Motu One, Tubuai, French Polynesia; By Andrew Cooper

Posted In Beach of the Month, Features
May
1

By Andrew Cooper, University of Ulster

Tubuai is a small island in the Austral Island Group of French Polynesia, about 600km south of Tahiti.
The volcanic island is surrounded by a lagoon and a nearly continuous reef. On the reef flat there are several small islands of sand and coral rubble, known as motus.

Most motus are quite well vegetated, but one small example at Tubuai is completely bare and composed of a white coral sand beach. Called Motu One (pronounced O-nay), it is barely 250m long and 50m wide and is located on the reef crest on the north side of Tubuai.

The fact that such a small and isolated pile of sand survives even hurricanes is a perfect illustration of the ability of natural beaches to adapt to changing conditions….
—Andrew Cooper

On its seaward edge, Motu One has a ridge of beachrock which encloses a small lagoon. There are also a few small patches of beachrock on the lagoon side of the motu. The motu is affected by ocean waves on the north side and lagoon waves on the south and so water flows into the enclosed lagoon from both sides.

The seaward-facing beach is very steep but it is sheltered from the direct effect of ocean waves by the reef platform that absorbs a lot of the incoming wave energy. On the lagoon side, waves are less energetic but they are still able to carry sand and shells onto the beach surface.

The motu has changed shape several times but is anchored by the beachrock that helps keep it in place.

Motu One survived Hurricane Oli in 2011, which caused much damage on adjacent Motus and beaches on mainland Tubuai. The fact that such a small and isolated pile of sand survives even hurricanes is a perfect illustration of the ability of natural beaches to adapt to changing conditions.

The accompanying photos (supra) show the motu sitting on the reef crest, the beachrock ridge on its seaward side and the small lagoon that it encloses. The steep slope on the seaward-facing beach contrasts with the more gentle slope of the beach on the island side.

Tags:

More / Beach Of The Month

“Beach Robbers”; By Charles O. Pilkey

December 1st, 2018

“Beach Robbers”, is a book chapter written and illustrated by Charles O. Pilkey, excerpted from “The Magic Dolphin: A Young Human’s Guide to Beaches, Sea Level Rise and Living with the Sea” by Charles O. Pilkey with Orrin H. Pilkey.

Read More

California’s Coastal Harbors, Beach Compartments and Sand Dredging; By Gary Griggs

October 1st, 2018

Every year the dredge at the Santa Cruz Small Craft Harbor along central California’s northern Monterey Bay sucks up about 250,000 cubic yards of sand, on average, from the entrance channel and pumps it out onto Twin Lakes Beach where it continues its journey down coast. If it were put in dump trucks, it would fill about 25,000 of them, but the waves can move all that sand without any human labor, and without any noise or carbon emissions.

Read More

Beyond Preservation: The Coral Restoration Foundation Bonaire; By Andrew Jalbert

August 1st, 2018

When avid scuba diver and famed Jurassic Park author Michael Crichton first visited Bonaire decades ago, he eloquently described the underwater environment as, “a world of riotous, outrageous color.” Years later, Bonaire has seen some changes but his assessment still largely rings true.

Read More

Management Strategies for Coastal Erosion Processes; By Nelson Rangel-Buitrago

June 1st, 2018

The Special Issue Management Strategies for Coastal Erosion Processes (MSforCEP) presents an international collection of papers related to the implementation of various management strategies for coastal erosion under specific objectives.

Read More

Sand volcanos on a flat and sandy beach in the Netherlands; By Bert Buizer, PhD

May 1st, 2018

In 2013, some interesting water escape structures were observed near the coastal resort of Bergen aan Zee, in the Netherlands.

Read More

Te Pito O Te Henua shore (Rapa Nui or Easter Island): a remote and mysterious place with rare beaches; By Nelson Rangel-Buitrago, William J. Neal & Adriana Gracia

April 1st, 2018

One of the most remote and youngest inhabited volcanic islands in the world is Te Pito o Te Henua Island, or as more commonly known: Easter Island (Rapa Nui or Isla de Pascua). World famous for its mysterious monumental statues (moai) erected by the early Rapa Nui people, the island is located in the southeastern Pacific Ocean nearly 3,650 km west of Chile.

Read More

Newfoundland’s Sandy Beaches: A Glacial Legacy; By William J. Neal & Joseph T. Kelley

February 1st, 2018

“Newfoundland” as a coastal place does not conjure up images of sandy beaches, but rather scenes of wave-cut rocky cliffs, bird rookeries on small rock islands, sea stacks, and boulder and cobble beaches if wave deposits are present. But scattered among the latter are genuine sand beaches.

Read More

Torrevieja, Spain; By Norma J. Longo

January 1st, 2018

Torrevieja, a former fishing village on the southeast coast of Spain (Costa Blanca) in Alicante province, is now a thriving tourist city with a 2016 population of around 85,000, down from a high of over 105,000 in 2013.

Read More

Archive / Beach Of The Month