EARTH 119 Midterm: Exam 2 Study Guide
31 Jul 2016
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Lava that erupts from under water and solidi es as rounded masses that resemble pillows. Deposits contain ne-grained ash, small lapilli, blocks and bombs, and welded tuff. Lava can erupt on the anks of a volcano as well as from the central vent. Successive layers of ejected pyroclasts dip away from the crater at the summit. Central vent lled with lava from previous eruptions. Lava that has solidi ed in ssures forms radiating dikes that strengthen the cone. Forms at convergent margins where one plate descends beneath an adjacent place at the site of a subduction zone. Transformation of pre-existing rocks and minerals into new equilibrium assemblage. Reordering of atoms into new minerals through solid-state diffusion within minerals. Occurs in the absence of dissolution of original mineral. Differing processes lead to different pressure/temperature conditions and produce different kinds of stress on rocks. Minerals that form as at sheets form so that the sheets are perpendicular to the direction of stress.
