Eruptiivsed

Eruptiivsed are extrusive igneous rocks formed when magma erupts onto the surface as lava and cools rapidly. The rapid cooling usually produces a fine-grained texture in which individual mineral grains are too small to see with the naked eye. In some cases, lava releases gases and forms vesicular rocks, or it may solidify so quickly that it becomes volcanic glass.

Two broad groups exist within eruptiivsed rocks. One consists of rocks that crystallize from lava as it erupts at or near the surface, yielding fine-grained or glassy textures. The other comprises pyroclastic rocks formed from volcanic ash and other fragmented material ejected during eruptions, which later lithify into rock. Lava-derived eruptiivsed rocks tend to be fine-grained or glassy, while pyroclastic rocks can range from ash-sized particles to pumice and larger fragments, depending on eruption dynamics.

Eruptiivsed rocks cover a range of magmatic compositions, from mafic to felsic, and their textures reflect eruption style and cooling rate. They contrast with intrusives, which crystallize below the surface under slower cooling and typically form coarser crystals. Eruptiivsed rocks are studied to understand volcanic processes, magmatic differentiation, and tectonic settings. They also have practical relevance in construction, mineral resources, and hazard assessment, illustrating how surface volcanism records the history of Earth’s crust and plate tectonics.