Pillow lavas and the Leidenfrost effect

Abstract

Field observations of the formation of pillows by hot, de-gassed lava entering the sea have proved that their generation involves the underwater exposure and movement of incandescent material. This is made possible by the Leidenfrost effect, the phenomenon whereby film boiling replaces the usual nucleated boiling above a certain temperature, thereby forming an insulating sheath of vapour around any sufficiently hot body immersed in a liquid. Only on cooling below a certain temperature (defined here as the Nukiyama temperature) will rapid heat exchange occur between water and hot, gas-free lava. Near the surface, this could produce phreatic explosions and extensive clouds of steam.

Characteristics and origin of peperite involving coarse-grained host sediment

“…In interactions with wet sediment, preservation of high temperatures requires insulation of the magma from direct contact with pore water. By analogy with the mechanism of pillow formation and the Leidenfrost e¡ect (Mills, 1984), insulation depends on the formation of stable vapour ¢lms at the magma^host sediment interface (Kokelaar, 1982). Such vapour ¢lms can be generated and maintained providing a certain critical temperature (the Nukiyama temperature; Mills, 1984) is exceeded and there is a su⁄cient supply of pore £uid.…”

“…By analogy with the mechanism of pillow formation and the Leidenfrost e¡ect (Mills, 1984), insulation depends on the formation of stable vapour ¢lms at the magma^host sediment interface (Kokelaar, 1982). Such vapour ¢lms can be generated and maintained providing a certain critical temperature (the Nukiyama temperature; Mills, 1984) is exceeded and there is a su⁄cient supply of pore £uid. In cases involving intrusions into wet sediment, these conditions will be met most readily during initial stages of interaction at the leading edges of advancing intrusions.…”

“…In cases involving intrusions into wet sediment, these conditions will be met most readily during initial stages of interaction at the leading edges of advancing intrusions. With time, the magma will cool to the point where nucleation boiling rather than ¢lm boiling occurs (Mills, 1984) and the magma will no longer be insulated.…”

Field Characteristics and Erosional Processes Associated With Komatiitic Lavas: Implications for Flow Behavior

“…The very high heat budget of komatiites would also have produced significant physi-cal erosion. When magma comes in contact with water, the water at the interface boils and flashes to steam in a process called film boiling (Mills 1984). Film boiling produces a turbulent, high-temperature, high-pressure film of vapor, perhaps only millimeters to centimeters thick (Fig.…”

“…This temperature difference would have set up very high temperature-gradients, and should have triggered extreme supercooling, chilling and quench-induced fragmentation. That hyaloclastites are relatively rare can only be explained by extremely efficient film boiling at the boundary between the lava and the seawater (Mills 1984). The film of steam produced insulates the lava and buffers the cooling gradient below that required to induce quench fragmentation.…”