Ongoing eruption of Tungurahua volcano

Juliet Biggs

Tungurahua volcano, Ecuador, has been continuously erupting since 1999, sending hot ash and mud flows down towards the town of Banos with its hydroelectric plant and key transport links. We use satellite radar images to look for small amounts of surface movement caused by the magma moving underground and compare our measurements to other indicators used in volcano monitoring, such as seismicity, gas emission, and estimates of the volume of erupted material.

The eruption of February 2008 was preceded by several months of high seismicity – lots of small earthquakes and explosions which mark the build up of pressure beneath the volcano. Eventually, over one million cubic metres of ash and other volcanic material was erupted, enough to fill Wembley stadium.  Usually we might expect to see the ground subside during an eruption, since the pressure in the underground chamber drops as the magma escapes. At Tungurahua however, the ground moved upwards by nearly 20 cm during the eruption; we estimate that this represents another one million cubic metres of magma being forced into the volcanic edifice. So the volcano grew in two ways – through ash falling on the outside, and new magma being added on the inside.

There are several ways to estimate the size of an eruption, but the volume of material is a convenient measure. Modern eruptions can then be compared to earlier eruptions by looking at the volume of erupted products preserved in the surrounding rocks. This study shows that the total volume of magma movement during an eruption may be many times larger than that which erupts at the surface. Although this particular batch of magma did not make it to the surface, its fate remains uncertain: will it cool and solidify or is it lurking temporarily, just waiting for another opportunity to erupt?

Click on image to see more detail.

Figure 1: Tungurahua volcano grows during recent eruptions. Upper image: Photograph of eruptions in January 2010. Lower Image: Radar interferogram of Tungurahua spanning the eruption in January 2008 from the Japanese satellite ALOS. Each colour cycle (fringe) represents 2.8 cm of motion towards the satellite, and shows magma being injected inside the volcanic edifice.

Reference

Biggs, J., P. Mothes, M. Ruiz, F. Amelung, T.H. Dixon, S. Baker, and S.-H. Hong (2010), Stratovolcano growth by co-eruptive intrusion: 2008 eruption of Tungurahua, Ecuador., Geophys. Res. Lett., doi:10.1029/2010GL044942 [PDF]