EES 1030 Lecture 14Outline of Last Lecture I. The Earth’s InteriorII. SeismologyIII. Global Network of Seismic StationsIV. Body WavesV. The Crust-Mantle BoundaryVI. Seismic TomographyVII. Earth’s layered structureVIII.The CoreIX. Earth’s Magnetic FieldX. The MantleXI. The CrustXII. The Oceanic CrustXIII.The Continental CrustXIV. Layers defined with physical propertiesXV. Plate Tectonics and Internal HeatXVI. Mountain BeltsOutline of Current Lecture XVII. Mapping the ocean floorXVIII. Features on the Ocean FloorThese 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.XIX.Passive Continental MarginXX. Active Continental MarginXXI.ContinentsXXII. Continental ShieldsXXIII. Mountain BeltsXXIV. Mountain BuildingXXV. Three types of plate boundariesXXVI. Convergent Plate BoundariesXXVII. The Appalachian Fold BeltXXVIII. Continental vs. Oceanic CrustCurrent Lecture- Mapping the Ocean Flooro We know more about the surface of Mars and Venus than we do about the ocean floor.o < 5 % of ocean floor has been mapped in detail o SONAR – Sound Navigation and Rangingo Multibeam sonar: map bathymetry over a 10-20 km swath to +- m. slow.o Satellite gravity: 1990’s seamounts > 1000 m high- Features of the Ocean Flooro About 50% of the seamounts previously uncharted- Passive Continental Margino Oceanic crust and continental crust part of same tectonic plate (no volcanoes, rare earthquakes)o Continental shelf: -0.5 degrees, Continental slope: -5 degrees- Active Continental Margino Oceanic crust and continental crust part of different tectonic plates (lots of volcanoes and earthquakes)o Marked by deep ocean trench (7-11 km deep)- Continentso Marked variations in topography: Flat shields or platforms. Mountains.- Continental Shieldso Shields: stable interior of continent composed if ancient crystalline basement rocks (igneous and metamorphic) Low elevation and relatively flat- Mountain Beltso Young: American Cordillera, Alps, Himalayaso Older: Appalachians, Urals- Mountain Buildingo Orogeny or Orogenesis: Processes that collectively produce a mountain belt: folding, faulting, magmatism and metamorphismo Most mountain building occurs at convergent plate boundaries- Three types of plate boundarieso Interactions among individual plates occur along their boundaries – where most of the geological “action” is- Convergent Plate Boundarieso Continent-Continent collision: Example: Himalayas- The Appalachian Fold Belto Formed from three distinct episodes of mountain buildingo Taconic orogenyo Arcadian orogenyo Alleghany orogeny- Continental vs. Oceanic Crusto Continental Crust: andesitic composition, density – 2700 kg/m3o Thickness – 30 kmo Erosion and isostatic adjustmento Returns crust to normal thicknesso Exposes rocks formerly at deep crustal levels at Earth’s surfaceo Sediment deposited on adjacent areas causes subsidence- Origin & Evolution of Continentso Some continental crust formed early in Earth history: fragments preserved from 3.8 to 4.0 billion years ago in Canada &