That is sure a big stump! The white stuff looks like chalk in the first photos and like snow in the last one!
I'm melting in San Diego for a few days now - we are having a heat wave. My trees are in Boulder, Colorado - also on a hot day, when I was very glad for the shade on my hike.
https://steemit.com/treetuesday/@bxlphabet/boulder-colorado-shade