In early June, tiltmetre measurements had shown that the volcano was inflating.
This was due to the growing amounts of magma filling the reservoir beneath the summit.
Seismic activity shifted to shallow depths just below the summit.
On June 7th, the first magmatic eruptions took place with the formation of a lava dome at the summit of the volcano.
The dome grew quickly over the next five days, reaching a maximum diameter of about 200 m and a height of 40 m