{"id":235,"date":"2020-12-22T14:36:14","date_gmt":"2020-12-22T19:36:14","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/?post_type=chapter&#038;p=235"},"modified":"2020-12-22T16:41:10","modified_gmt":"2020-12-22T21:41:10","slug":"earth-system-change","status":"web-only","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/chapter\/earth-system-change\/","title":{"raw":"Earth-System Change","rendered":"Earth-System Change"},"content":{"raw":"<h5>Learn about how the Earth-system works, how humans can affect it, and amazing episodes in Earth's history.<\/h5>\r\n&nbsp;\r\n\r\n<em>If you're interested in how the Earth-system changes, you might also like this video:\r\n<\/em>\r\n<table class=\"lines landscape\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td><img class=\"wp-image-162 alignleft\" src=\"https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/valley-river2-publicdomain-300x274.jpg\" alt=\"\" width=\"90\" height=\"82\" \/><\/td>\r\n<td><strong>What Rivers Can Tell Us About Earth's History<\/strong> Believe it or not, changes in atmospheric CO<sub>2<\/sub> levels can alter the path and shape of rivers. <a href=\"https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/chapter\/landslides\/#TED-rivers\" target=\"_blank\" rel=\"noopener noreferrer\">Go!<\/a><\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n&nbsp;\r\n\r\n&nbsp;\r\n\r\n<img class=\"wp-image-237 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-300x300.png\" alt=\"\" width=\"165\" height=\"165\" \/>\r\n<h1><span style=\"color: #008000\">Feedback Loops: How Nature Gets Its Rhythms<\/span><\/h1>\r\nA video by Anje-Margriet Neutel for <a href=\"https:\/\/www.youtube.com\/channel\/UCsooa4yRKGN_zEE8iknghZA\" target=\"_blank\" rel=\"noopener noreferrer\">TED-Ed<\/a>. The resources accompanying this video were created by <strong>Owen Lloyd-Ellis<\/strong>, and are shared with a CC BY-NC-SA license.\r\n\r\n&nbsp;\r\n\r\nhttps:\/\/youtu.be\/inVZoI1AkC8\r\n<h2>Summary<\/h2>\r\nThrough the use of many analogies involving different animals playing music (wow fun!), this video explains how feedback loops are very important to nature and how a positive feedback in an environment increases or amplifies a certain effect whereas a negative feedback decreases or diminishes a certain effect in that environment. Positive feedback loops can be bad because they can lead to runaway situations that have a negative impact on the environment and the species that live in it. Different ecosystems have different complex systems of feedback loops between live and dead matter, often with wide-ranging negative feedback loops keeping the positive feedback loops in check and avoiding this \u201crunaway\u201d situation (Neutel, 2014).\r\n<h2>Why Watch This Video?<\/h2>\r\n<ul>\r\n \t<li>Would you like to know how using pesticides to kill insects can lead to a larger insect population in that area?<\/li>\r\n \t<li>Have you ever wondered how a change to one species in an ecosystem can affect almost every other species in that ecosystem?<\/li>\r\n \t<li>Did you know that a species\u2019 population numbers tend to go up and down in a sinusoidal fashion and that this is actually how it\u2019s supposed to work?<\/li>\r\n<\/ul>\r\n<h2>Key Terms<\/h2>\r\n<strong>Equilibrium<\/strong>. A steady state where the value in question stays in a constant range and has a constant overall average even if it waivers back and forth as time goes on. In this video the type of equilibrium we are talking about is more specifically \u201csteady-state equilibrium\u201d, meaning the population is always changing yet it keeps a constant unchanging overall trend or average. In this video, they talk about equilibrium in the sense that the population of an animal species goes up and down in a sinusoidal fashion, but still has a constant average the whole time. Although the populations are changing due to a negative feedback loop, they still waiver back and forth around a constant value.\r\n\r\n<strong>Food web<\/strong>. A system of multiple food chains that all depend on each other and can be affected by each other. A food chain is a system of predator and prey interactions that involves different species eating each other. An animal higher up in the food chain would kill and eat an individual of a species lower on that food chain. One of the most common types of feedback loops in nature greatly affects the food web and are very helpful at keeping various animal populations in check. These feedback loops are those between predator and prey.\r\n\r\n<strong>Oscillation<\/strong>. Movement back and forth at a constant rate. This has a lot to with equilibrium in the terms of this video. In the example talked about above in the definition of equilibrium, the population levels of the animals oscillate around a constant level, which stays relatively the same.\r\n<h2>Loose Ends<\/h2>\r\n<h3>\u201cEach feedback is the product of the links in the loop.\"<\/h3>\r\nThe effects of a feedback loop are multiplicative and so the number of negative links in the loop will determine whether a feedback loop is negative or positive. The other big thing to remember is how the strength of each loop affects the strength of the entire loop. \u201cOne very weak link in a chain of strong links reduces the feedback considerably\u201d (Neutel &amp; Thorne, 2014). This also means that one very strong link in the loop can cause a huge increase in the strength of that loop, whether that be a positive or negative feedback loop.