CIEN 203 Lecture Notes: The Universe and the Earth - PDF

The Universe and the Earth MRA, 2024 Learning Objectives At the end of the lecture, the student should be able to : ❏ Identify the events and processes that lead to the Earth’s formation; ❏ Explain the existence of Earth’s layers; ❏ Describe the large scale features of the Earth’s su...

The Universe and the Earth MRA, 2024 Learning Objectives At the end of the lecture, the student should be able to : ❏ Identify the events and processes that lead to the Earth’s formation; ❏ Explain the existence of Earth’s layers; ❏ Describe the large scale features of the Earth’s surface; and ❏ Discuss the theories of isostasy. Topic Outline Formation of the Universe Features of the Earth (Part II) and the Earth (Part I) ❏ The Big Bang Theory ❏ Layers of the Earth ❏ The Nebular Hypothesis ❏ Size of the Earth ❏ Formation of the Moon ❏ Large Scale Features ❏ The Iron Catastrophe ❏ Theories of Isostasy ❏ Formation of the Atmosphere Topic Outline Formation of the Universe Features of the Earth (Part II) and the Earth (Part I) ❏ The Big Bang Theory ❏ Layers of the Earth ❏ The Nebular Hypothesis ❏ Size of the Earth ❏ Formation of the Moon ❏ Large Scale Features ❏ The Iron Catastrophe ❏ Theories of Isostasy ❏ Formation of the Atmosphere PART I: Formation of the Universe and the Earth At first there was nothing.  At first there was nothing. lol but maybe there was something  At first there was nothing. lol but maybe there was something ok maybe there wasn’t  At first there was nothing. lol but maybe there was something ok maybe there wasn’t Welcome to the great nothingness.  At first there was nothing. lol but maybe there was something ok maybe there wasn’t Welcome to the great nothingness. and then... The Universe The Formation of the Universe The Big Bang Theory is the current prevailing theory for the beginning of the Universe It was first proposed by Georges Lemaître in the 1920’s. The Formation of the Universe 13.7 BILLION YEARS AGO The Singularity - an infinitely small region with virtually zero volume; but it contained everything in the universe MATTER – ENERGY – SPACE – TIME were created! The Formation of the Universe The Formation of the Universe: The Evidence Some of the more popular evidence are: 1. Cosmic Microwave Background (CMB) 2. Abundance of hydrogen and helium and primordial elements 3. Hubble’s Red-shift The Formation of the Universe: The Evidence Cosmic Microwave Background Radiation (CMBR) Believed to be residual radiation from the Big Bang One second after the Big Bang, subatomic particles scattered everywhere The Universe would have been opaque because free electrons would have caused photons to scatter The Formation of the Universe: The Evidence Cosmic Microwave Background Radiation (CMBR) As everything eventually cooled down and the subatomic particles decayed and “recombined”, free electrons being absorbed to form neutral atoms, photons stopped being emitted and the Universe became transparent. The afterglow of that event is the CMB. Read more: https://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang The Formation of the Universe: The Evidence The Formation of the Universe: The Evidence Abundance of Hydrogen and Helium If the Big Bang started from an undifferentiated mass, it makes sense that the first elements to form are the simplest: hydrogen and helium Hydrogen and helium are the primary building blocks of stars and other gas clouds in the Universe The Formation of the Universe: The Evidence Hubble’s Redshift In the 1920’s, Hubble made two discoveries that changed our perspective of the Universe: 1) The Universe is larger than what we thought it was (1923), and; 2) The Universe was getting bigger (1929). Andromeda Galaxy, NASA / JPL-Caltech The Formation of the Universe: The Evidence The Formation of the Universe: The Evidence Hubble’s Redshift In the 1920’s, Hubble made two discoveries that changed our perspective of the Universe: 1) The Universe is larger than what we thought it was (1923), and; 2) The Universe was getting bigger (1929). The degree of galaxy’s redshift was proportional to its distance from us. If the Universe is expanding, it must Doppler Effect (Redshift/Blueshift) Demonstration have been smaller in the past. The Formation of the Universe: In a nut shell The Singularity BIG BANG! Inflation Opaque Universe Transparent Universe The Solar System  The Nebular Hypothesis - Formation of the Solar System - The Hypothesis was first proposed by Immanuel Kant and Pierre Simon de Laplace in the 18th century. Watch for a visual summary: https://www.youtube.com/watch?v=x1QTc5YeO6w The Nebular Hypothesis Inner and outer planets emerged, separated by the frost line. The Nebular Hypothesis/Theory Inner/terrestrial planets: Outer/Jovian planets: rocky, largely composed of lacks a solid surface, in gaseous or silicates and metals (Si, Fe, O) liquid form, composed of lighter elements (H, He, Ar, C, O, N) The Solar System to Scale From NASA/JPL-Caltech (https://www.jpl.nasa.gov/edu/learn/video/solar-system-size-and-distance/) Composition of Mass of Solar System: Body % Mass Sun 99.85% Jupiter 0.10% All other planets 0.04% Comets 0.01% Satellites and rings 0.00% Asteroids 0.00% Meteoroids and dust 0.0000001% The Sun The Sun - Middle aged star - Made up of hydrogen The Pluto Controversy  The Pluto Controversy - Orbits the Sun - Has enough mass to be round - Has NOT cleared it orbit of debris FUN FACTS (Incase gusto niyo magmukang smort pag may ka-date kayo) The Earth The