I think we can say that it is a permanent visual record of a space at a moment in time captured on a 2-dimensional plane. Well, why do we take photos in the first place? To remember a time in our lives that we would not like to forget or like to revisit some time in the future. In this rapidly changing world, places (especially big cities) that were photographed many years ago might not look the same today. Photos of people taken at different stages of their lives will definitely be very different.

Apart from their emotional and reminiscent value, photos are great tools to identify and measure how a place or life form physically changes over time. From the above picture, we can understand that almost all the greenery and natural boulders that were near the building in 2001 have been destroyed to make way for the concrete structures that we see in 2023. If we had more photos (or data points) during this period, we could determine exactly when the trees were cut and even when all the structures were built. All this sounds good, but how does it connect to polar ice sheets and atmosphere? Let us get there in two steps.

We have all heard of acid rain, right? In areas with heavy industries, harmful gases like SO₂ and NOₓ are released into the atmosphere and pollute it. Our atmosphere contains abundant water in the form of both vapor and droplets (especially in clouds), and these pollutants react with it to form sulfuric and nitric acids.

The rain clouds form at an altitude where the temperature is above the freezing point of 0ºC. These clouds can travel hundreds of kilometers before raining down, so acid rain often falls far from its pollution source. This is an example of how rain that falls to the ground has a chemical signature of the atmosphere it was formed in. Something similar happens with another kind of precipitation falling from the clouds…

Freshly fallen snow is made almost entirely of air, often around 90% by volume, making it feel very light. Snow crystals form in cold cloud layers where temperatures are below freezing. These clouds, similar to rain clouds, can travel hundreds of kilometers before they finally precipitate as snowfall.

When it keeps snowing for months in the same place without significant melting, new snow accumulates on top of older layers. As the stack thickens, the weight of the overlying snow compresses the lower layers, squeezing out air and compacting the crystals. Over time, this pressure causes the snow to harden and recrystallize into coarser grains, passing through an intermediate stage called firn (it takes one year for snowflakes to form firn), until it eventually becomes solid glacial ice.

This process is a bit like pressing loose coffee grounds into a compact puck in a filter, or packing a loose handful of fresh snow into a firm snowball, but happening more intensely and on a much larger scale over years to centuries. Even as the light snowflakes get turned into glacial ice (after several years of compression), they retain nearly 10% of the air they initially had when they were formed in the atmosphere a.k.a the chemical signature of the atmosphere at a point in time. Sounds more like a photograph, right?

Glaciers are formed when glacial ice accumulates over a large area of land, ideally in areas with very high snowfall in winter and low summer temperatures to prevent the ice from completely melting away (Himalayas, Patagonia, Alaska to name a few). And yes, glaciers are formed in high altitudes like mountains and slowly move downhill with time. As they slowly slide down on their way to the sea, they carve or erode parts of the mountains (like chiseling wood) to create beautiful fjords like those in Norway and New Zealand.

Ice sheets are large masses of glacial ice sitting on continental scale lands that span more than 50,000 square kilometers! We only have two ice sheets on Earth at the moment sitting or sliding atop Greenland and Antarctica. Fresh snow on these ice sheets takes a tiny part of today’s atmosphere and locks it into ice over the coming decades. These polar ice sheets are usually several kilometers deep. As we go deeper, we encounter ice that is older in age, and within that ice, photographs or chemical signatures of atmosphere from those times.

As these regions were very cold and hosting ice sheets from several hundreds of thousands or even millions of years, the air trapped inside the ice holds information about how our atmosphere was like throughout those years. Scientists went to expeditions in Antarctica to drill deep into this ice to study the chemical composition of the ancient atmosphere. Why drilling in Antarctica, and why is this important?

As seen in previous AlterEarth posts, Earth’s atmosphere was constantly changing its composition due to biological, physical and chemical processes occurring on Earth. In the very recent history of the Earth, polar regions like Antarctica were relatively stable, with temperatures continuously cold enough to host large ice sheets and minimal tectonic activity to disrupt them. Due to this, we have a near-continuous record of the atmosphere trapped in these ice sheets. This means we have very frequent pictures of the ancient atmosphere (with annual resolution near the surface, stretching to spanning decades as we go deeper), or should we say photo albums :)

Air bubbles trapped in ice from a 3.2 km hole drilled at a location in Antarctica gave us a very clear picture of how the atmosphere on Earth varied over a span of 800,000 years (resolution of decades is very good in this time scale)! Cross referencing this historical atmospheric data with fossil data and other geological markers from similar time periods in different parts of the Earth helps scientists better understand how and why the Earth evolved the way it did. Cracking this problem can shed some light on how the Earth might change in the future based on what is happening in the present.

How was today’s post?

If you liked it, please hit the Like button at the bottom and share it with a friend. Hit the ‘send message’ button if you want to share feedback. Also, please Subscribe to AlterEarth if you haven’t already. Have a great day!

Here are the references that I used for figures and guidance while writing this piece.

References:

1. https://dec.ny.gov/environmental-protection/acid-rain

2. https://www.epfl.ch/labs/lapi/wp-content/uploads/2020/03/Clouds.pdf

3. https://nsidc.org/learn/parts-cryosphere/glaciers

4. https://www.antarcticglaciers.org/glacier-processes/from-snow-to-glacier-ice/

5. https://www.antarcticglaciers.org/glacial-geology/glacial-landforms/glacial-erosional-landforms/fjords/

6. https://www.bas.ac.uk/news/how-antarctic-ice-cores-give-us-clues-about-earths-future-climate/

7. https://www.antarcticglaciers.org/antarctica-2/why-study-antarctic-glaciers/

8. Whitehouse PL, Gomez N, King MA, Wiens DA. Solid Earth change and the evolution of the Antarctic Ice Sheet. Nat Commun. 2019 Jan 30;10(1):503. doi: 10.1038/s41467-018-08068-y. https://pmc.ncbi.nlm.nih.gov/articles/PMC6353952/.

9. Lambert, F., Delmonte, B., Petit, J. et al. Dust-climate couplings over the past 800,000 years from the EPICA Dome C ice core. Nature 452, 616–619 (2008). https://doi.org/10.1038/nature06763.

As the Earth was very warm due to a strong greenhouse effect, somewhere in the shallow freshwater or terrestrial environments around the equator, tiny green microbes called cyanobacteria first started to appear ~3.5–2.7 billion years ago (possibly earlier). They used sunlight to split water molecules, releasing Oxygen as waste while converting CO₂ into sugars. In a fascinating twist of fate, the descendants of these very microbes live inside the leaves of today's trees and plants, powering them as parts of chloroplasts (where photosynthesis occurs)!