\r\n<h3>What determines whether a positive feedback loop is good or bad?<\/h3>\r\nPositive feedback loops tend to make \u201cmore:\u201d more biomass, more carbon in the air, more individuals in a population. So what makes these good or bad? It all depends on who is deciding. A biologist with a keen drive for improving the planet might refer to a positive feedback loop kills more coyotes in an area as a bad thing, but a local farmer might see this as a good thing. Although positive feedback loops always amplify an effect and negative feedback loops always diminish an effect, the words good and bad are not a descriptor of how that loop works, but more reflect how a person feels about the changes that the feedback loop causes.\r\n<h3>Feedback loops aren't just for living organisms.<\/h3>\r\nThe video only talks about feedback loops between living organisms in a biology sense. Feedback loops exist in so many other aspects. Some examples of some of the most prominent climate feedback loops, as shown in <a href=\"https:\/\/earthhow.com\/climate-feedback-loops\/\" target=\"_blank\" rel=\"noopener noreferrer\">this article<\/a> are:\r\n<ul>\r\n \t<li>Increased cloudiness reflects more incoming solar radiation.<\/li>\r\n \t<li>Increased rainfall from more moisture in the atmosphere.<\/li>\r\n \t<li>Chemical weathering as a carbon dioxide sink.<\/li>\r\n<\/ul>\r\nThese are just some examples, many more exist in Earth science studies and in the world in general.\r\n<h2>Self-Test<\/h2>\r\nTry these questions to test your understanding.\r\n\r\n&nbsp;\r\n\r\n[h5p id=\"125\"]\r\n<h2>References<\/h2>\r\nNeutel, A. (2014, August 25). <a class=\"\" href=\"https:\/\/www.youtube.com\/watch?v=inVZoI1AkC8\" data-preview-alt=\"Feedback loops: How nature gets its rhythms - Anje-Margriet Neutel\">Feedback loops: How nature gets its rhythms - Anje-Margriet Neutel<\/a>. Retrieved October 12, 2020.\r\n\r\nNeutel, A., &amp; Thorne, M. (2014, March 14). <a href=\"https:\/\/www.ncbi.nlm.nih.gov\/pmc\/articles\/PMC4285907\/\" target=\"_blank\" rel=\"noopener noreferrer\">Interaction strengths in balanced carbon cycles and the absence of a relation between ecosystem complexity and stability<\/a>. Retrieved October 12, 2020.\r\n\r\n<a href=\"https:\/\/earthhow.com\/climate-feedback-loops\/\" target=\"_blank\" rel=\"noopener noreferrer\">15 Climate Feedback Loops and Examples<\/a>. (2020, June 22). Earth How. Retrieved October 13, 2020.\r\n\r\n&nbsp;\r\n\r\n<img class=\"wp-image-237 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-300x300.png\" alt=\"\" width=\"154\" height=\"154\" \/>\r\n\r\n&nbsp;\r\n<h1><span style=\"color: #125d96\"><a id=\"TEDEd-Biello\"><\/a>How Long Will Human Impacts Last?<\/span><\/h1>\r\nA video by David Biello for <a href=\"https:\/\/www.youtube.com\/channel\/UCsooa4yRKGN_zEE8iknghZA\" target=\"_blank\" rel=\"noopener noreferrer\">TED-Ed<\/a>. The resources accompanying this video were created by <strong>Madeline Muir<\/strong>, and are shared with a CC BY license.\r\n\r\n&nbsp;\r\n\r\nhttps:\/\/youtu.be\/Zsc8G0NnMTs\r\n<h2>Summary<\/h2>\r\nThis educational video outlines the topic of the impact humans have on our geological world. It talks about the timeframe of the Earth\u2019s history from a geological point of view and discusses some ways in which humans have changed this record and how it will continue to change. The influences we have on plants and animals and how this will form a new type of world is also explained.\r\n<h2>Why Watch This Video?<\/h2>\r\n<ul>\r\n \t<li>Have you ever wondered how human impacts on the world will extend past our lifetime and be clear to someone looking back on our current geological period?<\/li>\r\n \t<li>Would you like to know how the creation of new substances on Earth such as plastic will help geologists determine a timeframe for our impacts?<\/li>\r\n \t<li>Have you ever been confused why the plant and animal life we choose to favour is not sustainable and how it is less able to flourish after disasters?<\/li>\r\n<\/ul>\r\n<h2>Key Terms<\/h2>\r\nA <strong>stratum<\/strong> (plural form \u201cstrata\u201d used in video) is a layer of small rock particles that exists between other layers of rock particles that differ in grain size and texture.\r\n\r\nThe <strong>rock record<\/strong> tells us what happened during certain timeframes throughout Earth\u2019s history from a geological viewpoint, using the different types of rocks and the layers they occur in. This differs from the fossil record which also exists in layers of rocks but tells us what happened throughout Earth\u2019s history from a life viewpoint.\r\n\r\n<strong>Flora\/Fauna<\/strong>. A different name for plants and animals. Flora means plant (sounds like flower), and Fauna means animal.\r\n<h2>Loose Ends<\/h2>\r\n<h3>How do nuclear bombs scatter elements?<\/h3>\r\nNuclear bombs split the nucleus of an atom and by doing so, release a large amount of energy. Uranium-238 has the largest nucleus of any naturally occurring element, which causes it to have the largest release of energy when the nucleus is split during a nuclear fission reaction. Uranium-235 is a very small portion of U-238 which is highly unstable, and when it collides with a neutron it becomes U-236 a super unstable element that immediately splits into Krypton and Barium (Ash, 2018). A one-megaton nuclear explosion can cause winds up to 255 km\/hour, which is how these novel elements disperse and exist in our rock record (Macdonald, 2017).\r\n<h3>We are creating a new homogeneous world with favoured plants and animals such as corn and rats.