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Oxygen: A Four Billion Year History
The air we breathe is twenty-one percent oxygen, an amount higher than on any other known world. While we may take our air for granted, Earth was not always an oxygenated planet. How did it become this way? Oxygen is the most current account of the history of atmospheric oxygen on Earth. Donald Canfield--one of the world's leading authorities on geochemistry, earth history, and the early oceans--covers this vast history, emphasizing its relationship to the evolution of life and the evolving chemistry of the Earth. With an accessible and colorful first-person narrative, he draws from a variety of fields, including geology, paleontology, geochemistry, biochemistry, animal physiology, and microbiology, to explain why our oxygenated Earth became the ideal place for life.
Describing which processes, both biological and geological, act to control oxygen levels in the atmosphere, Canfield traces the records of oxygen concentrations through time. Readers learn about the great oxidation event, the tipping point 2.3 billion years ago when the oxygen content of the Earth increased dramatically, and Canfield examines how oxygenation created a favorable environment for the evolution of large animals. He guides readers through the various lines of scientific evidence, considers some of the wrong turns and dead ends along the way, and highlights the scientists and researchers who have made key discoveries in the field.
Showing how Earth's atmosphere developed over time, "Oxygen" takes readers on a remarkable journey through the history of the oxygenation of our planet.
Describing which processes, both biological and geological, act to control oxygen levels in the atmosphere, Canfield traces the records of oxygen concentrations through time. Readers learn about the great oxidation event, the tipping point 2.3 billion years ago when the oxygen content of the Earth increased dramatically, and Canfield examines how oxygenation created a favorable environment for the evolution of large animals. He guides readers through the various lines of scientific evidence, considers some of the wrong turns and dead ends along the way, and highlights the scientists and researchers who have made key discoveries in the field.
Showing how Earth's atmosphere developed over time, "Oxygen" takes readers on a remarkable journey through the history of the oxygenation of our planet.
216 pages, Hardcover
First published November 21, 2013
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April 16, 2016
An excellent example of what a popular science book should be. Some criticised it for being too technical. I disagree. With so much material on Internet, one can easily clarify some of the more difficult parts, even when admittedly some of the passages could be explained a bit better. The author is a prominent expert in his field and that's perhaps why. I prefer this to an approach, often used by journalists or the science popularisers, to ensure maximal understanding whilst oversimplifying the issue. The author very skilfully links the facts with references to his own scientific career, personal views on yet unresolved topics and his interaction with the other luminaries in the field.
My notes for future references follow.
Photosynthesis is a process used by plants and other organisms to convert light energy, normally from the Sun, into chemical energy that can be later released to fuel the organisms' activities. This chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. In most cases, oxygen is also released as a waste product. Photosynthesis maintains atmospheric oxygen levels.
The process always begins when energy from light is absorbed by proteins that contain green chlorophyll pigments. In these light-dependent reactions, some energy is used to strip electrons from suitable substances, such as water, producing oxygen gas. The hydrogen freed by water splitting is used in the creation of two further compounds: reduced nicotinamide adenine dinucleotide phosphate (NADPH) and adenosine triphosphate (ATP), the "energy currency" of cells.
The overall equation for the type of photosynthesis that occurs in plants is as follows:
6 CO2 + 6 H2O - > C6H12O6 + 6 O2
Carbon dioxide + Water plus light photons Sugar + Oxygen
Cyanobacteria is bacteria that obtain their energy through photosynthesis. By producing gaseous oxygen as a by-product of photosynthesis, cyanobacteria are thought to have converted the early reducing atmosphere into an oxidizing one, causing the Great Oxygenation Event, dramatically changing the composition of life forms on Earth by stimulating biodiversity and leading to the near-extinction of anaerobic organisms (that is, oxygen-intolerant). There is an evidence that cyanobacteria were producing oxygen as far back as 2.67 billion years ago.
Synechococcus is a unicellular cyanobacterium that is very widespread in the marine environment. Its size varies from 0.8 µm to 1.5 µm. The photosynthetic coccoid cells are preferentially found in well–lit surface waters where it can be very abundant (generally 1,000 to 200,000 cells per millilitre). Many freshwater species of Synechococcus have also been described.