6CO₂ + 6H₂O → C₆H₁₂O₆+ 6O₂

For millions of years after they first appeared, these cyanobacteria were reproducing and filling up the waters with Oxygen! When you keep adding water to a filled glass, it eventually spills out. The same thing happens when you keep adding gases to liquids. Once the liquid cannot contain more of the gas, it leaks into the atmosphere (called supersaturation).

Once Oxygen started to enter the atmosphere, growth in cyanobacteria population (that ate away the CO₂) consistently increased the Oxygen percentage in the air. Methane was also a good contributor in keeping the Earth warm when the Sun was Faint. This new Oxygen in the air started reacting with Methane to form Carbon dioxide, which is a much weaker greenhouse gas than Methane.

CH₄ + 2O₂ → CO₂ + 2H₂O

Furthermore, rainfall assisted in bringing atmospheric CO₂ to oceans and rocks on the surface, for it to react with silicate minerals in the rocks and get trapped in them, in a process known as silicate weathering. This has been a very important driver in the Carbon cycle that traps atmospheric CO₂ in rocks (more in a future post).

A combination of all the above processes happening together started to disrupt or remove the ‘heaters of the Early Earth (Methane and Carbon dioxide)’ from the atmosphere as Oxygen percentage increased. When we turn off the heater (heat source) on a cold winter night, it does not take long for the cold to creep into the house. This insane coup by Oxygen for place in our atmosphere is referred to as ‘The Great Oxidation Event (GOE)’ and it triggered the cooling of the Earth and led to one of the Earth’s earliest and longest ice ages (Huronian glaciation-nearly 300 million years)!!

A cumulative effect of the drastic reduction in Methane and Carbon dioxide in the atmosphere and the rapid cooling (in geologic time scale is millions of years) of the Earth that followed it led to the destruction of majority of thriving oxygen-averse life on Earth. In other words, Oxygen almost poisoned most of the life on Earth.

When more than 75% of life on Earth dies in a particular span of time, we call it a ‘Mass extinction event’. There were multiple global mass extinction events in the history of the Earth, but this (GOE) is not included in the five major ones as there are no bodies or fossil evidence to prove the magnitude of microscopic lives lost. If there is no proof of bodily remains from a period, does it mean there was no life or death?

Writing this post reminded me of an excerpt from a comic named Absolute Zero, written by director Christopher Nolan as a spin-off from Interstellar. A good friend and I were admiring it a decade ago. It reads as:

If darkness is only the absence of light…

If cold is only the absence of heat…

If silence is just the absence of sound…

If death is simply the absence of life, then is good the absence of evil, or evil the absence of good?

But, out of this frozen silence, rose an invisible savior. The oxygen overdose on Earth also led to the formation of the Ozone layer when it reacted with solar radiation in the atmosphere. Today, we understand how important the Ozone layer has been throughout its history by saving trillions of life forms from harmful radiation for billions of years. With the protection of the Ozone layer and easy availability of Oxygen, evolution pushed life towards ‘aerobic’ respiration or breathing Oxygen that eventually led to us!

How was today’s post?

If you liked it, please hit the Like button at the bottom and share it with a friend. Hit the ‘send message’ button if you want to share feedback. Also, please Subscribe to AlterEarth if you haven’t already. Have a great day!

Here are the references that I used for figures and guidance while writing this piece.

References:

1. https://www.imperial.ac.uk/news/171487/imperial-scientist-explains-oxygen-triggered-earths/#:~:text=The%20Great%20Oxidation%20Event%2C%20GOE,evolution%20of%20oxygen%2Dbased%20life.

2. https://ora.ox.ac.uk/objects/uuid:51bceb86-2983-497d-a986-67657c01e975/files/sww72bc81t

3. Sato N. Are Cyanobacteria an Ancestor of Chloroplasts or Just One of the Gene Donors for Plants and Algae? Genes (Basel). 2021 May 27;12(6):823. doi: 10.3390/genes12060823. https://pmc.ncbi.nlm.nih.gov/articles/PMC8227023/#abstract1.

4. https://www.monash.edu/student-academic-success/biology/photosynthesis/the-process-of-photosynthesis#:~:text=PhotosynthesisThe%20process%20by%20which,oxygen%2C%20supporting%20life%20on%20Earth.

5. Bekker, A. (2011). Huronian Glaciation. In: Gargaud, M., et al. Encyclopedia of Astrobiology. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-11274-4_742. https://link.springer.com/rwe/10.1007/978-3-642-11274-4_742#citeas.

6. https://news.cnrs.fr/articles/when-earth-was-a-snowball

7. M.R. Warke, T. Di Rocco, A.L. Zerkle, A. Lepland, A.R. Prave, A.P. Martin, Y. Ueno, D.J. Condon, & M.W. Claire, The Great Oxidation Event preceded a Paleoproterozoic “snowball Earth”, Proc. Natl. Acad. Sci. U.S.A. 117 (24) 13314-13320, https://doi.org/10.1073/pnas.2003090117 (2020). https://www.pnas.org/doi/10.1073/pnas.2003090117.

8. Olejarz, J., Iwasa, Y., Knoll, A.H. et al. The Great Oxygenation Event as a consequence of ecological dynamics modulated by planetary change. Nat Commun 12, 3985 (2021). https://doi.org/10.1038/s41467-021-23286-7. https://www.nature.com/articles/s41467-021-23286-7.

9. https://asm.org/articles/2022/february/the-great-oxidation-event-how-cyanobacteria-change

10. https://interstellarfilm.fandom.com/wiki/Absolute_Zero_(comic)

11. https://slate.com/technology/2014/07/the-great-oxygenation-event-the-earths-first-mass-extinction.html

12. https://www.sciencedirect.com/science/article/pii/S2772883822000152.

Just like many scientific hypotheses that cannot be solidly proven, there are multiple theories behind the origin of the atmosphere (the thick layer of gases hugging the Earth). One of the theories states that the atmosphere came from inside the Earth through millions of years of volcanic activity that brought gases from inside the Earth outside the surface- volcanic outgassing. The other theory states that the atmosphere (also water) was brought to the Earth by meteors and asteroids over millions of years. Most scientists believe that it wasn’t just one or the other, but a chaotic mixture of both processes!

On a lighter note, volcanic outgassing can be imagined as a very prolonged ‘burp’ of the Earth as it gave out the early atmosphere.

The Early atmosphere did not have any free oxygen, but was mainly made of:

• Water vapor (H₂O)

• Nitrogen (N₂)

• Carbon Dioxide (CO₂)

• traces of Sulphur dioxide (SO₂), carbon monoxide (CO), methane (CH₄) and ammonia (NH₃).

