Some examples of those are a lighter-than-water rock, pumice, as well as obsidian.
These things can produce rocks with highly vesiculated texture, as well as a certain glass that can be dated by observing its degree of hydration. Some large-scale versions of these things in Siberia are implicated in the Great Dying. A bomb is a large piece of tephra, a type of pyroclast that is emitted from these things. When they collapse, they form calderas. The appearance of these things away from plate boundaries is attributed to hot spots. Extrusive rocks are formed at these places. Some examples of those are a lighter-than-water rock, pumice, as well as obsidian. For 10 points, name these ruptures in the crust that allow magma to flow out and become lava.
These things can produce rocks with highly vesiculated texture, as well as a certain glass that can be dated by observing its degree of hydration.
volcanoes [generously accept flood basalts or trap basalts]