Physical Geology – Spring 2006 Review Sheet – Midterm II Chapter 4 What are two ways that igneous rocks form? You should know three methods of producing a melt, and where in a plate tectonic setting each situation would occur. (be sure to review Figure 4.3) Know how the relative proportion of silica to Fe/Mg minerals is used to categorize magma (e.g., silicic(felsic), intermediate, mafic, ultramafic) What two factors influence the viscosity of a magma/lava? You should know the trends for each factor (e.g., higher temperature = lower viscosity…etc) Where would a high (low) viscosity magma originate? (what would you have to melt) What 4 factors influence the composition of a melt? You should be familiar with Bowen’s Reaction Series and what the order of crystallization means in terms of mineral stability at the surface of the Earth. (Figure 4.6) How do the cooling rates differ between intrusive and extrusive igneous rocks? What does this mean in terms of crystal size? What two factors are used to classify igneous rocks? Know the terms are used to describe the texture of an igneous rock (phaneritic, aphanitic, glassy, porphyritic, phenocryst, matrix, pegmatite, pyroclastic) You should know the intrusive and extrusive examples for all 4 compositional groups (see Figure 4.16) (granite, diorite, gabbro, peridotite, rhyolite, andesite, basalt, komatiite) Key Terms: lava magma decompression melting viscosity partial melting fractional crystallization plutonic igneous rock volcanic igneous rock country rock stoping xenolith intrusive contact dike sill pluton ash fall Chapter 5 By what 2 methods do sedimentary rocks form? How do the products of the 4 chemical weathering reactions we covered vary? (the reactions are dissolution, hydrolysis, oxidation, hydration) How do physical and chemical weathering work together to speed the breakdown of rock? What 5 steps are involved in forming sedimentary rocks? (e.g., weathering, erosion,…..) Know the following terms associated with soil horizons: topsoil, subsoil, zone of leaching, zone of accumulation, O-A-B-C-Horizons How does a caliche soil differ from a lateritic soil? What are the 4 main categories for classifying sedimentary rocks? How does each form? What 3 properties are used to classify clastic/detrital sedimentary rocks? For each of the following rocks, you should know: (conglomerate, breccia, sandstone, siltstone, shale, fossiliferous limestone, coal, halite, travertine) the category the rock belongs to the properties of the rock an example of the type of environment that could form it How do these sedimentary structures form? bedding plane, cross beds, turbidity current, graded bedding, ripple marks, mudcracks, fossils For the main terrestrial and marine environments, know what type/size of clasts are common, and know what type of rock might be formed What do the rounding and sorting of grains tell us about transport history? Key Terms: physical weathering chemical weathering jointing frost wedging root wedging differential weathering pedalfer pedocal transgression regression Chapter 6 What 3 processes form metamorphic rocks? (heat, pressure, stress) Know how each causes change How is mineral stability used to identify the pressure/temperature conditions a rock has been exposed to? (our example was for aluminum silicates) What is the difference between pressure and differential stress? What textural property results from a normal differential stress? What are the 3 types of metamorphism? In what tectonic setting might each form? How do foliated and nonfoliated metamorphic rocks differ? Know 3 examples of nonfoliated metamorphic rocks Know the metamorphic grade sequence of a shale (shale, slate, phyllite, schist, gneiss) Know the conditions of the 3 main metamorphic facies (pressure/temperature), and know what type of metamorphic rocks are formed in each You should know the rock cycle and how it applies to each rock type we’ve studied. (Be sure to read Interlude B, pp. 175-180) Key Terms: metamorphism protolith recrystallization metasomatism shear stress normal stress tensional stress compressional stress contact aureole mylonite **************************************************************************** If you are interested in viewing either of the videos again, AND/OR you are interested in viewing the metamorphic rock video, you can do so at: Non-print Media Services – Hornbake Library (go in front entrance, on bottom floor) intrusive igneous rocks: QE26.2.E37 1992 pt 13-14 sedimentary rocks: QE26.2.E37 1992 pt 17-18 metamorphic rocks: QE26.2.E37 1992 pt 17-18