When India crashed into Asia around 45 million years ago, this CO2 factory—in operation for tens of millions of years—shuttered its doors and the volcanoes went quiet. As the collision pushed the Himalayas into the sky, these volcanic rocks and this newborn mountain range began to weather, drawing down CO2 even further. As with the creation of the Appalachians and the Ordovician ice age 400 million years prior, when the uplift and weathering of the Himalayas began, the long, slow decline to the modern ice age was set in motion.
