Earth notes chapter one

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2240

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Geology

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Oct 30, 2023

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Earth-sci Chapter one Philosophy: Geology and Religion - Many early principles of geology were widely rejected, as they often conflicted with religious dogma (especially the Catholic church in Europe!) Geology helped lead Darwin to his principle of Evolution, and he was hated for it! Nicolaus Steno, regarded as the father of stratigraphy, renounced his life’s work (after heavy persuasion) and joined the Catholic Church It is undeniable the interconnection of religion and politics played a huge role in slowing scientific breakthroughs, where findings that conflicted with the Church’s teachings were ridiculed and denounced. Catastrophism - o Stemming from the postulation of Thomas Burnet, the theory of Catastrophism was the predominant dogma of geology through the late 1700s-early 1800s. o The most vocal proponent of Catastrophism was Baron Georges Cuvier, a French nobleman and scientist. Cuvier published a paper describing the stratigraphy and sediments within the Paris Basin and noted some unusual, repeating layers of fine sediments and boulders. He determined the abnormal layers were due to sudden, immense floods driven by vast, unpredictable catastrophes. Using the story of Noah’s Flood and supporting narratives from older cultures, Cuvier formed a timeline of a series of massive flooding events throughout Earth’s history. The main beliefs of Catastrophists were: o The Earth was a record of unique events. o No such thing as evolution – biological, geological, or otherwise! o No possible way to predict nature. In many ways, these apprehensions slowed scientific breakthroughs. However, people were not dumber back then – just uninformed. - Baron Cuvier amassed a huge collection of fossils, and his contribution to biology and the understanding of many species is recognized today.

- Cuvier’s Christian faith was shaken many times in his scientific research, but he chose to ignore findings that conflicted with the Church and Catastrophism If you were a believer in Catastrophism, you would think: o The Earth began as a molten ball. o While it cooled/solidified, a few random, seizure-like global convulsions whipped up the semi- molten material into peaks and formed mountains (even those including fossils!). o Valleys were all eroded at once as a global signature of the Biblical Noah’s Flood. o Fossils represent previous life forms, fully erased from the Earth by intermittent catastrophes. o There is no biological connection between any species through time – each one was a unique, hand-made gift from (specifically Christian) God. Uniformitarianism - o Originally called Gradualism, the geological and biological theory of Uniformitarianism was first introduced in 1795 by James Huttonan important dude! in his book “Theory of Geology”. Hutton spent long hours watching creeks pick up and move sediments downstream – and concluded that if these sediments pile up day after day and year after year, landforms can change over time rather than all at once. o Then came Charles Lyell, a much more convincing orator of the theory of Uniformitarianism, drawing heavily from Hutton’s work in his book, “Principles of Geology”. Lyell single-handedly changed Geology and led the new revolution into Uniformitarianism. Many breakthroughs in Biology and Geology were made thanks to Lyell – especially after ditching the Christian Church’s earth age. o Finally, we come to the Law of Uniformitarianism – the one line that easily summed up the new, breakthrough idea: Basically, the various geologic processes we see operating today are not new, have always operated, and will continue to operate at similar rates. Uniformitarianism dominated until Plate Tectonics – and many took it to extremes.

The scientific method: Step One: Observation – seeing an object or process occurs. Step Two: Hypothesis - forming an idea based on the observation. Step Three: Experiment – testing the idea but trying to limit outside influence as much as possible. Step Four: Conclusion – forming a theory based on the idea and outcome of the experiment. Step Four.5: The theory can be turned into a law if tested enough and found to be fully valid. Disasters vs. Catastrophes - Disaster: a sudden or great misfortune; a calamity. Catastrophe: a widespread disaster; a disastrous end This scale gives a description of each natural disaster and catastrophe: Disaster -  Local Disaster: significant disruption to specific communities (ie. A flood in downtown London)  Regional Disaster: a larger event occurring over a larger area (ie. A flood in the GTA) Catastrophe -  Regional Catastrophe: an even worse event occurring over the area of a province or state (ie. A meteor impact in Ontario)  Global Catastrophe: The catastrophe is so strong; that it has global consequences no matter where it occurs (e.g., The Moon colliding with Earth) The Cost of Catastrophes - o As human populations soar worldwide, catastrophes are more likely to produce high death rates. o The infrastructure damage from large catastrophes will often cost billions to repair. o As well, climate change continues to produce stronger and stronger natural disasters.