Prochlorococcus is a genus of very small (0.6 µm) marine cyanobacteria with an unusual pigmentation (chlorophyll b). These bacteria belong to the photosynthetic picoplankton and are probably the most abundant photosynthetic organism on Earth and responsible for a large percentage of the photosynthetic production of oxygen.
The amount of oxygen in the air is 21%, regardless of the altitude. However, at higher elevation there is a less of air and therefore we pull less of oxygen. At an elevation of 2100 m the atmospheric pressure is about 77% of the sea level and therefore for the same breath we pull only 77% of oxygen. On the peak of Mount Everest, the pressure is only 33% of the sea level.
In South Africa goldmines at depth of over 3.9 km an ancient river deposits are dated to some 2.8 to 3.1 billion years. They contain uranium oxide (UO2), which indicates that at that time there were only “trace” amount of oxygen. The UO2 reacts easily with oxygen, and that’s why we don’t find it rivers today.
Based on analysis of rocks for the contents of uranite it has been noted that concentration of atmospheric oxygen increased substantially around 2.3 to 2.35 billion years ago. It is referred to as the “great oxidation event” (GOE). The exact reason behind it is still being argued about. One theory refers to the evolution of cyano-bacteria. A more convincing theory, and supported by the author relies on combination of Oxygen released from the organic carbon and the reducing flux of gases from the mantle (through volcanos). Once the flax started slowing down an excess oxygen was left in the atmosphere.
Following GOE, with more oxygen, the oxidation of rocks has increased. This in turn liberated enormous quantities of Phosphorus to the oceans, and consequently vast amount of organic matter, and its burial in the rocks.
The high amounts of buried organic carbon represented in turn a huge oxygen sink, drawing down levels of atmospheric oxygen. It’s expected they were less than 10% of the present levels.
Around 580 million years ago the oldest fauna can be found on sea floor, where they operated without light. At that time oxygen rose to at least 15% of present levels.
Around 300 million years ago the land plants become so diversified and developed a series of tough organic molecules like cellulose to grow tall and resist microbial decay. The vast expanses of low-laying swampland collected and buried massive amounts of organic plant debris, and this is why so much coal was formed during that time. During that time the gigantic insects developed.
The drop in oxygen concentration that followed was probably due to changes in paleogeography. A supercontinent called Pangea became fully assembled and as result, far fewer low-laying swampy areas were available. These sandy continental sediments are virtually free of organic matter and thus provides no input of oxygen to the atmosphere. This reduced the supply of oxygen to the atmosphere and drop in oxygen concentration.
Over the last 350 million years, a continuous record of charcoal in continental sedimentary rocks suggests that O2 has always comprised at least ~15% of the atmosphere, because wood cannot burn below this threshold.
In broad outline, oxygen is regulated because an increase in oxygen increases the consumption of oxygen and/or decreases the rate of oxygen production. A decrease in oxygen has opposite effects.
Oxygen and the Rise of Vascular Land Plants. The data of Fig. 2 show a pronounced and extended rise in atmospheric O2 over the period 375–275 mega-annum (Ma) spanning the Carboniferous and Permian periods. What could have brought this rise about? The modelling shows that increased oxygen production caused by increased burial of organic carbon was the chief suspect. This increased burial is attributed to the rise and spread of large woody vascular plants on the continents beginning at about 375 Ma. The plants supplied a new source of organic matter to be buried on land and carried to the oceans via rivers. This ‘‘new’’ carbon was added to that already being buried in the oceans, thus increasing the total global burial flux. This is especially true of lignin, a substance that is decomposed only with difficulty by micro- organisms. The rise of ligniferous plants and an initial level of microbial lignin breakdown lower that that at present may have contributed to increased organic matter burial and better preservation. This high burial rate is reflected by the abundance of coals during this period, which is the greatest abundance in all of earth history.
Another factor favouring extensive Permo-Carboniferous organic matter burial was the presence of vast swamps on the continents, brought about by the presence of extensive poorly drained flatlands, and large areas of coastal plains, brought about by glacially induced fluctuations of sea level. This situation enabled the preservation of organic debris, leading ultimately to coal formation, because of the relative lack of organic decay in stagnant anoxic waters. Why coal formation, organic burial, and oxygen production dropped toward the end of the Permian period (Fig. 2) is not clear, but it may be tied up with sea level drop and a general drying of the continents.
