Geology Demo - Liquid Nitrogen Base Surge and Downburst

CAUTION: Liquid nitrogen is very cold and presents a serious frostbite hazard, especially if it gets trapped against your skin (e.g.in your clothing). Additionally, gaseous nitrogen occupies more volume than the same quantity of liquid nitrogen. Gaseous nitrogen produced quickly enough in sufficient quantities can displace oxygen from the air. Containers filled with liquid nitrogen could fail without warning due to thermal shock or gas pressure. Protect yourself accordingly.

Base surges and downbursts occur when dense gases sink rapidly down through less dense gases and spread outward upon impacting the ground. Base surges are clouds of gas and dust that move along the ground away from a volcanic eruption or a nuclear explosion. It is often produced when a column of these clouds collapses to the ground. Downbursts, and smaller microbursts, occur when cold air sinks to the ground from a thunderstorm. A similar phenomenon seems to occur during the filling of a typical 4 liter Dewar flask with a relatively narrow neck from a liquid nitrogen supply line. As the liquid nitrogen (boiling at 77 K) first passes through the supply line and into the flask at room temperature (about 298 K), the liquid nitrogen flashes into pressurized vapor. The vapor rushes out of the Dewar flask, creating a column of cool nitrogen vapor and condensed water droplets. As the supply line cools, liquid nitrogen actually makes it into the Dewar flask. The liquid nitrogen boils away less rapidly and the pressure forcing the nitrogen vapor up from the Dewar flask decreases. The cold dense vapor column then collapses down and spreads across the ground, resembling a base surge or a downburst.

References:

Clark Johnson. Base Surge. http://www.geology.wisc.edu/~g111/Terms/base_surge/base_surge.htm (accessed June, 2006).

Denton County, Texas. Downbursts. http://www.co.denton.tx.us/dept/main.asp?Parent=82&Link=84#Mistaken (accessed June, 2006).

BELOW: A liquid nitrogen base surge: (FIRST) Formation of the column of cool nitrogen vapor and condensed water and (MIDDLE) collapse of the column.  (LAST) Surge of air moving out from a thunderstorm rain column near Carlsbad, NM, in June, 2012.