{"id":225,"date":"2018-04-19T00:51:59","date_gmt":"2018-04-19T04:51:59","guid":{"rendered":"https:\/\/opentextbc.ca\/physicalgeologyh5p\/part\/chapter-7-igneous-rocks-3rd-ed\/"},"modified":"2023-06-20T13:44:18","modified_gmt":"2023-06-20T17:44:18","slug":"igneous-rocks","status":"publish","type":"part","link":"https:\/\/opentextbc.ca\/physicalgeologyh5p\/part\/igneous-rocks\/","title":{"raw":"Chapter 7. Igneous Rocks","rendered":"Chapter 7. Igneous Rocks"},"content":{"raw":"[caption id=\"attachment_224\" align=\"aligncenter\" width=\"864\"]<a href=\"https:\/\/opentextbc.ca\/physicalgeologyh5p\/part\/igneous-rocks\/nyiragongo\/\"><img class=\"wp-image-224 size-full\" src=\"https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-content\/uploads\/sites\/360\/2017\/10\/Nyiragongo.png\" alt=\"\" width=\"864\" height=\"559\" \/><\/a> <strong>Figure 7.1<\/strong> Lava lake of Mount Nyiragongo, a volcano in the Democratic Republic of Congo. Igneous rocks form when melted rock freezes. Source: Karla Panchuk (2018), CC BY-NC-SA 4.0. Click for more attributions.[\/caption]\r\n<h2>Chapter Goals<\/h2>\r\nComplete this chapter so you can:\r\n<ul>\r\n \t<li>Explain partial melting and the geological processes that lead to melting.<\/li>\r\n \t<li>Describe the range of chemical compositions of magmas.<\/li>\r\n \t<li>Discuss the processes that take place during magma cooling, and the order of crystallization in Bowen's reaction series.<\/li>\r\n \t<li>Explain how fractional crystallization and partial melting alter magma composition.<\/li>\r\n \t<li>Classify igneous rocks according to the proportions of minerals within them.<\/li>\r\n \t<li>Describe the origins of aphanitic, phaneritic, and porphyritic textures<\/li>\r\n \t<li>Classify plutons according to their shapes and relationships to surrounding rocks.<\/li>\r\n \t<li>Explain how chilled margins form.<\/li>\r\n<\/ul>\r\n<h1>Two Main Types of Igneous Rocks<\/h1>\r\nIgneous rocks form when molten (liquid) rock cools and solidifies. The characteristics of igneous rocks differ depending on whether the melt cools on Earth\u2019s surface, or in Earth\u2019s interior. For that reason, we use different terms to distinguish between the two cases.\r\n\r\nMelted rock on Earth\u2019s surface is called <strong>lava<\/strong>. The rocks that form when lava solidifies are called <strong>extrusive igneous rocks<\/strong> or <strong>volcanic igneous rocks<\/strong>. The latter term highlights the fact that extrusive igneous rocks are associated with volcanic eruptions. Melted rock within the Earth is called <strong>magma<\/strong>. Rocks that form when magma solidifies are called <strong>intrusive igneous rocks<\/strong> or <strong>plutonic rocks<\/strong>.\r\n<div class=\"textbox shaded\">\r\n\r\n<strong>Concept Test: Intrusive or Extrusive?<\/strong>\r\n<div class=\"offline\">Bear Lodge (also known as Devils Tower) in Wyoming, USA, is thought to be a volcanic plug. This means it formed when melted rock froze inside of a volcano about 40 million years ago. The rock that formed was harder than the surrounding volcano, and remains long after the volcano itself was eroded away.<strong>Is the rock of Bear Lodge intrusive or extrusive?<\/strong>\r\n\r\n<img class=\"alignnone size-full wp-image-1832\" src=\"https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-content\/uploads\/sites\/360\/2018\/04\/file-5f4d48f060590.jpg\" alt=\"A tall column of rock rises above grassy slopes.\" width=\"932\" height=\"780\" \/>\r\n\r\n<strong>Answer<\/strong>\r\n\r\nBear Lodge is an intrusive (also called plutonic) igneous rock. It's true that its formation is related to volcanic activity, but it cooled from magma that was never erupted from the volcano, not from lava that escaped the volcano.\r\n\r\n<\/div>\r\n<div class=\"h5p\">[h5p id=\"69\"]<\/div>\r\n<\/div>","rendered":"<figure id=\"attachment_224\" aria-describedby=\"caption-attachment-224\" style=\"width: 864px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/opentextbc.ca\/physicalgeologyh5p\/part\/igneous-rocks\/nyiragongo\/\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-224 size-full\" src=\"https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-content\/uploads\/sites\/360\/2017\/10\/Nyiragongo.png\" alt=\"\" width=\"864\" height=\"559\" srcset=\"https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-content\/uploads\/sites\/360\/2017\/10\/Nyiragongo.png 864w, https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-content\/uploads\/sites\/360\/2017\/10\/Nyiragongo-300x194.png 300w, https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-content\/uploads\/sites\/360\/2017\/10\/Nyiragongo-768x497.png 768w, https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-content\/uploads\/sites\/360\/2017\/10\/Nyiragongo-65x42.png 65w, https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-content\/uploads\/sites\/360\/2017\/10\/Nyiragongo-225x146.png 225w, https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-content\/uploads\/sites\/360\/2017\/10\/Nyiragongo-350x226.png 350w\" sizes=\"auto, (max-width: 864px) 100vw, 864px\" \/><\/a><figcaption id=\"caption-attachment-224\" class=\"wp-caption-text\"><strong>Figure 7.1<\/strong> Lava lake of Mount Nyiragongo, a volcano in the Democratic Republic of Congo. Igneous rocks form when melted rock freezes. Source: Karla Panchuk (2018), CC BY-NC-SA 4.0. Click for more attributions.