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Earth scientist’s Q&A explained newfound submerged continent

Jerry Dickens ESCI faculty scientist Jerry Dickens

Rice’s Jerry Dickens taught tens of thousands of people about the submerged continent of Zealandia on Thursday and never had to leave his office.

Dickens, professor of Earth science, participated in a “ask me anything,” or AMA, Internet science forum on Reddit, the popular social news and social media aggregator. Reddit Science AMAs are among the forum’s most popular features and reach as many as 100,000 users.



“I hadn’t even heard of it before a couple of weeks ago, but it was pretty easy to do,” said Dickens, who was asked to participate by colleagues at the International Ocean Drilling Program (IODP) based at Texas A&M University.

Dickens is co-chief scientist on IODP Expedition 371, which will drill core samples from the seafloor of the Tasman Sea between Australia and New Zealand later this summer. He’s also the editor of GSA Today, a journal of the Geological Society of America (GSA).

“The journal had a paper about Zealandia in its March/April issue, and the staff asked me to write a blurb about it for the press,” Dickens said. “That wound up going viral and appearing in hundreds of publications all over the world. Several media tracking services then wrote GSA stating that more than 900 million people had read something about Zealandia.

“IODP thought, ‘Hey, we’ve got an expedition that’s drilling Zealandia later this summer, so maybe we should capitalize on this,’ and they asked me to do the Reddit AMA,” Dickens said.

Dozens of questions came within minutes, and Dickens spent the next few hours composing answers and follow-up responses. When a user asked for an “eli5” about Zealandia, Dickens had to do a quick Google search to find the meaning: Explain like I’m 5.To kick off the AMA, Dickens simply had to post the following on Reddit’s moderated Science AMA site: I am Jerry Dickens, science faculty member at Rice University and co-chief scientist for the drilling expedition to understand the submerged continent of Zealandia — ask me anything!

Here’s his response:

The real basic question is “how does one define a continent?” For example, why are North America and South America generally considered separate continents when they are connected by the Isthmus of Panama?

So, we then get into the realm of definitions, where probably the best one is: “A continent is a large area of Earth’s surface underlain by continental crust mostly separated from other such areas by oceanic crust.” This nicely explains the well-known continents.

For reference, think of continental crust as the rocks on hipster kitchen counters, such as granite or schist, which have a density somewhere around 2.7 g/cm3, and oceanic crust as the dark rocks sometimes used in gardens, called basalt, which have a density somewhere around 2.9 g/cm3.

Now, consider the principle of isostacy – here think of ice and cork pieces in a glass of wine (although this is a bit confusing, because with the Earth, it’s continental crust (cork) and oceanic crust (ice) somewhat floating in the mantle, and most people would not want cork or ice in their wine!). The thickest and least dense pieces float the highest. So, the continents are high because they are floored by relatively thick and less dense continental crust (often > 30 km), and oceans are low because they are floored by relatively thin and dense oceanic crust (typically < 10 km). And the water — the ocean — fills in the low portions.

Then, we have Zealandia, which is floored by thin continental crust, so most of it sits much higher than typical regions of the ocean but much lower than typical regions of continents!

We have known about this aspect of our Earth around New Zealand and New Caledonia for well over 20 years. However, it has only recently become clear, through seafloor mapping, that the region is one connected continental block. Hence, a mostly submerged continent — a thin but expansive region of cork.

To see the entire discussion and learn more about Zealandia, visit:

To learn more about IODP Expedition 371, visit:

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