The extraordinary earthquake that devastated parts of coastal Japan this morning has triggered tsunami activity currently propagating across the Pacific ocean. Fifty countries are under tsunami warnings. At the same time, a flood of information is pushing through cyberspace that could easily overwhelm anyone seeking the basic facts. Let’s break down what we know based on information from sources we trust.

What is a tsunami?

NOAA’s National Ocean Service writes: “Tsunamis are giant waves caused by earthquakes or volcanic eruptions under the sea. Out in the depths of the ocean, 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. The speed of tsunami waves depends on ocean depth rather than the distance from the source of the wave. Tsunami waves may travel as fast as jet planes over deep waters, only slowing down when reaching shallow waters.”

More information

When will the tsunami affect different areas?

The tsunami is already coming shore across portion of the U.S. West Coast including California and Oregon and will continue to do so through early this afternoon eastern time. It will impact the Alaska coastline through this evening. A complete listing of the time of arrival for the tsunami at different West Coast points is available at NOAA or keep reading after the jump for the full list for U.S. coastal locations.

The Weather Channel reported the first waves reached the Oregon coast around 11 a.m. ET.

Recent Tweets from The Weather Channel also indicate the following:

* Some of the West Coast tsunami reports....Charleston, OR: 1.6ft, Crescent City, Calif. 3.7ft, Arena Cove, Calif. 2.7 ft

* From NWS in Los Angeles: Tsunami currents impacting Santa Cruz, Calif. with boat and dock damage.

* At 11:30 a.m.: Tsunami arriving in Southern California right now and threat will continue for several hours.

Here is a video of the predicted propagation (forward progression) of the tsunami across the Pacific ocean from NOAA.

The tsunami hit the coast of Hawaii earlier this morning with a wave height of over three feet.

What are the estimated wave heights for U.S. West Coast?

AccuWeather has a list of projected wave heights which range from 2 to 8 feet in California and Oregon.

See also this incredible visual of wave height propagation forecast from NOAA.

Projected tsunami arrival times:

Add three hours to Pacific time (PST) to convert to Eastern Time (EST) and add four hours to convert from Alaska time (AKST) to EST. Subtract five hours to convert UTC to Eastern time

Charleston, Oregon 0715 PST MAR 11 1515 UTC MAR 11

Cascade Head, Oregon (70 miles SW of Portland) 0716 PST MAR 11 1516 UTC MAR 11

Douglas/Lane County Line, Oregon (10 miles SW o 0717 PST MAR 11 1517 UTC MAR 11

Cape Mendocino, California 0717 PST MAR 11 1517 UTC MAR 11

Tillamook Bay, Oregon 0718 PST MAR 11 1518 UTC MAR 11

Horse Mountain, California (50 miles SW of Eure 0719 PST MAR 11 1519 UTC MAR 11

Fort Bragg, California 0721 PST MAR 11 1521 UTC MAR 11

Humboldt Bay, California 0722 PST MAR 11 1522 UTC MAR 11

the Oregon-California border 0723 PST MAR 11 1523 UTC MAR 11

Crescent City, California 0723 PST MAR 11 1523 UTC MAR 11

Seaside, Oregon 0724 PST MAR 11 1524 UTC MAR 11

Westport, Washington 0725 PST MAR 11 1525 UTC MAR 11

Newport, Oregon 0726 PST MAR 11 1526 UTC MAR 11

Point Arena, California 0726 PST MAR 11 1526 UTC MAR 11

Gualala Point, California (80 miles NW of San F 0727 PST MAR 11 1527 UTC MAR 11

Point Reyes, California 0739 PST MAR 11 1539 UTC MAR 11

Davenport, California (10 miles NW of Santa Cru 0739 PST MAR 11 1539 UTC MAR 11

Point Sur, California 0742 PST MAR 11 1542 UTC MAR 11

Astoria, Oregon 0744 PST MAR 11 1544 UTC MAR 11

Monterey, California 0744 PST MAR 11 1544 UTC MAR 11

Port Angeles, Washington 0748 PST MAR 11 1548 UTC MAR 11

Ragged Point, California (45 miles NW of San Lu 0750 PST MAR 11 1550 UTC MAR 11

DART 46412 0752 PST MAR 11 1552 UTC MAR 11

Point Concepcion, California 0757 PST MAR 11 1557 UTC MAR 11

Port San Luis, California 0803 PST MAR 11 1603 UTC MAR 11

Bella Bella, British Columbia 0805 PST MAR 11 1605 UTC MAR 11

San Francisco, California 0808 PST MAR 11 1608 UTC MAR 11

Cape Newenham, Alaska 0716 AKST MAR 11 1616 UTC MAR 11

Santa Barbara, California 0817 PST MAR 11 1617 UTC MAR 11

Rincon Point, California (15 miles SE of Santa 0828 PST MAR 11 1628 UTC MAR 11

Santa Monica, California 0831 PST MAR 11 1631 UTC MAR 11

San Pedro, California 0832 PST MAR 11 1632 UTC MAR 11

Newport Beach, California 0837 PST MAR 11 1637 UTC MAR 11

La Jolla, California 0841 PST MAR 11 1641 UTC MAR 11

Seattle, Washington 0844 PST MAR 11 1644 UTC MAR 11

Alamitos Bay, California (20 miles SE of L.A.) 0846 PST MAR 11 1646 UTC MAR 11

the California-Mexico border 0847 PST MAR 11 1647 UTC MAR 11

Hooper Bay, Alaska 0846 AKST MAR 11 1746 UTC MAR 11

Little Diomede Island, Alaska 0856 AKST MAR 11 1756 UTC MAR 11

Dillingham, Alaska 0938 AKST MAR 11 1838 UTC MAR 11

Nome, Alaska 1051 AKST MAR 11 1951 UTC MAR 11

Unalakleet, Alaska 1422 AKST MAR 11 2322 UTC MAR 11

Please feel free to share links, video and photos of interesting or important coverage of the earthquake and tsunami in the comment area below.