EESA06H3 Chapter Notes - Chapter 5: Mantle Plume, Asthenosphere, Magma Chamber
Document Summary
Have millimeter-to centimeter-sized crystals or some have meter-long crystals and others are noncrystalline glass. Vary from white to black or have mixed colors. May contain holes, fragments, or compacted ash. Rocks with crystals visible to the eye are called phaneritic. Rocks with crystals not visible to the eye are called aphanitic formed from magma that solidifies too rapidly. Very coarse igneous rocks are called pegmatite. Many volcanic rocks contain small holes called vesicles referred to as vesicular. Some volcanic rocks contain angular fragments and are called a volcanic breccia. The different textures of igneous rocks reflect the environment in which the magma solidified. Magma can solidify at depth, erupt onto the surface as molten lava, or be explosively erupted a volcanic ash. Vesicles form when gases dissolved in magma accumulate as bubbles. They can form only under low pressures on the surface or very near the surface.