<\/h3>\r\nCorn is unique because it wouldn\u2019t exist without humans. It is a genetically modified version of teosinte (a grass) that doesn\u2019t exist naturally and doesn\u2019t disperse seeds (Fedoroff, Langin, Pain, &amp; Gruber, 2017). By continuing to farm this plant we are favouring it and creating something that wasn\u2019t on Earth before. Rats exist because of a similar idea. We all know that we are dependent on them for things such as research and medical advancements, but we also continue to allow for their existence to thrive due to the lack of knowledge about rat borne diseases and which environments causes an increase in rats (Belmain, 2015).\r\n<h3>Smudge (soot) corresponds to a meteoric rise of CO<sub>2<\/sub> in the air.<\/h3>\r\nThe burning of natural gas, oil, and coal creates CO2 as a result of the combustion reaction which produces H2O and CO2. We burn so many fossil fuels there is now roughly 412 parts per million of CO2 in our atmosphere (Buis, 2020).\r\n<h2>Self-Test<\/h2>\r\nTry these questions to test your understanding.\r\n\r\n&nbsp;\r\n\r\n[h5p id=\"124\"]\r\n<h2>References<\/h2>\r\nBelmain, S. (2015, February 25).\u00a0<em><a href=\"https:\/\/www.theguardian.com\/commentisfree\/2015\/feb\/25\/rats-disgusting-people-world-thrive-mutually-dependent\" target=\"_blank\" rel=\"noopener noreferrer\">Rats may be disgusting, but it's people who have made the world they thrive in<\/a><\/em>. The Guardian.\r\n\r\nBuis, A. (2020, March 3).\u00a0<a href=\"https:\/\/climate.nasa.gov\/news\/2915\/the-atmosphere-getting-a-handle-on-carbon-dioxide\/\" target=\"_blank\" rel=\"noopener noreferrer\"><em>The Atmosphere: Getting a Handle on Carbon Dioxide \u2013 Climate Change: Vital Signs of the Planet<\/em>.<\/a> NASA.\r\n\r\n<em><a href=\"https:\/\/aghires.com\/corn-history-human-invention\/\" target=\"_blank\" rel=\"noopener noreferrer\">Corn is a Human Invention<\/a>: AgHires: See More Ag Facts<\/em>. AgHires. (2020, June 10).\r\n\r\nThe Editors of Encyclopaedia Britannica (Ed.). (2010, February 18).\u00a0<a href=\"https:\/\/www.britannica.com\/science\/stratum-geology\" target=\"_blank\" rel=\"noopener noreferrer\"><em>Stratum<\/em><\/a>. Britannica.\r\n\r\nMacDonald, F. (2017, January 30).\u00a0<em>WATCH: <a href=\"https:\/\/www.sciencealert.com\/watch-how-far-away-would-you-need-to-be-to-survive-a-nuclear-blast\" target=\"_blank\" rel=\"noopener noreferrer\">How Far Away Would You Need to Be to Survive a Nuclear Blast?<\/a><\/em> Science alert.\r\n\r\nFedoroff, N. (Oct. 1, 2004). <a href=\"https:\/\/www-sciencemag-org.ezproxy.library.ubc.ca\/careers\/2004\/10\/ancestors-science-prehistoric-gm-corn\" target=\"_blank\" rel=\"noopener noreferrer\"><em>Ancestors of Science - Prehistoric GM Corn<\/em>.<\/a> Science.\r\n\r\nArvin Ash. (2018). <a href=\"https:\/\/www.youtube.com\/watch?v=NrjW-11Y9sY\" target=\"_blank\" rel=\"noopener noreferrer\"><em>How Does an Atom Bomb Work? And why don't more countries have it?<\/em><\/a>\u00a0Youtube.\r\n\r\n&nbsp;\r\n\r\n<img class=\"wp-image-237 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-300x300.png\" alt=\"\" width=\"154\" height=\"154\" \/>\r\n\r\n&nbsp;\r\n<h1><span style=\"color: #5c2306\"><a id=\"SciShow-Snowball\"><\/a>Is the Mystery of Earth's 1.2 Billion Missing Years Solved?<\/span><\/h1>\r\nA video by <a href=\"https:\/\/www.youtube.com\/channel\/UCZYTClx2T1of7BRZ86-8fow\" target=\"_blank\" rel=\"noopener noreferrer\">SciShow<\/a>. The resources accompanying this video were created by <strong>Lauren Alice<\/strong>, and are shared with a CC BY-NC-SA license.\r\n\r\n&nbsp;\r\n\r\nhttps:\/\/youtu.be\/xeWAkvZoN1k\r\n<h2>Summary<\/h2>\r\nCertain places in Earth\u2019s geological record appear to skip large chunks of time\u2014sometimes by over 1 billion years\u2014a phenomenon which has mystified scientists for centuries. But in 2019, a paper was published in the National Academy of Sciences which suggested that a period of global glaciation might be responsible for the gaps. This video dives into the findings of the 2019 paper and explains how, if true, this glaciation event could not only help explain a great geological mystery; it might also help us understand how life developed on the planet.\r\n<h2>Why Watch This Video?<\/h2>\r\n<ul>\r\n \t<li>Have you ever wondered if environmental change can alter the geological record?<\/li>\r\n \t<li>Would you like to know how scientists are able to date rock layers?<\/li>\r\n \t<li>Have you ever been confused by the way some rock layers appear thicker or thinner than others and what it means?<\/li>\r\n<\/ul>\r\n<h2>Key Terms<\/h2>\r\n<strong>Unconformity.<\/strong> A place in the geological record where time appears to suddenly skip.\r\n\r\n<strong>Snowball Earth<\/strong>. A hypothesis which suggests that in the distant past the Earth\u2019s surface was entirely frozen over.\r\n\r\n<strong>Cambrian explosion<\/strong>. An event approximately 542 million years ago during which most major animal groups began appearing in the fossil record.\r\n<h2>Loose Ends<\/h2>\r\n<h3>How can zircon crystals \u201ccapture environmental conditions when they form?\u201d<\/h3>\r\nZircon crystals form early in the cooling of magma, and layers of the crystal grow in rings around the initial fragment, like tree rings. Both the layers\u2019 structure and chemical composition can provide information about the conditions under which they formed. \u00a0Zircon crystals contain uranium, which can be used to date the crystals according to uranium\u2019s half-life; with a half-life of about 4.5 billion years (the time it takes to radioactively decay into lead), the ratio of uranium to lead isotopes present in samples can be used to identify very old zircon crystals and provide a window into distant history of the geological record.