ATOC 1060 1nd EditionBased on Chapter 10 & some of 5 Lecture 14 Outline of Last Lecture I. Review From Last LectureII. Short Term/ Long Term Reservoirs III. CarbonIV. CO2 Ocean ChemistryV. Carbon Released from Limestone VI. Summary Longer Term Carbon CycleOutline of Current Lecture Current LectureI. Geologic TimeII. Radiometric age datingThese 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. We use unstable isotopic decay to estimate earths age and the age of old deadorganic material.Key Points:1. Unstable isotopes decayto become stable isotopes at a known exponential rate. 2. Half Life = time when 50% of the material has decayed.III. Solar System FormationAn interstellar cloud of dust and gas is a denser-than-average region of the interstellar medium- Our solar system formed 4.6 billion years ago when an interstellar cloud collapsed! - Gravitational collapse of an interstellar cloud to form the solar nebula Timeline of Formation4.55 billion years ago -Solar system, Meteorites, Planets form 4.4 billion years ago -Moon formed 3.8-4.55 billion years ago -Heavy Bombardment Period, Lots of impacts but number tapering off with time. Atmosphere and Ocean formed.- The rotation rate of a nebula dictates how many stars are formed. - Faster rotation=more stars. In our case, one star formed (the sun) and planets formed in the disk around it.IV. Formation of Earth The solar system/Earth formed 4.55 billion years ago Formed during the Heavy bombardment periodFormed by Accretion in ~100 million years- Planetesimals formed as condensed materials attracted to the mid-plane of nebula. Planets formed by the accretion (‘sticky collisions’) of planetesimals- Craters on Mars, Mercury, and Moon provide good evidence for the Heavy bombardment periodHow did the moon form?- Likely formed from a high-energy impact with a Mars sized body “Giant Impact Hypothesis”- Low-density debris accretes to create moon- The moon keeps Earth’s obliquity (tilt) constant, maintaining seasonal regularity. - Without the moon, we could lean 85º at times instead of 22-24º. V. Atmospheric/ Ocean FormationAtmosphere and oceans began forming as Earth itself formed during the Heavy bombardment period (4.6-3.8 billion years ago) Impact degassing: bombardment of Planetismals releasing water and other volatile compoundsIV. Composition of Early Earths AtmospherePlenty of nitrogen (N2) since impactors brought Ammonia (NH3) - Likely that there was CO2. Impacts released the reduced gases CO and CH4, which can turn irreversibly into CO2- Very little oxygen (O2) because: 1) no photosynthetic biology 2) O2 reacts quickly with CH4and CO to form