As this early atmosphere was being formed, the surface temperature of the Earth was reducing (as the land started to solidify) and this cooling allowed the precipitation of water vapor from the atmosphere to form our oceans.

The Faint Young Sun Paradox

From nearly 4 - 2.5 billion years ago, our Sun was not as bright and hot as it is now. It was in fact 20-30% fainter. During this time, the Earth should have been a frozen ball of ice with surface temperatures dropping drastically. But, water on Earth was in its liquid form throughout this period (geologic evidence) and scientists call this the ‘Faint Young Sun Paradox’.

Greenhouse effect kept the Earth warm when the Sun was ‘Faint’ or ‘Cooler’

In today’s metrics, as the solar radiation travels from the Sun to the Earth, it first interacts with the thick atmosphere. About 23% of this incoming radiation is absorbed directly by the atmosphere. Another 30% of it gets reflected back to space by scattering (7%), clouds (17%) and the surface (6%). The remaining 47% of the radiation that successfully makes its way through gets absorbed by the Earth’s surface.

The Earth eventually emits some of this absorbed energy back to the space in the form of long-wave infrared radiation.

When infrared radiation hits surfaces or complex molecules, it causes them to vibrate. This vibration is exactly what we feel as heat!

This infrared radiation on its way back to outer space has to go through the atmosphere. And remember some of the incoming radiation was also absorbed by the atmosphere?

Well, out of all the gases in our atmosphere, the ones with three or more atoms, like H₂O, CO₂, CH₄, NH₃, etc, have molecular structures that like to absorb (and vibrate or dance!) and re-emit or radiate this infrared radiation in all directions (just like we love grooving to our favorite songs!). Some of this re-emitted radiation comes back towards the Earth and heats (or warms) it up, causing what we call Global Warming. And this phenomenon right here is called the ‘Greenhouse effect’ as it mimics how temperatures inside a greenhouse are warmer than the outside due to the glass trapping the hot air. The gases in the atmosphere that dance to infrared radiation are called ‘Greenhouse gases’.

With time, scientists could explain that a lot of Carbon Dioxide was already part of our early atmosphere, but it was not enough to keep the Earth as warm as it was. The secret extra ingredient was ‘Methane’, which is a much stronger greenhouse gas than Carbon dioxide (on a 100-year timescale, Methane’s global warming potential is ~30 times that of carbon dioxide and 82.5 times more on a 20-year timescale).

But the main question is- where did so much Methane come from??! If you have been following the previous posts of AlterEarth, you can guess where this is leading to- Early life on Earth.

Early life on Earth was anaerobic (living without oxygen), and some of the earliest microbes evolved metabolisms that consumed Carbon dioxide and released Methane into the atmosphere

The microbes that produced Methane from Carbon dioxide and Hydrogen are called Methanogens and this process is called Methanogenesis. They lived entirely underwater and Carbon isotope data from fossils suggests that Methane of biological origin (from microbes) dates back to ~3.5 billion years ago, confirming that the rise in Methanogen population led to the increase in Methane in the atmosphere.

The temperatures of the oceans around this period were estimated to be in the 55ºC - 85ºC range despite the weak Sun!

This was the work of a rising Methane percentage along with an already immense amount of Carbon dioxide in the atmosphere.

In simple words, these methanogens ‘unintentionally engineered’ a Global warming during the Faint Young Sun period that kept the Earth thriving with life and laid the foundation for further evolution that eventually led to us. Without them, the Earth would have been a frozen ball of ice (back then) and who knows if any of us would be here to read this now.

This is a clear example of how life on Earth can influence the coupled Earth system processes on a planetary scale in a positive way. The next post will talk about a very interesting phase in the Earth’s history- the next stage of evolution.

How was today’s post?

If you liked it, please hit the Like button at the bottom and share it with a friend. Hit the ‘send message’ button if you want to share feedback. Also, please Subscribe to AlterEarth if you haven’t already. Have a great day!

Here are the references that I used for figures and guidance while writing this piece.

References:

1. https://www.noaa.gov/jetstream/atmosphere/layers-of-atmosphere

2. https://earthhow.com/origin-of-water-comets-volcanoes-outgassing/

3. https://www.manchester.ac.uk/about/news/earths-atmosphere-came-from-outer-space-find-scientists/

4. https://astrobiology.nasa.gov/news/earths-early-atmosphere-an-update/

5. Avice, G., Marty, B. & Burgess, R. The origin and degassing history of the Earth's atmosphere revealed by Archean xenon. Nat Commun 8, 15455 (2017). https://doi.org/10.1038/ncomms15455

6. https://www.britannica.com/science/evolution-of-the-atmosphere-1703862

7. https://ugc.berkeley.edu/background-content/greenhouse-effect/

8. https://rwu.pressbooks.pub/webboceanography/chapter/8-1-earths-heat-budget/#:~:text=Just%20under%20half%20(47%25),phase%20change)(Figure%208.1.

9. https://niwa.co.nz/atmosphere/what-are-greenhouse-gases#:~:text=In%20general%2C%20any%20gas%20with,is%20quite%20a%20different%20effect.

10. https://eartharxiv.org/repository/view/108/

11. https://www.museumoftheearth.org/changing-climate/greenhouse-effect

12. https://energy.ec.europa.eu/topics/carbon-management-and-fossil-fuels/methane-emissions_en#:~:text=After%20carbon%20dioxide%2C%20methane%20is,comes%20from%20the%20energy%20sector

13. https://www.quantamagazine.org/the-sun-was-dimmer-when-earth-formed-how-did-life-emerge-20220127/

14. https://news.mit.edu/2018/mit-researchers-determine-timing-of-methanogen-evolution-0404

15. https://astrobiology.com/2026/01/methanogens-through-geological-time-and-space-impact-on-planetary-evolution-and-significance-for-life-beyond-earth.html

16. https://astrobiology.nasa.gov/news/how-hot-were-the-oceans-when-life-first-evolved/#:~:text=Earlier%20geological%20evidence%20has%20suggested,silicon%20isotopes%20in%20marine%20rocks.

A single-celled organism (early ones were nanometers to micrometers in size) is a microscopic world in itself, consisting of billions or even trillions of molecules based on its size, all of which perform dedicated tasks to ensure proper functioning of the cell. For the first one to form on Earth nearly 4.2 - 3.8 billion years ago, various external factors like geological setting, temperature of the water, pH (acidity), etc, had to be just right.

