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class="breadcrumb_last" aria-current="page">Great Oxygenation Event: How Oxygen Filled the Atmosphere</span></span></div><h1 class="entry-title">Great Oxygenation Event: How Oxygen Filled the Atmosphere</h1><div class="entry-meta entry-meta-divider-customicon"> <div class="meta-comments"><span class="kadence-svg-iconset"><svg class="kadence-svg-icon kadence-comments-alt-svg" fill="currentColor" version="1.1" xmlns="http://www.w3.org/2000/svg" width="28" height="28" viewBox="0 0 28 28"><title>Comments</title><path d="M10 14c0 1.109-0.891 2-2 2s-2-0.891-2-2 0.891-2 2-2 2 0.891 2 2zM16 14c0 1.109-0.891 2-2 2s-2-0.891-2-2 0.891-2 2-2 2 0.891 2 2zM22 14c0 1.109-0.891 2-2 2s-2-0.891-2-2 0.891-2 2-2 2 0.891 2 2zM14 6c-6.5 0-12 3.656-12 8 0 2.328 1.563 4.547 4.266 6.078l1.359 0.781-0.422 1.5c-0.297 1.109-0.688 1.969-1.094 2.688 1.578-0.656 3.016-1.547 4.297-2.672l0.672-0.594 0.891 0.094c0.672 0.078 1.359 0.125 2.031 0.125 6.5 0 12-3.656 12-8s-5.5-8-12-8zM28 14c0 5.531-6.266 10-14 10-0.766 0-1.531-0.047-2.266-0.125-2.047 1.813-4.484 3.094-7.187 3.781-0.562 0.156-1.172 0.266-1.781 0.344h-0.078c-0.313 0-0.594-0.25-0.672-0.594v-0.016c-0.078-0.391 0.187-0.625 0.422-0.906 0.984-1.109 2.109-2.047 2.844-4.656-3.219-1.828-5.281-4.656-5.281-7.828 0-5.516 6.266-10 14-10v0c7.734 0 14 4.484 14 10z"></path> </svg></span><a class="meta-comments-link anchor-scroll" href="#comments">5 Comments</a></div></div></header> <div class="entry-content single-content"> <figure class="wp-block-image is-style-default"><img fetchpriority="high" decoding="async" width="678" height="378" src="https://earthhow.com/wp-content/uploads/2018/08/Great-Oxygenation-Event-678x378.png" alt="Great Oxygenation Event" class="wp-image-1143"/></figure> <div class="wp-block-group" style="padding-top:var(--wp--preset--spacing--30);padding-bottom:var(--wp--preset--spacing--30)"><div class="wp-block-group__inner-container is-layout-constrained wp-block-group-is-layout-constrained"> <h3 class="wp-block-heading">The Great Oxygenation Event</h3> <p>Over <a href="https://earthhow.com/earth-timeline-geological-history-events/">Earth’s geologic timeline</a>, our <a href="https://earthhow.com/atmosphere-history/">atmosphere history</a> has seen wild shifts.</p> <p>The early Earth’s atmosphere had no free oxygen in it. But as we know today, we live and breathe free oxygen from the air.</p> <p>The Great Oxygenation Event marks a time when free oxygen filled the atmosphere.</p> <p>What sparked this event?</p> <p>And how did it affect life on our planet?</p></div></div><div class="wp-block-group" style="padding-top:var(--wp--preset--spacing--50);padding-bottom:var(--wp--preset--spacing--50)"><div class="wp-block-group__inner-container is-layout-constrained wp-block-group-is-layout-constrained"> <h3 class="wp-block-heading">Cyanobacteria release oxygen as a waste product</h3> <div class="wp-block-image is-style-default"> <figure class="alignright"><a href="https://earthhow.com/wp-content/uploads/2018/10/Great-Oxygenation-Event-0.png"><img decoding="async" width="290" height="300" src="https://earthhow.com/wp-content/uploads/2018/10/Great-Oxygenation-Event-0-290x300.png" alt="Great Oxygenation Event" class="wp-image-1564" srcset="https://earthhow.com/wp-content/uploads/2018/10/Great-Oxygenation-Event-0-290x300.png 290w, https://earthhow.com/wp-content/uploads/2018/10/Great-Oxygenation-Event-0.png 407w" sizes="(max-width: 290px) 100vw, 290px"/></a></figure></div><p>Long ago, oceanic cyanobacteria evolved to <a href="https://earthhow.com/photosynthesis-process/">carry out photosynthesis</a> to make energy for themselves.</p> <p>The key to their existence at this time was that they didn’t need oxygen. They were completely anaerobic. In fact, oxygen was poison for cyanobacteria.