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Science Journey: "Snowballs in the Desert: Studying Climate Transitions in Earth's Deep Past"

Dustin Morris, Graduate Student in Geology

This video premiered on Friday, January 15, 2021.


How does Earth’s climate really work? Why does the climate change, and what does CO2 have to do with it? What are the extreme limits of Earth’s climate?

This program includes a discussion of how geologists unravel the climate history of our planet and how that helps us respond to climate change today.

In this video, Caltech graduate student Dustin Morris explains how Earth's climate functions and how it was pushed to the extreme millions of years ago during a time known as "Snowball Earth."

Q&A with Dustin

I'ts hard to give an exact number of years, but research from modern climate scientists suggests that we need to make fundamental changes to our energy system by 2030 to avoid the worst effects of climate change.

Generally, we need to cut back on the burning of fossil fuels and switch our energy production to renewables like solar and wind power. But there are also ways to draw out and sequester carbon from the atmosphere, the most low-cost and low-tech way being to just plant lots of trees! The reforestation (with proper maintenance) pulls carbon from the atmosphere and stores it as biomass in the form of trees. Though relatively short-term storage by geologic standards, it could make a big difference for combatting current climate change.

It does via volcanic eruptions and the silicate weathering cycle I mention in the talk. Also, many of the fossil fuels that we are burning are themselves buried in rocks.

Increasing the greenhouse gas concentrations will generally cause warming of the climate.

They are similar ideas. The "Ice Ages" that we usually think about (with saber tooth tigers and mammoths) involve a series of large scale glaciations that have fluctuated over the last ~400,000 years. They involved a lot of ice over much of the high latitude continents, however the ice sheets never made it down to the equatorials. Snowball Earth is a similar but much more extreme event were ice sheets entirely covered the continents and sea ice covered most if not all the oceans.

Climate change might affect plate tectonics in some minor ways, but not substantially .

Rocks are cool and all around us! Plus, I like going outside for my job.

I've been doing this project of Earth's ancient climate now for my three and a half years of graduate school. I also did a somewhat similar project over my last year of college for my senior thesis.

Carbon dioxide (CO2) and methane do absorb/scatter infrared light very efficiently, due to their molecular rotational and vibrational energy transitions. And if greenhouse gas concentrations continue to rise then average global temperatures will continue to rise as well. Hence the importance to reduce our greenhouse gas emissions.

FULL QUESTION: Regarding the causative agents for past "Snowball Earth Events" and recovery from them, I would think there must be an interplay between Milankovitch cycles, plate tectonic events (for instance, latitudinal locations of land masses, resultant ocean current patterns, prevalence or absence of large igneous province events, erosion and resultant effect on oceanic and atmospheric geochemical cycles), biotic evolution (especially oxygen levels) and probably significant factors I've not mentioned. Is there a "common denominator?"

There is certainly an interplay between all these factors for causing Snowball Earth events. I would say our current thought is that the positioning of continents and large igneous province events (for weathering and albedo) are the main driving forces for triggering the Snowball Earth events during the Neoproterozoic (the age my rocks are). But biotic evolution is potentially an important factor as well, and is seen as the main driving force for the Great Oxidation Event (GOE) Snowball Earth periods during the Paleoproterozoic.

Volcanoes! They keep pumping out CO2 to warm the Earth when everything else was covered in ice.

Great question! We do fly to get to Namibia, thankfully we are able keep most of the equipment (like rock hammers) in our checked baggage where they don't raise any issues.

I didn't give an exact number because it is still a hotly debated topic. Just the melting of all the ice probably took about 2–10 thousand years. However, the lingering after effects of the climate transition likely lasted tens of thousands to hundreds of thousands of years.

About the Speaker

picture of child in blue windbreaker standing on rocks
Dustin Morris, then

Dustin Morris a PhD candidate in geology at Caltech, where he uses the rock record to study extreme changes in Earth's past climate. Our planet's climate is dynamic, having changed in various ways throughout its long history. By studying these past climate changes, Dustin hopes we can better understand Earth's climate overall, along with its impact on sea level and the evolution of life. Hopefully this work can help us better understand and tackle our current climate crisis caused by human activity. To conduct this work, Dustin travels to Namibia to study the sedimentary rocks that record the end of the Snowball Earth event, one of the most extreme climate transitions in Earth's history.

Beyond research, Dustin works to teach others the wonders of Earth history and geology with various outreach events in order to help spark curiosity and to build an inclusive and diverse community within the sciences. He relishes exploring of all kinds, loves to travel, and finds adventures in the outdoors, as well as in fantasy worlds by reading novels and playing tabletop role-playing games.

About the Series

Science Journeys online programs are recommended for grades 8 and up, but everyone is welcome to attend. All events are held on Friday mornings at 10:00 a.m. Pacific Time.

Programs are FREE through the generosity of the Friends of Beckman Auditorium, but reservations are required.

If you have questions, please email Mary Herrera at mhh@caltech.edu.

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