As explored in one of our previous posts on plate tectonics, the pieces of Earth’s crust are constantly moving and when two oceanic plates move away from each other, hot mantle material comes to the surface creating new crust from what we call ‘mid oceanic ridges’. The most famous hypotheses about the origin of life on Earth- one suggests that life originated on land and the other suggests that it happened inside water. The commonality between them is that they think life might have started close to a hydrothermal vent as it is chemically very active and warm. One of these theories, put in simple words, states that-

About 4.2 - 3.8 billion years ago, somewhere in a mysterious location near the ocean floor, there was a mid-oceanic ridge heating up the deep dark waters. Hydrothermal vents in this region created a chemically rich environment in the warm waters, setting the stage for the first breath of life. Oh, and yes, there was no oxygen on the Earth back then, so the ‘breath’ is just metaphoric.

Studies also suggest that the first life form could have been Ribonucleic Acid or RNA, which is one of the building blocks of life alongside DNA. In our bodies, DNA stores the genetic blueprint of our ancestors and RNA reads the genetic data from DNA and sends messages to build proteins and performs other important tasks. However, the earliest form of RNA is predicted to have had the capability to store the genetic material, perform important tasks and reproduce!

Over billions of years, life evolved from single-celled organisms to multi-organ complex organisms, from anaerobic (without oxygen) to aerobic respiration, from thriving underwater to conquering the land and skies. While this may sound like a great step up, most of the evolution was shaped by life responding to the dynamic processes on Earth and trying to adapt to them, and even influencing them at times.

An interesting perspective to take away is that most of all living organisms on the planet have a very simple single-celled organism called - Last Universal Common Ancestor (LUCA) as our ancestor. LUCA is said to have come after the RNA, but the timelines are still a point of debate.

How was today’s post?

If you liked it, please hit the Like button at the bottom and share it with a friend. Hit the ‘send message’ button if you want to share feedback. Also, please Subscribe to AlterEarth if you haven’t already. Have a great day!

Here are the references that I used for figures and guidance while writing this piece.

References:

1. https://www.thoughtco.com/how-many-atoms-in-human-cell-603882#:~:text=Scientists%20estimate%20the%20average%20cell,of%20cells%20in%20the%20body.

2. Biro JC. The concept of RNA-assisted protein folding: the role of tRNA. Theor Biol Med Model. 2012 Apr 2;9:10. doi: 10.1186/1742-4682-9-10. https://pmc.ncbi.nlm.nih.gov/articles/PMC3359187/#:~:text=The%20tRNA%20seemingly%20solves%20the,its%20neighbor%20(Figure%201).

3. https://www.nature.com/scitable/topicpage/what-is-a-cell-14023083/#:~:text=As%20previously%20mentioned%2C%20a%20cell’s,changes%20that%20underlie%20cell%20division.

4. https://asm.org/articles/2022/august/single-cell-rna-sequencing-to-study-salmonella-inf

5. https://naturalhistory.si.edu/education/teaching-resources/life-science/early-life-earth-animal-origins

6. Omran A, Pasek M. A Constructive Way to Think about Different Hydrothermal Environments for the Origins of Life. Life (Basel). 2020 Apr 9;10(4):36. doi: 10.3390/life10040036. https://pmc.ncbi.nlm.nih.gov/articles/PMC7235985/

7. https://www.chemistryworld.com/features/hydrothermal-vents-and-the-origins-of-life/3007088.article

8. https://www.frontiersin.org/news/2022/01/19/frontiers-microbiology-origin-of-life-energy-hydrothermal-vents

9. Robertson MP, Joyce GF. The origins of the RNA world. Cold Spring Harb Perspect Biol. 2012 May 1;4(5):a003608. doi: 10.1101/cshperspect.a003608. https://pmc.ncbi.nlm.nih.gov/articles/PMC3331698/#:~:text=There%20is%20now%20strong%20evidence,on%20p%2DRNA%20or%20PNA.

10. https://www.science.org/content/article/how-life-could-have-arisen-rna-world

11. https://www.technologynetworks.com/genomics/articles/what-are-the-key-differences-between-dna-and-rna-296719#:~:text=and%20RNA%20differ:-,Function,1

12. https://www.quantamagazine.org/all-life-on-earth-today-descended-from-a-single-cell-meet-luca-20241120/

The crust that we stand on and the oceans rest upon is not a single solid block, but it is a bunch of broken pieces that are always moving around. This movement is neither the rotation of the Earth along its axis nor the revolution around the Sun, but rather, the surface we are on is literally moving all the time. This process, technically known as ‘plate tectonics’ is constantly creating and destroying parts of the crust as you are reading this post, but in a very slow pace that is similar to how fast our fingernails grow (around 10 mm/year). But, when and how did all this start?

Nearly 4 billion years ago, when the Earth started to cool down, its hot surface was getting solidified into a very thin layer like a thin layer of skin forming on hot milk as it cools down.

The early mantle was very active back then. So, as the crust started to solidify, the strong convection currents in the mantle started breaking it up nearly everywhere and adding new material to the surface. The mantle sent its material out on to the crust through millions or hundreds of millions of years of continuous volcanic explosions and magmatic outbursts from the cracks in the crust. Along with the mantle material expelled by volcanoes that solidifies to form the crust, immense amounts of gases and ash was also released that formed the first atmosphere in a process called volcanic outgassing.

Over hundreds of millions of years, thick layers of new land got solidified and all the expelled gases created the first atmosphere. The main contents of our early atmosphere were:

• Water vapor (H₂O)

• Carbon dioxide (CO₂)

• Nitrogen (N₂)

• Other gases like methane (CH₄), ammonia (NH₃), and sulfur dioxide (SO₂).

When the Earth cooled down a bit, the water vapor in the atmosphere started to precipitate, it was raining heavily for centuries or millions of years all over the Earth that formed the world’s oceans, along with some contribution from comets and asteroids carrying water. This further cooled down our accumulated ‘thick’ crust and formed oceans. This thick crust was not one continuous piece of solid material, it was made of many large broken pieces that were moving slowly, all thanks to the convection currents of magma in the mantle.

The earliest stable plates or large rock masses are called cratons and are found in:

• Parts of Canada and Greenland (nearly 4 billion years old)

• Large rocks in South Africa, Asia and Australia (nearly 3 billion years old or more)

Jigsaw puzzle on Earth

Did you ever take a close look at the world map and think that South America could fit right into the western part of Africa although they are very far away? They were indeed attached together millions of years ago!

There are seven large ‘plates’ that make up nearly 94% of the surface. The other plates are much smaller and cover the rest of the surface. Continental plates are the ones we are standing on and have depths ranging from 40 - 70 km from the surface until the upper mantle. Oceanic plates are the blocks of rocks upon which the oceans rest and they range from 5 - 10 km in thickness. The figure beneath shows the current layout of all the ‘tectonic plates’ on Earth.

