What Would Tokyo Look Like if Sea Levels Rise 10 Meters?

Will Tokyo be underwater in the next 100 years? Find out what Tokyo’s coastline would look like if sea levels rise 10 meters!

August 9, 2021
  • Climate change and the resulting rise in sea levels will have great impacts on cities around the world in the next century
  • Japanese geologist goes viral on Twitter after posting a map of what Tokyo’s coastline would look like if sea levels rise by 10 meters, then another of if all the ice on earth melted
  • The findings in the map also reveal an interesting part of Japanese history

Climate change, global warming, and rising sea levels have been a hot topic for what seems like decades now.  While many seem to be on board, like almost any other thing in modern media, many believe climate change is a sham.

With rising global temperatures and the resulting rising sea levels, the cold-hard truth is that if we don’t do something about it now, we may see very impactful consequences in around 100 years. 

Rising sea levels. Image sourced from Inhabitat

While each of us can do our best to stay eco-friendly, large corporations, governments, and organizations must get involved.  Something else we can all do now is to raise attention.  

Who is Shusaki Miyaji?

Raise attention is exactly what Shusaki Miyaji, a geography lecturer and award-winning geographical columnist who teaches at the Yoyogi Seminar, a long-standing Japanese preparatory or “cram” school, has been utilizing the powers of the internet to get the conversations going. 

An award-winning geographical columnist Shusaki Miyaji. Image sourced from NewsPicks.

Miyaji’s geography courses and lectures are distributed across Yoyogi Seminar locations nationwide and to various schools.  As a columnist, Miyaji has sold over 60,000 copies of his book “Learn About the Economy through Geography” and won the 2017 Association of Japanese Geographers Award in the Social Contribution Category. 

On top of this, Miyaji has his own website and his own YouTube channel called “Miyajiman Channel,” which focuses on geographical content has over 2,000 subscribers since his first video was released a year ago.

Will Tokyo Be Underwater in the Future?

While you’ve likely heard of Venice and Amsterdam “going under” when it comes to talking about the consequences of rising sea levels, Miyaji recently went viral on Twitter after posting a topographical map of the greater Tokyo area known as the Kanto Plains that would show what the impact of a 10-meter rise in sea level would look like.

The picture Miyaji posted on Twitter. Image sourced from Yahoo News.

What was so interesting about this was what it implied.  The areas where the elevation was less than 10 meters above sea level were shaded black, revealing the areas that would be underwater. 

Further, Miyaji’s image has small blue flags plotted down where each of Kanto’s many ancient shell middens are found.  Shell middens, also called shell heaps, are human-made archeological features consisting mainly of various mollusk shells and human activity.

Shell middens are usually the site where a village would have thrown its garbage and provide evidence on what kinds of foods were once being eaten, what kind of tools were used, and what kind of goods people had, making them a critical focus point for archeologists. 

Shell midden. Image sourced from SpringerLink.

As shells are high in calcium carbonate, this results in slower rates of decay and breakdowns of soil and organic material.  However, shell middens are very difficult to excavate fully.

An Interesting Piece of History

The key finding that Miyaji hypothesized about was that the locations of shell middens would reflect where the sea level once was hundreds of thousands of years ago when the earth was warmer, and sea levels were higher.

As he expected, the shell middens of the Kanto Plains almost perfectly align with the coastline that would exist with a 10-meter rise in sea level.  These coastlines may reflect what the Kanto Plains looked like during the roughly 10,000 years long Jomon Period that spanned from 14,000 to 300 BCE.  

Jomon pottery example. Image sourced from

This is because one of the first excavations of a shell midden was in Tokyo at the Omori Shell Mounds back in 1877.  It was during this excavation that a style of pottery that was named Jomon was found.  Jomon is translated to “cord-marked,” as the pottery was described this way. 

The excavated Omori Shell Midden. Image sourced from Turumigawa915.
A closer look at the Omori Shell Midden wall that was excavated. Image sourced from Atlas Obscura.

Miyaji mentioned in an interview with Yahoo Japan that sea levels in Japan could rise 10 meters within 100 to 200 years from now, so action must be taken, or most of Tokyo may be underwater in the future.  

What Would Tokyo Look Like If All the Ice on Earth Melted?

Following this, Miyaji posted another image of what Tokyo’s coastline would look like if all the ice in Earth’s oceans melted. He calculated that if this were to happen, sea levels would rise by 66 meters. The image shows the areas below an altitude of 66 meters above sea level shaded in black that would essentially be underwater. Take a look at the image and his Tweet below.

Tokyo with areas below 66 meters above sea level shaded in black. Image sourced from Maidona News.

Miyaji also included an image of what the actual coastline would look like with the areas below 66 meters above sea level completely gone and replaced by ocean.

This is the kind of thing that Miyaji strives to use to fuel the conversation about tackling climate change, and of course, rising sea levels.  He also seeks to get more people, particularly younger people, to uptake an interest in geography.  

Check out his website, Youtube channel, or attend one of his lectures if you’re in Japan!  You are likely to be intrigued! 


Kevin Murasaki

Kevin Murasaki grew up moving back and forth between Chicago and Yokohama, Japan. Known as a "hafu", Kevin is half Japanese, and half American. Now a videographer and drone operator based in Fukuoka, Japan, Kevin enjoys playing basketball, driving on mountain or "touge" roads, and fishing in his free time. Kevin is a recent graduate of the University of British Columbia.

More articles by Kevin Murasaki

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