In April 1815, Mount Tambora on the Indonesian island of Sumbawa suffered a catastrophic VEI-7 eruption, ranking as the most powerful volcanic event in recorded human history. The eruption ejected an estimated 100 cubic kilometers of material into the atmosphere, including massive quantities of sulfur dioxide gas. Reaching the stratosphere, this sulfur dioxide oxidized to form persistent sulfate aerosols that spread globally within months.
These aerosol layers reflected incoming solar radiation back into space, driving a global cooling effect known as volcanic forcing. By the spring and summer of 1816, often remembered as 'The Year Without a Summer,' the northern hemisphere experienced severe atmospheric disruptions. In New England, atmospheric circulation anomalies destabilized the jet stream, pulling arctic air masses deep into the northeastern United States.
This caused unprecedented unseasonal late spring and mid-summer severe frosts. Snow fell in Massachusetts in June, and ice froze ponds in July. The localized repeat frosts repeatedly destroyed emerging corn, rye, and vegetable crops across Vermont, New Hampshire, and Maine.
The resulting localized famine accelerated the historical western migration from New England into the Midwest.