After 140 million years, it’s finally time for an ancient super volcano in Hong Kong to have a moment in the limelight … and fortunately not the limelight of its own fiery eruption.

According to Xinhua News, Hong Kong government scientists announced last Thursday that they had located the supervolcano in southeastern China. The volcano, known as the High Island Supervolcano, spewed forth 1,300 cubic kilometers of ash about 140 million years ago — enough to blanket all of Hong Kong.

Last Thursday’s press release says that the resulting caldera suggests that the original diameter of the High Island Supervolcano spanned a distance of about 18 kilometers (or just over 11 miles).

A handout from Hong Kong’s Geotechnical Engineering Office said that the supervolcanic eruption on China’s southeastern seaboard would have produced a global environmental impact and could be related to the extinction of the dinosaurs.

I don’t know a T-Rex tough enough not to run from a cataclysm like that.

What makes a volcano “super”?

For a volcano to be classified as a “supervolcano,” it has to have the potential to eject more than 1000 cubic kilometers, or 240 cubic miles, of volcanic material. The city of New York, meaning all five boroughs — Manhattan, The Bronx, Brooklyn, Queens and Staten Island — is 300 square miles. We’re talking about almost that many cubic miles. In other words, a LOT of volcanic material.

The scope of such an eruption is one thousand times greater than any volcanic eruption seen by modern humans. The power behind such an eruption lies deep within the Earth’s crust, where gargantuan chambers of magma form under the intense 2500 degree Fahrenheit heat rising from the planet’s mantle.

Is an extinct volcano still dangerous?

It’s important to note the difference between extinct and dormant volcanoes — but the determination between the two can be difficult. Volcanoes that no longer have a magma supply are extinct, while dormant volcanoes may still have a magma supply but have not shown activity for a long time.

Scientists have determined the High Island Supervolcano is extinct, and that it poses no risk of erupting again. This means that people living in southeast China (and any lingering dinosaurs) can breathe easy.

Main photo credit: dmourati/Flickr