GEOL 100 Chapter Notes - Chapter 5: Magma Chamber, Volcanic Rock, Volcanic Ash

• School: University of Maryland
• Department: Geology
• Course: GEOL 100
• Professor: Centorbi

Document Summary

Phaneritic: crystals visible to the human eye. Pegmatite: igneous rocks that contain very large crystals. Aphanitic: rocks consisting of microscopic crystals, resulting from magma that solidifies too rapidly. Porphyritic: include larger crystals in a finer grained matrix. Phenocrysts: the crystals in a porphyritic rock. Vesicular: rocks with vesicles, or small holes in volcanic rock. Volcanic breccia: contain angular fragments in a matrix composed of smaller fragments, volcanic ash, or fine-grained solidified magma. Vesicles: form when gases dissolved in magma accumulate as bubbles. Can only form under low pressures on the surface or very near the surface. Volcanic breccia: form in explosive eruptions or ash and rock fragments, lava flow that breaks apart as it solidifies while flowing, or form volcano-triggered mudflows and landslides. Volcanic glass: forms when magma erupts on the surface, cools so quickly that crystals do not have time to form. Porphyritic: magma needs sufficient time in subsurface magma chamber to grow visible crystals.