<a href=\"#RLM1\"><sup>1<\/sup><\/a>\r\n<h3>How do zircons provide evidence of a global ice age?<\/h3>\r\nAnalysis of the isotopes contained in the zircon crystals showed that the crystals dated to the approximate period of the Snowball Earth event were formed largely from continental crust-derived magma. This implies that an abnormally large amount of continental crust was melted and recycled through subduction around the time of the hypothesized Snowball Earth period, which would support the idea of global glaciation causing erosion and runoff of large amounts of land towards subduction zones.<a href=\"#RLM2\"><sup>2<\/sup><\/a>\r\n<h3>Why would Snowball Earth trigger the sudden appearance of new life?<\/h3>\r\nMulticellular animals began appearing suddenly and en masse in the fossil record during a period called the Cambrian explosion, from 542 to 530 Ma. Some scientists have proposed that Snowball Earth could have resulted in this explosion of biodiversity due to factors ranging from elevated levels of oxygenation and the addition of minerals to water<a href=\"#RLM3\"><sup>3<\/sup><\/a>, to changing sea chemistry resulting in isotopes favorable to forming life<a href=\"#RLM4\"><sup>4<\/sup><\/a>, and even to extreme climatic shifts triggering gene expression in some early organisms<a href=\"#RLM5\"><sup>5<\/sup><\/a>. Such theories have been largely founded on data-based speculation but require more significant research to support them.\r\n<div class=\"page\" title=\"Page 2\">\r\n<div class=\"section\">\r\n<div class=\"layoutArea\">\r\n<h2>Self-Test<\/h2>\r\nTry these questions to test your understanding.\r\n\r\n&nbsp;\r\n\r\n[h5p id=\"123\"]\r\n<h2>References<\/h2>\r\n<a id=\"RLM1\"><\/a>1. <a href=\"https:\/\/www.amnh.org\/learn-teach\/curriculum-collections\/earth-inside-and-out\/zircon-chronology-dating-the-oldest-material-on-earth\" target=\"_blank\" rel=\"noopener noreferrer\">Zircon Chronology: Dating the Oldest Material on Earth<\/a>: AMNH. (n.d.). Retrieved October 14, 2020.\r\n\r\n<a id=\"RLM2\"><\/a>2. Keller, C., Husson, J., Mitchell, R., Bottke, W., Gernon, T., Boehnke, P., . . . Peters, S. (2019, January 22). <a href=\"https:\/\/www.pnas.org\/content\/116\/4\/1136\" target=\"_blank\" rel=\"noopener noreferrer\">Neoproterozoic glacial origin of the Great Unconformity<\/a>. Retrieved October 14, 2020.\r\n\r\n<a id=\"RLM3\"><\/a>3. Maruyama, S., &amp; Santosh, M. (2008, February 08). <a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S1342937X0800004X\" target=\"_blank\" rel=\"noopener noreferrer\">Models on Snowball Earth and Cambrian explosion: A synopsis.<\/a> Retrieved October 14, 2020.\r\n\r\n<a id=\"RLM4\"><\/a>4. Shields, G. (2003, April 11). <a href=\"https:\/\/ui.adsabs.harvard.edu\/abs\/2003EAEJA....10859S\/abstract\" target=\"_blank\" rel=\"noopener noreferrer\">From Snowball Earth to the Cambrian explosion: The interpretative potential of the isotope record<\/a>. Retrieved October 14, 2020.\r\n\r\n<a id=\"RLM5\"><\/a>5. Baker, M. (2006, March 30). <a href=\"https:\/\/onlinelibrary.wiley.com\/doi\/abs\/10.1111\/j.1472-4669.2006.00067.x\" target=\"_blank\" rel=\"noopener noreferrer\">The genetic response to Snowball Earth: Role of HSP90 in the Cambrian explosion<\/a>. Retrieved October 14, 2020.\r\n\r\n&nbsp;\r\n\r\n<img class=\"wp-image-237 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-300x300.png\" alt=\"\" width=\"154\" height=\"154\" \/>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n&nbsp;","rendered":"<h5>Learn about how the Earth-system works, how humans can affect it, and amazing episodes in Earth&#8217;s history.<\/h5>\n<p>&nbsp;<\/p>\n<p><em>If you&#8217;re interested in how the Earth-system changes, you might also like this video:<br \/>\n<\/em><\/p>\n<table class=\"lines landscape\">\n<tbody>\n<tr>\n<td><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-162 alignleft\" src=\"https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/valley-river2-publicdomain-300x274.jpg\" alt=\"\" width=\"90\" height=\"82\" srcset=\"https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/valley-river2-publicdomain-300x274.jpg 300w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/valley-river2-publicdomain-65x59.jpg 65w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/valley-river2-publicdomain-225x205.jpg 225w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/valley-river2-publicdomain-350x319.jpg 350w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/valley-river2-publicdomain.jpg 500w\" sizes=\"auto, (max-width: 90px) 100vw, 90px\" \/><\/td>\n<td><strong>What Rivers Can Tell Us About Earth&#8217;s History<\/strong> Believe it or not, changes in atmospheric CO<sub>2<\/sub> levels can alter the path and shape of rivers. <a href=\"https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/chapter\/landslides\/#TED-rivers\" target=\"_blank\" rel=\"noopener noreferrer\">Go!