Tran-Review Lecture 4

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Geology

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Dec 6, 2023

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Review Lecture 4 4. Planet Earth 4.1 Formation How did the layers of Earth form? The layers of the Earth formed through a complex process that began with the creation of our solar system about 4.6 billion years ago. This process can be described in three stages: - Formation of the core: +The center of our earth is the core. + As the dust and materials from the interstellar disk came together to form Earth, the heavier elements, primarily iron and nickel, began to gravitate towards the center of the growing planet. This concentration of heavy elements led to the formation of the Earth's core. - Formation of mantle: + Surrounding the core is the mantle. + The lighter elements formed the mantle, mostly molten in the early days. - Formation of the Crust: + At the surface of the mantle, a thin layer cooled and become the crust. + As this crust underwent cycle of melting and cooling, lighter elements within the crust rose to the surface and solidified to form the continental crust. This process led to the differences between the continental crust and the oceanic basins. How did the Moon form? - The moon has formed when a small planet collided with the young Earth. - This impact caused the mantle of the small one, including the Earth’s mantle, to be ejected into space. Some of this material eventually coalesced to form the Moon, while the core of the smaller planet joined up with Earth's core, becoming part of it. The Moon formed from the ejected mantle material and continues to rotate around the Earth. 4.2 Ocean, Atmosphere, Life Explain the formation of the oceans, atmosphere, life, and the Moon. - Formation of oceans: + The Earth's oceans formed around 4 billion years ago. Initially, the Earth was a molten mass, and as it cooled, water vapor in the atmosphere condensed to form liquid water on the surface. +Comets and asteroids, rich in water, also bombarded the early Earth, contributing to the accumulation of water in the form of oceans. +The ocean basins gradually took shape through tectonic processes, including the movement of tectonic plates and the opening of oceanic rifts.

- Formation of atmosphere: the first atmosphere was made od of nitrogen, hydrogen sulfide and carbon dioxide, which also were supplied by the mantle. - Formation of life: - Formation of the Moon: +The most widely accepted theory for the Moon's formation is the giant impact hypothesis. This suggests that a Mars-sized object collided with the early Earth about 4.5 billion years ago. + The impact caused a significant portion of the Earth's mantle to be ejected into space, forming a disk of debris. Over time, this debris accreted to form the Moon. + The Moon's formation influenced the Earth's rotation and tides, playing a crucial role in shaping the planet's geophysical and climatic conditions. Generally speaking, when did oceans, atmosphere and life first appear on Earth? - Ocean, atmosphere and life first appear on earth 4 billons years ago Briefly explain the origin of life and evolution by natural selection. - Origin of life: + Prebiotic Earth Conditions:Around 4 billion years ago, Earth had a very different environment, characterized by volcanic activity, a reducing atmosphere (lacking free oxygen), and an abundance of various chemicals. + Formation of Simple Organic Molecules:Simple organic molecules, such as amino acids and nucleotides, were likely formed through natural processes, such as lightning, UV radiation, or reactions at hydrothermal vents. + Formation of Complex Molecules: Over time, these simple organic molecules may have combined to form more complex molecules, such as proteins, nucleic acids, and lipids. - Evolution by natural selection—the idea that thpse better adapted to the environment are more likely to reproduce What is the relative strength of our understanding of the Big Bang, the origin of life, and evolution by natural selection. - Big Bang: The Big Bang theory is a well-established cosmological model supported by a substantial body of observational evidence, including the cosmic microwave background radiation and the observed distribution of galaxies.While some details about the early moments of the Big Bang remain speculative, the overall framework is widely accepted within the scientific community. - Origin of Life:The origin of life is a complex and challenging scientific question that has not been definitively answered. Several hypotheses exist, but none has been universally accepted.Researchers study the early Earth conditions, experiment with prebiotic chemistry, and explore the potential for life's emergence in various environments, but much is still unknown.

- Evolution by Natural Selection: proposed by Charles Darwin, is a foundational concept in biology and has amassed overwhelming evidence from various scientific disciplines, including paleontology, genetics, and comparative anatomy. The theory is widely accepted within the scientific community, and ongoing research continues to refine our understanding of the mechanisms driving evolution. 4.3 Interior Briefly explain Earth’s core (two parts), mantle, crust (two parts), and asthenosphere. - Earth’s core: is mostly iron and nickel and has two parts: a solid inner core and a liquid outer core. - Mantle: about 2900km thick and has three parts. The lower part is solid and makes up most of the mantel. From roughly 50 to 300 km below the surface is asthenosphere, which is a soft layer. Above the asthenosphere is another solid layer of the mantle - Crust: crust is thinnest under the oceans and thickest under the continents + The oceanic crust is made of denser rock material with a lot of magnesium and iron. + The continental crust is less dense and has lots of mineral quartz and feldspars - Asthenosphere— From roughly 50 to 300 km below the surface is asthenosphere, which is a soft layer. 4.4 Age of Earth Explain radioactive decay including the concept of half-life: Radioactive decay is a process by which unstable atomic nuclei lose energy by emitting radiation. This phenomenon occurs in certain isotopes, which are variants of a chemical element with the same number of protons but different numbers of neutrons. The time it takes for decay to occur varies with istope. We use the term half-life to describe the rate of decay. What’s the difference between catastrophism and uniformitarianism? Catastrophism and uniformitarianism are contrasting geological theories explaining Earth's changes. Catastrophism, popularized by Georges Cuvier, posits that Earth's features result from sudden, violent events or catastrophes, shaping the landscape in brief, intense episodes. In contrast, uniformitarianism, championed by James Hutton and later by Charles Lyell, asserts that the Earth's geological features are primarily the result of gradual, ongoing processes observed today, advocating that the same natural laws and processes have been at work throughout Earth's history. While catastrophism emphasizes sudden and catastrophic events, uniformitarianism emphasizes the principle that "the present is the key to the past," suggesting that the processes shaping the Earth have operated consistently over vast periods of time. What did Ussher and Hutton contribute to our understanding of the age of Earth? - Ussher attempted to calculate the age of the Earth using a literal interpretation of the Bible. He famously proposed that the Earth was created on the evening preceding October 23, 4004 BC. Ussher's chronology was widely accepted in the Christian world for centuries, and his calculations influenced ideas about the Earth's age until the rise of modern geology.

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- Hutton's observations of rock formations led him to propose the principle of uniformitarianism. This principle suggests that geological processes observed today, such as erosion and sedimentation, have operated in the past at similar intensities and rates. Hutton argued that the Earth is immensely old and that its features could be explained by the slow and gradual processes acting over vast periods of time. He famously stated, "The present is the key to the past."Hutton's ideas laid the groundwork for the development of the science of geology and were later championed by geologists like Charles Lyell. How old is Earth and how did we get that number? Earth is 4.6 billion years old, based on the ages of rocks on earth, the Moon and meteorites.

Tran-Review Lecture 4

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