Analysis of the gas emissions from volcanic activity in the East African Rift System using remote sensing over the past two decades

Abstract

Monitoring volcanic gas emissions is crucial for assessing volcanic hazards, as they vary across spatial and temporal scales more than most other natural hazards and have significant environmental impacts. They can directly affect climate change, which in turn poses challenges to human society and global sustainable development. Satellite remote sensing plays a pivotal role in monitoring and studying atmospheric gases, particularly in regions like the East African Rift System (EARS) that hosts large and active intra-continental rift-related volcanoes. These predominantly mafic volcanoes sit above a major mantle upwelling, which are contributing to the breakup of the East African continent. Volcanic activity in this region has been persistent since Tertiary. Recent advancements in satellite remote sensing technology have greatly enhanced our ability to monitor gas emissions from volcanoes across the globe. However, data on gas composition and emissions in the EARS remains limited. Therefore, the present study focuses on eight volcanoes, including Erta Ale, Alu Dalafilla, Manda Hararo, Fentale, Mount Longonot, Ol Doinyo Lengai (from the eastern branch of the EARS), and Mt. Nyiragongo and Nyamulagira (from the western branch of the EARS). At each volcano, we used data from the atmospheric infrared sounder (AIRS) to measure H₂O, CO, and CH₄ gases, along with the spatial and temporal variability of NO₂ and SO₂ gases from the Ozone Monitoring Instrument (OMI). This combined dataset offers the most comprehensive dataset of gas variations during EARS activity from 2004 to 2024, establishing a robust baseline for future monitoring efforts. To assess the vertical profile of volcanic gases in atmosphere above the EARS, we analyzed Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) lidar data from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission over a 12-month period from 2014 to 2024. June 2011 and January 2019 are selected as the representative months, reflecting periods of high and low gases anomalies, respectively. These analyses, which conducted for these months were evaluated using sea level pressure, geopotential height at 850 and 500 hPa, and meridional and zonal winds components, providing a detailed three-dimensional structure of volcanic gases over the EARS. These measurements can also support the development of effective policies to manage air pollution emissions from these volcanoes, which influence various aspects of human life and ecosystems in this region.