<\/a><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-237 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-300x300.png\" alt=\"\" width=\"165\" height=\"165\" srcset=\"https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-300x300.png 300w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-1024x1024.png 1024w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-150x150.png 150w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-768x768.png 768w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-1536x1536.png 1536w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-65x65.png 65w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-225x225.png 225w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-350x350.png 350w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_.png 1833w\" sizes=\"auto, (max-width: 165px) 100vw, 165px\" \/><\/p>\n<h1><span style=\"color: #008000\">Feedback Loops: How Nature Gets Its Rhythms<\/span><\/h1>\n<p>A video by Anje-Margriet Neutel for <a href=\"https:\/\/www.youtube.com\/channel\/UCsooa4yRKGN_zEE8iknghZA\" target=\"_blank\" rel=\"noopener noreferrer\">TED-Ed<\/a>. The resources accompanying this video were created by <strong>Owen Lloyd-Ellis<\/strong>, and are shared with a CC BY-NC-SA license.<\/p>\n<p>&nbsp;<\/p>\n<p><iframe loading=\"lazy\" id=\"oembed-1\" title=\"Feedback loops: How nature gets its rhythms - Anje-Margriet Neutel\" width=\"500\" height=\"281\" src=\"https:\/\/www.youtube.com\/embed\/inVZoI1AkC8?feature=oembed&#38;rel=0\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<h2>Summary<\/h2>\n<p>Through the use of many analogies involving different animals playing music (wow fun!), this video explains how feedback loops are very important to nature and how a positive feedback in an environment increases or amplifies a certain effect whereas a negative feedback decreases or diminishes a certain effect in that environment. Positive feedback loops can be bad because they can lead to runaway situations that have a negative impact on the environment and the species that live in it. Different ecosystems have different complex systems of feedback loops between live and dead matter, often with wide-ranging negative feedback loops keeping the positive feedback loops in check and avoiding this \u201crunaway\u201d situation (Neutel, 2014).<\/p>\n<h2>Why Watch This Video?<\/h2>\n<ul>\n<li>Would you like to know how using pesticides to kill insects can lead to a larger insect population in that area?<\/li>\n<li>Have you ever wondered how a change to one species in an ecosystem can affect almost every other species in that ecosystem?<\/li>\n<li>Did you know that a species\u2019 population numbers tend to go up and down in a sinusoidal fashion and that this is actually how it\u2019s supposed to work?<\/li>\n<\/ul>\n<h2>Key Terms<\/h2>\n<p><strong>Equilibrium<\/strong>. A steady state where the value in question stays in a constant range and has a constant overall average even if it waivers back and forth as time goes on. In this video the type of equilibrium we are talking about is more specifically \u201csteady-state equilibrium\u201d, meaning the population is always changing yet it keeps a constant unchanging overall trend or average. In this video, they talk about equilibrium in the sense that the population of an animal species goes up and down in a sinusoidal fashion, but still has a constant average the whole time. Although the populations are changing due to a negative feedback loop, they still waiver back and forth around a constant value.<\/p>\n<p><strong>Food web<\/strong>. A system of multiple food chains that all depend on each other and can be affected by each other. A food chain is a system of predator and prey interactions that involves different species eating each other. An animal higher up in the food chain would kill and eat an individual of a species lower on that food chain. One of the most common types of feedback loops in nature greatly affects the food web and are very helpful at keeping various animal populations in check. These feedback loops are those between predator and prey.<\/p>\n<p><strong>Oscillation<\/strong>. Movement back and forth at a constant rate. This has a lot to with equilibrium in the terms of this video. In the example talked about above in the definition of equilibrium, the population levels of the animals oscillate around a constant level, which stays relatively the same.<\/p>\n<h2>Loose Ends<\/h2>\n<h3>\u201cEach feedback is the product of the links in the loop.&#8221;<\/h3>\n<p>The effects of a feedback loop are multiplicative and so the number of negative links in the loop will determine whether a feedback loop is negative or positive. The other big thing to remember is how the strength of each loop affects the strength of the entire loop. \u201cOne very weak link in a chain of strong links reduces the feedback considerably\u201d (Neutel &amp; Thorne, 2014). This also means that one very strong link in the loop can cause a huge increase in the strength of that loop, whether that be a positive or negative feedback loop.<\/p>\n<h3>What determines whether a positive feedback loop is good or bad?<\/h3>\n<p>Positive feedback loops tend to make \u201cmore:\u201d more biomass, more carbon in the air, more individuals in a population. So what makes these good or bad? It all depends on who is deciding. A biologist with a keen drive for improving the planet might refer to a positive feedback loop kills more coyotes in an area as a bad thing, but a local farmer might see this as a good thing. Although positive feedback loops always amplify an effect and negative feedback loops always diminish an effect, the words good and bad are not a descriptor of how that loop works, but more reflect how a person feels about the changes that the feedback loop causes.<\/p>\n<h3>Feedback loops aren&#8217;t just for living organisms.