A burl. They can be very valuable.

That is VERY impressive.

Think of it as the wood cells losing track of which way they are supposed to grow. There was likely a wound there and the encapsulation process went a little crazy.

Would I be correct it is a structural problem?

Light reading.

http://arborscape.com/tree-growths-treatment/

Thank you for all the great answers this tree runs along the bluff line at the back away from the house. Will the growth continue to grow as the tree grows

Its just crazy the way trees grow here is a different one I have

I bet the first one continues to grow. The 2nd one looks like more typical encapsulation. Trees in the wild are neat. The density gives you infinately more trunks to look at than the same amount of yard space.

That is fascinating. If that tree has to come down in your lifetime, the burl would be a fantastic piece of "garden art". But I hope it stays standing for a long, long time

Burl on the first tree (oak?) looks like it might be nectria canker, having the characteristic "target" pattern at its center. https://ag.umass.edu/fact-sheets/perennial-nectria-canker