Physics of surfing

videos Science of Big Waves (KQED) Garrett McNamara w/ GoPro, 90’+ Teahupoo raw 2013

The energy of a wave travels ahead but the water itself does not

Why are there consistently bigger waves in the Pacific?

Factors determining wave power: wind v, wind duration, and fetch

Why are the conditions so different?

Ground swell vs. wind swell

Seafloor determines wave (shape)

Wave energy consolidates due to DIFFRACTION

To what depth would a seasick scuba diver have to go for relief?

Breakers form In roughly ½ of the wavelength. So if there is a longer period, you have bigger waves.

What is shown here?

So what are ideal surf conditions?

So what are ideal surf conditions? Wind: off-shore, not too strong

So what are ideal surf conditions? Wind: off-shore, not too strong Period: long (ground swell)

So what are ideal surf conditions? Wind: off-shore, not too strong Period: long (ground swell) Tide: dependent on particular break location

So what are ideal surf conditions? Wind: off-shore, not too strong Period: long (ground swell) Tide: dependent on particular break location Substrate: sudden rise, reef, often a point

how heavy is a big wave?

> 1 ton per 1 m3

Forces in balance while riding

Useful sites Magic Seaweed Surf-forecast.com

Other types of waves

CAPILLARY WAVES

A seiche is a standing wave in an enclosed or partially enclosed body of water. Seiches have been observed on lakes, reservoirs, swimming pools, bays, harbors and seas.

A tsunami (at one time incorrectly referred to as a tidal wave), is a series of water waves caused by the displacement of a large volume of a body of water, usually an ocean. Created by: Earthquakes, volcanic eruptions and other underwater explosions, landslides glacier calvings and meteorite ocean impacts

2004 Indian Ocean Tsunami - Indonesia - 35 meters high on shore - 176,000 fatalities Diffracted around world, even to RI

Tsunami videos Japan 2011-raw: video Japan 2011: National Geographic Tsunami 101: National Geographic Cartoon overview of tsunami: http://www.penmachine.com/podcast/audio/Entries/2008/3/5_Tsunami_video_from_VFS.html 2 interactives of 2004 tsunami: http://www.pbs.org/wgbh/nova/tsunami/ See 1st chapters of America’s Tsunami: Are We Next? How Stuff Works.com 2004 first waves: http://videos.howstuffworks.com/discovery/27966-assignment-discovery-first-waves-of-2004-tsunami-video.htm How the 2004 tsunami happened: http://videos.howstuffworks.com/discovery/27965-assignment-discovery-how-the-2004-tsunami-happened-video.htm 2004 Plate shift: http://videos.howstuffworks.com/discovery/14049-tsunami-2004-indian-ocean-plate-shift-video.htm 2004 teletsunami, India: http://videos.howstuffworks.com/discovery/27976-assignment-discovery-teletsunami-video.htm Pacific Warning System: http://videos.howstuffworks.com/discovery/27978-assignment-discovery-pacific-warning-system-video.htm Tsunami warning system: http://videos.howstuffworks.com/discovery/29454-assignment-discovery-tsunami-warning-system-video.htm Mega Tsunami: http://videos.howstuffworks.com/discovery/27977-assignment-discovery-mega-tsunami-video.htm

Megatsunami videos Alaska Deep Impact Could RI be hit tomorrow? La Palma, Canary Islands (no sound)

Seismic Waves (shallow) Period ≈ 20 seconds Period ≈ 20 minutes Celerity (another name for speed) C = L/T L = wavelength (m) C = 1.25√L d = depth (m) C = 1.56 T C = celerity (m/s) C = √gd = 3.1√d T = period (s) Wind Waves (deep) Seismic Waves (shallow) Period ≈ 20 seconds Period ≈ 20 minutes L to ≈ 600 m L to ≈ 200 km So C can reach 112 km/hr So C can reach 760 km/hr