Hot vs Cold - the asteroid against the snowball!
Welcome back to your one and only Science that Stuff! I know, I know I’ve had a long break since October but never fear, Palaeontology is here!
Recently, researchers at Curtin University have speculated the relationship between the Palaeoproterozoic Impact of Yarabubba and the Snowball Earth. They believe this impact, being the oldest impact on our planet at 2.229 billion years old, may have lifted the Earth from the wrath of the Snowball Earth, increasing the rate at which global warming occurs. Here, I will give you a brief summary of this research area and my own opinions on it and possible implications in the future.
These researchers say that “the age of the Yarabubba impact matches the demise of a series of ancient glaciations. After the impact, glacial deposits are absent in the fossil record for 400 million years…suggests that the large impact may have influenced global climate”. This implies that there is a possible connection between both the glacial melting and the infamous Yarrabubba impact, as the (lack of) evidence could suggest this here. Whether this theory is true or not, Earth scientists still believe that the impact could have sent a whopping 0.5 trillion tonnes of water vapour into the atmosphere. Now, with water vapour as one of the most abundant greenhouse gases, this would have had very drastic implications on the climate of the Earth, speeding up the greenhouse effect, moving closer and closer to global warming. This would eventually lead to the melting process of the glaciers over a 400-million-year period continuing into the Proterozoic period.
I think we could examine the link between the impact and the changes in the Earth’s polarity. To do this we can use Palaeomagnetism to distinguish changes or reversal in the polarity of the Earth. Some rocks record the direction and intensity of the polarity of the Earth’s magnetic field, which I think we can use to date the rocks back to Yarrabubba and see if there were any changes to the Earth’s magnetic field. Next, we could investigate the implications of asteroid impacts on this magnetic field and relate the three together. This could be done with Magnetostratigraphy, where we date sedimentary and volcanic activity by observing changes in magnetic signals over specific time periods.
We can calculate the date of the volcanic activity or sediment around the time of the Yarrabubba impact with Magnetostratigraphy or even the radiometric dating technique of Uranium-Lead, observing shock recrystallisation of zircon and monazite minerals. This allows us to assume that this major impact triggered the expansion of magma chambers and very explosive volcanic activity to occur. This grants us to calculate the date of the sediment with the methods stated above and see if they correlate with the polarity reversal with Palaeomagnetism. Then we can use this information to predict whether the impact correlated with the reversal of the polarity and relate this to the change in climate.
In addition to this, we can use Aeromagnetic surveys. This is a systematic geophysical survey that involves using a magnetometer on an aircraft to analyse the magnetic structure of the ground below it. This also detects changes in the magnetism, strength and direction of the strata below the aircraft. The magnetometer is mainly used to observe magnetic anomalies in the local geology. I think this could be used to recognise variations in the magnetic fields at the Yarrabubba site to illustrate and possibly prove the distortion and alteration of the Earth’s polarity from the impact 2.229 billion years ago.
So, we’ve predicted and measured the changes in the Earth’s polarity, what’s next?
I think we could use geochemistry to detect the levels of Oxygen, Carbon and their geochemical cycles to make assumptions about the state of the atmosphere at that time. Despite this, many say that a direct link between alterations in the Earth’s polarity and changes in climate is yet to be proven. However, some records have shown that the Yarabubba impact coincides with the glacial melting that occurred simultaneously. During the Proterozoic era, the atmosphere and the oceans became more oxygenated, allowing the local rocks deposited onto the Earths’ crust to record the existence of glacial deposits. However, earth scientists have found that records for a period of 400 million years are absent in this stratum, providing some evidence for the climate change occurring due to the Yarabubba asteroid impact.
These techniques could really help in the future as it may assist in the prediction of the severity of possible asteroid impacts, also allowing us to assess the knock-on effects due to it; enhanced global warming like Yarrabubba? Maybe even an extinction that mimics the Permian-Triassic extinction, wiping out 96% of life on Earth? This simply helps us to be more prepared for a similar scenario by understanding the geology of the Earth in new light and different perspectives, showing us how we will be affected by it.
Stay tuned for more of my thoughts and input on some of the latest scientific discoveries and news!
The Dinosaurs Rediscovered - Michael J Benton - Thames and Hudson - Published 2020 - Date of Access (17/02/20)