{"id":175,"date":"2019-06-28T19:30:01","date_gmt":"2019-06-28T19:30:01","guid":{"rendered":"https:\/\/pressbooks.usnh.edu\/methods\/chapter\/framework-structure-form-composition\/"},"modified":"2023-03-24T15:03:19","modified_gmt":"2023-03-24T15:03:19","slug":"framework-structure-form-composition","status":"publish","type":"chapter","link":"https:\/\/pressbooks.usnh.edu\/methods\/chapter\/framework-structure-form-composition\/","title":{"raw":"Earth\u2019s Structure: At the Surface and Underground","rendered":"Earth\u2019s Structure: At the Surface and Underground"},"content":{"raw":"Layers of Earth<\/strong>\n\n[caption id=\"attachment_174\" align=\"aligncenter\" width=\"247\"]\"\" \"Earth's Layers<\/a>\" by NASA Space Place<\/a>[\/caption]\n\nEarth is made up of four layers. The outermost layer is called the [pb_glossary id=\"269\"]crust[\/pb_glossary]. The crust is made up rocks such as basalt and granite and it is very thin in comparison to the other layers. The crust is broken into many pieces called plates. There are two types of plates: [pb_glossary id=\"267\"]continental plates[\/pb_glossary] and [pb_glossary id=\"268\"]oceanic plates[\/pb_glossary]. Continental plates are much thicker than oceanic plates. Picture the depth of the ocean floor compared to the land; the ocean floor is much far below the land and, therefore, oceanic plates are thinner than continental plates.\n\nThe next layer is the [pb_glossary id=\"270\"]mantle[\/pb_glossary] which is between the crust and core. This is the largest and thickest layer of Earth. The upper part of the mantle is made of magma; the tectonic plates float on this layer which is how they move.\n\nFinally, Earth's [pb_glossary id=\"271\"]core[\/pb_glossary] is made of two layers: the outer and inner core. The liquid outer core is mostly made of iron and nickel. It is incredibly hot, so the metals remain in a liquid state. The flow of the liquid metals creates Earth's magnetic field which is why compasses always point north. Additionally, the magnetic field protects the planet from extreme weather and radiation in space. The solid inner core is also made of iron and nickel. However, this layer is solid because the materials are under intense pressure at the center of Earth. Scientists know that the inner core is solid because of how seismic waves from earthquakes travel through the interior of Earth. The waves are unable to travel straight through the layers; instead they are refracted or bent by the dense inner core, so scientists believe this layer is solid.\n\nhttps:\/\/www.youtube.com\/watch?v=4AxZ-6MOznY&feature=youtu.be\n
Video credit: \"Structure of the earth<\/a>\" by Khan Academy<\/a> is licensed under CC BY-NC-SA 3.0<\/a>. Note: All Khan Academy content is available for free at khanacademy.org<\/a>.<\/h5>\nPlate Tectonics<\/strong>\n\n[pb_glossary id=\"295\"]Plate tectonics[\/pb_glossary] explains how Earth\u2019s plates move. Earth's [pb_glossary id=\"269\"]crust[\/pb_glossary] is divided into many plates which float on the molten upper layer of the [pb_glossary id=\"270\"]mantle[\/pb_glossary]. This area is called the [pb_glossary id=\"274\"]lithosphere[\/pb_glossary]. The movement of the plates is driven by convection currents in the mantle. Heat rises from the mantle and cools as it gets closer to the surface; from there, it sinks down where it is reheated and the cycle repeats. This creates a current that moves the plates. Although they are constantly moving, each plate moves very slowly--about 3 to 5 centimeters (1 to 2 inches) per year.\n
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K-6 Standards<\/p>\n\n<\/header>\n

\n\n2-ESS1-1. Use information from several sources to provide evidence that Earth events can\noccur quickly or slowly.\n\nMS-ESS2-2. Construct an explanation based on evidence for how geoscience processes have\nchanged Earth\u2019s surface at varying time and spatial scales.\n\nMS-ESS2-3. Analyze and interpret data on the distribution of fossils and rocks, continental\nshapes, and seafloor structures to provide evidence of the past plate motions.\n\n<\/div>\n<\/div>\n \n\nTectonic Plate Boundaries<\/strong>\n
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There are three types of tectonic plate [pb_glossary id=\"272\"]boundaries[\/pb_glossary]:\u00a0<\/strong><\/p>\n\n<\/header>\n

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    \n \t
  1. Transform boundary: plates sideswipe each other\u00a0<\/span><\/li>\n \t
  2. Divergent boundary: plates pull apart from each other<\/span><\/li>\n \t
  3. Convergent boundary: plates push into each other\n\n[caption id=\"attachment_168\" align=\"aligncenter\" width=\"391\"]\"\" Transform, divergent, and convergent plate boundaries. \"Plate tectonics<\/a>\" by USGS<\/a> is public domain.[\/caption]<\/li>\n<\/ol>\n<\/div>\n<\/div>\nDepending on the type of tectonic plate and the type of plate boundary, different landforms can occur along plate boundaries.\n