A tsunami is a series of waves generated by the sudden, massive displacement of a large volume of water. This displacement is most often caused by seismic activity, such as an underwater earthquake, but can also result from volcanic eruptions or large landslides. Given the catastrophic damage tsunamis have caused globally, coastal residents in Texas are naturally concerned about their vulnerability, especially regarding the Gulf of Mexico.
The Historical Record for Texas
The Texas coast has never experienced a documented, destructive tsunami generated by seismic activity within the Gulf of Mexico basin in modern recorded history. The last documented tsunami-like wave was a minor, non-destructive 0.6-foot surge recorded in 1964 on a tide gauge in Freeport, Texas, following the Magnitude 9.2 Great Alaska Earthquake.
Prior to 1964, two other small waves were recorded on the Galveston tide gauge in the early 20th century, neither causing public concern or damage. A small wave was detected in October 1918, linked to a major earthquake near Puerto Rico. A 2.1-foot wave was recorded in Galveston in 1922, though experts consider this reading questionable and likely amplified by local conditions.
Why the Gulf Coast is Geologically Protected
The primary reason the Texas coast is largely protected from major tsunamis is the geological structure of the Gulf of Mexico. Unlike the Pacific Ocean, which is ringed by active tectonic plate boundaries, the Gulf basin is characterized by a passive continental margin. The Pacific Ring of Fire involves subduction zones where one plate slides beneath another, which is the mechanism for most massive tsunamis.
The Gulf of Mexico lacks these active plate boundaries, meaning there is no source for the large-magnitude earthquakes required to create a damaging, basin-wide tsunami. Additionally, the geography of the Caribbean islands, including Cuba and the Bahamas, creates a natural barrier that reduces the energy and wave height of any potential far-field tsunami generated in the Atlantic or Caribbean.
Distinguishing Between Tsunamis and Storm Surges
The most frequent confusion for coastal residents is mistaking the effects of a severe hurricane for a tsunami. A true tsunami is a series of waves that affects the entire water column, from the ocean floor to the surface, caused by a sudden displacement event. These waves travel at high speeds in deep water and strike the coast as a rapid, powerful flood.
A storm surge, which is the major wave threat to the Texas coast, is an entirely different phenomenon. It is an abnormal rise of water level generated by the high winds and low atmospheric pressure of a tropical storm or hurricane. This meteorological event only affects the surface layers of the ocean, resulting in a more gradual rise in sea level. The primary destructive force is the sustained elevation of the water, not the speed or height of a single wave.
Localized Tsunami Risk Factors
While major seismic tsunamis are highly improbable, the Texas coast faces a very low but real risk from non-seismic sources. The most significant potential source is a massive underwater landslide, known as a submarine mass failure, along the continental shelf, which could displace enough water to generate a localized tsunami.
Geological studies indicate that the most active period for these large-scale slides was over 7,000 years ago, with the estimated recurrence interval for a major event being between 5,000 and 8,000 years. A more likely event is a meteotsunami, a large wave generated by severe atmospheric pressure disturbances associated with fast-moving squalls or thunderstorms. Although not seismically generated, these events can produce waves up to six feet in height and are considered a more probable, localized threat to the Gulf Coast.