</p> <p>Over time, these cyanobacteria released oxygen as a waste product. So much oxygen, that it kept building up in the oceans.</p> <p>Eventually, oxygen entered the atmosphere. This marked the start of the Great Oxygenation Event.</p> <p>Free oxygen had profound effects on the planet. It triggered an oxygen crisis, it <a href="https://earthhow.com/ice-ages-glaciations-geologic-history/">froze over the whole planet</a> and it rusted iron to form <a href="https://earthhow.com/banded-iron-formation-bif/">banded iron formations</a>.</p></div></div><div class="wp-block-group" style="padding-top:var(--wp--preset--spacing--50);padding-bottom:var(--wp--preset--spacing--50)"><div class="wp-block-group__inner-container is-layout-constrained wp-block-group-is-layout-constrained"> <h3 class="wp-block-heading">Oxygen poisons cyanobacteria almost wiping them away</h3> <p>Without oxygen, anaerobic life flourished. But in an oxygen-rich environment, oxygen was poisonous for cyanobacteria.</p> <p>The irony of cyanobacteria is that the oxygen they released was toxic to them.</p> <p>As a whole, the number of anaerobic organisms dwindled to the brink of extinction. This wiped out over 90% of life on earth.</p> <p>The reason why this event is called an “oxygen crisis” is that they threatened their own existence through their own waste of oxygen.</p> <p>Cyanobacteria didn’t completely vanish. By hiding in low-oxygen environments, cyanobacteria avoided a <a href="https://earthhow.com/mass-extinctions/">mass extinction</a>.</p> <p>Eventually, <a href="https://earthhow.com/theory-of-evolution/">life evolved</a> to use this oxygen and now the ecosystem keeps itself in balance this way.</p> <figure class="wp-block-image is-style-default"><img decoding="async" width="675" height="253" src="https://earthhow.com/wp-content/uploads/2018/07/Archean-Era-Timeline-Light-3-675x253.png" alt="Archean Era Timeline" class="wp-image-2278" srcset="https://earthhow.com/wp-content/uploads/2018/07/Archean-Era-Timeline-Light-3-675x253.png 675w, https://earthhow.com/wp-content/uploads/2018/07/Archean-Era-Timeline-Light-3-300x113.png 300w, https://earthhow.com/wp-content/uploads/2018/07/Archean-Era-Timeline-Light-3-425x159.png 425w, https://earthhow.com/wp-content/uploads/2018/07/Archean-Era-Timeline-Light-3-550x206.png 550w, https://earthhow.com/wp-content/uploads/2018/07/Archean-Era-Timeline-Light-3-678x255.png 678w, https://earthhow.com/wp-content/uploads/2018/07/Archean-Era-Timeline-Light-3.png 680w" sizes="(max-width: 675px) 100vw, 675px"/></figure></div></div><div class="wp-block-group" style="padding-top:var(--wp--preset--spacing--50);padding-bottom:var(--wp--preset--spacing--50)"><div class="wp-block-group__inner-container is-layout-constrained wp-block-group-is-layout-constrained"> <h3 class="wp-block-heading">The oxygen-filled atmosphere creates a “Snowball Earth”</h3> <div class="wp-block-image is-style-default"> <figure class="alignright"><a href="https://earthhow.com/wp-content/uploads/2018/11/Ice-Ages.png"><img loading="lazy" decoding="async" width="290" height="300" src="https://earthhow.com/wp-content/uploads/2018/11/Ice-Ages-290x300.png" alt="Ice Ages" class="wp-image-1739" srcset="https://earthhow.com/wp-content/uploads/2018/11/Ice-Ages-290x300.png 290w, https://earthhow.com/wp-content/uploads/2018/11/Ice-Ages.png 407w" sizes="(max-width: 290px) 100vw, 290px"/></a></figure></div><p>Oxygen played a key role in transforming the planet into a “Snowball Earth” or “Slushball Earth”.</p> <p>Remember that the atmosphere before the great oxygenation event was mostly methane and nitrogen.</p> <p>Methane is one of the most efficient <a href="https://earthhow.com/greenhouse-effect/">greenhouse gases</a> that exist. Long ago, it trapped heat in the atmosphere keeping temperatures warm.</p> <p>So when oxygen combined with methane, it produced carbon dioxide. Because there was less methane in the atmosphere, the greenhouse effect wasn’t as strong.