Reflections From Students
The following reflections were written by students on a reading assignment. Students read a Scientific American article on the evidence for Snowball Earth written by Harvard scientists Paul Hoffman and Dan Schrag. They had studied and investigated plate tectonics, geological time, rocks, the carbon cycle,and the concept of albedo. Short, relevant video clips of Schrag, Hoffman, and other scientists connecting classroom learning to what scientists are doing in the real world were integrated into the lessons and lab activities.
Student Reflections
CR (F): I thought it was cool that this article was written by both Dr. Schrag and Dr. Hoffman because, even though I don’t know them, I feel like I do because of the DVDs we watched in class. I also thought that it (the idea of an extreme Snowball Earth) was put in simpler terms so it was easier for me to understand. It’s also different from the other articles we’ve read because instead of talking about how bad global warming is, it explained the causes and effects of it in greater depth. It also explained the concept of Snowball Earth, which I didn’t quite understand until now.
DM (M): I think its interesting, the idea of a Snowball Earth. I remember we talked about albedo in class and what Dr. Hoffman and Schrag explained made sense. They talked about the albedo of ice and snow on Earth, and how ice would continue to cause more ice because it has a high albedo. So we had brainstormed ideas about how this Snowball Earth could have come out of it and CR and I thought that volcanoes would be the only way out. I was encouraged to realize I understand and could comprehend the ideas of this article despite vocabulary that is extremely scientific.
McN (F): The thing I found most interesting was how the Cambrian explosion happened after it (Snowball Earth), and how, after so many years of nothing (animals) living, there is all of a sudden a burst of life. I don’t really get why this would only happen if all the continents were around the equator and not in any other configuration. What would happen if all the continents were clustered around one pole? It’s cool how scientists can discover all these things about climate so long ago in only rocks.
SB (M): I found this article riveting, in that it answered countless questions. This article describes exactly how carbonate rocks and the water cycle play a role and are affected within the theory of Snowball Earth. This article was extremely revealing and taught me a great deal about this fascinating topic, it was at times quite difficult to understand in that the vocabulary was very advanced. I expect this is customary of an article in Scientific American, yet despite this fact, I still managed to extract the main ideas. The point that I found most interesting was toward the end, under the section titled “Survival and Redemption of Life.” I thought the idea that extreme climate events might have played a direct and active role in “spawning multicellular life” was
the climax of this article.
PS (M): How are isotopes formed? It is interesting looking at the graph of showing the mergence of bacteria eukaryotes, and animals form over time. Bacteria and eukaryotes emerge around the same time as oxygen and iron do on the x-axis of the graph. It is also interesting about how old bacteria is forming 3.5 billion years ago, about 1.5 billion years older than eukaryotes.
S: I was curious if life had to restart itself four times since four snowball earths have occurred. I was also wondering if there is a main difference between the causes of snowball earth as opposed to a partial ice age.
Frankie: I found this article absolutely mind blowing. I am amazed with the kinds of evidence researchers manage to find. I mean, finding carbon isotopic variations and cap carbonates are rather “random” places to find information, yet scientists are still able to prove their points.
C (F): The fact that the earth can so easily go from extreme cold to extreme heat amazes me. I still have a few questions. What is the important difference between carbon 12 and carbon 13? What will the next extreme heat period be? What has been the highest level of carbon dioxide ever?
K (F): Could a snowball earth every happen again? What would carbon dioxide levels have to be in order to have a snowball earth? Could humans (or any living organism) survive during a snowball earth? If all the life were to die during a snowball earth, would the evolution of life occur all over again?
LS (F): This article shows how unpredictable our planet is and how global warming is bringing us to an unknown zone. It’s unbelievable that it was as cold as it was warm in the past. This article shows how extreme our climate could become.
AH (F): I found out how scientists make interesting observations and with their observation, they make hypothesis. The most interesting thing about the hypothesis is the evidence. The evidence supports so greatly the hypothesis. They get tons of evidence and I like reading about it.
