Erosion is a physical or chemical process by which rock wears away into smaller pieces. At least, that's the basic idea. And because bones require rapid burial to be preserved as fossils, we would never see them if it weren't for erosion. Therefore, it is our best friend. Ashfall would never have been found if it weren't for a juvenile rhino jaw eroding out of the hill at just the right time for a paleontologist to walk by and find it. Had a creek not slowly eaten a valley into the flat area here, the ash layer never would have been exposed here to draw him here in the first place. Erosion means that fossils tend to follow the rule of gravity: they fall down the hill, and so while searching for them you start low and work your way up when you find fragments, slowly (hopefully) narrowing down the source (that is, the rest of the specimen.) In theory.
And this is where erosion also becomes less friendly. If we come to a fossil too late, it will have eroded completely out of the hill. It's gone, leaving just fragments. The deepest part of the watering hole was actually already taken out by the creek and the valley, and another section of it was devoured by an ancient river that was redirected here briefly after the ash fell, and stayed just long enough for us to lose part of the watering hole. It is also less than ideal, because fossils are often found in hill sides, for building on in the cases where there are enough fossils to support a park like this or Dinosaur National Monument. A lot of adaptations have to be made and structural feats have to occur for this to be pulled off, and in many cases it takes more than one try.
And so our mixed feelings for erosion will continue. It is a love-hate relationship for the danger to fossils that, in many cases, also causes them to be preserved for prosperity.
No comments:
Post a Comment