Volcanologists warn of the danger of shallow reservoirs of magma

Volcanologists warn of the danger of shallow reservoirs of magma
Volcanologists warn of the danger of shallow reservoirs of magma

Shallow and small magma reservoirs are rarely seen on seismographic surveys, but they can determine the activity of volcanoes.


Predicting volcanic eruptions, analyzing and modeling activity - all this is largely based on knowledge of where magma reservoirs are located beneath them, what shape, size and temperature they have. Such hollow chambers filled with molten lava are detected by seismography methods, registering small changes in the speed of propagation of vibrations through solid and liquid layers.

Unfortunately, this approach does not allow finding magma chambers that are too close to the surface. For example, when at the end of the 2000s, the Iceland Deep Drilling Project members were drilling in the active volcanic Krabla caldera, magma suddenly began to flow into the well already at a depth of 2.1 kilometers - from a reservoir that is quite shallow and turned out to be a big surprise for geologists.

It was assumed to be relatively "fresh" lava from a temporary magma pocket. However, new work by geologists at the University of Montreal has shown that this is not the case. The shallow magma turned out to be the same that erupted on Krable centuries ago - and this is "bad news", as scientists write about in an article published in the journal Geology.

Shane Rooyakkers and her colleagues compared the composition of this magma with samples of volcanic glass, solidified lava left over from the 1724 Krabla eruption (in the photo above, the glass is visible as a brown ring around the central crater). They turned out to be identical, which means that the same magma pocket has been feeding the eruptions for many years, although it was noticed almost by accident. The authors believe that such shallow, relatively small reservoirs may be much wider than believed and play a significant role in volcanic activity.

They are able to set not only its pace, but also its shape: for example, basaltic magma tends to erupt in a slow stream, without accumulating pressure, which leads to an explosion. This usually happens on Crable. At the same time, the shallow hidden reservoir contains rhyolite magma, the presence of which, on the contrary, is often associated with explosive eruptions. Without making sure that we have identified all the hidden magma reservoirs and their composition, predicting the activity of a volcano is much more difficult.

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