Earth: A Dynamic PlanetQuestions to PonderOutlineWhat do we mean by “dynamic”?PowerPoint PresentationThe earth system can be subdividedSlide 7Interactions of major earth systemsThus, Dynamic only means Reactive and Ever-changing. As opposed to “static” systemsSlide 10Controls on Dynamic behaviorThus, Second Law helps explain:DifferentiationDifferentiation: Solar system scaleGravitational attraction forces heavier materials towards centerSlide 16Differentiation: Earth scaleSlide 18Slide 19Slide 20How does differentiation contribute to earth being “dynamic”?Development of Lithospheric PlatesSlide 23Heat convectionThe exact mechanism of convection is not completely defined, butSlide 26Earth’s lithosphere (Crust) is subdivided into two typesEarth’s lithosphere (Crust + upper mantle) is subdivided into two typesContinental crust then is more buoyant than oceanic crust3 Types of plate boundaries1. Divergent boundarySlide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Features of Divergent boundaries2. Convergent boundarySlide 46Subduction v. CollisionSlide 48Slide 49Slide 50Slide 51Features of Convergent boundaries3. Transform boundarySlide 54Slide 55Transform boundaries, comparedFeatures of Transform boundariesThe movement of plates, creation of new crust, and subduction of old crust makes earth “Dynamic”Earth: A Dynamic PlanetQuestions to Ponder•What do we mean by “dynamic” Planet?•What do the First and Second Laws of thermodynamics state?•What is differentiation and how is it exhibited?•How does plate tectonics affect earth?•What are the types of plate boundaries are their relative movement?Outline•Earth, the dynamic planet•Physical Laws and Differentiation of materials•Solar system and Planetary differentiation•Plate tectonics–Defined–Mechanisms for movement•The types of plate boundariesWhat do we mean by “dynamic”?•Closed system - a system that only exchanges energy across its boundary•Open system - a system that will exchange both matter and energy across its boundary•Dynamic system - a system in which matter & energy react•Keep in mind that systems can be easily subdivided into smaller “subsystems” or grouped into larger “supersystems”.Earth SystemSolar SystemThe earth system can be subdividedThe earth system can be subdividedInteractions of major earth systemsThus, Dynamic only meansReactive and Ever-changing.As opposed to “static” systemsControls on Dynamic behavior•Physical Laws–Whatever you do, you can NEVER break these laws•First and Second Laws of thermodynamics•First Law (Conservation)–Energy (matter) is neither created nor destroyed, but only changes form•Second Law (Entropy)–Systems move from High energy states to Low energy states (sometimes referred to as “equilibrium”)Thus, Second Law helps explain:•Why water flows downhill•Why unstable minerals react or change to form more stable products•Why elements bond to form minerals (later discussion)•The dynamics of earth•The process of differentiationDifferentiation•Separation of materials by various properties–Density–Size–Thermal characteristics, etc.•The solar system is differentiated•Earth is differentiated•Dynamic processes continue to differentiate materialsDifferentiation: Solar system scaleGravitational attraction forces heavier materials towards centerDense PlanetsLighter planetsDifferentiationDifferentiation: Earth scale•When earth first formed, it was a molten, homogenous blob, but, as it cooled, remarkable changes occurredDifferentiation: Earth scale•Heavier elements migrated towards center and formed “core”; lighter elements formed crust (ex. Ice cube “floats” on water)DifferentiationHow does differentiation contribute to earth being “dynamic”?•Less dense material cooled and crystallized to form earth’s crust•Heavier material including radionuclides, such as Uranium, that decay and release heat, moved towards the core•Crust serves as insulation – helps retain the heat generated inside the earth•Thus, rigid cooler crust overlies molten internal material•(Note: differentiation of earth material proceeds with all of the processes that occur on earth. We’ll describe these throughout the semester!)Development of Lithospheric Plates•Cooler rigid crust forms discrete plates of less dense (lighter material) that “floats” over hot, plastic- to molten- material•Thus, continents and oceans change shape, size and position over time•The interactions of the lithospheric system helps control the geologic features of earth!How do these lithospheric plates move?Heat convectionHigh energy(hot)Low energy(cooler)But cool material is denser, and it sinksThe Second law of Thermodynamics at work:From High energy to Low energy statesThe exact mechanism of convection is not completely defined, butEarth’s lithosphere (Crust)is subdivided into two types•Crust–Continental crust•Thicker than oceanic crust - up to 75 km•Less dense - 2.7 g/cm3•Strongly deformed•Much older - may be billions of years oldEarth’s lithosphere (Crust + upper mantle)is subdivided into two types•Crust–Oceanic crust•Thinner than continental crust - about 8 km•More dense - 3.0 g/cm3•Comparatively undeformed•Much younger - < 200 million years old•Composed of basaltContinental crust then is more buoyant than oceanic crust3 Types of plate boundaries1. Divergent boundary•Spreading apart – new crust is usually made at such boundariesMid Ocean Ridge2. Convergent boundary•Plates move towards one another•Because either of the two crust types is involved we get 3 subcategories•A. Oceanic-continental crust–Subduction•B. Oceanic-oceanic crust–Subduction•C. Continental to continental crust–Collision3. Transform boundary–Plates move laterally past each other–Commonly associated with mid-ocean rift systems•Space accommodation–Continental zones•San Andreas Fault1. Divergent boundary•Spreading apart – new crust is usually made at such boundariesMid Ocean RidgeMid Ocean Ridge system actually extends onto continental crust!Features of Divergent boundaries•In oceans–Volcanism–Undersea mountain ranges (ridges)•On continents–Some volcanism–Rift valleys2. Convergent boundary•Plates move towards one another•Because either of the two crust types is involved we get 3 subcategories•A. Oceanic-continental