EVSC 2800 Study Guide - Midterm Guide: Oceanic Crust, Pumice, Basalt

• School: University of Virginia
• Department: Environmental Sciences
• Course: EVSC 2800
• Professor: Herman Janet

Document Summary

They are also referred to as volcanic mudflows or debris flows. As the lithospheric plate moves across the stable hot spot, a chain of volcanoes results. The remnant extinct volcanoes are increasingly older away from the hot spot: shield volcanoes. Built by the eruption of fluid, basaltic lava. Low-viscosity mafic lava spreads out widely from the central vent and builds up successive thin layers of basalt. May exhibit a ropy surface texture as it cools and solidifies on the surface (this type of lava flow is called pahoehoe) Viscous lava that flows with a blocky texture is called aa. Cavities left from escaping bubbles of gas are called vesicles: flood basalts are formed from fissure eruptions. In a fissure eruption, basaltic lava pours out quietly from a long fissure (crack). Repeated outpourings of basaltic lava from the fissures at the mid-ocean ridges build new oceanic crust. Without a central vent, fissure eruptions of mafic lava form widespread layers.