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Weird Science: Extreme Surf

NGSS Crosscutting Concepts
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The North Shore of O‘ahu, Hawai‘i

Surf-rich locations with lots of coastline, consistent swell, and favorable winds are found all over the world. One of the most famous surf destinations is the seven-mile stretch of beach and rocky points on the North Shore of O‘ahu, Hawai‘i. This stretch of coast is called the “Seven Mile Miracle,” and it is well known for its consistent winter swells. During the months of October through March, it is typical for storms that begin off the coast of Japan to spin across the north Pacific basin toward Alaska and send organized swells directly to the North Shore. Long period swells (12–20 seconds) can bring waves that average 1.5–4.5 m in height, with extraordinary extreme wave heights of up to 15 m. This stretch of coastline has a rich diversity of sandy beaches, reef breaks, and rocky point breaks that create waves suitable for almost any surfer’s taste.


Dramatic North Shore beach breaks like Keiki Point and Waimea Bay break provide hollow, plunging barrels. Reef breaks like Pipeline can also provide barreling waves. Other, more sloping reefs, like Puena Point, provide waves suitable for beginners.


Waimea Bay

SF Fig. 5.1. Surfers ride a large wave at Waimea Bay, Hawai‘i

Photo by Betty Depolito

At Waimea Bay, ocean swells reaching shore sometimes crest and break at heights of 10 meters or more. This is partly due to the bottom contour at Waimea Bay, where the ocean floor rises abruptly, and deep-water swells change rapidly to steep-crested waves when they move into the shallow area (SF Fig. 5.1). The swells that make large waves at Waimea Bay arrive with long wavelengths and also with long periods. The swell periods may be as much as 22 to 30 seconds. When the swells touch the bottom, the fast moving water in back piles on top of the water in front, forming spectacular breakers.


People are able to surf large waves, such as those at Waimea, because the front surface of the advancing wave is moving upward as the wave moves to shore. The surfboard can remain at about the same position on the wave as the surfer rides the wave. A surfer who “goes over the falls” is swept up by the motion of the water on the wave face, and then thrown over with the lip of the wave. After going over the falls, a surfer can be pinned under water for up to a minute or more by the downward pressure of the plunging water.


Extreme Surf Spots

Extra-large surf events, like the storms that produce them, are relatively rare. Extreme surf spots places like Mavericks in Northern California, Waimea Bay in Hawai‘i, and Cortez Bank 100 miles off the shore of Southern California break only on the largest swells of the year. These extreme surf spots work like a point break, they have a deep water sloping contour that allows large waves (over 5 m) to break in relatively deep water the same way that smaller waves break in shallow water. Some extreme surf spots boast waves too big for people to paddle into. At these spots, personalized watercraft (jet skis) can help tow surfers into waves. Towing-in is similar to water skiing in that the surfer holds a rope and is usually strapped to their board with foot straps. As towing-in has evolved, people are using more advanced boards as well as using jet skis to tow-in. Surfers even tow-in at relatively smaller waves for practice, fun, and experience. The towing-in practice is controversial, however, and jet skis have been outlawed at some breaks because they are loud, use carbon fuels, and can be dangerous to surfers in a crowd.

Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.