Sensor

Our senses constantly provide us with information about our surroundings, when we record these things we can start to identify patterns that help us understand processes.

Perret spent a lot of time observing volcanoes around the world exploring his own senses and what they could tell him about what was happening below the surface. His reports, photos, sketches and letters to collegues provide a detailed record of changes at the Soufriere Hills volcano on Montserrat in the 1930s. 

Click on the images to see the full archive entry and learn more about how Perret "sensed" at volcanoes!

Sight: 

Perret made use of photographs and sketches to record visual changes in the landscape as well as noting down critical observations such as changes to the colour of rocks on the ground and the presence / absence of water and vegetation in valleys. Perret was even able to identify changes in emmited gas concentrations by shining his torch light over fumeroles and observing the abundance of condensation in the beam. 

Sometimes, useful observations were even made by accident! For example, the thermometers Perret used to track temperature changes in the ground were made of brass. Over time, Perret noticed these brass instruments began to turn black as the metal reacted with gases coming out of the volcano. This reaction helped Perret to narrow down what type of gas was being released! 

These basic observations all helped Perret build a detailed picture of activity at the volcano, without expensive instruments and people on hand to maintain them. 

Feel / Touch:

Sometimes, earthqukes on Montserrat were large enough to be felt. These earthquakes often caused damage to buildings and were easily identified and recorded. However, not all earthquakes at volcanoes are so easily detected. Smaller earthquakes called "volcanic tremor" can indicate magma is moving through the ground so are important to capture / record. 

When Perret was staying on the flanks of Vesuvius in the early 1900's collecting data and monitoring the volcano, he often found himself waking in the night with no explanation. Curious as to whether he was being awoken by tiny earthquakes, Perret buried his brass bed posts in the ground so they would better conduct vibrations in the Earth. The next time he awoke, he bit down on the metal to feel the tiny vibrations of the volcanic tremor! 

Other volcanic phenomena can result in physical sensations....for example, some volcanic gases are toxic and cause irritation to the eyes, nose and throat. During his stay at the observation hut at Gages Soufriere on Montserrat, Perret was hospitalised twice due to over-exposure to volcanic gasses. 

He recounted his experiences to his colleague Arthur Day (see below) and subsequently returned with protective eyewear and decided that overnight stays in the hut were no longer safe! 

Sound: 

All sorts of volcanic phenomena produce sounds such as explosions, the clinkering sounds of solid blocks falling off lava domes and rumbling from earthquakes.  

Perret found innovative ways to amplify and utilize the sounds of the volcano in his monitoring efforts. 

Inspired by the burial of his bed posts on Vesuvius, Perret started burying a sound amplifying device (kind of like a trumpet!) in the ground with a microphone attached so he could listen to the sounds produced by vibrations of the earth associated with volcanic tremor. On Montserrat, he was even able to lay cable from the monitoring station so that someone could monitor the sounds remotely! 

Perret would also record the pitch of volcanic gas jets as they came out of fumaroles in the ground. Perret was sure that doing so would give insights into changes ocurring below the surface, changing the pressure at which gasses were forced above ground. Though this may seem an unusual technique it demonstrates Perret's creativity in his endeavour to record as much information as possible about the volcano, at a time when instrumentation was relatively unsophisticated and extremely expensive. 

Smell:

Smell can be used to help identify what gases are being emitted around a volcano. In his letters, Perret gives detailed accounts of the smells at the Gages Soufriére in Montserrat. He also refers to Chemistry texts describing the smells of other gases in his endeavour to identify the gas before he is able to have samples analysed in the lab. 

On his first trip to Montserrat in the 1930s Perret describes how the smell of rotten eggs is clearly identifiable even out at sea. During the crisis of the 1930s, the capital of Plymouth was regularly inundated with the strong smelling volcanic gases. An alarming phenomenon which also indicated precautions must be taken to avoid irritation of the eyes, nose and throat in regions most affected. 

The gasses Perret smelled in Plymouth and then again in the Gages Soufriére are not pleasant and can be harmful. Perret was even hospitalised twice due to prolonged exposure to these gasses during his monitoring on Montserrat. Careful study of his accounts suggest that the damage caused to his respiratory system at this time may have reduced his ability to detect H₂S at the volcano (the classic rotten egg smell!). 

Sensor