EARTH × CLIMATE

A Plateau Makes a Monsoon

~40 to 10 million years ago

Phanerozoic · Cenozoic · Paleogene · Eocene

India drove into Asia and pushed up a plateau the size of western Europe to five kilometres above the sea. In summer that surface heats far faster than the ocean beside it, and the air rising off it pulls wet ocean air inland behind it. Half the world's people now live under the rain that arrives that way.

Why it matters

Tectonics wrote a climate here, and the writing can be followed step by step: the mountains rose in three pulses, the wind system appeared, and the fresh rock exposed by the uplift began pulling carbon dioxide out of the air as it weathered. What no rock records is the birth of a wind, so which pulse started the monsoon comes out of climate models rather than out of the ground.

Dating & uncertainty

Three pulses of uplift are read from the rocks, around 40 to 35, 25 to 20 and 15 to 10 million years ago. No rock records the birth of a wind system, so which pulse started the monsoon, and how much the plateau counts against falling carbon dioxide, comes out of climate models rather than out of the ground.

Sources

1. Tada et al. (2016), Progress in Earth and Planetary Science · Evolution and variability of the Asian monsoon and its potential linkage with uplift of the Himalaya and Tibetan Plateau
2. Fu et al. (2022), CATENA · Tectonic and climatic forcing of chemical weathering intensity in the northeastern Tibetan Plateau since the middle Miocene
3. Hutchinson et al. (2021), Climate of the Past · The Eocene-Oligocene transition: a review of proxy data, models and comparisons

Earth history as one day

23:47:1812 min 41 s before midnight

if Earth’s 4.54 billion years were compressed into a single day