{"id":1874,"date":"2026-01-28T10:00:09","date_gmt":"2026-01-28T10:00:09","guid":{"rendered":"https:\/\/vamosajeju.com\/?p=1874"},"modified":"2026-03-13T19:36:46","modified_gmt":"2026-03-13T19:36:46","slug":"the-birth-of-jeju-a-story-of-fire-and-stone","status":"publish","type":"post","link":"https:\/\/vamosajeju.com\/es\/the-birth-of-jeju-a-story-of-fire-and-stone\/","title":{"rendered":"El nacimiento de una isla: una historia de fuego y piedra"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"1874\" class=\"elementor elementor-1874\" data-elementor-post-type=\"post\">\n\t\t\t\t<div class=\"elementor-element elementor-element-c0e710d e-flex e-con-boxed e-con e-parent\" data-id=\"c0e710d\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-35a65de elementor-toc--minimized-on-desktop elementor-invisible elementor-widget 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page.&quot;,&quot;minimized_on&quot;:&quot;desktop&quot;,&quot;_animation&quot;:&quot;bounceInDown&quot;,&quot;marker_view&quot;:&quot;numbers&quot;,&quot;minimize_box&quot;:&quot;yes&quot;,&quot;hierarchical_view&quot;:&quot;yes&quot;,&quot;min_height&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]},&quot;min_height_widescreen&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]},&quot;min_height_laptop&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]},&quot;min_height_tablet_extra&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]},&quot;min_height_tablet&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]},&quot;min_height_mobile_extra&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]},&quot;min_height_mobile&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]}}\" data-widget_type=\"table-of-contents.default\">\n\t\t\t\t\t\t\t\t\t<div class=\"elementor-toc__header\">\n\t\t\t\t\t\t<h4 class=\"elementor-toc__header-title\">\n\t\t\t\tWhat You'll Find in This Article\t\t\t<\/h4>\n\t\t\t\t\t\t\t\t\t\t<div class=\"elementor-toc__toggle-button elementor-toc__toggle-button--expand\" role=\"button\" tabindex=\"0\" aria-controls=\"elementor-toc__35a65de\" aria-expanded=\"true\" aria-label=\"Open table of contents\"><svg aria-hidden=\"true\" class=\"e-font-icon-svg e-fas-chevron-down\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M207.029 381.476L12.686 187.132c-9.373-9.373-9.373-24.569 0-33.941l22.667-22.667c9.357-9.357 24.522-9.375 33.901-.04L224 284.505l154.745-154.021c9.379-9.335 24.544-9.317 33.901.04l22.667 22.667c9.373 9.373 9.373 24.569 0 33.941L240.971 381.476c-9.373 9.372-24.569 9.372-33.942 0z\"><\/path><\/svg><\/div>\n\t\t\t\t<div class=\"elementor-toc__toggle-button elementor-toc__toggle-button--collapse\" role=\"button\" tabindex=\"0\" aria-controls=\"elementor-toc__35a65de\" aria-expanded=\"true\" aria-label=\"Close table of contents\"><svg aria-hidden=\"true\" class=\"e-font-icon-svg e-fas-chevron-up\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M240.971 130.524l194.343 194.343c9.373 9.373 9.373 24.569 0 33.941l-22.667 22.667c-9.357 9.357-24.522 9.375-33.901.04L224 227.495 69.255 381.516c-9.379 9.335-24.544 9.317-33.901-.04l-22.667-22.667c-9.373-9.373-9.373-24.569 0-33.941L207.03 130.525c9.372-9.373 24.568-9.373 33.941-.001z\"><\/path><\/svg><\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<div id=\"elementor-toc__35a65de\" class=\"elementor-toc__body\">\n\t\t\t<div class=\"elementor-toc__spinner-container\">\n\t\t\t\t<svg class=\"elementor-toc__spinner eicon-animation-spin e-font-icon-svg e-eicon-loading\" aria-hidden=\"true\" viewBox=\"0 0 1000 1000\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M500 975V858C696 858 858 696 858 500S696 142 500 142 142 304 142 500H25C25 237 238 25 500 25S975 237 975 500 763 975 500 975Z\"><\/path><\/svg>\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-3473ce3 e-flex e-con-boxed e-con e-parent\" data-id=\"3473ce3\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-36c329c elementor-widget elementor-widget-text-editor\" data-id=\"36c329c\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">As a host of tourists to Jeju, I&#8217;ve often been asked questions about the magnificent Jeju landscape. Why Hallasan looks like an umbrella. Why so many hills pepper the land. Why the coast is full of twisted rock.<\/span><\/p><p><span style=\"font-weight: 400;\">So I wanted to make sure I could answer their questions, and\u00a0<\/span>studied this book called\u00a0<i>Jeju Island Geology Tour<\/i>\u00a0by Kim Yong-je (2020). What I learned was that Jeju Island itself is a living geology textbook. And the more I learned about the volcanic history here, the more I understand why certain places look the way they do.\u00a0<\/p><p>So I wanted to summarize these basic concepts here, especially the formation of Seongsan Ilchulbong and Seopjikoji. Just in case I never get the chance to show you around this island that I love so much.<\/p><p>If you&#8217;re a traveler interested in geology, this is a must-read before visiting these spots. It makes everything so much more interesting, especially if like my co-host Ed, you love hiking.