6.7

6.7 The decompression rate influence bubbles number and size

In magma that is crystallizing or decompressing, there may be competition between bubble nucleation and bubble growth. The diffusion rate, affected by magma viscosity, may limit bubble size because volatile elements near the bubble walls become depleted. We can measure the size distributions of bubbles frozen in pyroclasts, which are rapidly quenched products of eruption, to reveal these nucleation and growth rates. The decompression rate affects the size and number of bubbles in the sense that magma has or not time to create bubbles and them to growth.

By Stephen A. Nelson

By Ariel Provost

Bubbles nucleation doesn’t appear every time. For instance, if the decompression rate is too important, bubble can’t nucleate and the final product of the eruption is rock without vesicles.