Science Reviewer Layers of the Earth Composition: Crust: Bimodal in composition, approximately covers 1% Of the Earth in volume and radius. There are two types of Crust: The oceanic which is rich in basaltic rocks, and: The continental is rich in granitic rocks. Mantle: Mostly Mg-silicates with some Fe and Al-bearing phases. The mantle also covers most parts of the earth. Core: Fe-Ni metal with minor light elements (such as H, O, C, S, or Sl) It has more Iron than nickels. Rheology: Lithosphere- rigid, solid Asthenosphere- ductile, semi-solid Mesosphere/Lower mantle- semi-solid, more rigid than asthenosphere but capable to flow Outer core- freely convecting fluid Inner core-rigid, the hottest and the most solid More! The mantle has convection currents and it is the reason why the mantle has a cycle. The Discontinuity Seismic Waves Body waves -A body wave is a seismic wave that moves through the interior of the earth, as opposed to surface waves that travel near the earth's surface. P and S waves are body waves. Each type of wave shakes the ground in different ways. P waves -pass through all layers of the earth -can pass through all states of matter, even gas -compressional waves, much faster than s waves -slows down when it reached a liquid state S waves -pass through solid state only -can’t pass through the inner core since its liquid -transverse waves, moves in a perpendicular way -obviously slower than the P waves Surface waves -Surface waves are typically generated when the source of the earthquake is close to the Earth’s surface. As their name suggests, surface waves travel just below the surface of the ground. Although they move even more slowly than S-waves, they can be much larger in amplitude and are often the most destructive type of seismic wave. Rayleigh Waves -named after John William Strutt or much known as lord Rayleigh -gives the most destruction -travels to solid state only Rayleigh waves, also known as ground rolls, spread through the ground as ripples, similar to rolling waves on the ocean. Like rolling ocean waves, Rayleigh waves move both vertically and horizontally in a vertical plane pointed in the direction in which the waves are traveling. Love waves -named after Augustus Edward Hough Love -much faster than the Rayleigh -travels through solid only Love waves have the same motion as S-waves but without the vertical displacement. They move the ground from side to side in a horizontal plane but at right angles to the direction of propagation. Love waves are particularly damaging to the foundations of structures because of the horizontal ground motion they generate.
