How does the transition from a midflow environment to a ventflow environment illustrate the effect of heat-loss rate on igneous textures?

Ventflow is the faster-cooling environment, so the contrast shows how a higher heat-loss rate affects the texture. Rapid cooling traps more gas bubbles before they can escape, producing more vesicles, while the cavities have a slightly smaller average diameter. Thus, the ventflow samples have more vesicles and slightly smaller cavities.

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