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-f340b38 e-flex e-con-boxed e-con e-parent\" data-id=\"f340b38\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-b2ab6cd elementor-widget elementor-widget-heading\" data-id=\"b2ab6cd\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Volcano 101 - The Basics  <\/h2>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-ac63071 elementor-widget elementor-widget-text-editor\" data-id=\"ac63071\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">Not all volcanic eruptions are the same. What comes out and what it builds depends on the magma&#8217;s temperature, how much gas is dissolved in it, and whether it meets water on the way up. Jeju has three main eruption types, and once you understand them, you&#8217;ll start recognizing which one made what.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-2e839fe elementor-widget elementor-widget-heading\" data-id=\"2e839fe\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h3 class=\"elementor-heading-title elementor-size-default\">Hawaiian-Style Eruptions<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-d2e0a3c elementor-widget elementor-widget-image\" data-id=\"d2e0a3c\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img fetchpriority=\"high\" decoding=\"async\" width=\"800\" height=\"286\" src=\"https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Aa-Lava-1024x366.jpg\" class=\"attachment-large size-large wp-image-1887\" alt=\"\" srcset=\"https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Aa-Lava-1024x366.jpg 1024w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Aa-Lava-300x107.jpg 300w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Aa-Lava-768x274.jpg 768w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Aa-Lava-1536x549.jpg 1536w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Aa-Lava.jpg 1750w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-925edf5 elementor-widget elementor-widget-text-editor\" data-id=\"925edf5\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">These are the calm ones because hot, fluid basaltic lava just&#8230; flows. You get two types of lava from this. Pahoehoe lava moves slowly and smoothly, and when it hardens it looks shiny and ropy, almost like glass. This is how Jeju&#8217;s famous lava tubes formed &#8211; the outside cooled while hot lava kept flowing inside, creating caves like Manjanggul. Aa lava is the rougher, faster kind that leaves behind jagged, reddish surfaces.<\/span><\/p><p><span style=\"font-weight: 400;\">Hallasan was built by these kinds of eruptions over hundreds of thousands of years. It&#8217;s what geologists call a shield volcano, with broad and gently sloped, like an upside-down shield.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-b152e12 elementor-widget elementor-widget-heading\" data-id=\"b152e12\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h3 class=\"elementor-heading-title elementor-size-default\">Strombolian Eruptions<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-d6fb30a elementor-widget elementor-widget-image\" data-id=\"d6fb30a\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img decoding=\"async\" width=\"800\" height=\"534\" src=\"https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Strombolian-Eruption-1024x683.jpg\" class=\"attachment-large size-large wp-image-1886\" alt=\"\" srcset=\"https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Strombolian-Eruption-1024x683.jpg 1024w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Strombolian-Eruption-300x200.jpg 300w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Strombolian-Eruption-768x512.jpg 768w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Strombolian-Eruption-1536x1024.jpg 1536w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Strombolian-Eruption.jpg 1800w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-82cc7bf elementor-widget elementor-widget-text-editor\" data-id=\"82cc7bf\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">When magma has a lot of dissolved gas like water vapor and carbon dioxide that rises to the surface, that pressure has to go somewhere. Think about shaking a cola bottle and then opening the cap. Boom! The volcano does the same thing, throwing hot lava fragments into the air. These fragments are called scoria (in Jeju dialect, &#8220;songi&#8221;), and they pile up around the vent to create scoria cones.<\/span><\/p><p><span style=\"font-weight: 400;\">Most of Jeju&#8217;s 368 oreums are scoria cones. That reddish color you see on many of them? That&#8217;s oxidation, created because the heat and gases kept affecting the rock even after the eruption stopped.