ENVS 101 1st Edition Lecture 4 Outline of Last Lecture I. Introduction to Earth’s External and Internal energy sourcesII. Comparison between various wavelengths (of light) present in the Earth energy cycle, as well as how the Atmosphere serves as a filter for certain types of energy coming towards EarthIII. Definitions for: Fusion, Geothermal Gradient, Radiogenic Heat, Accretionary Heat, Albedo, Nebula, Relative Age, Numerical AgeIV. Exploration of Earth’s energy cycle and the various roles of energy in the cycleV. Energy usage, developments, and innovations in modern societyVI. Introduction to the evolution of the Solar System, as well as to Time and ChangeOutline of Current Lecture VII. Introduction to Time and Change: Catastrophism and the Principal of UniformitarianismVIII. How old is the Earth? History of the Earth, how it has changed, and age estimateIX. Life from a Planetary perspective: Evolution, the History of LifeX. Cambrian “Explosion” StromatolitesXI. Mass Extinctions in the Phanerozoic/ Human EvolutionCurrent LectureIn measuring numerical age, the radioactive decay rate is observed. All decay rates follow the same basic law, essentially stating that the proportion of parent atoms that decay during each unit of time will always be the same. As decaying parent atoms decrease, the daughter atoms continually increase. The rate of decay is measured by: Half-life: The half-life of a radioactive (parent) is the time it takes for one half of the isotope to decay into its daughter product.Catastrophism: The idea of the 17th and 18th century that all of the Earth’s features were formed by a few great catastrophic events.Over time, James Hutton Used the scientific method and proposed a counter theory known as the principle of uniformitarianism: “the present is the key to the past” which indicates that the Earth is incredibly old. The overall concept is important to science, yet we recognize that some events are so large and damaging that they can cause catastrophic change.These 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.Investigation eventually led to the question of the age of the Earth, and attention was turned to using the salt within the oceans. However, large salt deposits such as the ones in southern New Mexico at the WIPP nuclear waste site show that the salt content of oceans will not be effective in revealing the age of the Earth.Thus, Lord Kelvin based the age of the Earth off of the question of heat content, rather than of salt content. Kelvin’s estimate for the Earth’s age, which started as a range from 20-400 million years, (and was later narrowed down to 20-40 million years), was based on the time needed for solid Earth to cool from an initially molten state.Kelvin carried on with the assumption that the Earth was like a giant steel ball, observingthat the outer core is the only molten liquid shell within the Earth’s interior. Everything else including the mantle of the Earth is solid but can still flow, and Earth’s process of heat loss is through both conduction as well as convection (although Kelvin did not consider convection).How else does the Earth generate heat? The Earth generates heat by the decaying of radioactive isotopes, a discovery made decades after Kelvin’s investigations of the age of the Earth. Because of the discovery of decaying radioactive isotopes, the age of the Earth was able to be accurately measured at 4.6 billion years. Early Solid Earth: Early Earth had a high surface temperature, as well as high atmospheric pressure. In addition, greenhouse gases were abundant along with acidic precipitation being a common occurrence within the environment. Over time, the compositions of the atmosphere, hydrosphere, and geosphere underwent dramatic change as materials continuously cycled through them.Early Life Forms: Stromatolites began forming around 3 billion years ago. They are layered growths that form in warm, shallow seas when photosynthetic bacteria cause dissolved salts to precipitate. There are modern examples of these growths in Shark Bay, located in Western Australia.The Cambrian Radiation (Explosion): The Cambrian Period beginning 542 million years ago, was the time of the introduction of skeletons, both internal as well as external. Examining the Burgess shale, which was deposited 505 million years ago, it is known that the Cambrian Period was a time of huge growth and diversity for the marine environment. During this period, the pace of evolution increased dramatically. The earliest living organisms essentially used the same genetic toolbox over thousands of years into their evolution, and eventually, around 300 million years ago, the evolution of plant life also came about.Later on around 125 million years ago, came about the evolution of the early birds and mammals. In the fossil of an Archaeopteryx shows skeletal and teeth structure similar to that of the dinosaurs. However, there were also very detailed impressions of feathers found in this fossil, identifying this animal as an early bird. Around this same period existed the Eomaia scansoria, which is the oldest known placental mammal (a mammal that gives birth to its offspring), and it also lived at the height of the dinosaur age. Eventually, a mass extinction occurred about 65 million years ago that was capable of wiping out the dinosaurs completely from the face of the Earth. There is evidence that the extinction may have been caused by the impact of a meteorite that was about 10 kilometers in diameter, and struck near Mexico’s Yucatan Peninsula. The impact likely caused a massive tsunami, scattered debris all over the hemisphere, and created continent wide forest fires. Soot from the fires likely remained in the atmosphere for months afterward, or even years. Thus, sunlight was completely blocked and photosynthesis ceased worldwide.Evolution and the History of Life: The emergence of Humans during the Cenozoic Era is one of the most complex and controversial fields in paleontology due to gaps in fossilized evidence of their evolution, as well as a lack of transitional forms. However, it remains quite clear that humanlike organisms are a relatively recent evolutionary development.The first hominid that was clearly a bipedal (meaning it walked upright routinely) was the Australopithecus, of which the famous “Lucy” fossil is an example. These