The 1840 Ahora earthquake occurred on 2 July at 16:00 local time, affecting Ağrı Province in the Eastern Anatolia Region of present-day Turkey.

The earthquake had an epicenter near Mount Ararat, where it triggered an eruption and caused a landslide that destroyed villages.

Earthquake catalogs place the surface-wave magnitude at Ms  7.4 and maximum Modified Mercalli intensity scale assigned IX (Violent).

Being at the junction of three tectonic plates, the region is prone to large shallow earthquakes, mainly of the strike-slip and thrust mechanism.

[7] Cities including Etchmiadzin, Yerevan, Garni, Van, Tbilisi, Tabriz and Gyumri were damaged.

[5] A Bandai-style phreatic eruption was triggered, melting the glacier on the summit, resulting in a lahar that buried villages.

It generated a pyroclastic flow from fissure vents along the upper northern flank of the volcano.

[3] A large landslide occurred on the northeastern flank of the volcano, forming the Ahora Gorge.

[3] In 2006, an academic study estimated 3 × 108 m3 of volcanic material and glacial melt flowed down the gorge at 175 m (574 ft) per second.

[10] The landslide consisted of blue liquid mud and large stones which traveled at high speed.

[3] An aftershock on 6 July caused a dam breach, releasing accumulated debris up to 21 km (13 mi) away.