As a celebration of Earth Day, Niantic hosted a worldwide campaign in conjunction with Playmob. The aim was to get the community out into the world, hosting clean up events across the globe, a mission which had huge success last year. Participants could tag Niantic in images of their efforts to be counted towards a community goal. This year's event was just as successful, and as a result, Pokémon Go players can now find some limited time rewards in-game, including a shiny Diglett.
The rewards take the form of a ground-type event, which will be running until May 2nd. A shiny Diglett has been added to the game, its first appearance on mobile, with Groudon returning to raids. Players will also receive double stardust and catch candy when catching the more frequently spawning ground-type Pokémon. This means the event is a great way to catch and evolve your ground types.
Groudon is well worth the effort of catching. He is arguably the best ground attacker in the game with Mud Shot and Earthquake abilities, and is a great choice for many situations. Since he is only back for a brief time, make sure you're claiming and using your free daily Raid Pass to have a chance to catch him.
If you have a smaller raid group, then Groudon is best faced with a team of Pokémon with ice, water, or grass-type moves. The following Pokémon are recommended for a strong team: Kyogre or Gyrados with Waterfall and Hydropump, Feraligatr with Waterfall and Hydrocannon, Roserade with Razer Leaf and Solar Beam, Breloom with Bullet Seed and Grass Knot, and Mewtwo with Confusion and Ice Beam.
Groudon can be beaten with other combinations, but the more ice, water, and grass-type moves you have, the quicker and easier the fight will be, since these directly counter Groudon's moves.
Since your team’s contribution also determines the number of chances you have to catch Groudon, it makes sense to optimize. Also remember that you get a bonus for having friends in the raid, and for the gym being your team’s color.
The ground event will end on May 2nd, so be quick if you want that shiny Diglett.