GEO-SCI 103 Lecture 4Outline of Last Lecture I. Exploring the Seafloor II. Advances in Seafloor ResearchIII. Methods of Gene Regulation at the Translational LevelIV. Introduction to MutationsOutline of Current Lecture: Continents and Ocean BasinsI. Earthquakes and Seismic Waves: Earth Structures RevealedA. Internal Structure of the EarthB. Reaction with Composition and DensityII. Continents, Ocean Basins and EquilibriumA. Comparing and Contrasting Ocean Basins and ContinentsIII. Features of the Ocean Floora. Features of the Continental Marginsb. Features of the Ocean BasinCurrent LectureI. Earthquakes and Seismic Waves: Earth Structures Revealed:A. Internal Structure of Eartha) Solid part of Earth is layered into the core, mantle and crustb) Earthquakes, from a geological standpoint, are the natural consequenceof the dynamic movements of the Earth’s crust and upper mantle. c) Earthquakescommonly caused by volcanic activity or by slip along a fault zone that suddenly releases energy locked up by frictional forces between solid bodies of rock.1. Focusenergy released by an earthquake radiates from the point of origin or focus2. Epicenterpoint on the Earth’s surface directly above the focus3. Seismic waves4. Rayleigh Waves transmit energy along the surface that are primarily responsible for damage produced near the epicenterThese 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.5. P-Wavesprimary or pressure waves, migrate through solid and liquid materials in an alternating push-pull, or compression motion similar to that of sound waves6. S-Wavessecondary or shear waves that migrate through solid materials in a transverse motion analogous to a wave initiated by whipping a rope or rug. Cannot travel through liquids 7. By comparing the difference in arrival times of the P and S waves at numerous locations around the Earth, it is possible to pinpoint the focus and epicenter of an earthquakeB. Reaction with Composition and Densitya) As P and S waves ravel through the Earth, they encounter materials of differing composition and densityb) Densitythe amount of mass per unit of volume, measured in grams per cubic centimeter (g/cm^3))1. P and S waves travel quicker through denser rocks c) These differences cause some of the energy to be reflected from the boundary between the materials, and the remainder of the energy is refracted (bent) due to the change in physical properties C. Conclusions derived from Study of Seismic Waves a) Studying the patterns in the arrival times of the seismic waves at multiple recording stations around the globe has revealed that the Earth’s interior must have a layered structure b) Concentric layers are arranged according to density1. Core (densest materials)—metallic iron and nickel 2. Mantle (intermediate in density)—consists largely of iron and magnesium rich materialsa. Asthenosphere low strength, ductile part of the upper mantle3. Crust (least dense)—oceanic crust (granite) rich in iron, magnesium, calcium and have more silicon than the mantle whereas the rocks of the continental crust (basalt) are rich in aluminum, potassium and contain the most silicon. a. Lithosphererigid outer layer of the Earth that includes the Crust (continental, oceanic and the uppermost mantle)II. Continents, Ocean Basins and Equilibrium A. Comparing and Contrasting Continents and Ocean Basinsa) Ocean Basins: thin, more dense1. Composed of dark colored mafic rocks like basalt2. Average density (2.9-3.0 grams per cubic centimeter)3. Thickness (4-10 km)4. Forms ocean basins5. Rocks undergo continuous recycling into the mantle6. Ocean basins are relatively young because they always get broken down and submerged by thicker rocksb) Continental Crust: Thick, less dense1. Composed of light colored felsic rocks (granite)2. Average density (2.7-2.8 grams per cubic centimeter)3. “Buoyant” continents stand high4. Rocks remain near the Earth’s surface once formed5. Continents are old c) Density: the mass of a substance per unit volumed) Continental Margin: found at various coastlines including the Eastern Coast of North America. Ocean crust and continental crust are connected at this type of continental margin called “passive”III. Features of the Ocean FloorA. Features of Continental Marginsa) Continental shelf: offshore extension of the continent (underlain by continental crust)1. Relatively shallow, gentle seaward slopeb) Continental Slope: variable slope, underlain by thinned continental crust1. Dissected by numerous submarine canyons that conducts for a downslope sediment transport to the deep sea.c) Continental Rise: only found along passive continental margins1. Characterized by deep-sea fans, thick accumulation of sediment atthe base of the slope, derived from the erosion of continents2. Underlain by the boundary between continental and oceanic crustB. Features of Ocean Basinsa) Abyssal Plains: covers a large area of the seafloor; virtually flat except when interrupted by volcanoesb) Volcanic islands: active, dormant or recently extinct volcanoes above sea level1. Atollssteep sided rings of coral reefs enclosing a lagoon perchedon top of an extinct volcano2. Guyotsflat topped volcanoes that were formerly atolls at sea level at which time they were flattened by wave erosion. Theyeventually subsided below sea level when their volcanic activity ended 3. Seamountssubmarine volcanic peaks that do not have their tops flattened and were never above sea level4. Abyssal Hillsvery small volcanic peaks that are found in deeper parts of the ocean basin.c) Deep Sea Trenches:1. Long narrow steep sided troughs2. Deepest parts of the ocean3. Occur where two tectonic plates collide4. Seismically active (shallow to very deep earthquakes)5. Associated with volcanism landward of trench: either island arcs or volcanic mountain ranges on land.d) Ocean Ridges and Rises1. Active volcanic mountain ranges (Mid-Atlantic Ridge, East Pacific Rise)2. Continuous through ocean basins3. Extensive hydrothermal activity and chemical recycling of seawater through oceanic crust.4. Transforms faults and fracture zones5. Seismically active6. Occur where tectonic plates move apart