</p> <p>Without heat trapped in the atmosphere, Earth froze over for about 300,000,000 years. This event was the first major ice age that Earth experienced known as the Pongola glaciation.</p></div></div><div class="wp-block-group" style="padding-top:var(--wp--preset--spacing--50);padding-bottom:var(--wp--preset--spacing--50)"><div class="wp-block-group__inner-container is-layout-constrained wp-block-group-is-layout-constrained"> <h3 class="wp-block-heading">Banded iron formations demonstrate a struggle for constant oxygen</h3> <div class="wp-block-image is-style-default"> <figure class="alignright"><img loading="lazy" decoding="async" width="290" height="300" src="https://earthhow.com/wp-content/uploads/2018/09/Banded-Iron-Formations-290x300.png" alt="Banded Iron Formations" class="wp-image-1531" srcset="https://earthhow.com/wp-content/uploads/2018/09/Banded-Iron-Formations-290x300.png 290w, https://earthhow.com/wp-content/uploads/2018/09/Banded-Iron-Formations.png 407w" sizes="(max-width: 290px) 100vw, 290px"/></figure></div><p>Banded iron formations (BIF) consist of alternating layers of red (oxidized) and (unoxidized) black iron. Because iron rusts when it reacts with oxygen, these layers were red.</p> <p>So the red (oxidized) layers mark a time when there was oxygen. The alternating layers give a sneak peek of how oxygenation was just starting to get a foothold.</p> <p>We can find <a href="https://earthhow.com/banded-iron-formation-bif/">banded iron formations</a> all over the world such as in Australia, Canada, and South Africa. Most of the world’s iron ore deposits were produced in the <a href="https://earthhow.com/archean-eon/">Archean Eon</a>.</p></div></div><div class="wp-block-group" style="padding-top:var(--wp--preset--spacing--50);padding-bottom:var(--wp--preset--spacing--50)"><div class="wp-block-group__inner-container is-layout-constrained wp-block-group-is-layout-constrained"> <h3 class="wp-block-heading">How come there wasn’t any free oxygen?</h3> <p>By nature, oxygen is a very volatile substance. This is because it steals electrons from other atoms.</p> <ul class="wp-block-list"> <li>Oxygen atoms existed at this time but were bonded with hydrogen in water molecules.</li> <li>Instead of H<sub>2</sub>S, cyanobacteria used H<sub>2</sub>0 as a source of electrons and hydrogen for fixing CO<sub>2</sub>.</li> <li>The CO<sub>2</sub> fixation was the process that filled free oxygen in the skies.</li> </ul> <p>Over time, life adapted to use oxygen for its own benefit. But that was not always the case for anaerobic organisms.</p></div></div><div class="wp-block-group" style="padding-top:var(--wp--preset--spacing--50);padding-bottom:var(--wp--preset--spacing--50)"><div class="wp-block-group__inner-container is-layout-constrained wp-block-group-is-layout-constrained"> <h3 class="wp-block-heading">The oxygen crisis almost ended cyanobacteria</h3> <div class="wp-block-image is-style-default"> <figure class="alignright"><img decoding="async" width="290" height="300" src="https://earthhow.com/wp-content/uploads/2018/10/Great-Oxygenation-Event-0-290x300.png" alt="Great Oxygenation Event" class="wp-image-1564" srcset="https://earthhow.com/wp-content/uploads/2018/10/Great-Oxygenation-Event-0-290x300.png 290w, https://earthhow.com/wp-content/uploads/2018/10/Great-Oxygenation-Event-0.png 407w" sizes="(max-width: 290px) 100vw, 290px"/></figure></div><p>For millions of years, cyanobacteria used heat from <a href="https://earthhow.com/igneous-rocks/">volcanoes or mid-ocean ridges</a> and then released oxygen into the oceans and air. Eventually, they filled the oceans with oxygen.</p> <p>The irony of cyanobacteria is that the oxygen they released was toxic to them. As a whole, the number of anaerobic organisms dropped in the <a href="https://earthhow.com/proterozoic-eon/">Proterozoic Eon</a>.