Question
I have a large oak tree that has vertical swollen areas on the trunk; the areas look like large veins under the bark.  They are about the width of an adult arm and 7 - 15 feet in length.  There are several on the tree.  Do you know what they may be?  Is the tree dying; it is at least 50 years old.

Answer
Hi there. Sounds like frost cracks
Frost cracks are often the result of some sort of predisposing factor, which occurred to the trunk years earlier. In late winter and early spring, water in the inner bark and in the wood expands and contracts under fluctuating temperatures. Defective wood does not contract as well as healthy wood. Rapid expansion and contraction of water within the wood and bark, particularly under falling night temperatures, can result in a crack. Frost cracks may be up to several feet long and are often found on the southwest side of the tree. These cracks may heal in the summer only to reopen again in winter. Successive cracking and healing over years can result in the formation of 揻rost ribs?on the sides of affected trees. Frost cracks can act as sites of entry for wood decay organisms.
Generally these don't hurt the tree but occasional monitoring won't hurt. Hope this helps,Bill