GEOG 1114 1st Edition Lecture 21 Outline of Last Lecture Four major environmental factors Adaptations of vegetation 11 Major Biomes Outline of Current Lecture Structure of the Earth Composition of the Crust Types of rocks Rock cycle Current Lecture Structure of the Earth Four 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 pliable These 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 km Inner 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 poles Composition of Crust Minerals 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 Rocks Igneous 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 texture Intrusive 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 grained Igneous 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 pressure Sandstone compacted sand formed mechanically Limestone chemically accumulated rock composed of calcium carbonate coral and sea animals Shale cemented clay and silt formed mechanically Coal originally accumulated compacted skeletal remains of organisms Metamorphic 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 shale Schist derived from shale basalt Gneiss derived from granite Quartzite derived from sandstone Marble derived from limestone Rock Cycle Rock 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 rock