Thunder Dunes

It may not be useful, but the interesting thing about the Thunder Dunes is I can tell you exactly when high tide is nearly 200 miles from the nearest coast.

— Jasper Cameron, Leader of the Bronze Ravens

Geography

The region known as Thunder Dunes (surrounding the town of the same name) can be found at the very southern reaches of the Myrdhor Desert. It is now known that its name comes from its unique system of underground caverns and vents. Covering several hundred miles, the surface looks much like any other sandy desert found throughout the world. Rolling dunes that migrate with the winds, some stabilized by dune grass, occasional sand flats, all hundreds to thousands of feet deep over bedrock.
It is the bedrock that gives the area its unique feature. There are a massive series of irregular tunnels and chambers found in the bedrock with the occasional vent to the sand. The largest entrances to these tunnels, though, are found on the coast of the area.
As the tide comes in, pockets of air form and pressurize. These pockets collapsing, or escaping to a vent, cause a massive booming sound similar to thunder, hence the name Thunder Dunes. As the tide comes in the thunder starts, as the tide turns, it quickly tapers off. Natives to the area claim to be able to tell different tides by the sound of thunder, but this largely considered boasting.
A peculiar phenomenon is occasionally observed, when a large enough pocket of air is able to escape through a vent, one can witness a "Sand geyser" as the air blows sand hundreds of feet into the air. Just be warned, the displacement of this much sand tends to destabilize the surrounding sand for many hundreds of yards.
Some poor souls have attempted to map the caverns and find the theorized "thunder chambers," with the results one would predict from attempting to explore hundreds of miles of tunnels of razor sharp rocks that fill and drain with each turn of the tide.

Location under

Myrdhor Desert