There are three types of tectonic plate boundaries-

• Plates that move apart from each other and the mantle material that comes to the surface forms new crust are called divergent (or constructive) plate boundaries. In these types of boundaries, the crust becomes very thin as both plates are pushed apart to let the magma out.

  In the figure above, divergent boundaries are indicated with the small red arrows are pointing away from each other. The middle of the Atlantic Ocean has an active divergent plate boundary called the Mid-Atlantic ridge that created a big underwater mountain range over millions of years. Iceland is just one part of it that popped out of the ocean starting from nearly 18 million years ago. In several million years from now, the landmass of Iceland would be much bigger as it is constantly growing!

• In the case where plates that move towards each other, the denser one out of them (usually the oceanic plate) goes below the other (continental or other oceanic plate) into the mantle and gets destroyed in the upper mantle. These kind of boundaries are known as convergent (or destructive) plate boundaries. The plate that goes into the mantle gets melted by the heat in the mantle and this melted material rises back the surface to create volcanoes on continental plates (Cascade mountains, West Andes mountains) or volcanic islands on other oceanic plates (Island chains in the Pacific). In the world map above, convergent boundaries are indicated by red arrows pointing towards each other.

  However, when two continental plates collide into one another, neither of them are dense enough to go beneath the other, so the push into each other and rise up to form fold mountain ranges like the Himalayas.

• The other kind of plates where they rub against each other without creating or destroying crust are called transform plate boundaries. The most common example is the San Andreas fault in California.

Evolution of the land on Earth over millions of years

We now know how the plates move and interact with each other, and that all of this started happening from nearly 3.5 billion years ago. In the early 1900s, Alfred Wegener proposed a theory that all continents were once joined together in a supercontinent called Pangaea. It received wide backlash from the scientific community at that time due to lack of evidence or physical explanation. But slowly, they started finding fossils of the same species of animals and plants on India and Australia, South America and Africa and this was very strong proof that they were once together. The reason these fossils were irrefutable proof of plate movement is because the animal and plant species could not travel large distances in the ocean from one continent to the other as they are in the current structure.

Based on this fossil evidence and other physical mechanisms that were discovered proving that continents actually move, scientists reconstructed how the Earth looked like millions or even billions of years ago. As the current continents were once together as one landmass, they were referred to as Supercontinents. The figure below shows how the Supercontinents on Earth evolved with time. After Pangea, the supercontinent started to split apart and eventually led to the current continent structure.

Throughout billions of years, many plates got created and some of them also got completely destroyed by melting into the mantle. There are also some cratons that survived all these hard times and are still intact like in Canada, Greenland, Australia, South Africa and many parts of Asia (from 3 - 4 billion years ago).

Today’s plates move at an average speed of 1 - 10 cm/year with the continental plates being slow (1 - 6 cm/year) and oceanic plates like Pacific plate move around 10 cm/year. So, around 50 - 100 million years from now, the landscape of the Earth will be completely different with new oceans and continents and maybe some parts of the known ones being destroyed.

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If you liked it, please hit the Like button at the bottom and share it with a friend. Hit the ‘send message’ button if you want to share feedback. Also, please Subscribe to AlterEarth if you haven’t already. Have a great day!

Here are the references that I used for figures and guidance while writing this piece.

References:

1. https://guidetoiceland.is/nature-info/geology-of-iceland

2. https://www.britannica.com/science/geologic-history-of-Earth/Development-of-the-atmosphere-and-oceans

3. https://earthobservatory.sg/earth-science-education/earth-science-faqs/geology-and-tectonics/where-do-we-find-the-oldest-continental-rocks-and-the-oldest-seafloor

4. https://www.gsi.ie/en-ie/education/our-planet-earth/Pages/Plate-Tectonics.aspx

5. https://commons.wikimedia.org/wiki/Category:Plate_tectonics

6. https://www.geologyin.com/2024/03/divergent-boundary-definition-features.html

7. https://geo.libretexts.org/Bookshelves/Geology/Book%3A_An_Introduction_to_Geology_(Johnson_Affolter_Inkenbrandt_and_Mosher)/02%3A_Plate_Tectonics/2.03%3A_Convergent_Boundaries

8. https://study.com/academy/lesson/transform-boundary-definition-facts-examples.html

9. https://oceaniq.co.uk/news/the-seafloor-is-constantly-changing-what-can-the-history-of-plate-tectonics-teach-us/

10. https://www.nature.com/articles/s43017-021-00160-0

11. https://www.britannica.com/science/plate-tectonics/Plate-tectonics-and-the-geologic-past

12. https://www.geologyin.com/2025/03/how-fast-do-tectonic-plates-move.html

In our last post, we saw how the Earth was created and how it was a piping hot ball of material mixed up together. With time, planetary differentiation segregated the material into different layers where heavier material sunk in to form the core and lighter materials came up. This is what led to the current internal structure of the Earth.

Internal structure of the Earth (and origin of the giant magnet)

If you start drilling from one point on the Earth and keep drilling in a straight line until we reach the other end of the planet, it takes nearly 12,700 km to get there. Our Earth is not a perfect sphere though, it is an oblate spheroid that is somewhat flat at the poles and bulged at the equator. But, for simplicity and calculation purposes, we consider it to be a sphere of radius around 6371 or 6400 km.

Let us begin our journey from the center of our Earth- we are inside the hottest part of our planet, the solid inner core (from 5155 km to 6371 km deep). It is mainly composed of Iron and Nickel, and gets as hot as around 6000ºC at the center, which is more or less the temperature on the surface of our Sun!!

As we move upwards towards the surface, we can see a phase transition from solid to liquid when we reach the outer core (from 2885 km to 5155 km deep), which has more or less the same composition of the inner core, but also a bit of Oxygen and Sulphur in temperatures ranging from around 2900ºC - 4000 or 5000ºC.

Moving further upwards, we encounter the mantle, which is the largest part of the Earth that makes up around 84% of the planet ranging from around 100 km to 2885 km deep with temperatures ranging from about 900ºC to 2900ºC. This part of the Earth is much richer in composition compared to the core. The mantle is dynamic, not as much as the liquid outer core, but its material also moves very slowly in convection cycles (hot material moves up and colder material moves down). Finally, the last layer is the tiny crust that we all are standing on that ranges from 0 to around 100 km deep and is the smallest part of the Earth. This tiny crust of solid rocks shields us from all the heat deep under the surface.

We will get into more details of the Mantle and Crust in a later post. But for now, the hero of this post is the outer core, i.e, the Giant Earth Magnet.

How do Magnets actually work?

