Ch2 - Energy Flows in Earth History and Natural Disasters...

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R. J. Ferguson, Geoscience U Calgary Energy Flows in Earth History and Natural Disasters
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Energy Sources for Disasters Four primary energy sources fuel Earth processes : Impact of extraterrestrial bodies – Asteroids and comets; abundant in early Earth history, rare now Gravity – Mass of Earth pulls objects (glaciers, hillsides) downhill • Earth’s internal heat – As Earth cools, heat ±ows from interior to surface – Volcanic eruptions, earthquakes – Plate tectonics; formation of continents, atmosphere and oceans • The Sun – Evaporation of water into atmosphere produces weather – With gravity, powers agents of erosion
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Origin of the Sun and Planets Solar system began as rotating spherical cloud of gas, ice, dust and debris Gravitational attraction brought particles together into bigger and bigger particles Cloud contracted , sped up and fattened into disk Formation o± Sun – Greatest accumulation o± matter ( H and He ) at center o± disk – Temperature at center increased to 1 million degrees centigrade Nuclear fusion o± hydrogen (H) and helium (He) began, producing solar radiation
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Origin of the Sun and Planets Accretion under the force of gravity must over come centrifugal forces and magnetic drag forces
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Origin of the Sun and Planets Figure 2.8
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Origin of the Sun and Planets Formation of planets – Rings of concentrated matter formed within disk – Particles within rings continued to collide to form planets – Inner planets (Mercury, Venus, Earth and Mars) lost much gas and liquid to solar radiation, becoming rocky (terrestrial) – Outer planets retained gas and liquid, as gas planets Impact origin of the Moon – Early impact of Mars-sized body with Earth – Impact generated massive cloud of dust (from Earth’s crust and mantle) and gas which condensed to form Moon – Lightweight gases and liquids lost to space – Lesser abundance of iron (from Earth’s core) in Moon
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Sketch of a Mars-sized impact on the early Earth–gives rise to the Moon
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Our Solar System
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10
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Amazing, what ʼ s out there!
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Earth History Earth forms about 4.6 billion (4,600,000,000 or 4.6 x 10 9 ) years ago 3.9 billion years ago : large oceans, small continents 3.5 billion years ago : life (photosynthetic bacteria) 2.5 billion years ago : large continent 1.5 billion years ago : plate tectonics
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Earth History Analogy with Mother Earth, 46-year-old woman : (1 Mother Earth year = 100 million geologic years) First seven years unaccounted for 42 years old: life appeared on continents 45 years old: Fowering plants 8 months ago: dinosaurs died out Last week: human ancestors evolved Yesterday: humans evolved Last hour: discovered agriculture , settled down 1 minute ago: Industrial Revolution
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14 From Wikipedia
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Ch2 - Energy Flows in Earth History and Natural Disasters...

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