Not Nanobeavers...but maybe a cousin?

I pulled my sparkplugs this morning to do a compression test in order to confirm that I am getting most of the 120hp from my 2011 Fiesta. Compression looked very good at 150-151-152-150. What did not look so good where the sparkplugs. According to previous owners records, these had 50k miles on them and I have put 3 hours of track time on them as well. The car seems to run fine and has no engine codes. 

The plugs are not OEM. The Denso plugs that are currently installed should look like this:

Two of the removed plugs looked like this:

The other two looked like this:

Any thoughts? I have ordered new plugs and will keep an eye on them after each track day to see if similar things happen to a more typical architecture plug.

My apologies Bob if Nanobeavers is already trademarked...let me know where to send the royalty :)

Ford, right?  Original plugs?  Two coils, with two wires? 

If so, power goes from coil to plug 1, jumps to the ground electrode, then through the block to plug 4 where it jumps from the ground electrode back to the center electrode, up the wire and back to the coil. The electrode the spark jumps from erodes less.  Ford even used to have half their plugs with platinum center electroded and half with platinum ground electrodes, because cheapskate.

If it has four coils, I dunno. 

Edit: The electrode the spark jumps TO erodes less.  I think.

Fairly sure that non-ST Fiestas have wasted spark coil packs.

As Streetwiseguy says, this is normal on wasted spark.  Betcha that the plugs that wore one way were on 1 and 4, and the plugs that wore the other way were 2 and 3.

Nano-beavers is a perfectly valid diagnostic term. It looks to me more like their cousin the nano-woodchucks.

In reply to Streetwiseguy :

Yes Ford, second set of plugs according to service records (non-OEM plug), all four wires come out of one coil assembly (not coil on plug). Plugs 1 and 3 wore the same way and plugs 2 and 4 wore the same. Doesn't sound like anything to get too concerned about but I will keep an eye on the new plugs to make sure the gaps don't grow to double the spec. Thanks for the feedback.

I was reading about evil plug wear like this among the twin turbo LF4 Caddy guys.  They were talking plugs every 20k miles.  That seems excessive unless they really easy to get to, which I strongly doubt they are.  Interesting how much the rowdy turbos like to munch plugs.