Every stable atom has tiny electron/s revolving around the nucleus at very high speeds. Each of these electrons have their own ‘spin’ while circling the nucleus. In most of the elements, the spin (either +1/2 and -1/2) usually cancels out as the electrons move in random directions.

In the figure below, each tiny house (blue underline), also known as an orbital, host a maximum of two electrons. The number preceding the letter (like ‘4’s and ‘3’d) denotes how far away the electrons are from the nucleus, with ‘4’ being farther than ‘3’ and the letters- s, p, d and f (only s and d here) have a predefined shape in the 3D space around the nucleus where the electron has a maximum probability to be found at.

Metals like Iron, Cobalt, Nickel, etc, have several unpaired electrons with the same spin, which makes each of the unpaired electron, and thereby the atom, behave like a tiny magnet. But, for something to be really meaningful and have a tangible impact, large numbers are required- just like drops of water in an ocean or trillions of atoms of a magnetic element (with similar spin electrons) are needed to form what is called a magnetic domain (these may be disoriented or oriented).

The materials with these disoriented magnetic domains need to be magnetized by passing a strong magnetic field through them. This magnetic field forces the magnetic domains to be aligned in the direction of the magnetic field and creates permanent magnets like the ones in all of our appliances.

If we need a strong magnetic field to create magnets, how were natural magnets created?

A very simple one worded answer to this question is ‘lightning’. As we studied in high school, a lightning strike is a massive electric discharge from the charged particles in clouds that hits the ground. Also, an electric current creates a magnetic field around it due to the movement of charged particles in a certain direction, and hence, lightning also creates a very strong magnetic field.

When a specific type of iron ore called magnetite is exposed to the surface and struck by lightning, the intense magnetic field aligns the previously disoriented magnetic domains in the magnetite and converts it to lodestone, the only ‘natural permanent magnet’.

The big Earth magnet!

We have established that we need a ‘push’ induced by a strong external magnetic field to create a permanent magnet from naturally magnetic materials (most common ones being Iron, Cobalt and Nickel) that have these magnetic domains. And guess what we have loads and loads of in the Inner and Outer Core- Iron and Nickel!

The inner core is solid because the immense pressure from the layers above it increases the melting point of the metals inside it. The outer core however, is in a liquid state and the materials (mostly Iron and Nickel) keep moving due to the rotation of the Earth and density differences due to variations in temperature. Where did the outer core get its magnetism from?? This continuous circulation and movement of gigantic amounts of charged particles in the outer core induces a large magnetic field that led to creation of the Earth’s self-sustaining magnetic field or Geodynamo.

When the outer core was newly created, the Sun was very young as well and had a weak magnetic field of its own. The Sun has immense quantities of super-hot ions and charged particles called plasma. This solar plasma is continuously in motion due to the Sun’s rotation and internal convection currents. With time, the Sun’s magnetic field became stronger and it started to eject its plasma, harmful radiation and strong magnetic fields out into the space. The magnetic field generated by the outer core of our Earth acts as a protective shield that deflects all these harmful radiation and particles emitted by the Sun.

If we had no Geomagnetic field, the solar radiation would strip away our atmosphere and all the water on the surface of our Earth in a slow process over millions of years. But, the harmful radiation and particles would impact surface life causing diseases like cancer to be more prevalent and significantly impacting all life in a span of centuries if not decades. So, this Geomagnetic field (magnetosphere) generated by the large Magnet in the outer core literally saves us all!

Our neighboring Red planet (Mars) had a magnetic field of its own a long time ago, but the shutting down of this magnetic field has led to the planet losing its atmosphere and all of its surface water in a slow process.

How is the Magnetosphere related to Auroras?

The magnetic field lines of our magnetosphere converge at the magnetic north and south poles. The shape of the magnetosphere at the magnetic poles allows some of the solar particles to funnel down into the upper atmosphere and interact with particles (usually Oxygen and Nitrogen) in our own atmosphere (Ionosphere).

When solar particles collide with gases in our atmosphere, the atoms of gases tend to get ‘excited’ due to energy provided by the collision. As any ‘excited’ thing or person needs to get back to normal conditions, these gases emit the extra energy as light in the visible wavelength. The green color we see in auroras is cause by Oxygen getting ‘de-excited’ and the shades of purple, blue and pink are cause by excited Nitrogen getting back to normal ways.

So the next time you see the captivating Auroras and get ‘excited’, remember that the beautiful colors are emitted by gases that are ‘tired of being excited’ and want to go back to business as usual.

In the upcoming posts, we will explore more details about the shallower parts of the Earth and some of their deeply hidden secrets.

How was today’s post?

If you liked it, please hit the Like button at the bottom and share it with a friend. Also, please Subscribe to AlterEarth if you haven’t already. Have a great day!

Here are the references that I used for figures and guidance while writing this piece.

References:

1. https://sketchplanations.com/earth-is-a-big-magnet

2. Gervilla, Fernando & González-Jiménez, Jose & Hidas, Károly & Marchesi, Claudio & Piña, Rubén. (2019). Geology and Metallogeny of the Upper mantle Rocks from the Serranía de Ronda. https://www.researchgate.net/publication/334132194_Geology_and_Metallogeny_of_the_Upper_mantle_Rocks_from_the_Serrania_de_Rondaç

3. https://education.nationalgeographic.org/resource/mantle/

4. https://www.space.com/earths-magnetic-field-explained

5. https://www.chemguide.co.uk/atoms/properties/atomorbs.html

6. https://www.eia.gov/energyexplained/electricity/magnets-and-electricity.php

7. https://www.sciencedirect.com/science/article/abs/pii/S0926985123003038

8. https://geomag.nrcan.gc.ca/mag_fld/fld-en.php

9. https://science.nasa.gov/science-research/earth-science/earths-magnetosphere-protecting-our-planet-from-harmful-space-energy/

10. https://www.rmg.co.uk/stories/space-astronomy/what-causes-northern-lights-aurora-borealis-explained#:~:text=This%20content%20is%20hosted%20by,in%20the%20Earth’s%20magnetic%20field.

11. https://www.newscientist.com/article/mg24432590-500-see-the-northern-lights-or-aurora-borealis-follow-this-easy-guide/

The serendipitous birth of our Sun

Billions of years ago, in a small part of the milky way galaxy called the Orion arm (Figure 1), extremely large clouds of dust and gas, called nebula, slowly started to come close to each other due to gravity. These specific clouds, were either very shy or lazy to get close enough to each other in masses and speeds that would create the perfect ground for nuclear fusion.

