A professor of physical geography has put together the most detailed map yet of the sunken medieval town of Dunwich using underwater acoustic imagining.

The port town, often referred to as "the British Atlantis," was a hub of activity up until its collapse in the 1400s. This was brought about after a series of epic storms battered the coastline in the 1200s and 1300s, causing repeated flooding, submerging parts of the town, and flooding the harbor and river with silt. Today it stands as a small village, but up until its demise it was around the same size as medieval London. Despite still existing at depths of just three to 10 meters (or, 9.8 ft to 32.8 ft) below sea level, the murky conditions have made investigating what lies beneath particularly tricky.

Since 2010, however, Southampton's David Sear—along with the GeoData Institute, the National Oceanography Center, Wessex Archaeology, and local divers from North Sea Recovery and Learn Scuba—has been exploring the muddy depths using dual-frequency identification sonar (DIDSON) acoustic imaging.

"DIDSON technology is rather like shining a torch onto the seabed, only using sound instead of light," said Sear. "The data produced helps us to not only see the ruins, but also understand more about how they interact with the tidal currents and sea bed."

The camera uses high frequency sound and acoustic lenses to refract sound waves and create film footage without light. The technology is usually reserved for creating a fly-by of sunken ships, but it has now picked up the wreckage of the former trading hub in astonishing detail. In addition, old naval navigation charts helped in the tracking and mapping of where the former coastline stood.

We can now see where the local churches stood, and crumbling walls pinpoint the ancient town's remits. A one kilometer (0.6 mile) square stronghold stood in the center of the 1.8km2 space (about 0.7 square miles), with what looks like the remains of Blackfriars Friary, three churches, and the Chapel of St Katherine standing within it. The northern region looks like the commercial hub with lots of smaller buildings largely made of wood. It's thought that the stronghold, as well as its buildings and a possible town hall, may date back to Saxon times.

The loss of Dunwich, and our analysis of it, now stands as a stark reminder of what could be, argues Sear: "Global climate change has made coastal erosion a topical issue in the 21st Century, but Dunwich demonstrates that it has happened before. The severe storms of the 13th and 14th centuries coincided with a period of climate change, turning the warmer medieval climatic optimum into what we call the Little Ice Age.

"Our coastlines have always been changing, and communities have struggled to live with this change. Dunwich reminds us that it is not only the big storms and their frequency ... that drives erosion and flooding, but also the social and economic decisions communities make at the coast. In the end, with the harbor silting up, the town partly destroyed, and falling market incomes, many people simply gave up on Dunwich."

The find could perhaps not be more timely. Last year it was reported that 7m (about 23 ft) of Yorkshire coastline was lost to the sea (well above the average erosion of 1.7m/5.6 ft), and by January 2013 a recorded 8m (26.2 ft) had disappeared in the six months prior. More recently, a huge crack appeared in the chalky earth of the Jurassic Coast in March and holidaymakers were told to avoid the area lest the cliff collapse under them. Particularly wet weather has been weakening the land, while storms have continued to thrash the coastline.

Meanwhile in Brazil, the discovery of a large lump of granite rock 1,500km (932 miles) off the coast of Rio de Janeiro has led to claims that the real Atlantis has been discovered. The mythical land would be somewhat in the right position, being apparently created when Africa broke away from South America. Geologists are arguing that the rock—and others like it spotted by Japanese mini-submarine Shinkai 6500—suggests something is awry, considering granite forms on land and not thousands of kilometers out at sea.