Yes! Our Earth is the third big rock from the Sun and no, we are not talking about E.T in this article. We are going to talk about something that is usually perceived to be boring- GEOLOGY (A science that deals with the history of the earth as recorded in rocks).
Folks, you wil be surprised to learn that, deep in the forests of Odisha near Champua, in Keonjhar district, a 4.2 billion year old rock has been discovered. Yes, that makes it the second oldest rock found on planet Earth. The oldest rock, which is 4.4 billion years old, was found in Western Australia. Just to give you an idea of how old it is – the moon (which you look up to and sing paeans to) is just 4 billion years!
A team of researchers, led by Dr. Rajat Mazumder from the Curtin University along with Ms. Trisrota Chaudhuri, a research scholar from CSIR who have been on the prowl, sifting through layers of rock since 2009, finally hit pay dirt.
The rock tells us a lot about the formation of the Earth and it’s terra firma. It also provides interesting insights about the formation of our world and other planets. No, wait! We are not talking about building the ‘Death Star’, but yes, the study of such ancient rocks gives mankind the hope of finding inhabitable planets in other galaxies.
Team ‘Coffee Bytes’ is delighted with the opportunity to learn more from Dr. Rajat Mazumder about his team’s sensational discovery, while taking our readers back and forth in time through our time machine. So strap on your seat belts as we zoom back in time by 13 billion years.
The Universe forms after the ‘Big Bang’ and temperatures are extremely hot and its total chaos everywhere amidst gas clouds – hot soup of particles which takes around 2 million years to cool. The Universe, as we know it, begins to take shape. It’s now cool enough for atoms to form and stars and planets later on. Ok, this is where it gets too hot to handle so let’s forward in time to roughly 7 billion years. We see in our solar system, a young star called the Sun. The Earth starts to form as gravity plays around, clouds of dust and debris start to turn into a huge ball of swirling hot debris, rapidly cooling as it takes the orbit around the Sun. Gravity collapses the material in itself, as it begins to spin, forming the sun at the center of the nebula.
With the rise of the sun, the remaining material begins to clump up, just like in the climax of the movie ‘Teenage Mutant Ninja Turtles’. Small particles draw together, bound by the force of gravity, into larger particles. The solar wind sweeps away lighter elements, such as hydrogen and helium, from the closer regions, leaving only heavy, rocky material to create smaller terrestrial worlds like Earth and Mars. But farther away, the solar winds have less impact on lighter elements, allowing them to coalesce into gas giants. Asteroids, comets, planets, and moons were thus created.
Earth’s rocky core formed first, with heavy elements colliding and binding together. Dense material sank to the center, while the lighter material created the crust. The planet’s magnetic field probably formed around this time. Gravity captured some of the gases that made up the planet’s early atmosphere.
Sometime around this age the Earth suffered an impact by a large body that catapulted pieces of the young planet’s mantle into space. Gravity caused many of these pieces to draw together and form the moon, which took up the orbit around its creator.
Incoming message- Dr. Mazumder – “Hi guys hope you are enjoying the formation of planet earth?”
Hey! Dr. Mazumder we are pretty good, but I tell you the moon almost did us in. Had the impact been slightly bigger, we would have been done for.
Well guys, I told you that’s why study of geology is necessary for it gives us an idea of how our Universe gets formed and even destroyed. Elements like Zircon are like a snapshot of space and time which record these events through which we can analyze how the planet had formed.
So, doc tell us. Why are you interested in research and analysis on the oldest rocks in India? What was the motivation behind this research?
India, is one of those few countries in the world that bear rocks that can be decoded to gain insights into the early earth processes. This is extremely important at the moment because such old rocks are being used as a yardstick to infer on other planetary processes, including the search for life in Mars and other planets. Unlike countries like Australia, Canada, Brazil and China, where very old rocks are well known and active scientific investigation is being undertaken in the last two decades, scientists in India are somewhat reluctant. Although the Indian Government is spending a lot of money in Astrophysical and Space research over the years, research on oldest rocks of India are underfocused and in a rudimentary stage.
What is the age of the oldest rock in India? And give us a background on the present research done by your team?
