It’s the highest tsunami ever recorded. In 1958, a 7.7 magnitude earthquake triggered a landslide and the partial draining of a glacial lake in Alaska. As a result, Lituya Bay saw a tsunami of 1,720 feet! That’s about the same height as the tips on the antennas on Willis Tower, formerly Sears Tower, in Chicago. Two died that day but a fishing boat, out on the open water of the bay, miraculously successfully rode out the historic wave. Learn more about the biggest tsunami ever at this great site. The tragedy in Japan has clearly demonstrated, once again, the power of a tsunami. We often think of this destructive wave as a Hawaii Five-O surfing wave. But it’s not a big, breaking wave at all. As you’ve seen in the amazing and horrific videos from Japan, it’s a surge of water that comes in several waves. Regular ocean waves may have a wavelength of 300 feet between crests. A tsunami’s wavelength in open water may be 100 miles. A tsunami in the open ocean can go 500 miles per hour, bring the water level up just a foot, take 15 to 30 minutes to move through, and pass ships totally unnoticed. The tsunami rises and slows down as it encounters the rising terrain of shore and acts differently in a harbor than along an open shoreline. A tsunami is considered major if it’s 3+ meters high (1 meter = 3.3 feet). This one was up to 10 meters, or 33 feet, high! An earthquake was responsible for this tsunami, but they can also be caused by landslides or other disturbances that displace water, as was the case of the 1,720 foot Alaskan tsunami of 1958. Here’s a map of the bay and water heights recorded. The few people at the bay had only the earthquake as a warning that a tsunami could develop. Today, we have warning systems in place that can at least give some notice to get to higher ground. You can learn more about tsunami warning systems at the National Oceanic and Atmospheric Administration’s site.