<\/h3>\n<p>The video only talks about feedback loops between living organisms in a biology sense. Feedback loops exist in so many other aspects. Some examples of some of the most prominent climate feedback loops, as shown in <a href=\"https:\/\/earthhow.com\/climate-feedback-loops\/\" target=\"_blank\" rel=\"noopener noreferrer\">this article<\/a> are:<\/p>\n<ul>\n<li>Increased cloudiness reflects more incoming solar radiation.<\/li>\n<li>Increased rainfall from more moisture in the atmosphere.<\/li>\n<li>Chemical weathering as a carbon dioxide sink.<\/li>\n<\/ul>\n<p>These are just some examples, many more exist in Earth science studies and in the world in general.<\/p>\n<h2>Self-Test<\/h2>\n<p>Try these questions to test your understanding.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"h5p-125\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-125\" class=\"h5p-iframe\" data-content-id=\"125\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"2020T1-OLE\"><\/iframe><\/div>\n<\/div>\n<h2>References<\/h2>\n<p>Neutel, A. (2014, August 25). <a class=\"\" href=\"https:\/\/www.youtube.com\/watch?v=inVZoI1AkC8\" data-preview-alt=\"Feedback loops: How nature gets its rhythms - Anje-Margriet Neutel\">Feedback loops: How nature gets its rhythms &#8211; Anje-Margriet Neutel<\/a>. Retrieved October 12, 2020.<\/p>\n<p>Neutel, A., &amp; Thorne, M. (2014, March 14). <a href=\"https:\/\/www.ncbi.nlm.nih.gov\/pmc\/articles\/PMC4285907\/\" target=\"_blank\" rel=\"noopener noreferrer\">Interaction strengths in balanced carbon cycles and the absence of a relation between ecosystem complexity and stability<\/a>. Retrieved October 12, 2020.<\/p>\n<p><a href=\"https:\/\/earthhow.com\/climate-feedback-loops\/\" target=\"_blank\" rel=\"noopener noreferrer\">15 Climate Feedback Loops and Examples<\/a>. (2020, June 22). Earth How. Retrieved October 13, 2020.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-237 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-300x300.png\" alt=\"\" width=\"154\" height=\"154\" srcset=\"https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-300x300.png 300w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-1024x1024.png 1024w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-150x150.png 150w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-768x768.png 768w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-1536x1536.png 1536w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-65x65.png 65w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-225x225.png 225w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-350x350.png 350w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_.png 1833w\" sizes=\"auto, (max-width: 154px) 100vw, 154px\" \/><\/p>\n<p>&nbsp;<\/p>\n<h1><span style=\"color: #125d96\"><a id=\"TEDEd-Biello\"><\/a>How Long Will Human Impacts Last?<\/span><\/h1>\n<p>A video by David Biello for <a href=\"https:\/\/www.youtube.com\/channel\/UCsooa4yRKGN_zEE8iknghZA\" target=\"_blank\" rel=\"noopener noreferrer\">TED-Ed<\/a>. The resources accompanying this video were created by <strong>Madeline Muir<\/strong>, and are shared with a CC BY license.<\/p>\n<p>&nbsp;<\/p>\n<p><iframe loading=\"lazy\" id=\"oembed-2\" title=\"How long will human impacts last? - David Biello\" width=\"500\" height=\"281\" src=\"https:\/\/www.youtube.com\/embed\/Zsc8G0NnMTs?feature=oembed&#38;rel=0\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<h2>Summary<\/h2>\n<p>This educational video outlines the topic of the impact humans have on our geological world. It talks about the timeframe of the Earth\u2019s history from a geological point of view and discusses some ways in which humans have changed this record and how it will continue to change. The influences we have on plants and animals and how this will form a new type of world is also explained.<\/p>\n<h2>Why Watch This Video?<\/h2>\n<ul>\n<li>Have you ever wondered how human impacts on the world will extend past our lifetime and be clear to someone looking back on our current geological period?<\/li>\n<li>Would you like to know how the creation of new substances on Earth such as plastic will help geologists determine a timeframe for our impacts?<\/li>\n<li>Have you ever been confused why the plant and animal life we choose to favour is not sustainable and how it is less able to flourish after disasters?<\/li>\n<\/ul>\n<h2>Key Terms<\/h2>\n<p>A <strong>stratum<\/strong> (plural form \u201cstrata\u201d used in video) is a layer of small rock particles that exists between other layers of rock particles that differ in grain size and texture.<\/p>\n<p>The <strong>rock record<\/strong> tells us what happened during certain timeframes throughout Earth\u2019s history from a geological viewpoint, using the different types of rocks and the layers they occur in. This differs from the fossil record which also exists in layers of rocks but tells us what happened throughout Earth\u2019s history from a life viewpoint.<\/p>\n<p><strong>Flora\/Fauna<\/strong>. A different name for plants and animals. Flora means plant (sounds like flower), and Fauna means animal.<\/p>\n<h2>Loose Ends<\/h2>\n<h3>How do nuclear bombs scatter elements?