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-3c14d3b elementor-widget elementor-widget-heading\" data-id=\"3c14d3b\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h3 class=\"elementor-heading-title elementor-size-default\">Hydrovolcanic Eruptions (When Magma Meets Water)\n<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-e50cfa7 elementor-widget elementor-widget-image\" data-id=\"e50cfa7\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img decoding=\"async\" width=\"800\" height=\"534\" src=\"https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Lava-Meets-Water-1024x683.jpg\" class=\"attachment-large size-large wp-image-1885\" alt=\"\" srcset=\"https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Lava-Meets-Water-1024x683.jpg 1024w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Lava-Meets-Water-300x200.jpg 300w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Lava-Meets-Water-768x512.jpg 768w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Lava-Meets-Water.jpg 1440w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-8b6523a elementor-widget elementor-widget-text-editor\" data-id=\"8b6523a\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">This is where things get dramatic. When rising magma hits water such as seawater or groundwater, the water instantly turns to steam and expands more than a thousand times. Massive explosion. The magma shatters into fine ash and rock fragments. It&#8217;s similar to what happens when you put a hot glass in cold water and it cracks.<\/span><\/p><p><span style=\"font-weight: 400;\">These eruptions create three different landforms depending on the details:<\/span><\/p><p><b>Tuff rings:<\/b><span style=\"font-weight: 400;\">\u00a0low, wide, ring-shaped hills. Magma + surface water like seawater. Examples: Songaksan, Suwolbong.<\/span><\/p><p><b>Tuff cones:\u00a0<\/b><span style=\"font-weight: 400;\">taller and steeper, from stronger eruptions. Example: Seongsan Ilchulbong.<\/span><\/p><p><span style=\"font-weight: 400;\"><b>Maars:\u00a0<\/b>\u00a0wide, shallow craters from magma + groundwater deep underground. Example: Sangumburi.<br \/><\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-7f9a02b elementor-widget elementor-widget-image\" data-id=\"7f9a02b\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"800\" height=\"391\" src=\"https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Seongsan-Ilchubang-from-distance-scaled-e1768894556263-1024x500.jpg\" class=\"attachment-large size-large wp-image-993\" alt=\"\" srcset=\"https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Seongsan-Ilchubang-from-distance-scaled-e1768894556263-1024x500.jpg 1024w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Seongsan-Ilchubang-from-distance-scaled-e1768894556263-300x146.jpg 300w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Seongsan-Ilchubang-from-distance-scaled-e1768894556263-768x375.jpg 768w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Seongsan-Ilchubang-from-distance-scaled-e1768894556263-1536x750.jpg 1536w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Seongsan-Ilchubang-from-distance-scaled-e1768894556263-2048x1000.jpg 2048w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Seongsan-Ilchubang-from-distance-scaled-e1768894556263-18x9.jpg 18w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-93ff582 elementor-widget elementor-widget-heading\" data-id=\"93ff582\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">How Jeju Was Born (The Short Version)\n<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-22ed2a3 elementor-widget elementor-widget-text-editor\" data-id=\"22ed2a3\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">About 1.8 million years ago, volcanoes started erupting on what was then a muddy seabed in the South Sea. For over a million years, most eruptions were hydrovolcanic, comprising magma pushing up through water-saturated sediments, building layers of ash and debris.<\/span><\/p><p><span style=\"font-weight: 400;\">Between 500,000 and 200,000 years ago, Jeju finally emerged above sea level for good. The eruption style shifted to Strombolian and Hawaiian types, piling up lava flows and building the island&#8217;s main body. Hallasan grew during this period. Most of the lava you walk on today erupted between 400,000 and 20,000 years ago.<\/span><\/p><p><span style=\"font-weight: 400;\">And here&#8217;s the wild part: Seongsan Ilchulbong is only about 5,000 years old. That&#8217;s basically yesterday in geological terms. The last recorded eruption on Jeju was around 1002 AD. We don&#8217;t know exactly where, but it happened. This island is young.<\/span><\/p><p><span style=\"font-weight: 400;\">One more thing. During the ice ages, sea levels dropped as much as 130 meters, which means Jeju was connected to the Korean mainland multiple times. And you know how Jeju has almost no rivers even though it rains so much? That&#8217;s because the volcanic rock is full of cracks and cavities. Water just drains straight through. Even during heavy rain (200-300mm in a day!), the rivers only fill for a few hours.