One of the most powerful earthquakes ever recorded has sent a tsunami crashing into a Russian port and smaller waves barreling across the Pacific to the Americas and south to New Zealand.

A powerful magnitude 8.8 earthquake off Russia's far-eastern Kamchatka Peninsula Tuesday triggered tsunami waves across the Pacific Ocean. Russia said the shallow quake caused damage in Petropavlovsk-Kamchatsky and elsewhere on the peninsula and flooded the Kuril Islands with waves as high as 19 feet.

Russia’s magnitude 8.8 earthquake spawned serious tsunami warnings, but waves have been moderate so far. Here’s the geological reason why