</p> <p>The reason why this event is called an “oxygen crisis” is that they threatened their own existence through their own waste of oxygen.</p> <p>Cyanobacteria didn’t completely vanish in the Proterozoic Eon. By hiding in low-oxygen environments, cyanobacteria avoided <a href="https://earthhow.com/mass-extinctions/">their own mass extinction</a>.</p></div></div><div class="wp-block-group" style="padding-top:var(--wp--preset--spacing--50);padding-bottom:var(--wp--preset--spacing--50)"><div class="wp-block-group__inner-container is-layout-constrained wp-block-group-is-layout-constrained"> <h3 class="wp-block-heading">The Great Oxygenation Event (GOE)</h3> <p>There wasn’t always a breath of fresh air on Earth. Methane and nitrogen choked any potential life in <a href="https://earthhow.com/atmosphere-history/">Earth’s early atmosphere</a>. But this doesn’t mean that life didn’t exist.</p> <p>Long ago, tiny microscopic cyanobacteria (blue-green algae) flourished in ocean environments. They evolved to carry out photosynthesis anaerobically.</p> <p>Their evidence is from stromatolites which are layered, mound-shaped fossils found in rocks. Stromatolites were made by cyanobacteria, trapping sediment on the sea floor. For example, we can observe stromatolites in <a href="https://www.sharkbay.org" target="_blank" rel="noopener noreferrer">Shark Bay, Australia</a>, which has been <a href="https://whc.unesco.org/en/list/578/" target="_blank" rel="noopener noreferrer">designated a UNESCO World Heritage Site</a>.</p> <p>The key to their existence was that they didn’t need oxygen to survive. As a byproduct, these anaerobic organisms released oxygen which was toxic to them.</p> <p>Eventually, oxygen filled the oceans. Then, it made it all the way to the atmosphere. This event is known as the great oxygenation event. This paved the way for aerobic organisms to carry the torch.</p></div></div><div class="newsletter1"><span style="color:#FFFFFF">Subscribe to our newsletter:</span> <div class="tnp tnp-subscription-minimal"><form action="https://earthhow.com/wp-admin/admin-ajax.php?action=tnp&na=s" method="post" style="text-align: center"><input type="hidden" name="nr" value="minimal"> <input type="hidden" name="nlang" value=""> <input class="tnp-email" type="email" required name="ne" value="" placeholder="Email"><input class="tnp-submit" type="submit" value="Subscribe" style=""> </form></div></div><div class="kb-row-layout-wrap kb-row-layout-id18750_45f50e-c9 alignnone wp-block-kadence-rowlayout"><div class="kt-row-column-wrap kt-has-1-columns kt-row-layout-equal kt-tab-layout-inherit kt-mobile-layout-row kt-row-valign-top"> <div class="wp-block-kadence-column kadence-column18750_dbe7c4-7f kvs-sm-false kb-section-dir-horizontal"><div class="kt-inside-inner-col"><div class="wp-block-kadence-posts kb-posts kb-posts-id-18750_1e09ed-10 content-wrap grid-cols kb-posts-style-unboxed grid-sm-col-2 grid-lg-col-3 item-image-style-above"><article class="entry content-bg loop-entry post-2448 post type-post status-publish format-standard has-post-thumbnail hentry category-geology category-volcanoes mv-content-wrapper"> <a class="post-thumbnail kadence-thumbnail-ratio-2-3" href="https://earthhow.com/igneous-rocks/"> <div class="post-thumbnail-inner"> <img width="425" height="319" src="https://earthhow.com/wp-content/uploads/2018/12/Igneous-Rocks-425x319.png" class="attachment-medium_large size-medium_large wp-post-image" alt="igneous rocks" decoding="async" loading="lazy" srcset="https://earthhow.com/wp-content/uploads/2018/12/Igneous-Rocks-425x319.png 425w, https://earthhow.com/wp-content/uploads/2018/12/Igneous-Rocks-300x225.png 300w, https://earthhow.com/wp-content/uploads/2018/12/Igneous-Rocks-675x507.png 675w, https://earthhow.com/wp-content/uploads/2018/12/Igneous-Rocks-550x413.png 