Geological_I_notes

Geological_I_notes - 1 The geological hazards discussed in...

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The geological hazards discussed in this lecture are earthquakes, volcanic eruptions, and tsunamis. 2
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If one were to cut the Earth in half, they would find that our planet is made up of a series of layers. These layers are sorted by density and were formed as the Earth began to cool, shortly after its formation. The innermost layer of the Earth is the inner core. The inner core is a solid iron and nickel sphere that has a radius of approximately 758 miles. Surrounding the inner core is a hot, liquid outer core. The outer core is believed to be made up of iron and nickel as well, including trace amounts of less dense elements. Surrounding the outer core is the Earth’s Mantle. The Mantle extends to a depth of approximately 1800 miles. It is th thickes laye o th Earth and i make up abou 80% o th Earth’ tota volume Within the thickest layer of the Earth and it makes up about 80% of the Earth s total volume. Within the mantle, there is a strong temperature gradient. The mantle consists of two layers: inner mantle and the outer mantle. It is made up of mostly iron, silicates and magnesium. Surrounding the mantle is the Earth’s crust, which is discussed over the next few slides. 4
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The Earth’s crust can be divided into two distinct categories: continental crust and oceanic crust. Continental crust is mostly made up of granite and is high in both silica and aluminum. Because of the latter, it is sometimes referred to as SIAL. On average, continental crust is about 19 miles thick, but this thickness can vary. Continental crust is much thicker below Earth’s topographical regions (areas where we have mountains). There, the crust can be over 40 miles in thickness. It is also much older than oceanic crust, a phenomena we will discuss later on in this lecture. One other note that is worth mentioning i tha continenta crus i les dens than oceanic crus Th importance o thi poin wil be is that continental crust is less dense than oceanic crust. The importance of this point will be made clear when we discuss continental drift. 5
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Unlike continental crust, oceanic crust is less thick, averaging about three miles in thickness. Although it is thinner than continental crust is does have a higher density. It is also not as old as continental crust, meaning that is was formed much more recently. The oldest oceanic crust is found at the ocean/continent interfaces, while the youngest oceanic crust is found near the middle of our ocean floors. Oceanic crust is comprised mostly of basalt and is consists mostly of silica and magnesium. As a result, it is sometimes called SIMA. 6
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The above slide shows the average thickness of the Earth’s crust across our planet. Note that the crust is thicker on our continents than it is at the oceans. Also note that the crust is thickest where we find our mountain chains, specifically, along the west coasts of North America (Rocky Mountains) and South America (The Andes), and in northern India and southern China (Himalayas).
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Geological_I_notes - 1 The geological hazards discussed in...

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