EAR 105 1st Edition Lecture 2Outline of Last Lecture I. Class LogisticsII. Ten Reasons to Care About Earth ScienceOutline of Current Lecture III. Introduction to Earth ScienceIV. Origin of the EarthV. Constituency of the EarthCurrent LectureIII. Introduction to Earth Science- Earth Science: combination of geology, meteorology, oceanography, astronomy- Made of testable ideas and repeatable observations- Scientific Inquiry: assumes the natural world is consistent & predictable - Ideasbecome:Hypotheses: tentative, untested possible explanationsTheories: tested, confirmed hypothesesParadigms: theories that explain many interrelated concepts- Scientific Method:1. Collects observations from natural world2. Forms hypothesis3. Tests hypothesis4. Revise & retestIV. Origin of the Earth- Earth is 4.6 billion years old- Geologic time scale: divides history of earth into units- The early evolution of the Earth occurred 4.6 billion years ago at the same time as the other planets were forming.- Nebular Theory (Mokry calls this a hypothesis)o 13.7 billion years ago, the Milky Way formedo The solar nebula (big cloud of hydrogen and helium) set in rotating motionThese 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.o 5 billion years ago, the solar nebula began to contract, forming flat, disk-like shape with protosun (pre-sun) at the center (aka. Early formation of solar system)o Inner planets (Mercury, Venus, Earth, Mars) formed from metallic/ rocky clumps—since heavy objects can’t go as far.o Outer planets- were composed of farther traveling, lighter materials as fragments of ice, gases, methane.o The layered composition of the Earth can be interpreted as a product of this theory. Decay of radioactive elements and high-velocity impacts caused Earth’s temperature to increase Heavy elements as iron and nickel sunk to the core. Lighter components as aluminum, potassium, and oxygen floated to surface Very light gases escaped from the mass to form the atmosphere.V. Constituency of the Earth- Earth has four interactive spheres: biosphere, atmosphere, hydrosphere, and geosphereo Biosphere: forms very thin layer of Earth, originating at the bottom of theocean and extending to a few kilometers in the atmosphere.o Atmosphere: formed of a very thin layer of gas.  90% of the atmosphere exists below the height of 10 miles. 50% of it lies below 3.5 miles.o Hydrosphere: makes up 71% of earth’s surface. Constitutes 97% of Earth’s water  2.56% of Earth’s water is fresho Geosphere: Constitutes Earth’s mass, from surface to center The earth is divided into layers—categories are based on composition or on behavior Earth’s layers by composition:Crust,Mantle,Core- Crust:thin, rocky outer skino Continental crust- less dense, many rock types, generally granitic.o Oceanic crust- more dense, basaltic rock- Mantle: Solid, rocky shello Makes up 82% of Earth’s volume o Upper mantle: Lithosphere: makes up entire crust & uppermost mantle Asthenosphere: relatively soft layero Lower mantle: very hot layer, strengthens with depth- Core: innermost portion of Eartho Formed of an iron-nickel alloyo Outer core: Liquid layer. This generates Earth’s magnetic field.o Inner core: solid