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class="kt-blocks-post-footer-right"></div></footer></div></div></article><article class="kt-blocks-post-grid-item post-940 post type-post status-publish format-standard has-post-thumbnail hentry category-geology category-milestone-events mv-content-wrapper"><div class="kt-blocks-post-grid-item-inner-wrap kt-feat-image-align-left kt-feat-image-mobile-align-side"><div class="kadence-post-image"><div class="kadence-post-image-intrisic kt-image-ratio-66-67" style="padding-bottom:66.67%;"><div class="kadence-post-image-inner-intrisic"><a href="https://earthhow.com/late-heavy-bombardment-stage/" aria-label="Read More Was the Late Heavy Bombardment a Violent Stage in Earth’s History?" class="kadence-post-image-inner-wrap"><img width="300" height="225" src="https://earthhow.com/wp-content/uploads/2018/08/Late-Heavy-Bombardment-Stage-300x225.png" class="attachment-medium size-medium wp-post-image" alt="Late Heavy Bombardment Stage" decoding="async" loading="lazy" 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Piecing Together the Supercontinent Jigsaw Puzzle</a></h6><div class="kt-blocks-post-top-meta"></div></header><div class="entry-content"></div><footer class="kt-blocks-post-footer"><div class="kt-blocks-post-footer-left"></div><div class="kt-blocks-post-footer-right"></div></footer></div></div></article><article class="kt-blocks-post-grid-item post-2450 post type-post status-publish format-standard has-post-thumbnail hentry category-geology category-rock-and-minerals mv-content-wrapper"><div class="kt-blocks-post-grid-item-inner-wrap kt-feat-image-align-left kt-feat-image-mobile-align-side"><div class="kadence-post-image"><div class="kadence-post-image-intrisic kt-image-ratio-66-67" style="padding-bottom:66.67%;"><div class="kadence-post-image-inner-intrisic"><a href="https://earthhow.com/metamorphic-rocks/" aria-label="Read More Metamorphic Rocks: Heat, Pressure and Metamorphism" class="kadence-post-image-inner-wrap"><img width="300" height="225" src="https://earthhow.com/wp-content/uploads/2018/12/Metamorphic-Rocks-300x225.png" class="attachment-medium size-medium wp-post-image" alt="Metamorphic Rocks" decoding="async" loading="lazy" srcset="https://earthhow.com/wp-content/uploads/2018/12/Metamorphic-Rocks-300x225.png 300w, https://earthhow.com/wp-content/uploads/2018/12/Metamorphic-Rocks-675x507.png 675w, https://earthhow.com/wp-content/uploads/2018/12/Metamorphic-Rocks-425x319.png 425w, https://earthhow.com/wp-content/uploads/2018/12/Metamorphic-Rocks-550x413.png 550w, https://earthhow.com/wp-content/uploads/2018/12/Metamorphic-Rocks.png 678w, https://earthhow.com/wp-content/uploads/2018/12/Metamorphic-Rocks-326x245.png 326w, https://earthhow.com/wp-content/uploads/2018/12/Metamorphic-Rocks-80x60.png 80w, https://earthhow.com/wp-content/uploads/2018/12/Metamorphic-Rocks-267x200.png 267w" sizes="(max-width: 300px) 100vw, 300px"/></a></div></div></div><div class="kt-blocks-post-grid-item-inner"><header><h6 class="entry-title"><a href="https://earthhow.com/metamorphic-rocks/">Metamorphic Rocks: Heat, Pressure and Metamorphism</a></h6><div class="kt-blocks-post-top-meta"></div></header><div class="entry-content"></div><footer class="kt-blocks-post-footer"><div class="kt-blocks-post-footer-left"></div><div class="kt-blocks-post-footer-right"></div></footer></div></div></article></div></div></div></div></div></div></div></div></article> <div id="comments" class="comments-area"> <h2 class="comments-title">5 Comments</h2> <ol class="comment-list"> <li id="comment-28325" class="comment even thread-even depth-1"> <article id="div-comment-28325" class="comment-body"> <footer class="comment-meta"> <div class="comment-author vcard"> <b class="fn">Grace</b> <span class="says">says:</span></div><div class="comment-metadata"> <a href="https://earthhow.com/great-oxygenation-event/#comment-28325"><time