Grand Canyon you are going to be exposed to Uranium. There are a lot of mines in and around the place (see here: https://www.grandcanyontrust.org/grand-canyon-uranium https://www.grandcanyontrust.org/grand-canyon-uranium). It really isn't something to worry about unless you want to live their and/or eat food that has been contaminated.