<\/figcaption><\/figure>\n<h2>Chapter Goals<\/h2>\n<p>Complete this chapter so you can:<\/p>\n<ul>\n<li>Explain partial melting and the geological processes that lead to melting.<\/li>\n<li>Describe the range of chemical compositions of magmas.<\/li>\n<li>Discuss the processes that take place during magma cooling, and the order of crystallization in Bowen&#8217;s reaction series.<\/li>\n<li>Explain how fractional crystallization and partial melting alter magma composition.<\/li>\n<li>Classify igneous rocks according to the proportions of minerals within them.<\/li>\n<li>Describe the origins of aphanitic, phaneritic, and porphyritic textures<\/li>\n<li>Classify plutons according to their shapes and relationships to surrounding rocks.<\/li>\n<li>Explain how chilled margins form.<\/li>\n<\/ul>\n<h1>Two Main Types of Igneous Rocks<\/h1>\n<p>Igneous rocks form when molten (liquid) rock cools and solidifies. The characteristics of igneous rocks differ depending on whether the melt cools on Earth\u2019s surface, or in Earth\u2019s interior. For that reason, we use different terms to distinguish between the two cases.<\/p>\n<p>Melted rock on Earth\u2019s surface is called <strong>lava<\/strong>. The rocks that form when lava solidifies are called <strong>extrusive igneous rocks<\/strong> or <strong>volcanic igneous rocks<\/strong>. The latter term highlights the fact that extrusive igneous rocks are associated with volcanic eruptions. Melted rock within the Earth is called <strong>magma<\/strong>. Rocks that form when magma solidifies are called <strong>intrusive igneous rocks<\/strong> or <strong>plutonic rocks<\/strong>.<\/p>\n<div class=\"textbox shaded\">\n<p><strong>Concept Test: Intrusive or Extrusive?<\/strong><\/p>\n<div class=\"offline\">Bear Lodge (also known as Devils Tower) in Wyoming, USA, is thought to be a volcanic plug. This means it formed when melted rock froze inside of a volcano about 40 million years ago. The rock that formed was harder than the surrounding volcano, and remains long after the volcano itself was eroded away.<strong>Is the rock of Bear Lodge intrusive or extrusive?<\/strong><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-1832\" src=\"https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-content\/uploads\/sites\/360\/2018\/04\/file-5f4d48f060590.jpg\" alt=\"A tall column of rock rises above grassy slopes.\" width=\"932\" height=\"780\" srcset=\"https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-content\/uploads\/sites\/360\/2018\/04\/file-5f4d48f060590.jpg 932w, https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-content\/uploads\/sites\/360\/2018\/04\/file-5f4d48f060590-300x251.jpg 300w, https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-content\/uploads\/sites\/360\/2018\/04\/file-5f4d48f060590-768x643.jpg 768w, https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-content\/uploads\/sites\/360\/2018\/04\/file-5f4d48f060590-65x54.jpg 65w, https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-content\/uploads\/sites\/360\/2018\/04\/file-5f4d48f060590-225x188.jpg 225w, https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-content\/uploads\/sites\/360\/2018\/04\/file-5f4d48f060590-350x293.jpg 350w\" sizes=\"auto, (max-width: 932px) 100vw, 932px\" \/><\/p>\n<p><strong>Answer<\/strong><\/p>\n<p>Bear Lodge is an intrusive (also called plutonic) igneous rock. It&#8217;s true that its formation is related to volcanic activity, but it cooled from magma that was never erupted from the volcano, not from lava that escaped the volcano.<\/p>\n<\/div>\n<div class=\"h5p\">\n<div id=\"h5p-69\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-69\" class=\"h5p-iframe\" data-content-id=\"69\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Bear Lodge: Intrusive or Extrusive?\"><\/iframe><\/div>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"parent":0,"menu_order":7,"template":"","meta":{"pb_part_invisible":false,"pb_part_invisible_string":""},"contributor":[],"license":[],"class_list":["post-225","part","type-part","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-json\/pressbooks\/v2\/parts\/225","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-json\/pressbooks\/v2\/parts"}],"about":[{"href":"https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-json\/wp\/v2\/types\/part"}],"version-history":[{"count":4,"href":"https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-json\/pressbooks\/v2\/parts\/225\/revisions"}],"predecessor-version":[{"id":1839,"href":"https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-json\/pressbooks\/v2\/parts\/225\/revisions\/1839"}],"wp:attachment":[{"href":"https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-json\/wp\/v2\/media?parent=225"}],"wp:term":[{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-json\/wp\/v2\/contributor?post=225"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/opentextbc.ca\/physicalgeologyh5p\/wp-json\/wp\/v2\/license?post=225"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}