The level of atmospheric oxygen cannot rise indefinitely unless the frequency of forest fires becomes so excessive that plant life cannot persist. Fossil charcoal, as evidence of paleo fires, has been found for all times that trees have populated the land, and the lower limit for the production of charcoal has been estimated to be at about 13% O2.
My notes for future references follow.
Photosynthesis is a process used by plants and other organisms to convert light energy, normally from the Sun, into chemical energy that can be later released to fuel the organisms' activities. This chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. In most cases, oxygen is also released as a waste product. Photosynthesis maintains atmospheric oxygen levels.
The process always begins when energy from light is absorbed by proteins that contain green chlorophyll pigments. In these light-dependent reactions, some energy is used to strip electrons from suitable substances, such as water, producing oxygen gas. The hydrogen freed by water splitting is used in the creation of two further compounds: reduced nicotinamide adenine dinucleotide phosphate (NADPH) and adenosine triphosphate (ATP), the "energy currency" of cells.
The overall equation for the type of photosynthesis that occurs in plants is as follows:
6 CO2 + 6 H2O - > C6H12O6 + 6 O2
Carbon dioxide + Water plus light photons Sugar + Oxygen
Cyanobacteria is bacteria that obtain their energy through photosynthesis. By producing gaseous oxygen as a by-product of photosynthesis, cyanobacteria are thought to have converted the early reducing atmosphere into an oxidizing one, causing the Great Oxygenation Event, dramatically changing the composition of life forms on Earth by stimulating biodiversity and leading to the near-extinction of anaerobic organisms (that is, oxygen-intolerant). There is an evidence that cyanobacteria were producing oxygen as far back as 2.67 billion years ago.
Synechococcus is a unicellular cyanobacterium that is very widespread in the marine environment. Its size varies from 0.8 µm to 1.5 µm. The photosynthetic coccoid cells are preferentially found in well–lit surface waters where it can be very abundant (generally 1,000 to 200,000 cells per millilitre). Many freshwater species of Synechococcus have also been described.
Prochlorococcus is a genus of very small (0.6 µm) marine cyanobacteria with an unusual pigmentation (chlorophyll b). These bacteria belong to the photosynthetic picoplankton and are probably the most abundant photosynthetic organism on Earth and responsible for a large percentage of the photosynthetic production of oxygen.
The amount of oxygen in the air is 21%, regardless of the altitude. However, at higher elevation there is a less of air and therefore we pull less of oxygen. At an elevation of 2100 m the atmospheric pressure is about 77% of the sea level and therefore for the same breath we pull only 77% of oxygen. On the peak of Mount Everest, the pressure is only 33% of the sea level.
In South Africa goldmines at depth of over 3.9 km an ancient river deposits are dated to some 2.8 to 3.1 billion years. They contain uranium oxide (UO2), which indicates that at that time there were only “trace” amount of oxygen. The UO2 reacts easily with oxygen, and that’s why we don’t find it rivers today.
Based on analysis of rocks for the contents of uranite it has been noted that concentration of atmospheric oxygen increased substantially around 2.3 to 2.35 billion years ago. It is referred to as the “great oxidation event” (GOE). The exact reason behind it is still being argued about. One theory refers to the evolution of cyano-bacteria. A more convincing theory, and supported by the author relies on combination of Oxygen released from the organic carbon and the reducing flux of gases from the mantle (through volcanos). Once the flax started slowing down an excess oxygen was left in the atmosphere.
Following GOE, with more oxygen, the oxidation of rocks has increased. This in turn liberated enormous quantities of Phosphorus to the oceans, and consequently vast amount of organic matter, and its burial in the rocks.
The high amounts of buried organic carbon represented in turn a huge oxygen sink, drawing down levels of atmospheric oxygen. It’s expected they were less than 10% of the present levels.
Around 580 million years ago the oldest fauna can be found on sea floor, where they operated without light. At that time oxygen rose to at least 15% of present levels.
Around 300 million years ago the land plants become so diversified and developed a series of tough organic molecules like cellulose to grow tall and resist microbial decay. The vast expanses of low-laying swampland collected and buried massive amounts of organic plant debris, and this is why so much coal was formed during that time. During that time the gigantic insects developed.
