Chapter 13: Introduction to Landform StudyI. The Unknown InteriorA. vertical structure of the Earth1. crust: outermost solid layer of the Eartha. thicker below continents than oceans1) oceanic crust ~5-6 miles thick2) continental crust > 3 times thickerb. Moho (Mohorovicic discontinuity): boundary between the crust and mantle below2. mantle: layer of the Earth’s interior between the crust and the core; extends downward ~ 1,800 milesa. lithosphere: rigid outer layer of Earth that consists of the crust and upper mantleb. asthenosphere: plastic layer of the mantle that underlies the lithospherec. mesosphere: lower mantle where rocks are again rigid3. outer core: molten shell that underlies the mantle4. inner core: solid, very dense center of the Earth composed of iron/nickel or iron/silicateB. Geographers Focus on the Surface1. geographers focus on the zone of human habitation2. interest in how deeper portion influences topography and other surfacefeaturesII. Composition of the CrustA. intro1. minerals: naturally formed inorganic compounds and elements that have a specific chemical composition and characteristic crystal structure2. magma: molten material in Earth’s interior3. rock: solid material formed of aggregated mineral particles4. outcrop: surface exposure of bedrock5. bedrock: residual rock that has not experienced erosionB. Igneous Rocks1. igneous rock: rock formed by solidification of molten magmaa. shared trait: all have crystalline structureb. slow cooling  large crystals; very coarse-grained appearancec. rapid cooling  small, even microscopic crystals2. extrusive igneous rocks: molten rock ejected onto Earth’s surface, solidifying quickly in the open aira. ejection of lava from volcanoesb. oozing of magma from fissuresc. basalt: dark, fine-grained; most common of extrusive igneous rocks3. intrusive igneous rocks: rocks that cool and solidify beneath Earth’s surfacea. also called plutonic rocksChapter 13: Introduction to Landform Study – p. 1 of 5b. originally buried intrusive rocks may subsequently come to surface bybeing pushed up or by being exposed by erosionc. granite: light colored, coarse-grained; most common of intrusive igneous rocksC. Sedimentary Rocks1. sedimentary rock: rock formed by sediment that is consolidated by the combination of pressure and cementationa. mechanical and chemical processes cause rocks to disintegrateb. resulting sediment may be transported by water, wind, ice, and/or gravityc. sediments, often sorted by size, are deposited in quiet body of water, especially ocean floord. weight of thick deposits causes pressure and results in compaction and cementation of sediments into rock2. strata: more or less distinct horizontal layers of sedimenta. strata are characteristic feature of sedimentary rocks b. although originally deposited and formed horizontally, strata may subsequently be uplifted, tilted and deformed 3. sedimentary rock is classified based on how it is formed:a. mechanically: formed by the compaction of fragments of pre-existingrocks1) fragments may range in size from boulders to clay2) most common types:a) shale: composed of silt and clay particlesb) sandstone: composed of compacted sand grainsb. chemically: formed by precipitation of soluble materials1) calcium carbonate: most common cementing substance2) limestone: most widespread typec. organically: formed from accumulated remains of dead plants and animals1) coal 2) limestoneD. Metamorphic Rocks1. metamorphic rocks: rock that has been drastically changed by heat and/or pressurea. structure, texture, composition and appearance are alteredb. cooking process causes mineral components to be recrystallized andrearranged2. foliation: banding that gives metamorphic rocks a wavy-layered appearance3. metamorphic rocks:a. marble (from limestone)b. quartzite (from sandstone)c. slate (from shale)4. most common metamorphic rocks (high degree of metamorphism; original rock unknown)Chapter 13: Introduction to Landform Study – p. 2 of 5a. schist – very narrow foliationsb. gneiss – broad foliationsE. Relative Frequency of Rock Classes1. sedimentary a. most common exposed bedrockb. 75% of the continents c. sediments cover nearly all the seafloord. thin layer: averages < 1.5 miles e. 5% total volume of crust2. igneous rock make up bulk of crust 3. enormous amount of metamorphic rock beneath the crustal surfaceF. Focus: Common Rock-Forming Minerals1. only a few dozen of the 3,500 recognized minerals are important constituents of the Earth’s crust2. 7 principal categories of rock-forming minerals:a. silicates 1) compose bulk of rocks of crust2) combine 2 most abundant elements of the lithosphere:a) oxygenb) silicon3) hard and durable4) most abundant:a) feldspars b) quartz b. oxides1) element combined with oxygen2) most widespread are those that combine with iron, and are major sources of iron orea) hematiteb) magnetitec. sulfides1) composed of sulfur in combination with 1 or more other elements2) includes many of most important ore mineralsa) galena (lead)b) sphalerite (zinc)c) chalcopyrite (copper)3) abundant in veinsd. sulfates1) minerals that contain sulfur and oxygen in combination with some other element, principally calcium2) mostly found in sedimentary rockse. carbonates1) composed of one or more elements in combination with carbon and oxygen2) common in sedimentary rocksf. halidesChapter 13: Introduction to Landform Study – p. 3 of 51) salty minerals2) least widespreadg. native elements1) minerals that occur as discrete elements2) precious metals: gold, silver III. Some Critical ConceptsA. Basic Terms1. topography: surface configuration of Earth2. landform: individual topographic feature, of whatever size3. geomorphology: study of the characteristics, origin, and development of landforms4. relief: difference in elevation between the highest and lowest points in an areaa. maximum world relief:1) 12-13 miles2) between top of Mount Everest and bottom of Mariana TrenchB. Uniformitarianism1. uniformitarianism: processes that formed the topography of the past are the same ones that have shaped contemporary topography2. most processes are permanent and slow acting3. development of landforms is a virtually endless eventC. Geologic Time (Fig 13-18) 1. geologic history divided into 4 major eras:a. Precambrian – 7 or 8 times longer than the 3 other eras combinedb. Paleozoic c. Mesozoic d. Cenozoic: 66 billion years ago to present2. eras are divided into periods3. more