The frequency of explosive events continues at around 2-3 per day. The magnitude continues to be smaller than observed during some of the months earlier this year and during 2005. Ash dispersal has been minimal.
The highest continuous flux of SO2 since early 2003 was measured on 27 July, although the value is still relatively very low. A value of 20 - 38 t/d was measured from the Nevado station. The infrared camera recorded an increase in the temperatures of the northern fumaroles. The seismicity also has shown signs of an increase in terms of frequency of explosions and the number of small magnitude LP events. The indication from two different geochemical parameters, the thermal emission and the seismicity is that the activity is increasing with a possible ascent of a magma body within the system. It cannot be said to what depth. An increase in the boron concentration was also detected during July, with the highest values recorded since this monitoring began. This presents further evidence of magma ascent.
During June and early July the seismicity indicated that the activity had decreased since previous months in terms of magnitude and frequency of explosions. However, the indication of magmatic movement at some undetermined depth beneath the summit continued. Incandescence was not seen during our observations this period. The thermal emission remained stable. A large increase in the boron concentration at two of the three monitored springs was recorded during early June. If previous patterns are considered, this may indicate a rising magma body, which could reach the surface and result in a further period of dome growth and later lava flows. Further results of sampling will help to confirm the significance of this anomaly. We have been working to install a new infrasound and thermal monitoring station at a location close to the summit (1.5 km). Installation was carried out on 28 July and is now undergoing tests.
The activity remains relatively stable. The thermal emission of the fumaroles on the north rim has been fluctuating but not giving an apparent temperature above 35 °C. The seismicity changed a little in character during May with an increase in tremor and LP period events on some days. This development coincided with an increase in boron in the spring waters. This might be a reflection of some magma movement a bit higher in the system.
During a visit to the volcano a new pyroclastic flow deposit was discovered on the N flank. This was most likely to be a result of the explosion on 16 September 2005. Several explosions were also witnessed and ash samples collected from direct falls.
The activity remains stable. There has been an increase in the number of long-period events seen this month. This type of seismicity may indicate the movement of a magma body with the pressurization of a part of the system and subsequent decompression. The infrared camera showed a small increase in the fumarole temperatures during the previous month.
There are some indications of increased activity: increased magnitude of the explosions, more incandescence observed at night, increased temperature of the fumaroles. However, the activity still remains low when compared to the early part of 2005.
Small increase in magnitude of explosions. The readings from the infrared camera still indicate low fumarole temperatures. It is likely that the magma body remains at a deeper level within the system. Some minor ashfalls have been experienced in the city of Colima.