The drop in oxygen concentration that followed was probably due to changes in paleogeography. A supercontinent called Pangea became fully assembled and as result, far fewer low-laying swampy areas were available. These sandy continental sediments are virtually free of organic matter and thus provides no input of oxygen to the atmosphere. This reduced the supply of oxygen to the atmosphere and drop in oxygen concentration.
Over the last 350 million years, a continuous record of charcoal in continental sedimentary rocks suggests that O2 has always comprised at least ~15% of the atmosphere, because wood cannot burn below this threshold.
In broad outline, oxygen is regulated because an increase in oxygen increases the consumption of oxygen and/or decreases the rate of oxygen production. A decrease in oxygen has opposite effects.
Oxygen and the Rise of Vascular Land Plants. The data of Fig. 2 show a pronounced and extended rise in atmospheric O2 over the period 375–275 mega-annum (Ma) spanning the Carboniferous and Permian periods. What could have brought this rise about? The modelling shows that increased oxygen production caused by increased burial of organic carbon was the chief suspect. This increased burial is attributed to the rise and spread of large woody vascular plants on the continents beginning at about 375 Ma. The plants supplied a new source of organic matter to be buried on land and carried to the oceans via rivers. This ‘‘new’’ carbon was added to that already being buried in the oceans, thus increasing the total global burial flux. This is especially true of lignin, a substance that is decomposed only with difficulty by micro- organisms. The rise of ligniferous plants and an initial level of microbial lignin breakdown lower that that at present may have contributed to increased organic matter burial and better preservation. This high burial rate is reflected by the abundance of coals during this period, which is the greatest abundance in all of earth history.
Another factor favouring extensive Permo-Carboniferous organic matter burial was the presence of vast swamps on the continents, brought about by the presence of extensive poorly drained flatlands, and large areas of coastal plains, brought about by glacially induced fluctuations of sea level. This situation enabled the preservation of organic debris, leading ultimately to coal formation, because of the relative lack of organic decay in stagnant anoxic waters. Why coal formation, organic burial, and oxygen production dropped toward the end of the Permian period (Fig. 2) is not clear, but it may be tied up with sea level drop and a general drying of the continents.
The level of atmospheric oxygen cannot rise indefinitely unless the frequency of forest fires becomes so excessive that plant life cannot persist. Fossil charcoal, as evidence of paleo fires, has been found for all times that trees have populated the land, and the lower limit for the production of charcoal has been estimated to be at about 13% O2.
March 16, 2014
This book describes current research on the history of oxygen in earth's atmosphere. It was particularly good at conveying the collegiality of science and the way that data and conflicting hypotheses are built up, tested and rethought. While written for the general public, reading it requires close attention.
I found it sobering that the tremendous quantities of cyanobacteria existing in the oceans were only discovered in 1979 since they were too small to be caught in the netting used to gather specimens. Who knows what else is hiding in plain sight?
I found it sobering that the tremendous quantities of cyanobacteria existing in the oceans were only discovered in 1979 since they were too small to be caught in the netting used to gather specimens. Who knows what else is hiding in plain sight?
December 24, 2016
I often complain about popular science books written by journalists, and how they often elide over many of the technical details, which is where the mystery and the beauty lie. This book is kind of the opposite: a working scientist who writes moderately well, but gets a little too lost in the details, Which in the end it makes me wonder who the intended audience is.
The subject, how did the Earth's atmosphere get to have so much free oxygen, is massive and inspiring, and there seem to be few people that are more qualified to write this book than Canfield. It is quite interesting, but I found myself far too often bogged down in the details, losing sight of the big picture he was trying to convey. As such, it was more of a slog than a delight.
I cannot help but compare with the bio chemistry books written by Nick Lane and wonder what makes the difference; one was delightful and I have eagerly sought out subsequent work- the other is interesting but something I probably won't pursue any further.
The subject, how did the Earth's atmosphere get to have so much free oxygen, is massive and inspiring, and there seem to be few people that are more qualified to write this book than Canfield. It is quite interesting, but I found myself far too often bogged down in the details, losing sight of the big picture he was trying to convey. As such, it was more of a slog than a delight.
I cannot help but compare with the bio chemistry books written by Nick Lane and wonder what makes the difference; one was delightful and I have eagerly sought out subsequent work- the other is interesting but something I probably won't pursue any further.