Earth Accretion Heating Differentiation The Earth Accretion Heating Differentiation The dust would stick together due to gravity and slowly accrete to form the Proto-Earth. The Earth Accretion Heating Differentiation Heating during this early stage lead to the melting of some materials and creating a molten earth. The Earth Accretion Heating Differentiation Because the elements could move more freely in liquid form, the heavier elements sank towards the center of the Earth, while the lighter elements rose to the surface. The Iron Catastrophe Heavier: sank to the core Lighter: rose to the surface This specific event in Earth’s history is called the Iron Catastrophe The Iron Catastrophe What do you think were the sources of heat that caused the proto-earth to melt? The Iron Catastrophe The sources of heat causing the proto- earth to melt: Heat from collision Radioactive decay Solar radiation Contraction The Moon Formation of the Moon: Giant Impact Hypothesis Computational research: Mars- sized planetesimal collided with Probably occurred after the Iron the Earth and debris coalesced to Catastrophe. Why? form the Moon Formation of the Moon: Giant Impact Hypothesis What is the name of the mars-sized planetesimal that collided with the Earth to form the Moon? Formation of the Moon: Giant Impact Hypothesis What is the name of the mars-sized planetesimal that collided with the Earth to form the Moon? Theia Origin of the Atmosphere (and Ocean Basins) Important consequence of the Earth’s differentiation Occurred in stages: 1. Primordial atmosphere lost to solar wind (4.5 Bya) 2. Continual degassing and venting as the Earth differentiated (4.0 Bya) 3. Steady accumulation of gases allowing the atmosphere to thicken 4. Build-up of oxygen from cyanobacteria and subsequently plants (3.5 Bya to Present) Origin of the Atmosphere (and Ocean Basins) Important consequence of the Earth’s differentiation Occurred in stages: 1. Primordial atmosphere lost to solar wind (4.5 Bya) 2. Continual degassing and venting as the Earth differentiated (4.0 Bya) 3. Steady accumulation of gases allowing the atmosphere to thicken 4. Build-up of oxygen from cyanobacteria and subsequently plants (3.5 Bya to Present) Origin of the Atmosphere (and Ocean Basins) Important consequence of the Earth’s differentiation Occurred in stages: 1. Primordial atmosphere lost to solar wind (4.5 Bya) 2. Continual degassing and venting as the Earth differentiated (4.0 Bya) 3. Steady accumulation of gases allowing the atmosphere to thicken 4. Build-up of oxygen from cyanobacteria and subsequently plants (3.5 Bya to Present) Origin of the Atmosphere (and Ocean Basins) Important consequence of the Earth’s differentiation Occurred in stages: 1. Primordial atmosphere lost to solar wind (4.5 Bya) 2. Continual degassing and venting as the Earth differentiated (4.0 Bya) 3. Steady accumulation of gases allowing the atmosphere to thicken 4. Build-up of oxygen from cyanobacteria and subsequently plants (3.5 Bya to Present) End of PART I: Formation of the Universe and the Earth Let’s have a short break :> PART II: Features of the Earth Layers of the Earth Two types: Compositional and Mechanical Layers Compositional (chemical) layers are differentiated by the dominant lithology or chemical composition. Ex. Fe-Ni core vs. silica-rich crust Mechanical (physical) layers are differentiated by their rigidity or strength. Ex. Brittle lithosphere vs. ductile asthenosphere Layers of the Earth: Compositional Layers Crust ❏ Solid outer shell composed of : ❏ Thickness varies ❏ Continents: 15 – 60 km ❏ Oceans: 3 – 15 km ❏ Less than ~1% of the Earth’s mass and volume. Layers of the Earth: Compositional Layers Mantle ❏ Still iron-rich compared to crust, but diluted with oxygen, silicon, magnesium, etc. ❏ ~2,900 km thick ❏ ~83% of Earth’s volume ❏ ~68% of Earth’s mass Convection in the mantle causes the Earth’s plates to move! Layers of the Earth: Compositional Layers Core ❏ Iron-nickel alloy ❏ iron rich sphere with small amounts of Ni and other elements ❏ ~3,500 km in radius ❏ ~16% of Earth’s volume ❏ ~31% of Earth’s mass Movement in the Earth’s outer core generates a giant dynamo producing the Earth’s magnetic field! Layers of the Earth: Mechanical Layers What are the different mechanical layers that you know of? Layers of the Earth: Mechanical Layers The inner core is solid, while the outer core is liquid. Why is this the case? Layers of the Earth: Mechanical Layers Variability in the different layers’ rigidity: differences in Temperature and Pressure Increase in T: melting, increased fluidity, decreased viscosity Increase in P: solidification, increases interaction between molecules: compaction Rigidity: response of the material to the T&P condition at depth Layers of the Earth: The Evidence Layers of the Earth: The Evidence Mantle xenoliths: mantle rocks Fe-Ni meteorites: leftovers from the brought up to the surface by formation of the Solar System; must magmatic activity have been one the building blocks of proto-Earth Earth’s Size Equatorial circumference = 40,076 km Polar circumference = 40,008 km What 3D shape does that give the Earth? Earth’s Size Equatorial circumference = 40,076 km Polar circumference = 40,008 km What 3D shape does that give the Earth? Oblate spheroid. Eratosthenes: calculated the Earth’s circumference as 41,000 km! Basic calculation: 𝐶𝑖𝑟𝑐𝑢𝑚𝑓𝑒𝑟𝑒𝑛𝑐𝑒 360 𝑑𝑒𝑔𝑟𝑒𝑒𝑠 = 800 𝑘𝑚 7 𝑑𝑒𝑔𝑟𝑒𝑒𝑠 Theories of Isostasy Isostasy - state of equilibrium between parts of the Earth’s lithosphere Airy Isostasy Pratt Isostasy