I came across this round rock on the side of Libby’s Island (a.k.a Wildflower Island and Barataria) when we were stumbling about one of the dry parts of the lake bed on a recent visit. I’m surprised I’d never seen it before given how much we visit this island and how the rock was just sitting there in an obvious place, waiting to be found.
What especially interests me is the round-rock-within-a-round-rock. I’ve seen quite a few of my round rocks that have been cleft more-or-less cleanly in half, and many show the more-or-less concentric rings of the rock’s “growth” over the more-or-less millions of years in the mineral soup. (The soup was created by the meteor impact in the shallow sea that once covered this part of the earth we now call the great state of Missouri several hundred million years ago, but you know that already. In case you don’t, though, you might want to go here.)
The round rocks all grew around some nucleus stone, but I’ve always thought that the gradations in the growth were mostly continuous, not like rings of a tree that happen in a sequence based on growing seasons. The fact that this rock broke along what seems to be a clear point of transition within the sphere makes me wonder about my conclusion. I really don’t think these rocks were subject to periods of growth and then periods of stasis. That might explain why this rock seems to have the transition point though. Perhaps some dramatic change in the chemistry of the soup one day caused a hiccup in the growth process. (I’m speculating wildly, of course, and you are welcome to jump in and correct me.)
I suspect this poor rock was just going about its business when the bulldozer arrived one day to begin building the lake. I’m guessing that the rock got under the treads of the dozer and got partly crushed, breaking off the outer layer and exposing the inner sphere. Maybe that is why it broke so differently from the other round rocks I find crushed in the lake bed and on the hillsides.
- Newly emerged zebra swallowtail butterflies fly in woodlands.
- Gooseberries begin blooming.
- Swallows return.
Today in Missouri history:
- On this date in 1804, Congress divided the Louisiana Territory into two areas, one of which became the District of Louisiana with government in St. Louis. Missouri was formed from this.