<\/h3>\n<p>Nuclear bombs split the nucleus of an atom and by doing so, release a large amount of energy. Uranium-238 has the largest nucleus of any naturally occurring element, which causes it to have the largest release of energy when the nucleus is split during a nuclear fission reaction. Uranium-235 is a very small portion of U-238 which is highly unstable, and when it collides with a neutron it becomes U-236 a super unstable element that immediately splits into Krypton and Barium (Ash, 2018). A one-megaton nuclear explosion can cause winds up to 255 km\/hour, which is how these novel elements disperse and exist in our rock record (Macdonald, 2017).<\/p>\n<h3>We are creating a new homogeneous world with favoured plants and animals such as corn and rats.<\/h3>\n<p>Corn is unique because it wouldn\u2019t exist without humans. It is a genetically modified version of teosinte (a grass) that doesn\u2019t exist naturally and doesn\u2019t disperse seeds (Fedoroff, Langin, Pain, &amp; Gruber, 2017). By continuing to farm this plant we are favouring it and creating something that wasn\u2019t on Earth before. Rats exist because of a similar idea. We all know that we are dependent on them for things such as research and medical advancements, but we also continue to allow for their existence to thrive due to the lack of knowledge about rat borne diseases and which environments causes an increase in rats (Belmain, 2015).<\/p>\n<h3>Smudge (soot) corresponds to a meteoric rise of CO<sub>2<\/sub> in the air.<\/h3>\n<p>The burning of natural gas, oil, and coal creates CO2 as a result of the combustion reaction which produces H2O and CO2. We burn so many fossil fuels there is now roughly 412 parts per million of CO2 in our atmosphere (Buis, 2020).<\/p>\n<h2>Self-Test<\/h2>\n<p>Try these questions to test your understanding.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"h5p-124\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-124\" class=\"h5p-iframe\" data-content-id=\"124\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"2020T1-MM\"><\/iframe><\/div>\n<\/div>\n<h2>References<\/h2>\n<p>Belmain, S. (2015, February 25).\u00a0<em><a href=\"https:\/\/www.theguardian.com\/commentisfree\/2015\/feb\/25\/rats-disgusting-people-world-thrive-mutually-dependent\" target=\"_blank\" rel=\"noopener noreferrer\">Rats may be disgusting, but it&#8217;s people who have made the world they thrive in<\/a><\/em>. The Guardian.<\/p>\n<p>Buis, A. (2020, March 3).\u00a0<a href=\"https:\/\/climate.nasa.gov\/news\/2915\/the-atmosphere-getting-a-handle-on-carbon-dioxide\/\" target=\"_blank\" rel=\"noopener noreferrer\"><em>The Atmosphere: Getting a Handle on Carbon Dioxide \u2013 Climate Change: Vital Signs of the Planet<\/em>.<\/a> NASA.<\/p>\n<p><em><a href=\"https:\/\/aghires.com\/corn-history-human-invention\/\" target=\"_blank\" rel=\"noopener noreferrer\">Corn is a Human Invention<\/a>: AgHires: See More Ag Facts<\/em>. AgHires. (2020, June 10).<\/p>\n<p>The Editors of Encyclopaedia Britannica (Ed.). (2010, February 18).\u00a0<a href=\"https:\/\/www.britannica.com\/science\/stratum-geology\" target=\"_blank\" rel=\"noopener noreferrer\"><em>Stratum<\/em><\/a>. Britannica.<\/p>\n<p>MacDonald, F. (2017, January 30).\u00a0<em>WATCH: <a href=\"https:\/\/www.sciencealert.com\/watch-how-far-away-would-you-need-to-be-to-survive-a-nuclear-blast\" target=\"_blank\" rel=\"noopener noreferrer\">How Far Away Would You Need to Be to Survive a Nuclear Blast?<\/a><\/em> Science alert.<\/p>\n<p>Fedoroff, N. (Oct. 1, 2004). <a href=\"https:\/\/www-sciencemag-org.ezproxy.library.ubc.ca\/careers\/2004\/10\/ancestors-science-prehistoric-gm-corn\" target=\"_blank\" rel=\"noopener noreferrer\"><em>Ancestors of Science &#8211; Prehistoric GM Corn<\/em>.<\/a> Science.<\/p>\n<p>Arvin Ash. (2018). <a href=\"https:\/\/www.youtube.com\/watch?v=NrjW-11Y9sY\" target=\"_blank\" rel=\"noopener noreferrer\"><em>How Does an Atom Bomb Work? And why don&#8217;t more countries have it?<\/em><\/a>\u00a0Youtube.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-237 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-300x300.png\" alt=\"\" width=\"154\" height=\"154\" srcset=\"https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-300x300.png 300w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-1024x1024.png 1024w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-150x150.png 150w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-768x768.png 768w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-1536x1536.png 1536w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-65x65.png 65w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-225x225.png 225w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_-350x350.png 350w, https:\/\/pressbooks.bccampus.ca\/showmeearthscience\/wp-content\/uploads\/sites\/1111\/2020\/12\/river-water-publicdomainvectors.org_.png 1833w\" sizes=\"auto, (max-width: 154px) 100vw, 154px\" \/><\/p>\n<p>&nbsp;<\/p>\n<h1><span style=\"color: #5c2306\"><a id=\"SciShow-Snowball\"><\/a>Is the Mystery of Earth&#8217;s 1.2 Billion Missing Years Solved?<\/span><\/h1>\n<p>A video by <a href=\"https:\/\/www.youtube.com\/channel\/UCZYTClx2T1of7BRZ86-8fow\" target=\"_blank\" rel=\"noopener noreferrer\">SciShow<\/a>. The resources accompanying this video were created by <strong>Lauren Alice<\/strong>, and are shared with a CC BY-NC-SA license.<\/p>\n<p>&nbsp;<\/p>\n<p><iframe loading=\"lazy\" id=\"oembed-3\" title=\"Is the Mystery of Earth&#39;s 1.2 Billion Missing Years Solved? | SciShow News\" width=\"500\" height=\"281\" src=\"https:\/\/www.youtube.com\/embed\/xeWAkvZoN1k?feature=oembed&#38;rel=0\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<h2>Summary<\/h2>\n<p>Certain places in Earth\u2019s geological record appear to skip large chunks of time\u2014sometimes by over 1 billion years\u2014a phenomenon which has mystified scientists for centuries. But in 2019, a paper was published in the National Academy of Sciences which suggested that a period of global glaciation might be responsible for the gaps. This video dives into the findings of the 2019 paper and explains how, if true, this glaciation event could not only help explain a great geological mystery; it might also help us understand how life developed on the planet.