Fracking uses high-pressure liquid pumped deep underground to fracture shale rock and release gas.

BBC: Fracking firm Cuadrilla plans new well at St Annes site

When water velocity is high, the pressure within the liquid drops to below the vapour pressure of water, allowing tiny air bubbles to expand.

BBC: Shrimp, bubble and pop

Liquid-fuelled rocket engines work by mixing the fuel (in this case kerosene) with liquid oxygen at high pressure.

ECONOMIST: On a rotor-blade and a prayer | The

Either way, the CO2 must be put somewhere, for which strategies include pumping it into rocky formations (such as depleted oil and gas wells) at a pressure of 100 atmospheres, or even piping it in liquid form under pressure onto the sea-floor where it is cold enough and the pressure high enough that it is hoped the material will stay there, assisted by the formation of CO2-hydrate.

FORBES: Carbon Capture And Storage: Yea Or Nay?