The ocean’s largest waves are immense natural formations, a testament to powerful forces. From distant storms to seafloor contours, various elements combine to create these awe-inspiring walls of water.
Defining Big Waves
A “big wave” is defined by oceanographic measurements and the perspective of those who interact with them. For surfers, a wave is “big” when its face height reaches at least 20 feet (6.2 meters).
Beyond height, wave power is determined by its wave period, the time it takes for two successive wave crests to pass a fixed point. Longer periods (5-25 seconds) indicate powerful waves that have traveled greater distances and carry substantial energy. These swells often result in larger, more organized waves once they encounter shallower water.
Common Names for Giant Waves
Exceptionally large waves are known by various terms. In surfing, common descriptive terms include “bomb,” “monster wave,” or “mountain of water.”
Renowned big waves are identified by the names of specific surf breaks where they consistently appear. Examples include Jaws (Peahi) in Maui, Mavericks in California, and Nazaré in Portugal. These locations produce colossal waves due to unique underwater topography that funnels and amplifies ocean swells. Teahupo’o in Tahiti is another famous break, known for its heavy, hollow waves over a shallow reef.
Distinct from consistent surf breaks are “rogue waves,” also called “freak waves” or “killer waves.” These are unusually large, spontaneous waves, often more than twice the height of surrounding waves, appearing unpredictably from unexpected directions. Tsunamis are fundamentally different, originating from seismic activity like underwater earthquakes or landslides. They possess extremely long wavelengths, barely noticeable in deep water, but gain immense height near shore.
How Colossal Waves Form
Colossal waves form from a complex interplay of atmospheric and oceanic dynamics. Large ocean swells originate from powerful storms. These storms generate strong, sustained winds over a vast expanse of uninterrupted water, known as the “fetch.” Wind speed, duration, and fetch length determine the initial size and energy of these swells.
As swells travel across the ocean, their energy moves through the water. Upon reaching shallower coastal waters, waves undergo “shoaling.” During shoaling, the wave’s speed decreases due to seafloor friction, causing height to increase and wavelength to shorten as energy concentrates in a smaller water column.
Underwater topography, or bathymetry, amplifies shoaling waves. Deep ocean canyons, reefs, and steeply sloping seafloors focus and channel wave energy, increasing wave height at specific locations. For instance, the Nazaré Canyon off Portugal funnels incoming swells, creating a constructive interference effect that contributes to the formation of exceptionally large waves. Local factors like currents and tides also influence their final size and shape.