<\/p>\n<h2>Why Watch This Video?<\/h2>\n<ul>\n<li>Have you ever wondered if environmental change can alter the geological record?<\/li>\n<li>Would you like to know how scientists are able to date rock layers?<\/li>\n<li>Have you ever been confused by the way some rock layers appear thicker or thinner than others and what it means?<\/li>\n<\/ul>\n<h2>Key Terms<\/h2>\n<p><strong>Unconformity.<\/strong> A place in the geological record where time appears to suddenly skip.<\/p>\n<p><strong>Snowball Earth<\/strong>. A hypothesis which suggests that in the distant past the Earth\u2019s surface was entirely frozen over.<\/p>\n<p><strong>Cambrian explosion<\/strong>. An event approximately 542 million years ago during which most major animal groups began appearing in the fossil record.<\/p>\n<h2>Loose Ends<\/h2>\n<h3>How can zircon crystals \u201ccapture environmental conditions when they form?\u201d<\/h3>\n<p>Zircon crystals form early in the cooling of magma, and layers of the crystal grow in rings around the initial fragment, like tree rings. Both the layers\u2019 structure and chemical composition can provide information about the conditions under which they formed. \u00a0Zircon crystals contain uranium, which can be used to date the crystals according to uranium\u2019s half-life; with a half-life of about 4.5 billion years (the time it takes to radioactively decay into lead), the ratio of uranium to lead isotopes present in samples can be used to identify very old zircon crystals and provide a window into distant history of the geological record.<a href=\"#RLM1\"><sup>1<\/sup><\/a><\/p>\n<h3>How do zircons provide evidence of a global ice age?<\/h3>\n<p>Analysis of the isotopes contained in the zircon crystals showed that the crystals dated to the approximate period of the Snowball Earth event were formed largely from continental crust-derived magma. This implies that an abnormally large amount of continental crust was melted and recycled through subduction around the time of the hypothesized Snowball Earth period, which would support the idea of global glaciation causing erosion and runoff of large amounts of land towards subduction zones.<a href=\"#RLM2\"><sup>2<\/sup><\/a><\/p>\n<h3>Why would Snowball Earth trigger the sudden appearance of new life?<\/h3>\n<p>Multicellular animals began appearing suddenly and en masse in the fossil record during a period called the Cambrian explosion, from 542 to 530 Ma. Some scientists have proposed that Snowball Earth could have resulted in this explosion of biodiversity due to factors ranging from elevated levels of oxygenation and the addition of minerals to water<a href=\"#RLM3\"><sup>3<\/sup><\/a>, to changing sea chemistry resulting in isotopes favorable to forming life<a href=\"#RLM4\"><sup>4<\/sup><\/a>, and even to extreme climatic shifts triggering gene expression in some early organisms<a href=\"#RLM5\"><sup>5<\/sup><\/a>. Such theories have been largely founded on data-based speculation but require more significant research to support them.<\/p>\n<div class=\"page\" title=\"Page 2\">\n<div class=\"section\">\n<div class=\"layoutArea\">\n<h2>Self-Test<\/h2>\n<p>Try these questions to test your understanding.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"h5p-123\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-123\" class=\"h5p-iframe\" data-content-id=\"123\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"2020T1-LM\"><\/iframe><\/div>\n<\/div>\n<h2>References<\/h2>\n<p><a id=\"RLM1\"><\/a>1. <a href=\"https:\/\/www.amnh.org\/learn-teach\/curriculum-collections\/earth-inside-and-out\/zircon-chronology-dating-the-oldest-material-on-earth\" target=\"_blank\" rel=\"noopener noreferrer\">Zircon Chronology: Dating the Oldest Material on Earth<\/a>: AMNH. (n.d.). Retrieved October 14, 2020.<\/p>\n<p><a id=\"RLM2\"><\/a>2. Keller, C., Husson, J., Mitchell, R., Bottke, W., Gernon, T., Boehnke, P., . . . Peters, S. (2019, January 22). <a href=\"https:\/\/www.pnas.org\/content\/116\/4\/1136\" target=\"_blank\" rel=\"noopener noreferrer\">Neoproterozoic glacial origin of the Great Unconformity<\/a>. Retrieved October 14, 2020.<\/p>\n<p><a id=\"RLM3\"><\/a>3. Maruyama, S., &amp; Santosh, M. (2008, February 08). <a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S1342937X0800004X\" target=\"_blank\" rel=\"noopener noreferrer\">Models on Snowball Earth and Cambrian explosion: A synopsis.<\/a> Retrieved October 14, 2020.<\/p>\n<p><a id=\"RLM4\"><\/a>4. Shields, G. (2003, April 11). <a href=\"https:\/\/ui.adsabs.harvard.edu\/abs\/2003EAEJA....10859S\/abstract\" target=\"_blank\" rel=\"noopener noreferrer\">From Snowball Earth to the Cambrian explosion: The interpretative potential of the isotope record<\/a>. Retrieved October 14, 2020.<\/p>\n<p><a id=\"RLM5\"><\/a>5. Baker, M. (2006, March 30). <a href=\"https:\/\/onlinelibrary.wiley.com\/doi\/abs\/10.1111\/j.1472-4669.2006.00067.x\" target=\"_blank\" rel=\"noopener noreferrer\">The genetic response to Snowball Earth: Role of HSP90 in the Cambrian explosion<\/a>. 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