February 17, 2022
Honestly, parts of this book were hard to follow for me (I have a bachelors of science degree but I’m not the best with chemistry, and this book talks a lot about chemical reactions, etc). The graphs and diagrams were helpful, but at times, it felt like the author was rambling and repeating himself, which could be confusing. However, it was an interesting read.
October 27, 2020
Good book, by a student of Bob Garrels. See notes.
Sadly, it's due. I'll have to get it back to finish it. Too many books!
Set back to "want to read" for now.....
Sadly, it's due. I'll have to get it back to finish it. Too many books!
Set back to "want to read" for now.....
September 12, 2019
DensitoooooO2
March 6, 2018
When I first heard about Oxygen I immediately wanted to read it. This is an amazingly important topic for understanding the history of life on Earth and it was written by a true renowned specialist, Prof. Donald Canfield. Although the positives hugely outweigh the negatives, such as the author's clear and precise use of language and the careful selection and exposure of data, there were some distracting features such as the oversimplification of relatively simple geological and biological processes. I also think that some topics, such as the evolution of oxygenic photosynthesis, could have been developed further. It would have added depth and length to a rather short book that left me wanting more.
December 4, 2018
In Oxygen: A Four Billion Year History, ecology professor Donald E. Canfield recounts the history of Earth's atmosphere, focusing on one of the most important elements of life: oxygen. The author describes scientific theories around the oxygenation of our planet and their evolution precisely and in a very detailed manner.
This book is a bit more technical than your typical popular science book, which I enjoy but it might not be everyone's cup of tea. Nevertheless, it is a very informative book about a fascinating subject.
This book is a bit more technical than your typical popular science book, which I enjoy but it might not be everyone's cup of tea. Nevertheless, it is a very informative book about a fascinating subject.
July 26, 2020
Solid, interesting science. The writing, however, falls far below the (admittedly high) standard set by Andrew Knoll in Life on a Young Planet: The First Three Billion Years of Evolution on Earth.
January 28, 2017
Although this is a popular science book written for a general audience, there are a few technical spots. Canfield does a superb job describing the great oxygen event and the subsequent reducing atmosphere that caused the great rusting or oxidizing event. Banded iron formations are evidence of this. The rise in oxygen brought an increase in biodiversity. Canfield does an excellent job of detailing the history of oxygen on Earth.
March 10, 2021
Borrow.
Much more technical and advanced than I expected. This is not a bad thing, but it is not for the general audience and tough even for casual science readers. The author does a good job of trying to keep things fun and light when possible. An interesting subject matter with my major takeaway being that there is still so much we do not know.
Much more technical and advanced than I expected. This is not a bad thing, but it is not for the general audience and tough even for casual science readers. The author does a good job of trying to keep things fun and light when possible. An interesting subject matter with my major takeaway being that there is still so much we do not know.
May 15, 2017
This might be better if you have a more thorough chemistry background. The topic was interesting, but the book was weighed down by chemical diagrams and reaction equations.
February 20, 2016
This is a quite readable, and interesting, book by one of the world's leading authorities on geochemistry, earth history, and the early oceans. It covers the evidence gathered over the last several decades (and before) concerning the evolution of Oxygen in Earth's atmosphere. Other popular science accounts on this and related topics have given a more detailed (and maybe misleading?) account of the changes in the Oxygen content of the atmosphere, but Canfield is much more conservative in his account of what happened, and when. Up until about 2.4 billion years ago, there was virtually no Oxygen in the Earth's atmosphere. At this point, the Great Oxygenation Event occured and free Oxygen first appeared in the Earth's atmosphere. Between this point and the start of the Phanerozoic Eon (540 million years ago), it is extremely difficult to put numbers on the evolution of Oxygen in the atmosphere based on the geochemical evidence we have to date. The most that Canfield will admit to is that Oxygen levels in the atmosphere during the early stages of the Phanerozoic Eon were in the range 10% to 20% of present atmospheric levels, and only displayed a significant increase during the Late Silurian and Early Devonian Periods (some 420 million years ago). There is considerable evidence of very high rates of oxygen liberation during the Carboniferous and early Permian Periods when atmospheric oxygen concentrations may have significantly exceeded modern levels. What is particularly interesting in Canfield's account is how the evolution of the Oxygen content of the atmosphere and oceans interacted with other geophysical cycles including the carbon-silicate weathering, phosphorus and nitrogen cycles. If you have an interest in the modern understanding of Earth systems science, this book is well recommended.
