Posted on 2014-03-01, by LatestNews123.
TTC Video - The Origin and Evolution of Earth (Part 3 of 3) [16 wmv]
English | Size: 7.16 GB
The story of Earth is an epic filled with crises, catastrophes, and remarkable, repeated change. Earth traces its origin to simple atoms that were created in the big bang, transformed into heavy elements in stellar explosions,and then forged into a planet inside the nebula that gave birth to the solar system.
Like many other planets, Earth went through phases of melting, volcanism, and bombardment by asteroids. But only on Earth did events lead to a flourishing biosphere-life. And once life was established, it drove the evolution of our planet in startling new directions.
Most amazing of all, the evidence for every step in this intricate process is all around us-in the thousands of minerals in rocks above and below ground. Consider these intriguing clues:
*Diamond: Created under extreme pressure, diamond may very well be the first mineral formed in the universe. Together with a dozen other minerals, it helped seed the solar nebula with dust that became the planets.
*Great Oxidation Event: Earth's iron deposits are a relic of the earliest photosynthetic life, which introduced large amounts of oxygen into the atmosphere, promoting the oxidation of rocks and the production of metal-rich minerals.
*Plate tectonics: Many distinctive minerals are associated with plate tectonics, the ceaseless motion of Earth's crustal plates for more than 3 billion years. This process has had a profound impact on climate, the atmosphere, the oceans, and the development of life.
*Cambrian explosion: Changes over billions of years led to altered mineral chemistry in the oceans that made animal shells, bones, and teeth possible. Life exploited these structures in a burst of evolution 540 million years ago called the Cambrian explosion.
Minerals are fundamental to the story of Earth in many ways. Not only are we living beings nourished by minerals, but minerals provide the resources and energy that are crucial to modern civilization. Beyond that, the evolution of minerals has played a central role all across the surface of the planet and throughout its interior. Minerals turn out to be much more than beautiful crystals; they provide outstanding clues to our origins and they are major players in a drama of unimaginable scope.
The Origin and Evolution of Earth: From the Big Bang to the Future of Human Existence lets you experience firsthand the thrill of piecing together the epic story of Earth in an enlightening new perspective. In 48 half-hour lectures available in both video and audio formats, you follow events from the big bang to the formation of Earth to the many twists and turns in our planet's evolution. You discover how a young universe populated with only a few elements became a cosmos of infinite variety characterized by life-thanks to minerals. Your professor is the noted scientist who pioneered the study of mineral evolution, Professor Robert M. Hazen of George Mason University and the Carnegie Institution's Geophysical Laboratory.
A prominent field geologist, laboratory mineralogist, collector, popular author, and award-winning teacher, Professor Hazen is also a nationally recognized advocate for science education and the perfect guide for an in-depth investigation of breakthrough scientific concepts. In a course suitable for scientists and nonscientists alike, he recounts Earth's story through 10 stages of mineral evolution. Each stage resculpted our planet's surface, introducing new planetary processes and phenomena. By stage 6, life was an integral part of this process, and you learn that life is ultimately responsible for almost two-thirds of the mineral species on Earth-thousands of unique crystals that could only exist on a living world.
A New Way of Looking at Our Planet
In The Origin and Evolution of Earth, you study mineral evidence for milestones that are mind-bogglingly deep in the past:
*Rocks older than Earth: Rocks that date to the early stages of the formation of the solar system arrive on our planet all the time. They are chondrite meteorites, which are 4.567 billion years old, older than Earth itself.
*Formation of Earth's moon: Studies of Earth and moon rocks show differences best explained by a collision between the proto-Earth and a Mars-sized planet. The smaller body disintegrated and reformed as the object we know as the moon.
*First continents: Continents did not exist until the formation of granite, a rock less dense than basalt, which constituted Earth's earliest crust. Islands of granite floating on moving basaltic plates gradually collected into the first continents.
*First supercontinent: Supercontinents have formed and broken up at least six times in Earth's past. The best known is Pangaea, but geological evidence shows a series of these mammoth landmasses forming and splitting apart for almost 3 billion years.
Professor Hazen was inspired to promote his new approach to the study of minerals by a simple question asked by biologist Harold Morowitz, who wanted to know if there were clay minerals on Earth in the eon when life began. Clays are common on Earth now, but how widespread were they 3.8 billion years ago? The question is important because clay minerals figure in many theories about the origin of life.
"What was really mind-bending about this simple question," says Professor Hazen, "is the even bigger underlying suggestion that Earth's near-surface mineralogy might have differed in the past from what we see today. In 35 years as a professional mineralogist, I had never heard of such a question!" Professor Hazen goes on to point out that the living world we see around us is just the latest iteration in a long sequence of startlingly different Earths. Working backward in time, he describes these major phases:
*Green Earth: The view of Earth from space shows an inviting oasis of blue, brown, white, and, most important, green. The green of photosynthetic life is the most visible sign of the living world.
*White Earth: Plants and animals need an oxygen-rich atmosphere-a situation made fully possible 700 million years ago by conditions on a very different Earth, encased in ice from the poles to the equator.
*Red Earth: The ice-covered Earth could not have happened without a convergence of landmasses to form a supercontinent called Rodinia, tinted red due to the Great Oxidation Event 2.2 billion years ago.
*Gray Earth: Microbial life responsible for oxygenation developed only after plate tectonics began to control Earth's surface more than 3 billion years ago, when gray continents of granite first appeared.
*Blue Earth: Plate tectonics is one of the many outcomes of a globe-spanning blue ocean, which started to form as early as 4.4 billion years ago. The oceans also play a role in the formation of many minerals.
*Black Earth: The blue ocean world would not exist without water vapor from steaming volcanoes, which also paved the planet with dense black basalt starting more than 4.5 billion years ago.
Some worlds, such as Earth's moon and Mercury, never advanced beyond the black, basaltic phase. But for Earth, it was just the beginning.
Minerals as a Signature of Life
The Origin and Evolution of Earth explains how many distinctive minerals, including the semiprecious stone turquoise, deep blue azurite, and brilliant green malachite, are unambiguous signs of life, since they form only in an oxygen-rich environment that results from living processes. The discovery of such rocks on another planet would resolve one of the biggest unanswered questions in science: Did life form elsewhere besides Earth? You also learn that we don't need to travel very far to make this discovery. Meteorites could bring us telltale evidence of extraterrestrial life, or telescopic studies of planets orbiting other stars might reveal light spectra that signal the presence of life.
Throughout these 48 lectures, you range across the fields of mineralogy, geology, chemistry, cosmology, planetary astronomy, and biology, absorbing major concepts and also learning about groundbreaking researchers, many of whom are known personally by Professor Hazen. His anecdotes are both enlightening and entertaining. For example, he recounts the thrilling moment in graduate school when he was on hand as his professor, Dave Wones, received one of the first lunar samples from the Apollo missions. Hear how everything did not go according to plan that day. And you discover the clandestine world of meteorite trading in North Africa, where Professor Hazen was offered a deal on a priceless meteorite from Mars. Or was it an ordinary Earth rock? Without sophisticated analysis back in the lab, there was no way of knowing.
If you have ever admired the beauty of a crystal, marveled at the complexity of the natural world, wondered about the amazing story locked inside a rock-or a fossil-or the moons of Jupiter; or if you are simply a person who likes a good mystery, sprinkled with surprising clues, then The Origin and Evolution of Earth is the course for you. Join Professor Hazen-a born teacher, scientist, storyteller, guide, and companion-in this unrivaled investigation.
TTC Video - The Origin and Evolution of Earth (Part 3 of 3) [16 wmv]
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