The rock-type event returns to Pokemon Go! Here is the official information:
Starting on May 24 at 1:00 P.M. PDT, unique Field Research will be available with some exciting rewards, including a Raid Battle appearance by Pokémon such as Aerodactyl.
Throughout the celebration, Rock-type Pokémon such as Geodude, Lileep, and Nosepass will appear more frequently in the wild. There are also incentives to trek around: your Buddy Pokémon will earn Candy 4× faster throughout the event! Plus, you’ll receive extra XP for spinning the Photo Discs at PokéStops or Gyms—up to 10 times the usual amount if this is your first time encountering a unique PokéStop or Gym!