There are countless challenges facing humanity, but few people show the perseverance required to answer the most pressing questions. For Ella Xu (YC ’26), a double major in Earth and Planetary Sciences and Applied Mathematics, the drive to study Earth’s systems stems from a fascination with the invisible forces shaping our planet, from tectonic shifts beneath our feet to the gradual buildup of greenhouse gases in the atmosphere., Using quantitative tools such as statistical modeling and machine learning, she seeks to understand Earth’s dynamics in the face of climate change.
In the fall of her first year at Yale, Xu began conducting geophysics research in an earthquake lab with Maureen Long, the Bruce D. Alexander ’65 Professor of Earth and Planetary Sciences at Yale. By analyzing data from seismometers around the world, scientists can develop an idea of what different boundaries of the Earth look like based on comparing various wave types and the delay time in seismograms. Xu imaged the core mantle boundary of Earth by studying different seismic waves that travel through Earth’s mantle and liquid outer core. Such imaging provides rare glimpses into Earth’s inaccessible interior, offering clues about how heat and materials circulate between the mantle and core. Based on this experience, Xu felt encouraged to continue pursuing scientific research.
By her junior summer, Xu turned toward carbon dioxide removal and quickly immersed herself in the field. “I love how fast-paced climate technology is and how quickly the carbon dioxide removal industry is developing. Every day, there seems to be another twist, and it’s a great way for me to apply my skills,” Xu said.
This past summer, she interned at an enhanced rock weathering (ERW) company in the San Francisco Bay Area. ERW is a carbon removal technique that typically involves spreading crushed basalt, a naturally occurring volcanic rock, across farmland. As the basalt breaks down, it releases cations into the soil, sparking biogeochemical reactions that consume carbon dioxide to form bicarbonate, a stable compound similar to baking soda. Rainwater carries the bicarbonate from the soil to the ocean, where it eventually becomes locked away as calcium carbonate, the same material found in seashells and limestone. Beyond removing carbon, basalt improves soil health and crop yields.
The company emphasizes agricultural benefits alongside climate goals. “ERW helps us fight many issues relating to climate change and global warming, and the co-benefit is that it also helps farmers,” Xu said. “It acts as a replacement for traditional fertilizers such as lime, which can be difficult to access due to cost or infrastructure.” Working with a team, she used statistical analyses to quantify the amount of carbon ERW deployments removed from the atmosphere, drawing on soil samples from hubs nationwide. She now continues with the company part-time as a research and development associate.
For her senior thesis, Xu is working in the lab of Noah Planavsky, a professor of geochemistry at Yale University, where she is conducting uncertainty quantification on sampling techniques used in ERW, with an eye toward cost-effectiveness and commercial scaling. She is analyzing data from farms across the United States to evaluate these climate-friendly solutions and demonstrate their financial viability for larger companies.
At a senior research symposium last spring, Xu recalls Pincelli Hull, Associate Professor of Earth and Planetary Sciences at Yale, encouraging students to remain in science despite uncertainty. Hull told them that the world needs people willing to pursue knowledge even in difficult times. These words, Xu said, continue to guide her as she considers her future.
After graduation, Xu plans to continue working at her current ERW company for another year before pursuing a PhD in either earth systems science or environmental engineering. She hopes to further specialize in climate solutions, particularly carbon removal.
“I think the practice of chasing down questions that people don’t know the answers to is really important. At times, it can be difficult to keep up the motivation and the reason for going, but reminding yourself of your core values is crucial,” Xu said. She hopes to dedicate her life and career to advancing science and doing work that will benefit others and the world.