Ancient earth in a drop of rain

Goldblatt (left) and Kavanagh (right)Undergrad's research yields big results for climate science

How much history can be found in one raindrop? According to UVic alumnus Lucas Kavanagh, raindrop imprints—the craters created when raindrops impact earth—can teach us a lot about ancient earth, evolution, and could even inform future space exploration. 

With the help of his supervisor, School of Earth and Ocean Sciences Assistant Professor Colin Goldblatt, Kavanagh’s Honours undergraduate research project looked at the size of craters created by raindrops as an indicator of atmospheric density. He compared raindrop imprints in present day Victoria with ancient fossilized imprints in South Africa. 

“First and foremost, knowing more about the early earth atmospheric conditions gives a better picture of the world in which life first evolved and how this world stayed warm despite a fainter sun at the time,” says Kavanagh. “This knowledge helps us understand how our atmosphere has evolved physically since then, through major compositional changes such as the introduction of oxygen. It also widens the scope for what we consider to be a ‘habitable’ world when searching for new planets outside of our solar system.” 

His work drew on a theory by Charles Lyell who, in 1851, suggested that raindrop speed was limited by atmospheric density—the less dense the atmosphere, the faster the raindrop and the larger the crater formed by that raindrop. With this, in 2012 a team from the University of Washington used fossilized raindrop imprints to posit that the early earth’s atmospheric density was not very different from that of today. 

Kavanagh tested this theory by dropping water into a tray of sand from a point more than 12 meters up the stairway in the Bob Wright Centre, and comparing the resulting craters with those created in a similar process on the beach at Cadboro Bay as well as ancient fossilized raindrop craters. His results showed that ancient atmospheric density was, in fact, no more than ten times that of today. 

His research was published in Earth and Planetary Science Letters, quite a feat for an undergraduate research project. 

“Lucas was an obvious choice for this Honours research project,” says Goldblatt. “He had taken a 200-level course on Earth System Evolution with me and was one of the top students.” 

Goldblatt’s research program is on the evolution of the Earth’s atmosphere—understanding how the climate and composition of the atmosphere have evolved together with life and geology of Earth. “Lucas’s project directly complements work done by other students in the group, including projects on the amount of nitrogen in the earth’s atmosphere, early earth greenhouse gasses, and the energy balance of Earth’s tropics,” says Goldblatt. 

Kavanagh’s research was made possible through funds provided by the Jamie Cassels Undergraduate Research Awards. The awards are designed to provide support for exceptional undergraduate students who might otherwise not be able to obtain a direct research experience as a part of their undergraduate degrees. As Kavanagh puts it, “the program is an excellent way of introducing undergraduate students to research, by providing a relatively accessible source of funding.” 

Now an MSc student at McGill University, Kavanagh has shifted his focus from the ancient skies to the modern oceans. “I’m using records of ocean chemistry from sediment cores to examine the role of fish in controlling the cycling carbon and nutrients,” he says. “While my focus has shifted slightly, my decision to do a research-based masters degree was a direct result of my undergraduate research experience at UVic and the encouragement I received from a number of professors in the School of Earth and Ocean Sciences.”