Earthquake Stardew Valley: Cracking the Seismic Mysteries!

Stardew Valley has a guaranteed Year 1 earthquake and a separate random meteorite event. They use different messages, timing, and outcomes: the earthquake opens the Railroad/Spa route, while a meteorite places a breakable resource clump on the farm.

There was an earthquake during the night.

The Guaranteed Railroad Earthquake

The earthquake occurs overnight before Summer 3 of Year 1—after you sleep on Summer 2. On Summer 3, the rockfall north of the Mountain is cleared and the path to the Railroad and Spa becomes accessible. It does not happen on the first night of summer.

The earthquake itself does not place a meteorite and does not kill crops. It is a progression event that opens a location.

The newly opened pathway to the railway and bathhouse — The newly opened pathway to the Railroad and Spa becomes accessible on Summer 3.

The Spa and Railroad

Spa: standing still in the pool restores Energy and Health.
Railroad: trains can pass on eligible days and may drop items such as Stone, Coal, Wood, or Geodes.

The Separate Random Meteorite

On a meteorite night, the message reports an explosion and a purple meteorite appears on a valid 2×2 farm area. A Gold Pickaxe or Iridium Pickaxe is required to break it.

In Stardew Valley 1.6.15 build, breaking the meteorite yields:

10 Iridium Ore;
8 Stone;
2 Omni Geodes; and
a 25% chance of 1 Prismatic Shard.

These are raw Iridium Ore, not Iridium Bars. Bars require smelting five Iridium Ore with one Coal in a Furnace.

a screenshot where the meteorite has caused some damage on the farm

Final Thoughts

When the message says earthquake, visit the newly opened Railroad/Spa area on Summer 3. When it says explosion, search the farm for a meteorite and bring a Gold-or-better Pickaxe. The first event unlocks a route; the second provides ore and geodes.