Learn about how the Earth-system works, how humans can affect it, and amazing episodes in Earth’s history.

If you’re interested in how the Earth-system changes, you might also like this video:

What Rivers Can Tell Us About Earth’s History Believe it or not, changes in atmospheric CO2 levels can alter the path and shape of rivers. Go!

Feedback Loops: How Nature Gets Its Rhythms

A video by Anje-Margriet Neutel for TED-Ed. The resources accompanying this video were created by Owen Lloyd-Ellis, and are shared with a CC BY-NC-SA license.

Summary

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 “runaway” situation (Neutel, 2014).

Why Watch This Video?

• Would you like to know how using pesticides to kill insects can lead to a larger insect population in that area?
• Have you ever wondered how a change to one species in an ecosystem can affect almost every other species in that ecosystem?
• Did you know that a species’ population numbers tend to go up and down in a sinusoidal fashion and that this is actually how it’s supposed to work?

Key Terms

Equilibrium. 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 “steady-state equilibrium”, 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.

Food web. 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.

Oscillation. 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.

Loose Ends

“Each feedback is the product of the links in the loop.”

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. “One very weak link in a chain of strong links reduces the feedback considerably” (Neutel & 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.

What determines whether a positive feedback loop is good or bad?

Positive feedback loops tend to make “more:” 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.

Feedback loops aren’t just for living organisms.

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 this article are:

• Increased cloudiness reflects more incoming solar radiation.
• Increased rainfall from more moisture in the atmosphere.
• Chemical weathering as a carbon dioxide sink.

These are just some examples, many more exist in Earth science studies and in the world in general.

Self-Test

Try these questions to test your understanding.

References

Neutel, A. (2014, August 25). Feedback loops: How nature gets its rhythms – Anje-Margriet Neutel. Retrieved October 12, 2020.

Neutel, A., & Thorne, M. (2014, March 14). Interaction strengths in balanced carbon cycles and the absence of a relation between ecosystem complexity and stability. Retrieved October 12, 2020.

15 Climate Feedback Loops and Examples. (2020, June 22). Earth How. Retrieved October 13, 2020.

How Long Will Human Impacts Last?

A video by David Biello for TED-Ed. The resources accompanying this video were created by Madeline Muir, and are shared with a CC BY license.

Summary

This educational video outlines the topic of the impact humans have on our geological world. It talks about the timeframe of the Earth’s 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.

Why Watch This Video?

• 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?
• 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?
• 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?

Key Terms

A stratum (plural form “strata” 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.

The rock record tells us what happened during certain timeframes throughout Earth’s 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’s history from a life viewpoint.

Flora/Fauna. A different name for plants and animals. Flora means plant (sounds like flower), and Fauna means animal.

Loose Ends

How do nuclear bombs scatter elements?

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).

We are creating a new homogeneous world with favoured plants and animals such as corn and rats.

Corn is unique because it wouldn’t exist without humans. It is a genetically modified version of teosinte (a grass) that doesn’t exist naturally and doesn’t disperse seeds (Fedoroff, Langin, Pain, & Gruber, 2017). By continuing to farm this plant we are favouring it and creating something that wasn’t 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).

Smudge (soot) corresponds to a meteoric rise of CO₂ in the air.

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).

Self-Test

Try these questions to test your understanding.

References

Belmain, S. (2015, February 25). Rats may be disgusting, but it’s people who have made the world they thrive in. The Guardian.

Buis, A. (2020, March 3). The Atmosphere: Getting a Handle on Carbon Dioxide – Climate Change: Vital Signs of the Planet. NASA.

Corn is a Human Invention: AgHires: See More Ag Facts. AgHires. (2020, June 10).

The Editors of Encyclopaedia Britannica (Ed.). (2010, February 18). Stratum. Britannica.

MacDonald, F. (2017, January 30). WATCH: How Far Away Would You Need to Be to Survive a Nuclear Blast? Science alert.

Fedoroff, N. (Oct. 1, 2004). Ancestors of Science – Prehistoric GM Corn. Science.

Arvin Ash. (2018). How Does an Atom Bomb Work? And why don’t more countries have it? Youtube.

Is the Mystery of Earth’s 1.2 Billion Missing Years Solved?

A video by SciShow. The resources accompanying this video were created by Lauren Alice, and are shared with a CC BY-NC-SA license.

Summary

Certain places in Earth’s geological record appear to skip large chunks of time—sometimes by over 1 billion years—a 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.

Why Watch This Video?

• Have you ever wondered if environmental change can alter the geological record?
• Would you like to know how scientists are able to date rock layers?
• Have you ever been confused by the way some rock layers appear thicker or thinner than others and what it means?

Key Terms

Unconformity. A place in the geological record where time appears to suddenly skip.

Snowball Earth. A hypothesis which suggests that in the distant past the Earth’s surface was entirely frozen over.

Cambrian explosion. An event approximately 542 million years ago during which most major animal groups began appearing in the fossil record.

Loose Ends

How can zircon crystals “capture environmental conditions when they form?”

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’ structure and chemical composition can provide information about the conditions under which they formed.  Zircon crystals contain uranium, which can be used to date the crystals according to uranium’s 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.¹

How do zircons provide evidence of a global ice age?

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.²

Why would Snowball Earth trigger the sudden appearance of new life?

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 water³, to changing sea chemistry resulting in isotopes favorable to forming life⁴, and even to extreme climatic shifts triggering gene expression in some early organisms⁵. Such theories have been largely founded on data-based speculation but require more significant research to support them.