Lab 4D Geo Dimensions Part A- Video Notes

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South Texas College *

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Geology

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Oct 30, 2023

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Frida Galvan Lab 4D Geo Dimensions Part A: Video Notes A1 It is hard to imagine the 4.5 billon years of the Earth’s age, but geologists used a football field to explain what happened in all the 4.5 billon years. For the first few hundred million years, the earth was bombarded with rocks from outer space, in 4.3 billon years ago, it started to calm down and at 3.8 billion years ago life begins. It wasn’t human life, it was simple single cell life vesting from the ocean, the cells are trying to adapt to find new ways to get energy. Photosynthesis starts at 3.5 billion years, the air it is mostly carbon dioxide and nitrogen, but green cells start making oxygen. At 2.3 billion years ago, oxygen starts creating an atmosphere, we are in the middle age of the earth and now the earth has the atmosphere where humans can breathe. For the next billion and a half years cells start working together and multi-cellular begins, this started to happen 800 million years ago. At 600 million years ago, the earth has a ozone layer, an at this time it starts to be an explosion of diversity where fungi, sea anemones, and molluscs start to grow. At 530 million years ago, animals start to exist in land and in the ocean animals appear too. At 176 million years ago, mammals and dinosaurs are found, every single specie appears in different timelines. In 66 billion years ago a mass extinction happens and it kills 75% of all species, but life it is still there. In 200 thousand years ago, humans are found that look like us and, in the end, there is civilization, agriculture, and science. A2 Geologists have found that by looking in the layers beneath our feet, they can identify and describe the life of animals in history and the diversity and catastrophic events. Geologists use the geologic time scale to have a system. it was very hard to discover and compare rocks because rocks are not the same as the other ones in another continent, a geologist William smith figured out the solution to this problem. Fossils can be much easier help to identify and describe the history of earth. Smith could match the ages, regardless of how apart they were. The geologic time scale has been reworked many times to reflect the latest knowledge of earth’s history. Nowadays, the scale is organized by Eons, Eras, Periods, Epochs, and Ages. Eons are the largest slice of time ranging from half billion two nearly 2 billion years long. The earliest Eon is known as the hadean, it begins with the very formation of the earth itself, around 4.56 million years ago and ends 4 billion years ago. This is the only eon that doesn't have fossils because earth was like hell, in that time. The planet in that Eon, was wracked by volcanic activity, cosmic bombardments, raging storms, and high temperatures that where at times hot enough to melt rock. The Hadean ended by the cooling of the earth's crust and settled the continents to form. This cooling marked the beginning of the next phase, the Archean Eon from 4 billion to 2.5 billion years ago. During this time the atmosphere was mostly carbon dioxide, and this time it was the first sign of life appeared, it was the first time that life flourished forming mats of microbes in the ocean. The fossils from this time left behind microbes called stromatolites and sometimes stromatoliths. Then 2.5 billion years ago, the Archean gave way to the Proterozoic Eon which is around 2.5 billion years ago- 541 million years ago. Around this time photosynthesis bacteria along with some multicellular forms of life begins. In the Phanerozoic

Eon 541 million years ago – present, in this time life began to look obvious, this is the Eon that’s home to trees, dinosaurs, and humans. Paleozoic era began in 541 million years ago, this era was defined the diversification of visible life and it started with a bang, this gave the diversity and complexity in the world’s oceans. The desert was populated by ancestors of reptiles, but this growth didn’t last forever, the Paleozoic Era ended in cataclysm. 70% of land vertebrates and 96% of marine species disappeared from the fossil record. It took millions of years for life to recover but when it did, the Mesozoic Era begun. This era is famous for its reptiles the dinosaurs which after 66 million years ago ended with another episode of devastation. the Cenozoic era 66 million years ago to present, the climate changed and gave an habitat to horses, grassland and to the first cats. A3 Alfred Wegener spent years traveling the world, collecting geological and fossil evidence to argue that all the continents were once connected. In the 1950s and 60s, researchers studied the bottom of the ocean and found out that there was an enormous mountain range running through the middle of the Atlantic, eventually they found out that these undersea mountain rages are all around the world and are called mid-ocean ridges. Seafloor spreading and subduction are 2 primary mechanisms behind plate tectonics. The process of continents coming together and splitting apart is known as the supercontinent cycle. There are a lot of predictions of how the earth might look because the supercontinent cycle would happen again maybe in 50 million years, but there are a lot of theories. A4 Rock layers can tell us stories of the past geologic events. The layers in order can tell us the deposition, erosion, tilting, magmas, metamorphism, and faulting. Sedimentary rocks represent the deposition in the sand, beach, or desert. Igneous rocks represent events of the volcanic episodes. Metamorphic rocks represent events of the high temperature and pressure near volcanoes. Stratigraphy is the geologic record of part events, which can tell which can happen before and after. The principle of superposition says that the layer from the top is the youngest and the layer at the bottom the oldest. The relative dating is the science that determines the relative order of past events, it is used to arrange the geological events that rocks leave behind. A5 The radiometric dating calculates the age of geologic materials by measuring the short life of the radioactive element or the long life of the radioactive element and the decay process. It is based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products (decay rates). Depending on where the material was formed and how it is the best way to measure the material. The most used technique of radiometric dating is the potassium-argon because it is a common mineral to find the ages of igneous and metamorphic rocks.

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