I learn later that there is evidence of a mass extinction in this park! We find plenty of other things to look at on our morning hike of the self-guided nature trail and other trails. Next time I’ll have to keep my eye out for a dark layer in the sandstone that marks the Cretaceous-Tertiary extinction event. If Yellowstone blows, or we encounter a good-sized asteroid, maybe we could be part of a layer like that!