It turns out there are far more Damage Types than just Physical, Bleed, Poison, Disease, Magic, Flame, Shock, and Frost. Getting the Boulder Bash effect in The Parch allows you to deal Earth Damage to enemies:

Players don't have anything that specifically buffs Earth Damage or Earth Resistance.
I looked into this more, and
according to this UESP page, there are several other Damage Types used in various parts of the game, such as:
- Generic Damage
- Drown Damage
- Earth Damage
- None Damage
There are more types than the ones I listed. I just figured this was interesting and worth bringing up!
PC/NA — Lone Werewolf
Werewolf Should be Allowed to Sneak Prowling added in Update 50!
Please give us Werewolf
Skill Styles (for customizing our fur color) Added in Update 50!,
Grimoires/Scribing skills (to fill in the holes in our builds), and
Companions (to transform with).