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How were giant coastal sand dunes formed?

Published: 6 September 2018 (GMT+10)

Today’s feedback is from J.H. of the United States asking about the formation of barrier islands and beach ridge structures.

Fraser-Island-Parabolic-Sand-Dune
A large parabolic sand dune blows across older sand dunes on Fraser Island, a large sand island off the coast of Queensland.
Frase-Island-Podzol-Soil-Profile
Podzol soils (such as this on Fraser Island) are common on large older coastal sand dunes.

Hello,

I spend part of each year in Florida, and the last time I was there, I made a visit to a place which I was troubled by, feeling it might hold problems for a young earth.

I visited a town called Lake Wales, which is one of the highest points in Florida, at some several hundred feet above sea level. As I understand it, Lake Wales sits upon the Lake Wales Ridge, which (geologically) as it was explained to me is composed of rocks that give the appearance of being an ancient barrier island structure.

I couldn't find anything on your site about barrier islands or these beach ridge structures. As I learned from a geologist in Florida, there's more than one of these ancient beach ridges, and in fact there are several of them across the state. The problem for a young earth is that, while we do know that sea level was higher in the past, beach ridge structures take a while to form, at least in the young earth context. I fear they show that sea level must have descended very slowly.

CMI writer/speaker  responded:

Greetings J.H. and thank you for your email.

I agree that Creation Ministries International have little written on beach ridge and coastal dune structures, but this should change in coming years as research on such features will be published in forthcoming issues of the Journal of Creation and the Creation Magazine. The short answer to your question is that beach ridge and coastal dune structures do not pose a problem for a young earth.

Whilst I have not been to the Lake Wales Ridge, the site bears similarity to other large sand dune sites in other countries. I have for example spent much time on Fraser Island, the largest sand island in the world, and on Morton and Stradbroke Islands in southern Queensland, Australia.

Fraser Island sand dunes sit many hundreds of metres above sea level and appear largely to be parabolic sand dunes. It is argued that these successive dunes (that represent at least nine dune building periods) were laid down during differing periods of sea level rise over the past 700,000 years. Those to the west are considered older than those closer to the Pacific Ocean on the east side.

More recent research on Fraser Island shows that there may only be two dune building periods, that immediately before the post Flood Ice Age, and that after the post Flood Ice Age. During the latter dune building period the sea level was slightly higher. Dating techniques are ineffective in these environments, but soil profile development (in this case podzolic soils) show that whilst there is an age difference between the two dune systems, neither approach anywhere near 700,000 years in age.

The parabolic dunes on Fraser Island, and nearby parallel dunes to the south of Fraser Island (something you seem to have at Lake Wales) do not take long to form. On Fraser Island they are still growing today but would have grown even faster when the sediment supply was abundant (during both post Flood and post Flood Ice Age periods) and when temperature and rainfall conditions were significantly changing. It is because of the rapid dune growth associated with the Ice Age that these barrier islands and beach dunes do not pose a problem for young earth geology.

Your email does highlight an important area of landscape research that I trust we will have resources available online in the future.

Blessings,

Dr Ron Neller
Scientist, Writer, Speaker

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