ERTH1010 Geochronology Lecture Notes Sept 10, 2024 PDF

ERTH1010 Sept 10, 2024 Geochronology Summary: The Nebular Hypothesis represents the formation of the solar system from the accumulation of gas and dust which is called a nebular cloud. Ar...

ERTH1010 Sept 10, 2024 Geochronology Summary: The Nebular Hypothesis represents the formation of the solar system from the accumulation of gas and dust which is called a nebular cloud. Around 5.5 - 4.6 (GA) billion years ago, planets started to form materials like rock and metals which is called accretion. Earth specialty and some other planets then have undergone differentiation into parts like the core, mantle, inner and outer crust. Collision theory describes the origin of the moon (collision with a mars-sized body) and the ejection of only silicate material which explains the structure of the moon. Solar-System Composition Nebular Hypothesis ○ All bodies initially would have had the same composition and the solar system initially looked like one type of element. (homogenous) Can be determined by: 1) Solar Abundances 2) Meteorites (Chondritic meteorites (A.K.A C1) are droplets which are condensed directly from the solar nebula and contain a frozen material) 3) Average Earth (Since earth has undergone differentiation) The difference between solar abundances and Meteorites is that solar abundances are related to gaseous environments and refers to the composition of the sun and its elements, specifically Hydrogen and Helium, whereas meteorites are referred to the solid materials like metals and silicates. Also, aside from Li, N, C, and O. All other elements support the nebular hypothesis. This is due to the fact that their isotopes composition does not align for those that are in the sun. Meteorites → Pieces of materials around the solar-system like —-- that pass through earth’s atmosphere and fall to the earth/reach the surface of earth. Morphology: → shape or arrangement of part of something. Types of Meteorites 1) Chondritic Meteorite. Have spots all over it that consists of undifferentiated materials that are called condrools. 2) Stony (NO metal) Mostly made up of rocky material of differentiated planetary bodies. 3) Irony (Materials are not just made of iron, but mostly are) Fragments are made up of metallic cores from the differentiated planets. 4) Stony-irony Made up of both rocky and metallic elements. Meteorite activity is high in some areas and low in others due to the gravitational full and atmosphere conditions.  ERTH1010 Sept 10, 2024 Geochronology The Moon Split into two parts: 1) Highlands → lighter spots, lots of cratered areas, made up of low density feldspar, faces earth. Anorthosite is a white rock (the main element is calcium) which is in the crust of the moon. Some material called scum has a floating layer on (lunar crust) the surface, which formed in the early stages of the moon. In the early stages the moon was molten and as time went on it cooled so that material solidified and floats on top of the molten rock underneath 2) Maria → Dark spots, filled with lava 3.8 - 3.2 billion years ago, younger impact basins, faces away from earth. The moon is mostly covered with gray rocky and dusty debris called the lunar regolith which was made from the impact from the collision. Earth does not like the moon because it contains water and the carters have been eroded by it and as well as the weathering change and tectonic activity. Terrestrial Planets → Near planets are smaller in diameter but higher in density due to the metallic core they contain compared to the far planets called Jovian Planets. Mercury → Its core may still be liquid because it so hot (closest to the sun) Side facing sun (Day) → +427℃ Side facing away (Night) → -170℃ - 2nd smallest planet, highlands have craters, no atmosphere around due to the extremely hot environment Venus → Surrounded by CO2 atmosphere approximately 97% Surface of venus is fairly young but still has some meteorite impacts. (Similar to Earth) Mountain Ranges → 8-10 km high Temperature → up to +475℃ Inner core is solid and outer core is liquid Semi-fluid of mantle under crust but no presence of tectonic plates for around half a billion years. Mars → Mostly surrounded by CO2 and has little H2O 1% density of earth, half earth’s size, gravity lower than earth Surface is rocky and has sand dunes and deep valleys are caused by running water and slumps from the melting of ice in the soil. Massive Volcanoes 23 km high Geologically quiet, very little volcanic activity and was more active in the early formation period. Jupiter → Mass is 2.5x > all masses of other planets combined - Made up of original gasses that made up the solar nebular (H, He, CH4, NH3, H2O, S compounds) - Liquid Hydrogen in depths > 1000 km and may have a rocky or metallic core  ERTH1010 Sept 10, 2024 Geochronology - Trying to lose heat from its interior → Convection of gas to form the wavy pattern on the surface. - Gravitational pull is much larger than earth - Jupiter's Moon → IO exerts a gravitational pull which results in volcanic activity which it can survive due to the constant push and pull and has a molten inner part. Saturn, Uranus, Neptune → Atmospheres covered with H, He, CH4 NH3 is only present in Saturn out of the other three. Neptune → High Winds (1000 km/h) due to heat loss Horizontal axes of rings around the Uranus (Perpendicular rings to the orbit around the sun) Pluto → Dwarf Planet, discovered in 1930 - Atmosphere: 99.7% N2 little CH4. - Environment: 30-50% ice and 50-70% rock - Largest moon is called Charon (Always faces pluto) - Nix and Hydra are the other smaller moons (discovered in 2005) - Relativity small when compared to earth Early Earth - Scum at the surface is the first crust of earth - Inner core → Solid - Outer core → Liquid - Then a huge part of the interior was molten - Earth is cooling since its origin Earth First crust → Made up of fragmented rock (basalt) and is called a lava lake Continents → No continents or ocean existed 4.5 billion years ago Back then, earth was covered by a thin veneer from a volcanic rock and the ocean floor was made up of lava. Today → 30% of earth is covered by continents. Dating Rocks → Radiometric Dating is used to find how old the rock is. Isotope → Same # of protons, different # of neutrons. Which means the mass is different Parent/Daughter → produced from radioactive decay Mineral must be resistant to diffusion of isotopes ZrSiO4 is the best metal to use because it has a high melting point and hardness level Half Life → Blue curve shows decay, red is acclimation (Graph was shown) At time 1 (half life), the ratio is the same for daughter to parent atoms and a maximum of six half life can last until there is not much left in the parent. Instruments → Chemistry: Used to spare parent/daughter by extracting the element from minerals → Mass spectrometer Machine: Used by measuring the compound to determine the type, structure and the properties.  ERTH1010 Sept 10, 2024 Geochronology Two Kinds of Crust of Earth Oceanic Crust: Formed by the melting of mantle and is composed of fragmented rock (Basalt) Continental Crust: Formed by the melting of the oceanic crust and is composed of Granitic materials. This crust change happened because the oceanic crust is higher in density so it flows lower than the continental crust. The period between this change was around 1 billion years apart. The Eons of the Geological Time Scale IMPORTANT INFORMATION IN CHART TO KNOW