Meanwhile, a little before 4.6 billion years ago, somewhere in a region beyond this lazy nebula, an old star exploded in a massive supernova, emitting energy and hurling out the elements it created in all directions at high speeds. Some part of this energy and newly ejected material, full of kinetic energy, came as a shockwave directly into this lazy nebula and shook things up for good! This kick of energy and matter stirred up the contents in this lazy nebula, compressing (increasing its density) it in certain regions, just enough for gravity to take over, creating conditions for nuclear fusion that eventually led to the formation of our Sun (nearly 4.6 billion years ago).

The creation of our Earth (sizzling hot beginnings)

After our Sun was born, its intense gravity pulled almost all the material of the nebula towards itself and these clouds of dust and gas (protoplanetary disk) started to revolve around the sun at high speeds. With time, the protoplanetary disk started to cool down and solidify. The very dense material of the protoplanetary disk, consisting of all kinds of elements that we see in the planets today, eventually bumped into each other, forming progressively heavier bodies- from meteors (meters in width) to asteroids (meters to kilometers in width) and planetesimals (hundreds of kilometers in width).

In a few tens of millions of years after the formation of our Sun, many of these solid planetesimals collided into each other at rapid speeds forming our Earth and other inner rocky planets of our Solar system, in a process called planetary accretion (nearly 4.54 billion years ago).

When we strike two stones against each other, we can observe some sparks, and similarly, briskly rubbing our palms against each other generates heat. Now, imagine the same processes happening at a huge scale during planetary accretion. The Proto-Earth that was formed as a result of all these collisions was a piping hot ball of material all lumped together (much higher than 1000ºC) (Figure 2).

During this molten phase (heat from a number of collisions and decay of radioactive elements), the contents of our Proto-Earth had undergone a massive reorganization. Heavier elements like Iron and Nickel sunk in towards the center of the Earth, forming its Core, and lighter ones like Silicates and everything else came to the top, forming the Mantle (largest part of Earth between the Core and surface) and a very early, thin and unstable Crust (solid surface of the Earth) in a process called planetary differentiation (Figure 3).

This hot ball of molten rock or Proto-Earth, while trying to cool down, got hit by another Mars-sized planetesimal called Theia around 100-150 million years after its formation, which broke a chunk of our young planet and heated and remelted it even more. The chunk that broke out of our planet eventually went on to form our Moon. The extra heat due to this collision helped in the final stage of planetary differentiation (hotter materials move faster).

First atmosphere and oceans (4.5 - 3.8 billion years ago)

The early Earth at this stage had no atmosphere or water like today. Millions of years after the differentiation process, the Earth was cooling down and the crust started to solidify while temperatures were still in the 100s of ºC range. This process is similar to a thin layer of solid skin forming on hot milk as it cools off. As the newly formed crust was very thin and the Mantle was very dynamic, there was intense volcanic activity everywhere on Earth, which brought both solid material and gases from the mantle onto the surface in a process called volcanic outgassing (Figure 4). This massive emission of gases is what created the first atmosphere on Earth.

The main contents of our early atmosphere were:

• Water vapor (H₂O)

• Carbon dioxide (CO₂)

• Nitrogen (N₂)

• Other gases like methane (CH₄), ammonia (NH₃), and sulfur dioxide (SO₂).

Oxygen in its free form was not present in our atmosphere until much later!

Millions of years after the first atmosphere kept accumulating, the Earth cooled down to temperatures below 100ºC. This cooling, in combination with the pressures being low enough, facilitated the precipitation (or rainfall) of immense amounts of water vapor (H₂O) in the atmosphere. This intense rainfall that lasted for multiple centuries or maybe millions of years created the world’s first oceans (nearly 4 billion years ago). There are also some theories that say most of the water on the planet was brought by comets and asteroids. Some works propose that it might be the combination of the two processes. Whatever the cause of water’s origin on Earth, its existence is the reason our planet appears as a Pale Blue Dot from outer space (Figure 5).

From the tallest of mountains to the deepest of oceans, the lands home to gigantic dinosaurs and blue whales, are parts of a planet that is just a speck of dust or a Pale Blue Dot in the cosmic scale. In other words, the creation of our Earth was a mere act of cosmic insignificance that led to hosting trillions and trillions of life forms over billions of years, all of which happened by chance as all the building blocks were at the right place at the right time. Despite its insignificance, this Pale Blue Dot is the only known world (out of thousands we identified) that is home to life!

While the atmosphere and oceans were created on the surface of the Earth in the first 800 million years of its creation, something else was happening deep inside the Earth, something that helped sustain all that was created on the surface. Let us dig deeper into it in the next post.

How was today’s post?

If you liked it, please hit the Like button at the bottom and share it with a friend. Also, please Subscribe to AlterEarth if you haven’t already. Have a great day!

Here are the references that I used for figures and guidance while writing this piece.

References:

1. https://science.nasa.gov/sun/facts/

2. https://www.space.com/35151-supernova-trigger-solar-system-formation.html

3. https://science.nasa.gov/resource/the-milky-way-galaxy/

4. https://www.britannica.com/place/Earth/Accretion-of-the-early-Earth

5. https://science.nasa.gov/earth/facts/

6. https://www.universetoday.com/articles/the-moon-might-be-one-large-chunk-that-was-blasted-off-the-earth-billions-of-years-ago#:~:text=The%20widely%2Daccepted%20view%20is,between%20Earth%20and%20its%20Moon.

7. https://www.britannica.com/science/evolution-of-the-atmosphere-1703862

8. https://www.britannica.com/science/geologic-history-of-Earth/Development-of-the-atmosphere-and-oceans

9. https://oceanservice.noaa.gov/facts/why_oceans.html

10. https://science.nasa.gov/solar-system/comets/nasa-led-team-links-comet-water-to-earths-oceans/

11. https://www.abc.net.au/news/science/2020-08-28/where-did-earths-water-come-from/12598198

12. https://science.nasa.gov/mission/voyager/voyager-1s-pale-blue-dot/

The origin of elements

The Big Bang (Oh, it was silent by the way)

About 13.8 billion years ago, the Big Bang emitted gigantic amounts of subatomic matter, which then formed protons, neutrons and electrons that are the building blocks of all elements. As the universe expanded and cooled from its incredibly hot and dense state, conditions were perfect for the first, simplest elements to form: Hydrogen (H), the most common, Helium (He), the second simplest, and a tiny bit (on a cosmic scale) of Lithium (Li).

Nearly 200 million years later, vast clouds of Hydrogen and Helium got close to each other due to gravity until it got hot and dense enough to initiate nuclear fusion, creating the first stars. The stars that succeed in achieving nuclear fusion of Hydrogen enter their main sequence: proton-proton (p-p) chain, where Hydrogen fuses to make Helium. This process of creating new elements by fusion is called nucleosynthesis.

