GEOL 1001 Chapter : Geology
Document Summary
Scoria: tabular intrusions, dikes- cut across rock layering, dikes sometimes occur in swarms, three dikes radiate away from shiprock, new mexico, basalt (dark) intruded light sandstones in antarctica. Intrusive and extrusive rocks commonly co-occur: magma chambers feed overlying volcanoes, magma chambers may cool to become plutons, many igneous geometries are possible, with erosion, progressively deeper features are exposed, vertical dikes, horizontal sills, mushroom-shaped laccoliths. Influence on landscape: continued uplift and erosion exposes the pluton. Unroofing takes long periods of geologic time: plutons may amass into a batholith. Plutonic activity: immense volumes of intrusives, form above subduction zones, may add magma for tens of ma, batholiths mark former subduction. Interlocking mineral grains from solidifying melt: texture reveals cooling history, fine-grained, rapid cooling, crystals do not have time to grow, extrusive, coarse-grained, slow cooling, crystals have a long time to grow. Crystalline textures: texture reveals cooling history, porphyritic texture- a mixture of coarse and fine crystals.