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-fc02957 elementor-widget elementor-widget-heading\" data-id=\"fc02957\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Seongsan Ilchulbong: A Textbook Tuff Cone<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-935eae0 elementor-widget elementor-widget-image\" data-id=\"935eae0\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"800\" height=\"378\" src=\"https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Sungsan-Ilchubong-from-the-air-1024x484.jpg\" class=\"attachment-large size-large wp-image-1891\" alt=\"\" srcset=\"https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Sungsan-Ilchubong-from-the-air-1024x484.jpg 1024w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Sungsan-Ilchubong-from-the-air-300x142.jpg 300w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Sungsan-Ilchubong-from-the-air-768x363.jpg 768w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Sungsan-Ilchubong-from-the-air.jpg 1338w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-170c6c7 elementor-widget elementor-widget-text-editor\" data-id=\"170c6c7\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">Seongsan Ilchulbong, also known as Sunrise Peak, formed about 5,000 years ago when magma erupted through the shallow seafloor. The ice age had ended, sea levels were similar to today, and this area was shallow sea. When the hot magma met cold seawater&#8230; boom. Massive steam explosions shot wet volcanic ash high into the air.<\/span><\/p><p><span style=\"font-weight: 400;\">What makes Ilchulbong so special for geology nerds is that the sea has eroded away most of the original cone, exposing the internal layers like a cross-section diagram. You can literally read its formation history in the cliffs.<\/span><\/p><p><b>What to Look For<\/b><\/p><p><span style=\"font-weight: 400;\">The slopes here are steep and up to 45 degrees in places. Normally, dry volcanic ash settles at angles no steeper than 35 degrees. But wet ash clumps together and can pile steeper, like building a sandcastle with damp sand. So those steep slopes tell you the ash was wet when it landed.<\/span><\/p><p><span style=\"font-weight: 400;\">Look for layered deposits that drape down the slopes. These formed when clumps of wet ash slid downhill in broad sheets, stacking like roof tiles. And those wrinkled surfaces in the ash layers? They&#8217;re called adhesion marks. Pyroclastic flows swept across the wet ground and pushed it into wave-like patterns. It&#8217;s similar to what happens when you blow hard on thick soup.<\/span><\/p><p><span style=\"font-weight: 400;\">Here&#8217;s something I found really interesting: recent research shows Ilchulbong actually formed in three separate phases, not one continuous eruption. The original crater was about 600 meters east of where the current one is! Between eruption phases, erosion partially destroyed the growing cone before the next phase built it back up. The volcano kept moving.<\/span><\/p><p><b>Reading the Sea Level<\/b><\/p><p><span style=\"font-weight: 400;\">At the southwest coastal outcrop, you can see the boundary between two different environments. Above a certain line, rounded &#8220;coal sac&#8221; structures show ash that accumulated above sea level. Below that line, cross-bedded layers show material that was washed and redeposited by waves underwater. The boundary between them marks the approximate sea level when Ilchulbong formed. That&#8217;s roughly equal to today&#8217;s high tide line. How cool is that?<\/span><\/p><p><b>The Sinyang-ri Formation (How the Islands Connected)<\/b><\/p><p><span style=\"font-weight: 400;\">Seongsan Ilchulbong wasn&#8217;t always connected to Jeju. After the cone formed, waves eroded its rocks and deposited the fragments, along with shells, all along the surrounding coast. This sedimentary layer gradually built up the land bridge connecting Ilchulbong to the main island. Shell fossils in this formation date between 3,500 and 5,000 years old, meaning the connection happened within about a thousand years of the eruption.<\/span><\/p><p><span style=\"font-weight: 400;\">You can see these layers at Gwangchigi Beach near the entrance to Seopjikoji.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-d702e03 elementor-widget elementor-widget-heading\" data-id=\"d702e03\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Seopjikoji: Inside a Scoria Cone<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-a1919cf elementor-widget elementor-widget-image\" data-id=\"a1919cf\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"800\" height=\"320\" src=\"https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Seopjikoji-e1769583570220.jpg\" class=\"attachment-large size-large wp-image-1878\" alt=\"\" srcset=\"https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Seopjikoji-e1769583570220.jpg 996w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Seopjikoji-e1769583570220-300x120.jpg 300w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Seopjikoji-e1769583570220-768x308.jpg 768w, https:\/\/vamosajeju.com\/wp-content\/uploads\/2025\/12\/Seopjikoji-e1769583570220-18x7.jpg 18w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-c3fd07b elementor-widget elementor-widget-text-editor\" data-id=\"c3fd07b\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">The name Seopjikoji comes from Jeju dialect, and &#8220;seopji&#8221; means narrow land, and &#8220;koji&#8221; means cape. This is the only place on Jeju where you can see both the inside and outside of a scoria cone (the Bangdu Peninsula). That makes it really special for understanding how these volcanic structures work.