Ongoing nuclear fusion increases the temperature at the core of a star as it emits immense energy in the form of heat and light. When the core increases to a temperature of around 14-15 million Kelvin (human body is around 310 Kelvin), multiple Helium atoms undergo fusion and create Carbon (C), which subsequently creates Nitrogen (N) and Oxygen (O) by fusing with Hydrogen (Helium is also one of the by products) in what is known as the CNO cycle (Figure 2).

Simply put, fusion of lighter elements emits immense energy, increasing the temperature of the star, which creates a suitable environment to fuse heavier elements (need hotter temperatures (more kinetic energy) to overcome the electrostatic repulsion of combining the positively charged nuclei of elements).

Beyond the CNO cycle, based on the size of the stars (bigger stars can make heavier elements), further nucleosynthesis occurs through fusion of Carbon, Neon (Ne) and heavier elements, and it continues until Iron (Fe) is formed in the core of the star, which does not emit energy, but needs energy to undergo fusion. When a large star (more than 8 times the mass of the Sun) can no longer undergo fusion, its structure is similar to that of an onion, where it has the heaviest element (Iron) in the center and layers of lighter elements all the way up until Hydrogen at its surface (Figure 3). At this stage, due to intense gravity, the core implodes and the outer layers of the star are ejected into space in a colossal supernova explosion.

The supernova hurls out most of the elements that were created in the star into the outer space in enormously huge quantities at extremely high speeds. Here are some observations by NASA’s Chandra X-ray observatory of the Cassiopeia A (Cas A) supernova remnant located about 11,000 light years from Earth.

Cas A has dispersed about 10,000 Earth masses worth of sulfur alone, and about 20,000 Earth masses of silicon. The iron in Cas A has the mass of about 70,000 times that of the Earth, and astronomers detect a whopping one million Earth masses worth of oxygen being ejected into space from Cas A, equivalent to about three times the mass of the Sun.

To understand the scale, the mass of our Earth is 5.972 × 10²⁴ kg (nearly 6 followed by 24 zeros), and that of our Sun is 1.989 x 10³⁰ kg. Now, that amount of matter from the quote is expelled from just one exploding star! When these elements are emitted out in the supernova, they tend to create elements heavier than Iron, until maybe Zirconium (Zr) or Niobium (Nb) through a process called neutron capture (nuclei of elements tend to capture neutrons into them under high speeds and suitable conditions to form heavier elements).

As the outer elements are ejected into space during a supernova, the collapsed core turns into a neutron star (around 20 kilometers in width and weighing as much as our Sun). And when neutron stars in a binary system (two stars revolving around each other) lose their orbital energy, they collide into another one. And this collision of tiny giants, is the primary source of the heaviest stable elements in the universe (Figure 4).

Cosmic dust, planetesimals and planets

A supernova explosion is extremely hot and the ejected material, which is initially in a gaseous state, cools down and condenses into solid with time as it drifts away. The atoms of heavier elements stick together as they cool down and form cosmic dust (10 nanometers – 100 micrometers in diameter) that floats around space. Silicates (compounds of Silicon and Oxygen), and carbon are some components of the cosmic dust. This dust, being very cold and sticky, has the tendency to attract other elements floating around. When a bunch of elements come together on this dust, cosmic rays act as catalysts to break and create bonds between different elements to form compounds like water, methane, carbon monoxide, etc.

Vast amounts of cosmic dust, comprising a wide range of elements and compounds that just keep floating around in space without a care in the world, get dragged into the gravitational field of a newly born star and suddenly start revolving around it in extreme speeds. As they keep revolving, they bump into each other and coalesce (two or more entities merging to become one) into larger bodies called planetesimals (~1 km – hundreds of km in diameter), which, in turn, collide and merge to form planets (thousands to hundreds of thousands km in diameter).

As we reach the end of the first post, take a moment to cherish the fact that almost everything inside and around us that is made up of elements other than the primordial Hydrogen, Helium and traces of Lithium from the Big Bang, was created inside of or as a result of stars in processes spanning billions of years! And yes, almost all the Hydrogen present in the water of all our bodies is the same one from nearly 13.8 billion years ago.

In the next post, let us zoom into a more lively part of our vast universe, something that is near and dear to us.

How was today’s post?

If you liked it, please hit the Like button at the bottom and share it with a friend. Also, please Subscribe to AlterEarth if you haven’t already. Have a great day!

Here are the references that I used for figures and guidance while writing this piece.

References:

1. https://www.themarginalian.org/2012/11/15/the-birth-of-sound/

2. https://science.nasa.gov/universe/overview/

3. https://scienceready.com.au/pages/energy-source-of-stars?srsltid=AfmBOoqCPyanxhBDPj1bU5U5QbbamBoWaYm-udmX4Vqo4yoAQEeiKAgM

4. https://mcdonaldinstitute.ca/astroparticle-physics-news/borexino-cno-neutrinos/

5. https://arxiv.org/abs/1406.3462

6. https://science.nasa.gov/universe/stars/types/#:~:text=Main%20sequence%20stars%20make%20up,millions%20to%20billions%20of%20years.

7. https://ned.ipac.caltech.edu/level5/Sept16/Rauscher/Rauscher4.html

8. https://chandra.harvard.edu/elements/

9. https://chandra.harvard.edu/chemistry/

10. https://www.tandfonline.com/doi/pdf/10.1080/00223131.2002.10875153

11. https://www.sun.org/encyclopedia/supernova#:~:text=Core%20collapse%20happens%20when%20at,they%20have%20a%20companion%20star.

12. https://imagine.gsfc.nasa.gov/science/objects/neutron_stars1.html

13. https://cassaca.org/en/uncategorized-en/2024/02/researchers-discover-cosmic-dust-storms-from-a-type-ia-supernova/

This is a newsletter that sheds light on understanding Earth system processes, climate change, renewable energy, sustainability and allied topics.

Who I am

My name is Sri Kalyan Tangirala. I am a graduate of Geophysics and a PhD student working on Geothermal energy. If you do not know me, do check out my LinkedIn profile to know more. Here are a couple of my old works:

Global Warming is a Humble Warning!

Geothermal Energy: The long lost hero of Indian Renewable Energy

About AlterEarth

AlterEarth is a platform that presents highly-researched, concise and thought-provoking narratives of the Earth and various elements constituting it.

For us to think of potential solutions and courses of action for mitigating climate change, it is important to truly understand the Earth. The posts would be segregated into six elements- air, fire (or heat), water, Earth (land), plants and humans. Through this process, I also intend to cover stories of individuals and companies who are actively contributing to solving the problems we currently face.

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