A team of geoscientists from the Presidency College (now the Presidency University) Kolkata, reported about 3.8 Billion year old crustal rocks from eastern India, using the Samarium–Neodymium Isotopic analysis. Their research was published in the SCIENCE Magazine in 1981. Professor Asish Ranjan Basu (now at University of Texas, Arlington), was the lead author of the paper who analysed the samples collected by Late Prof Ajit K. Saha and his associates. A group of geoscientists from the University of Oxford, UK (led by Prof. S. Moorbath) strongly criticised their calculations and felt that the age should be around 3.3 billion years. Subsequently, a team of researchers from the Physical Research Laboratory, Ahmedabad (lead by Prof. J. N. Goswami) and Presidency College (Late Prof. Saha and his associates) reported a 3.5 billion year old mineral Zircon from metamorphosed sedimentary rocks (called detrital Zircon) of eastern India (near the town Champua, Odisha). The research paper appeared in Current Science (published by the Indian Academy of Science) in 1995 and the detailed paper appeared in the Elsevier Journal Precambrian Research in 1999. Then, researchers reported up to 3.6 billion year old Zircons from India. Since then, pockets in Odisha have been found to contain very old rocks.
What drove you guys to make this discovery?
I had keen interest in early earth geological processes since my college days. I read the research papers and had a strong desire to find the oldest rock from India. I undertook field work in parts of Odisha and Bihar (now Jharkhand) in late eighties till the early nineties on many occasions, when I was a student of the Durgapur Government College and subsequently, as part of my Postgraduate geological excursions. I started working on those rocks again when I joined the Indian Statistical Institute in 2006. I also convened one, UNESCO-IGCP funded International Conference and Field workshop in 2009 and collected samples to find the oldest rocks and minerals. Ms. Trisrota Chaudhuri, a CSIR Research Scholar, joined me and together we undertook several field trips in parts of Odisha, where we located potential rocks, sampled and examined them under Microscope at the Geological Laboratories of the Indian Statistical Institute, Kolkata.
Meanwhile, back on the time machine, we are seeing something happening. The flow of the mantle beneath the crust is causing plate tectonics, the movement of the large plates of rock on the surface of the Earth. Their collisions and friction gives rise to the first mountains and volcanoes, which begin to spew gases into the atmosphere, slowly forming our atmosphere.
Although the population of comets and asteroids passing through the inner solar system is sparse today, they were more abundant when the planets and sun were young. Collisions from these icy bodies deposited much of the Earth’s water on its surface. Yep folks, that’s how we got most of our water which is the real ET and nobody wants to talk about it because we take it for granted!
The water forms because the planet is in the Goldilocks zone, a region where liquid water neither freezes nor evaporates but can remain as liquid. Hence, water remained at the surface, which many scientists think played a key role in the development of life.
Ok, time to go a little further up to the point where the first super continent was formed. Activate time jump!! Oops! seems it is going to take sometime for the time drive to kick in. Meanwhile, let’s shoot another question to Dr. Rajat Mazumder.
So doctor, can you date rocks just by looking at them? Or do you need microscopes to date them precisely?
See guys, dating rocks by looking at them or taking their samples is the first step. Peering through the microscope and magnifying their texture gives us a fair idea of how the rock was formed- through volcanic eruption or plate tectonic movement or if it was a part of an asteroid which probably seeded water or some other element on planet Earth. But for dating we need specialized equipment like the SHRIMP (Sensitive High Resolution Ion Microprobe), a machine which does isotopic analysis. Sadly, this machine is not available in India. So, in the meantime, I went to Western Australia, to pursue my research in early earth geology. It is here that we got in touch with Dr. Yusheng Wan, a Senior Researcher at the Beijing SHRIMP Center, the Chinese Academy of Geological Sciences, Beijing. He kindly agreed to analyze only four samples, on collaboration basis, as I had no research fund to get the analysis done on payment basis. Dr. Yusheng confirmed our speculation about the oldest rocks (The Keonjhar samples) and the results confirmed the presence of two Zircon grains which were 4240 and 4030 million years old respectively.
Back in our time machine, we have made an erroneous jump and have reached a point where we see the super continent ‘Pangea’ has started to break up due to plate tectonics and the Indian sub-continent starts to move away from Africa and Madagascar going up and finally colliding with Asia. This entire process takes place around 175 million years prior to present day. Meanwhile the first oceans of the Earth have formed and we have taken a huge leap in the evolution of life right from single cellular organisms to complex creatures and even some ancestors of animals which we see today. India travels through the next 61 million years and hits the Asian continent, the impact creates what we call today, the Himalayas.
Doctor, a rock is a rock, how does it differ? Is there anything unique in the oldest rocks in India and how do Zircons play a role in identifying the age?
