What Is a Tombolo?

01
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Tombolo at Shiaram Mhor, Isle of Lewis, Scotland

Idyllic spot
Photo courtesy Richard Gollin; all rights reserved

A tombolo is a special kind of sandbar that forms in the shelter of an offshore rock, connecting it to the mainland. It is a depositional landfill, a term derived from the Italian language.

There is something tantalizing about a tombolo. It is a road of golden sand leading to an island that is revealed only at low tide. In addition to a single tombolo, there are also double tombolos.  A double tombolo can enclose a lagoon that then fills with sediment, as is the case off the coast of Italy.

Mostly, tombolos come about by wave refraction and diffraction. Waves slow down due to the shallow water around the island when they come close. The wave pattern creates a convergence of a longshore drift on the island's opposite side. Essentially, the waves push sediment together from both sides; then when enough has built up, it will connect with an island. 

02
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Tombolo Near Mealista, Isle of Lewis, Scotland

Small but exquisite
Photo courtesy Richard Gollin; all rights reserved

Tombolos are built as waves from two opposite directions. The water is what pushes the sand together.

03
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Tombolo at Castle Tioram, Scotland

Golden road to a castle
Photo courtesy William Pullar; all rights reserved

Castle Tioram sits on a rock in Loch Moidart's south channel on the west coast of Scotland.

04
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Tombolo at Goat Rock, California

A textbook shot
(c) 2007 Andrew Alden, licensed to About.com ( fair use policy)

This tombolo has been fortified to serve as a parking lot for Goat Rock State Park, at the mouth of the Russian River.

05
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Tombolo at Hog Island, California

An island's islet
Photo courtesy Christie Rowe, all rights reserved

Hog Island is a tiny bit of bedrock in Tomales Bay near San Francisco. At its south end is this islet, connected to it by a tombolo that emerges at low tide.

06
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Tombolo at St. Michael's Mount, Cornwall, England

A holy island
Photo by maggiew at Flickr, used under Creative Commons license

For centuries, this island that connected to the mainland by a tombolo was a holy site dedicated to Saint Michael.

07
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Tombolo at Mont St. Michel, Normandy, France

Un ile sainte
Photo by Ewen Roberts at Flickr, used under Creative Commons license

Across the English Channel from St. Michael's Mount is the exactly analogous Mont St. Michel, sitting at the end of its own (now fortified) tombolo.

08
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Tombolo at Popham Beach, Maine, USA

A Maine classic
Thanks for the tip from Virginia Peterson. Photo by Eric Hill at Flickr, used under Creative Commons license

This view showing the flank of the wide, shallow tombolo is from the small offshore island at low tide.

09
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Tombolo at Toyo Seco Beach, Peru

From near Lima
Photo by Miguel Vera at Flickr, used by permission

The beach is in Cañete province in the Department of Lima.

10
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Oronsay, off Vallay, Scotland

A tiny place far away
Gallery of Tombolos. Photo courtesy Richard Gollin; all rights reserved

Oronsay is a common place name in Scotland that apparently means "ebb island," or tombolo. This oronsay lies off Vallay, an islet on the north side of North Uist in the Western Isles.

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Tombolo at Elafonissos, Greece

What's the Greek for tombolo?
Gallery of Tombolos. Photo courtesy Richard Gollin; all rights reserved

Cape Elena, in the foreground, is connected to the island of Elafonissos in the Peleponnese near Crete, by this lovely tombolo dividing Sarakiniko Bay and Fragos Bay.

12
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Tombolo at St. Catherine's Island, Wales

A castle near a dinosaur park
Gallery of Tombolos. Photo courtesy Richard Gollin; all rights reserved

St. Catherine's Island is an island only at high tide. Castle Tenby sits on it just outside the harbor at Tenby, on the Bristol Channel. The nearby Dinosaur Park adds to the geologic attractions here.