The odd oak in Friday’s photos is shin oak, or Quercus sinuata var. breviloba:
This trunk “puddle” is a really cool adaptation called a lignotuber (good job Matilija!) or burl. These are common in woody plants found in wildfire zones. New sprouts can arise after fires have roared through, or perhaps after heavy browsing by deer, as the park ranger suggested to Ginny, our guest inquisitor.
Thanks, Ginny, for sharing the photos and question. If you have an interesting plant quiz topic, preferrably with pictures, feel free to pass it on for our Friday Question!