The age of the Earth, derived from meteoritic record is 4.568 billion years, while the oldest age recorded from rocks on Earth is 4.4 billion years which is the age of a zircon grain. You see Zircon, is a very robust mineral that can be used to date its parent rock because of the radioactive Uranium found inside it. Even if the original rock is now non-existent or reworked, analysis of Zircon provides us the correct age regardless of the changes the rock sample has gone through. The oldest 4.4 billion year old zircon was discovered from a small exposure of metamorphosed sedimentary rock (reworked Zircon known as detrital Zircon) at Jack Hill, Western Australia. Zircons are the only representatives of rocks older than 4 billion years and are extremely rare.
In contrast to the 4.4 billion year Australian Zircon, the 4.240 billion year Indian Zircon is magmatic (i.e. directly derived from magma and not reworked like detrital zircon occurring within sedimentary rocks). The other magmatic zircon reported from Canada is 4.200 billion years old and those from China and Brazil are between 4-4.1 billion years. Therefore, the Indian Zircon is the oldest magmatic Zircon on earth!
Woah! So this rock found in Keonjhar is the oldest magmatic Zircon on Earth. So what does it tell us about the Earth at that time?
The 4.240 billion year old rock comes from the Hadean age; 4000-4500 Million years- Indian Zircon crystallized from a silica rich felsic magma of granitic composition; the magma was produced deep within the mantle by melting of mafic (iron and magnesium-rich) rock. The hadean Indian Zircon occurs as a fragment (Xenocryst) within a younger granitic rock (TTG) which is ~3400 million years old. Actually the ~3400 million year old, during its upward migration to the surface, incorporated much older zircon that was present within Hadean rock of granitic composition.
According to our research with the Chinese team, shortly after accretion of the Earth at ~4.570 billion years ago, a global magma ocean was formed. Study of these zircons reveal that the Earth’s primitive crust was mafic in composition that crystallized from this magma ocean during the Hadean age i.e. ~4.5 billion years ago. Apart from Uranium-Lead dating, radiogenic Hafnium isotopic analysis of these zircons indicate that the Earth’s mantle was compositionally heterogeneous at that time. They also indicate that this primordial crust later re-melted to produce the oldest felsic rocks with ~4.240-4.030 billion years old zircon grains that are preserved till today even though the original rocks are now reworked.
Which simply means, that this Zircon element present in our Keonjhar sample was first formed 4.5 billion years ago and then re-melted around 4.2 billion years ago to form what we see today. It provides us immense information about how our land that we see today was formed and how plate tectonics on our planet has worked and explains a lot about the continental drifts since the Earth’s formation.
Okay, it seems our time machine is experiencing a technical problem (we apparently have found some dahi bara and sev in our fuel pod), so we are going back to the present day. As we step out of our time machine we can concur one thing. The study of Geology provides a window about the formation of our Earth and other planetary bodies. It tells us how we as human beings can become a ‘Type-2’ civilization by harnessing this knowledge to create a new land which can help us colonize other worlds and also learn to harness minerals more effectively, as a shorter goal. A science which explains to us how life was formed on planet Earth through the fossils found in the rocks, it also tells us something very important- that we all are a part of the Universe and a grander scheme of things. So, people of Odisha, rejoice and celebrate! Technically our land is a locked hidden chest that contains the secrets of the Universe.
Our final question doctor.What next for you and your team?
We strongly believe that an indepth study of metamorphosed granite, called as Older Metamorphic Tonalitic Gneiss, will hopefully yield much older zircon grains. Fluid, mineral inclusion and oxygen isotope study of these zircons will add valuable information about the presence of water in the first few hundred million years of the Earth’s history. It may also reveal exactly when, Plate Tectonics began on early Earth to corroborate the speculation from the Jack Hill Zircons of Western Australia.
As pointed out earlier, The GoI Funding agencies (DST, CSIR and MOES) should fund early earth research like the developed countries. They should seriously think about installing SHRIMP machines in leading Research Laboratories- the Indian Institute of Science, Bangalore or IISER or at the Geological Survey of India and employ skilled researchers to operate the SHRIMP machine. They should also encourage International Research collaboration between Indian Universities and Research Institutes with SHRIMP Laboratories abroad, just in case installing SHRIMP is difficult. We strongly believe TTGs of Central India and South India will also provide valuable insights in to the early earth processes and researchers should study both, detrital as well as magmatic zircons. We are looking for an opportunity to visit leading Laboratories and Universities in India for research collaboration on very old rocks and Hadean Zircons embedded in those rocks to unlock the mysteries of early earth. It is an under focused, but highly promising research area in India.
So, next time when you gaze at the next rock or a hill, pause for a bit and wonder what secrets lie trapped inside its Zircons!
By Aditya Nag