datetime="2024-02-05T09:03:34-06:00">February 5, 2024 at 9:03 am</time></a></div></footer> <div class="comment-content"> <p>I love this story</p></div></article> </li> <li id="comment-27744" class="comment byuser comment-author-earthhow bypostauthor odd alt thread-odd thread-alt depth-1"> <article id="div-comment-27744" class="comment-body"> <footer class="comment-meta"> <div class="comment-author vcard"> <b class="fn">earthhow</b> <span class="says">says:</span></div><div class="comment-metadata"> <a href="https://earthhow.com/great-oxygenation-event/#comment-27744"><time datetime="2024-01-22T19:32:24-06:00">January 22, 2024 at 7:32 pm</time></a></div></footer> <div class="comment-content"> <p>Metaphorically, of course.</p></div></article> </li> <li id="comment-27736" class="comment even thread-even depth-1"> <article id="div-comment-27736" class="comment-body"> <footer class="comment-meta"> <div class="comment-author vcard"> <b class="fn">Hank Schrader</b> <span class="says">says:</span></div><div class="comment-metadata"> <a href="https://earthhow.com/great-oxygenation-event/#comment-27736"><time datetime="2024-01-22T10:10:48-06:00">January 22, 2024 at 10:10 am</time></a></div></footer> <div class="comment-content"> <p>It’s crazy what you can learn from many years ago. Earth was a snowball?</p></div></article> </li> <li id="comment-27735" class="comment odd alt thread-odd thread-alt depth-1"> <article id="div-comment-27735" class="comment-body"> <footer class="comment-meta"> <div class="comment-author vcard"> <b class="fn">Hank</b> <span class="says">says:</span></div><div class="comment-metadata"> <a href="https://earthhow.com/great-oxygenation-event/#comment-27735"><time datetime="2024-01-22T10:08:15-06:00">January 22, 2024 at 10:08 am</time></a></div></footer> <div class="comment-content"> <p>I really liked this</p></div></article> </li> <li id="comment-18057" class="comment even thread-even depth-1"> <article id="div-comment-18057" class="comment-body"> <footer class="comment-meta"> <div class="comment-author vcard"> <b class="fn">Dennis Kennedy</b> <span class="says">says:</span></div><div class="comment-metadata"> <a href="https://earthhow.com/great-oxygenation-event/#comment-18057"><time datetime="2022-11-08T16:51:47-06:00">November 8, 2022 at 4:51 pm</time></a></div></footer> <div class="comment-content"> <p>I watched a documentary that told of a time on our planet when the oxygen concentration was much higher than the 21% figure that is generally accepted today. I seem to recall that it was said to be either 26% or 28% but I can no longer remember. It was also said to likely be responsible for the gigantic growth of 4-foot-long millipedes and also a time when the largest dinosaurs known roamed the planet. Can you possibly verify for me what the oxygen percentage was during these times? Thank you in advance for your time and consideration!</p></div></article> </li> </ol> <div id="respond" class="comment-respond"> <h3 id="reply-title" class="comment-reply-title">Leave a Reply</h3><form action="https://earthhow.com/wp-comments-post.php" method="post" id="commentform" class="comment-form" novalidate><p class="comment-notes"><span id="email-notes">Your email address will not be published.</span> <span class="required-field-message">Required fields are marked <span class="required">*</span></span></p><p class="comment-form-comment comment-form-float-label"><textarea autocomplete="new-password" id="i477054932" name="i477054932" placeholder="Leave a comment..." cols="45" rows="8" maxlength="65525" aria-required="true" required="required"></textarea><textarea id="comment" aria-label="hp-comment" aria-hidden="true" name="comment" autocomplete="new-password" style="padding:0 !important;clip:rect(1px, 1px, 1px, 1px) !important;position:absolute !important;white-space:nowrap 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