Noticed what I guess is rot at the base of a large tree with a huge circumference. For a few years, the lower branches have no leaves. The "rot" is a much lighter wood color (almost as if something has eaten away the outer layer of the tree) like a light tan (tree has a dark bark with ridges, and there is white surrounding the light wood color. How do I remedy this?
Unfortunately this is not a good sign. It suggests a rot, but there are other signs that this tree, and possibly others are in decline.
Take a look at this page that helps people decide when to remove a tree:
Given the proximity to your home, we suggest having that tree and others nearby evaluated for structural integrity. You will want to get evaluations and estimates from multiple companies and compare. Sooner rather than later.