November 19, 2014
كتاب جميل جدا استمتعت به وتعلمت منه كثيرا...لغة الكتاب علمية في الاغلب ولكن الكاتب احيانا يمزج معه الاسلوب الروائي والكوميدي مما يجعلك لاتستطيع التوقف عن المتابعة....
يتحدث الكتاب عن تكون الاوكسجين في الارض عبر العصور....كيف بدات ال ساينو باكتريا بستخدام وانتاج الاكسجين من قبل ٢ ونصف بليار سنة....عوامل وطرق اخرى لانتاج الطاقة كانت موجودة قبل الاوكسجين ولازالت كالسولفات والميتان وايونات الحديد.....كيف يتم الحفاض على مستوى الاوكسجين عن طريق
Negative and positive feedback mechanisms
وستغربت جدا كيف ان بقاية المواد او النفايات الغير صالحة للتفاعل تساعد مع الوقت على زيادة كمية الاوكسجين بطريقة غير مباشرة...شيئ لم اكن اتوقعه ابدا...
تم مناقشت تركيز الوكسجين عبر العصور بشكل عميق...وكيف كان هو السبب في وجود حيوانات وذباب عملاق في وقت من الاوقات.
يتحدث الكتاب عن تكون الاوكسجين في الارض عبر العصور....كيف بدات ال ساينو باكتريا بستخدام وانتاج الاكسجين من قبل ٢ ونصف بليار سنة....عوامل وطرق اخرى لانتاج الطاقة كانت موجودة قبل الاوكسجين ولازالت كالسولفات والميتان وايونات الحديد.....كيف يتم الحفاض على مستوى الاوكسجين عن طريق
Negative and positive feedback mechanisms
وستغربت جدا كيف ان بقاية المواد او النفايات الغير صالحة للتفاعل تساعد مع الوقت على زيادة كمية الاوكسجين بطريقة غير مباشرة...شيئ لم اكن اتوقعه ابدا...
تم مناقشت تركيز الوكسجين عبر العصور بشكل عميق...وكيف كان هو السبب في وجود حيوانات وذباب عملاق في وقت من الاوقات.
April 21, 2019
There’s a interesting story to be told about the enabling of life on earth by the creation of an oxygen rich environment in early geological history, but this story gets lost in the unnecessary details of this book. I am constantly irritated by academic writers who spend all sorts of energy and page space writing what good friend of theirs proposed an insignificant detail in an obscure academic journal. Yes, these details are important in your academic field, but the rest of us really don’t want to hear about it. I read this book immediately after reading David Quammen’s book, “The tangled tree of life“ and this book paled in comparison.
March 14, 2016
I thought this would be a pop-science introduction to geochemistry, but it turned out to have all the technical details I could have ever wanted (and more!). Some of the history-of-geochemistry tangents were of less interest to me, but overall this is a succinct and readable summary of what we know about the history of oxygen on Earth.
I read this as part of my ongoing project of getting to grips with *(big) history.
I read this as part of my ongoing project of getting to grips with *(big) history.
February 2, 2016
I have been wanting to read this book for awhile and so I had high expectations. It was a good book but it did not live up to my expectations. This book contained great information,much of it new to me, but I did not like the intellectual level it was written to. Canfield said that he was writing it for a broader audience than just scientists and I feel like he accomplished this goal. I just wished it had higher level science.
June 21, 2014
Purportedly a book written for the masses and including the latest research, Oxygen delivers on the latter but fails abysmally on the former. Only a geochemist could love this book, and most members of the public would find little that is comprehensible. Too bad; I was really looking forward to learning some interesting new information about the formation of the modern atmosphere.
January 5, 2015
Good and worth reading, although difficult at times. It gave me a new perspective on Earth's geological history and how it relates to the development of life. As someone who teaches about photosynthesis I was hoping for a more biochemical point of view (less about rocks.). I had considered having my students read it, but I am leaning against that now.
June 29, 2016
Interesting introduction to one of the hot topics in early planetary geology and biology.
Read
December 10, 2014Featured on Science for the People show #267 on May 30, 2014, during an interview with author Donald Canfield. http://www.scienceforthepeople.ca/epi...
May 26, 2016
Excellent overview of earth history.
Displaying 1 - 22 of 22 reviews