One of the most powerful earthquakes in modern history shook Russia’s remote east coast Wednesday, sending tsunami waves hurtling across the Pacific Ocean and putting nations from Japan to the United States to Chile on high alert with millions urged to evacuate.

A powerful earthquake off Russia’s coast triggered tsunami waves that reached across the Pacific, prompting evacuations as far as Chile and Peru. Experts explain how sudden shifts in the ocean can send waves traveling more than 500 mph thousands of miles away.

Officials from Japan to California issued warnings after an 8.8-magnitude quake off Russia’s coast. Hours later, there were no immediate reports of major damage, although some areas remained on alert.