<\/span><\/p><p><b>How Scoria Cones Form<\/b><\/p><p><span style=\"font-weight: 400;\">Unlike tuff cones (hydrovolcanic), scoria cones come from Strombolian eruptions, with gas-rich magma exploding and throwing molten chunks into the air. Small particles (under 6cm) that solidify in flight are scoria. Bigger chunks (over 6cm) are volcanic bombs or spatter.<\/span><\/p><p><span style=\"font-weight: 400;\">When volcanic bombs land while still hot, they can weld together into a mass called agglomerate. If they&#8217;re hot enough and pile up fast enough, they can even flow like lava. This is called clastogenic lava, and you can identify it by the elongated, stretched shapes of the original bombs preserved inside.<\/span><\/p><p><span style=\"font-weight: 400;\">Seondol Rock, that 10-meter pillar at Seopjikoji, marks the center of the original crater. It&#8217;s solidified lava that hardened right in the volcanic vent.<\/span><\/p><p><b>Lava Flow Features to Spot<\/b><\/p><p><span style=\"font-weight: 400;\">Walking the coastal paths, you can find lava channels, also known as the &#8220;fire paths&#8221; where molten rock once flowed, now hardened as grooves in the rock. Look for them on the east side of the hill path from the parking lot to Bongsu-dae. There are also vertical lava pillars about 5 meters tall, with agglomerate and clinker (broken rock fragments) still attached.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-2f32208 e-flex e-con-boxed e-con e-parent\" data-id=\"2f32208\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-7faaae4 elementor-widget elementor-widget-heading\" data-id=\"7faaae4\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Cracking The Code of the Jeju Landscape<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-37bf20c elementor-widget elementor-widget-text-editor\" data-id=\"37bf20c\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">Once you know this stuff, Jeju&#8217;s landscapes start making sense. That reddish hill? Scoria cone, oxidized by lingering volcanic heat. That dramatic coastal cliff? The exposed interior of a tuff cone, built from wet volcanic ash. Those rope-like rock patterns? Pahoehoe lava, frozen mid-flow.<\/span><\/p><p><span style=\"font-weight: 400;\">The island is still young and still being shaped. Seongsan Ilchulbong is only 5,000 years old. The last eruption was barely a thousand years ago. Jeju isn&#8217;t just showing you its volcanic past. You&#8217;re standing in the middle of its volcanic story.<\/span><\/p><p><span style=\"font-weight: 400;\">Did you find the story of Jeju&#8217;s land, created by wind, water, and fire, interesting? Knowing geology makes your trip so much more special. Next time you visit, I hope you experience the &#8220;time of the land&#8221; that stretches beyond the sea and mountains.<\/span><\/p><p>\u00a0<\/p><p><i><span style=\"font-weight: 400;\">Reference: <\/span><\/i><b><i>Jeju Island Geology Tour<\/i><\/b><i><span style=\"font-weight: 400;\"> (Kim Yong-je, Korea Institute of Geoscience and Mineral Resources, 2020)<\/span><\/i><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>La isla de Jeju es un libro de texto de geolog\u00eda viviente, con su historia grabada en piedra de lava. Una vez que conozcas la geolog\u00eda, \u00a1descubrir\u00e1s por qu\u00e9 las diferentes partes de Jeju tienen el aspecto que tienen! <\/p>","protected":false},"author":3,"featured_media":1898,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"h5ap_radio_sources":[],"footnotes":""},"categories":[15],"tags":[29],"class_list":["post-1874","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blogpost","tag-history"],"_links":{"self":[{"href":"https:\/\/vamosajeju.com\/es\/wp-json\/wp\/v2\/posts\/1874","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vamosajeju.com\/es\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/vamosajeju.com\/es\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/vamosajeju.com\/es\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/vamosajeju.com\/es\/wp-json\/wp\/v2\/comments?post=1874"}],"version-history":[{"count":31,"href":"https:\/\/vamosajeju.com\/es\/wp-json\/wp\/v2\/posts\/1874\/revisions"}],"predecessor-version":[{"id":3554,"href":"https:\/\/vamosajeju.com\/es\/wp-json\/wp\/v2\/posts\/1874\/revisions\/3554"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/vamosajeju.com\/es\/wp-json\/wp\/v2\/media\/1898"}],"wp:attachment":[{"href":"https:\/\/vamosajeju.com\/es\/wp-json\/wp\/v2\/media?parent=1874"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vamosajeju.com\/es\/wp-json\/wp\/v2\/categories?post=1874"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vamosajeju.com\/es\/wp-json\/wp\/v2\/tags?post=1874"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}