Sunday, May 26, 2024

Is Coronado an Island, Peninsula or a Tombolo?

The debate rages on.

Written by, and republished with permission of, Daron Case. 

This week we have been burning through geologists trying to determine whether Coronado is an island, or more specifically, whether Coronado can be deemed a “tied island.”

Map Image Courtesy of Google and Google Earth

Wikipedia describes a “tied island” or “land-tied island” as “landforms consisting of an island that is connected to land only by a tombolo: a spit of beach material connected to land at both ends.”

I started by going to Wes Danskin – a geologist at USGS (United States Geological Survey) – however, Wes is mainly a hydrologist, and had never heard of the term “tombolo.” Next, we went to Dr. Philip Pryde – Professor Emeritus of Geology at SDSU – however, he too, was unable to answer the question.

Wednesday morning, per a recommendation from a colleague, I reached out to SDAG (San Diego Association of Geologists)… and was put in touch with Joe Vettel, GE – President/CEO of Geocon Incorporated – who responded:

“The first time I ever heard the word ‘tombolo’ was from a PhD geologist that used to work for Geocon and it’s the word he used to describe the Silver Strand. You can consider the Strand a tombolo. The ‘Dictionary of Geological Terms’ prepared by the American Geological Institute defines a tied island as ‘an island connected to the mainland or to another island by a tombolo.’ A tombolo is defined as ‘a bar connecting an island with the mainland or with another island.'”

So there we have it… I don’t believe we can find a more authoritative source. From a geological perspective, Coronado is an island. A tied island is an ISLAND connected to the mainland via a tombolo, and the Silver Strand is a tombolo.

UPDATE: The geologist Wes Danskin from USGS wrote to me again this morning [Thursday] regarding whether Coronado is a “tied island” – he said:

“The technical answer for those who care is fairly straightforward and can be answered by any of several public websites and local geologists. The terms they may want to understand are island, barrier reef, sand bar, delta. My impression is that both North Island and Coronado Island are physically rooted islands as Pat Abbott from SDSU has stated and shown in videos. The San Diego River discharged into San Diego Bay up until 1953. It formed a delta from Old Town through what is now the airport, and when ocean levels were lower a few thousand years ago, out into much of San Diego Bay. This sediment and ocean circulation forms deposits including sand bars, spits, and likely tombolos.”

I ran a search on Professor Pat Abbott from SDSU to see what he believed on this topic – and found this video linked below. If you have a minute, watch from the 18:07 mark as he’s walking along the Silver Strand – it is truly remarkable.

UPDATE II:  For anyone interested in the conclusion of our research and study about whether Coronado is a “tied island,” I just heard back [Saturday] from SDSU Professor Pat Abbott who is the foremost expert on the geological formation of San Diego – his response:

“Coronado is a land-tied island. The Silver Strand is a tombolo. Coronado was dry land continuous with San Diego. Then, especially between 14,000 to 7,000 years ago, the ice sheets burying much of North America, Scandinavia and Siberia largely melted causing sea level to rise and surround Coronado, turning it into an island. Coronado was largely shielded from North Pacific storms by Point Loma. However, summer storms in the low latitudes send large waves northward; these waves push Tijuana River delta sands northward via longshore drift. These longshore-drifted sands built the Silver Strand which grew all the way to the island of Coronado thus tying it to the land.”


Some comments to Daron’s original publication are below:

  • I’ve never understood why people get so worked up about this. What/who has it ever hurt to refer to it as an island? Most tourists think it’s an island, and if you live here and get stuck with both the bridge AND Strand shut down (and I have)… sure feels like one!!!
  • Thank you for your time and energy. Never did your expert say Coronado is an “island”. He said it was a “tied island.” Certainly you can’t just drop the “tied” part of the description. I have reached out to my own “experts,” and I will defer to it being a “tied Island” until I hear differently.
  • I love that its called an island…Islanders forever. As I’ve said many times, my grandmother came here in ’24 and she and her friends referred to it as an Island…North and south islands. So many remember the Strand flooding and not able to cross in their model As until the tide receded. I don’t think this can ever be put to rest..or should it be. Makes for lots of comments and many diverse opinions.
  • 1. I think people should accept the greatness of Coronado, not try to make believe it is something it’s not (and it is not surrounded by water, as an island should be).
    2. It was promoted (is promoted?) as a way to bring in tourists; I am not really supportive of increasing tourism.
    3. Probably the least definitive reason; It seems that it is the tourists/business first folks, newbies (which is a state of mind not an actual time here on Coronado), and pretentious people who tend to call Coronado an “island.”
  • I grew up in the Seattle area and lived on an island. A REAL island in Puget Sound. I started coming here in the early ’70s. Got engaged at the Del over 30 years ago and have lived here for 14 years. Had always heard it referred to as an island. Thought it was a charming little quirk of the place. Never once felt the need to argue the point, even though it was so obviously attached to a spit of land.

An article from April 1, 2010 – Coronado Island Changes Name to Coronado Peninsula

What do you think?


Managing Editor
Managing Editor
Originally from upstate New York, Dani Schwartz has lived in Coronado since 1996. She is happy to call Coronado home and to have raised her children here. In her free time she enjoys reading, exercising, trying new restaurants, and just walking her dog around the "island." Have news to share? Send tips or story ideas to: [email protected]

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