CL (F): I think it’s cool how scientists can look at rocks and know where they come from and when by looking at their magnetism. The arguments for why there hasn’t been any runaway ice ages are very convincing and I’m surprised at how much evidence there is defending the theory.
MD (F): It’s amazing how one element, carbon, and carbon dioxide, can have such a big impact on earth sending it from an ice age or “snowball earth” to a hothouse. It’s also interesting how many connections there are between the different things we have been studying this year, such as plate tectonics, the greenhouse effect, carbon dioxide, life, and ice ages. The points made that plate tectonics causes volcanoes to form, which release carbon into the atmosphere, and the amount of carbon dioxide in the atmosphere effects the climate, which then effects the kind of life which is able to survive… helped me illustrate the connections in my mind. What would happen if something other than the co2 in the atmosphere were changing? Would this lead to different results in the
earth’s climate because they are all so closely related?
HY (F): Overall, reading this, I found myself surprisingly interested.
J (M): I hadn’t thought it (Snowball Earth) was such a complex issue. I was intrigued to learn about the different carbon isotopes. These isotopes play a large role in determining if the entire snowball earth theory is correct. It was interesting to find out the areas where many scientists were skeptical.
JM (F): This article provided a lot of information, data, and evidence to back up the snowball earth theory, which cemented my undertanding, and helped me to gain more knowledge.
MB (F): The fact that our earth has been to both ends of the climate spectrum is overwhelming. The Hadean brought it to one end, but to go back and forth numerous times on such a short amount of geological time is hard to reason with. I don’t know if I could truly trust the fact that in only a few hundred years our earth went from freezing to a hot house. The article stated how it went from cold to hot (volcanoes accumulating co2) but it never explained how it got from being so hot, to getting so cold again.
SB (F): I lilked how this article summed up everything we’ve learned in this unit, and adds some details about HOW the scientists know certain things. I find it fascinating that a tiny change of ratio in the carbon isotopes in the tiny shell of a creature dead for millions of years can mean so much about earth’s climate history, and how that has affected life.
MM (M): I think they put a lot of thought into this article and a lot of research must have been done to find all the information about past scientists. Why has it stopped occuring. Has the snowball earth hypothesis become a theory?
EN (F): This article explained the idea of “snowball earth’ very clearly and used specific details. For example, the carbon isotopes found in the rock mean a long decline in biological productivity. I also liked how each step in the freezing and melting of earth was explained and connected to each other. This made the concept much easier to understand. I think if I did not understand one step, then everything that followed would be unclear because everything that makes “snowball earth” possible is tightly connected. I find it interesting how all the different sciences and natural cycles connect. For example, the volcanoes leading to the greenhouse effect and the albedo slowing the warming. Also, I find how scientists can find out about the past by connecting evidience
that may seem to be unrelated interesting. Some of the evidence found seems, at first, to be unrelated but everything is. For instance, the fact that the magnetic orientation of the grains in glacial debris means the contents were gathered around the equator during the Neoproterozic. This means THAT THE TROPICS WOULD FREEZE EASIER BECAUSE LAND CHANGES TEMPERATURE FASTER THAN WATER (which I learned in class). From this article is seems that “snowball earth” is very possible and it happened in earth’s past.
TS (M): It seems like Earth is capable of far more violent and swift changes than I had expected. However, I found it interesting that this extreme change (may have) caused massive evolution very quickly (and) that no matter how much a climate change seems to get out of hand and become unstoppable, Earth always has built in brakes that eventually stop the climate change.
LD (F): It funny to think about how we evolved from eukaryotes that survived because other life forms were wiped out had been evolving steadily for ages. I wonder what Earth would have been like had they survived? Also, even the ones that did survive needed to mutate to make it, and I wonder what life would be like today if they had continued to evolve steadily instead of mutating. This article is very pertinent to climate science because it illustrates how quickly our climate can shift gears.
KJ (F): I thought this article really brought together what we’ve been learning about carbon. I liked the stuff about the carbon isotopes. I now see that it is another really solid data set that I can potentially use for the upcoming project.
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