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Chapter two: Geologic age dates The (True) Age of the Earth - o Advancements have led to the development of Absolute Age Dating, a geochemical method that uses the known rate of radioactive decay of atoms to measure age (or time since formation) o We say the Solar System formed 4.567 billion Years Ago. Or 4.567 Ga = 4,567.0 Ma = 4,567,000,000 a(a = year) (Get used to notation: Ga = billion yr, Ma = million yr, ka = thousand yr…) o Using the average age of the asteroids around Earth, we give Earth’s age as 4.54 Ga. o Since the Earth tends to eat up and recycle old rocks, not many from the original crust exist - The oldest crustal fragments on Earth are both found in Canada – the Acasta Gneiss, NWT (4.031±0.003Ga), and the Nuvvuagittuq Greenstone, QC (4.388/3.75Ga[disputed]) – yet neither are close to as old as the original crust. - Since we don’t have any rocks on Earth to sample directly, we look to space for clues (ie. Asteroid ages, instead of recycled-Earth-rock ages) o Many of these recycled rocks make up the grains within sedimentary rocks. o You often cannot date sediments with Absolute Age Dating, so we use Relative Age Dating instead. Relative Age Dating - o Nicholas Steno (see Chapter 1) proposed three fundamental principles in geology that are the basis for current geological mapping: 1. Principle of Superposition: Sedimentary rock layers are deposited on top of each other. 2. Principle of Original Horizontality: Sedimentary rock layers remain flat and horizontal when deposited. 3. Principle of Original Lateral Continuity: Sedimentary rock layers are deposited over large areas (such as the size of an ocean) o These principles are colloquially known as Steno’s Laws

o Unfortunately, Steno’s Laws couldn’t explain igneous intrusions, or the relationship between an eroded rock and the strata lain on top. o James Hutton added his own Principle of Cross-Cutting Relationships, which tells us: A fault is younger than the youngest rock it cuts. The strata above an unconformity are younger than the strata below. Any feature that crosscuts a rock must be younger than the rock it cuts. o In this diagram, the layers get younger as you move from A → K; try applying Steno’s Laws and interpret the ages of the layers yourself. o The final piece of the Relative Age Dating ‘toolbox’ is the application of Reference Horizons by William Smith - The previous principles were able to date rocks relative to each other within a small geographic area – though you couldn’t compare a clay layer with another visually similar clay layer even a few hundred km away because there was no way to effectively date each one. - Reference Horizons solves this problem by applying the Principle of Faunal Succession. - This allows geologists to compare the fossils found in one layer to another in order to determine if they were deposited at the same (or very close) time. It’s Naming Time - o Scientists were then left with the task of dividing up prehistoric time. - There are four Eras representative of the dominant life form (or lack of) - There are ten Periods, which we will mention frequently throughout the course. - Periods are often punctuated by apparent mass dying or mass extinctions (see Unit 4) - Eras are punctuated by revolutionary biological and environmental changes, such as the development of life or the event that killed all the dinosaurs.

Absolute Age Dating - o In the many rocks that aren’t sedimentary, we require more difficult methods to determine age – methods that often yield more accurate results. o Following Henri Becquerel’s discovery of Radioactivity, methods for determining the age of radioactive elements were applied widely. - It was found that as a radioactive atom decays, it does so at a consistent rate - By determining the ratio of parent atoms (the radioactive, decaying atom) to daughter atoms (the mostly stable product), scientists can easily find the time since decay started in a closed system - (The written notes go into great detail about the chemistry behind absolute age dating and radioactive decay! o In Geology and Geochemistry, there are a few naturally occurring radioactive minerals that we look for when trying to find the age of an igneous rock. - Zircon is a mineral that contains Uranium – By determining the ratio of Uranium to Lead in the Zircon crystal, we can find the age of the Zircon. o There are many radioactive relationships, but a few common ones are: o Some are more practical than others in the application, as C-14 is extremely effective at dating things less than 50,000 years old – though nothing older End of Chapter 1 review: Studying this chapter: o Know the key scientists in this chapter. - What were their names (Steno, Burnet, Ussher, Cuvier, Hutton, Lyell) - What were they famous for? (e.g., who was the father of geology?) - What did each of them believe in terms of how nature works? o Catastrophism vs. Uniformitarianism - Be able to define these terms. - Be able to explain the theories. - Give examples of what a catastrophist versus a uniformitarian believes. - Identify one or more problems with either of these theories.

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Chapter 3: Continental drift: o First formalized by Alfred Wegener in 1912, the idea of continental drift was radical and revolutionary. o Not many people could believe the landmasses had moved around and were continuing to move under their feet. o Wegener’s undisputable evidence was:  The jigsaw puzzle-fit of the continents on the globe and fossils.  Correlation of plant and animal fossils across the continents. o Still, few immediately accepted Wegener’s proposal, waiting for more evidence.