I'm sure you mean elaborate, and so I shall. :sun
Polymerization is a process by which monomers (similar subunits) are linked together to form a polymer (poly meaning many and mono meaning one).
Terpenes are known to polymerize under certain conditions. Most alkenes (C-C double bond is an alkene functional group) are fairly reactive, but
terpenes are made up of special monomers called isoprene, or isoprenoid, units (isoprene is short for isoterpene).
Under various conditions, not the least of which being presence of air and heat--previously stable
terpenes may begin to break apart/link together in a way not dissimilar to the linking together of isoprenoid units. A polymerization of polymers if you will.
In addition to this
terpenes are known to react with various compounds to give new compounds (in the case of ozone for example). Google
terpenes ozone and do some digging if you want to see how complex this can get in terms of side reactions--this reaction can give a hydroxyl radical which can go on to do all types of nasty shit.
In general I'm saying stuff doesn't just change color and consistency from losing less than a mL of solvent and a little heat. A reaction is occuring.
In terms of elaborating on the possible danger/non-danger. I can't. No one really can--this stuff amounts to a chemical soup in terms of how many compounds are present. You get to doing side reactions/polymerizations in a chemical soup and you could end up with some fairly terrible results. As a for instance, adding only 3 reactants in a research lab once left me with maybe 100 different compounds at the end of a reaction where an impurity had caused side reactions to take place. The NMR looked black clear across!
Now consider that there may already be 100's of compounds present in an extract.
I'm not trying to say its certainly unsafe--but it could potentially be creating carcinogens and other nasty things. I'm ultimately saying sans a lab and lots of fancy testing we won't know or even come close to knowing. Even then this could be on a plant to plant basis in terms of deciding whether this process is safe. Each plant has different relative levels of
terpenes and cannabinoids and different terpene profiles. That changes reaction conditions and confounds analysis.
This could also be a hydration reaction, as some
terpenes are known to complex with water to create--I believe--a trihydrate. This would be considerably less dangerous. Testing this might be easier. Weigh a beaker (with stirrer and oil already in) on an analytical scale. Whip up a batch. Re-weigh.
There should be a noticeable difference in weight if hydration is occuring. (depending on the mechanism the same will be true for oxidation)
TLDR:
You don't know what that is.
It looks like a polymerization/side reaction to me.