GEOG 1114 1st Edition Lecture 21Outline of Last Lecture -Four major environmental factors -Adaptations of vegetation-11 Major BiomesOutline of Current Lecture -Structure of the Earth-Composition of the Crust-Types of rocks -Rock cycleCurrent Lecture Structure of the EarthFour Regions of earth’s interior (shells)Crust- outermost shell -Depth of 5 km below ocean to near 20 km below land-Moho layer- base of the crust; significant change in minerals Mantle extends to depth of 2900 km (1800 miles)Three sub layers or zones Lithosphere: hard rigid layer- includes crust Asthenosphere: to about 200 miles; hot tar-like rocks; pliableThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Mesosphere: lower mantle; thick rigid rocks Outer Core-Molten (magma) extends to depth of 5000 kmInner Core-Dense mass with radius of about 1450 km-Primarily made of iron/nickel or iron/silicate-Magnetic field of the Earth controlled by outer core-Magnetic poles not the same as axial polesComposition of CrustMinerals: All rocks are composed of interlocking smaller particles called minerals, which are made up of elements held together by electrical bonds.-More than 2000- Silicates: principal rock forming material-Fewer than 20 minerals make up 95% of the composition of crustal rocks-Contains atoms that arrange in various patterns to form crystals Types of RocksIgneous: Rock formed by the solidification of molten material called magma. - “Fiery inception” -Formed by the solidification of molten material (magma) -Lava- molten rock when it flows onto Earths surface-Pyroclastic- hard molten rock spewed from volcano-Classification of igneous rocks is based on mineral composition and textureIntrusive Igneous Rocks: (plutonic) -Rocks cool beneath Earths surface-Surrounding rocks insulate the magma, cools slowly -Individual minerals in a plutonic rock can grow to large size Extrusive Igneous Rocks: (volcanic)-Form on Earth’s surface-Cools quickly -Fine grainedIgneous rocks, particularly granite, form about 80 percent of the earth’s crust (continents and oceans) but sedimentary rocks often cover them. They become important to landform development if exposed via uplift or erosion.Sedimentary Rocks: Rock formed of sediment that is consolidated by the combination of pressure and cementation.-Most widespread rock type of the land surface.-Consist of small particles of rock debris or organic material that were deposited by water, wind, or ice as sediments and were later consolidated by the combination of pressure and cementation-This cementing takes place when sediments are laid down, buried and compacted into horizontal layers called strata. -Although originally deposited and formed in horizontal layers, the strata may later be uplifted, tilted, and deformed by pressures within the Earth-There are many types distinguished on the basis of grain size. How they were formed (mechanically, chemically, or organically). Conglomerates – compacted gravel, formed mechanically- cemented under pressureSandstone - compacted sand formed mechanicallyLimestone -chemically accumulated rock composed of calcium carbonate; coral and sea animalsShale - cemented clay and silt, formed mechanically Coal - originally accumulated; compacted skeletal remains of organismsMetamorphic Rocks: Rock that was originally something else but has been drastically changed by massive forces of heat and/or pressure working on if from within the Earth.-Causes a “ cooking” of rocks -Rearranges the crystal structure of the original rock -Denser and less porous than its sedimentary or igneous parent-Very resistant to weathering (erosion)Types include:Slate: derived from shaleSchist: derived from shale, basaltGneiss: derived from graniteQuartzite: derived from sandstoneMarble: derived from limestoneRock CycleRock materials pass from one form to another in the rock cycle:New igneous rock is weathered and eroded producing sediments.Sediments are eventually stratified into sedimentary rock.This in turn may be weathered and eroded forming anther generation of sedimentary rock.At continental edges rock may be subducted and changed by heat and pressure producing metamorphic rock. Some subducted material is completely meted and becomes new magma, forming new igneous