All tsunami watches, warnings and advisories for Alaska's southern coast and the U.S. West Coast were canceled Tuesday after a powerful earthquake struck off Alaska's Kodiak Island.

Here is what we know now:

What happened?

A magnitude-7.9 earthquake was recorded about 175 miles southeast of Kodiak Island at 12:32 a.m. local time. The quake, which was felt hundreds of miles away in Anchorage, was centered deep below the surface in the Gulf of Alaska.

What is a tsunami?

A tsunami is a series of waves caused by earthquakes or undersea volcanic eruptions. Far out in the depths of a large body of water, tsunami waves do not dramatically increase in height. But as the waves travel inland, they build up to higher and higher heights as the depth of the ocean decreases. Tsunami waves may travel as fast as jet planes over deep waters, only slowing down when reaching shallow waters.

More: Tsunami warning canceled after magnitude 7.9 earthquake off Alaska

Was there a tsunami today?

Yes. "A tsunami has been confirmed," the National Tsunami Center said. However, little impact was felt. The center reported tsunami heights of less than 1 foot at several measuring stations.

What is the status of the warnings?

The National Tsunami Center dropped the warnings, watches and advisories for Alaska, Washington state, Oregon and California. "A tsunami was generated by this event, but no longer poses a threat," the center said. "Some areas may continue to see small sea level changes."