Earthquake Swarms 1933-1937

Soufrière Hills Volcano showed renewed signs of unrest in the 1930s, with repeated earthquakes causing damage and increased fumarole activity.

During the seismic swarms, the Agricultural Station on Montserrat made detailed notes on the type of earthquakes occurring. Although they did not have seismometers at this time they made a distinction between several types of earthquake including: tremors; double tremors; shocks and severe shocks. A compilation of the written accounts in the UK National Archive illustrates the pattern of seismicity in 1934 and 1935.

Details of disturbances recorded by the Agricultural Station on Montserrat during the 1930s earthquake swarms. Credit: UK National Archives

Compilation of seismicity during 1934-1935 using the written accounts found in the UK National Archives. Credit: Jenni Barclay

American inventor and volcanologist Frank Perret visited the island 12 times between 1934 and 1937. In his report on the unrest, he notes the strong resemblance of the events to the unrest in 1897-1900:

“It seemed as though there was being descibed the very period we were experiencing, the same gas emission, the same type of shocks with damage to churches necessitating outdoor services, and the blocking of the coast-to-coast road by landslides.” (Perret, 1939)

This is Frank Perret's own painstaking analysis of the unrest episode from his 1939 report. He measured both gas and seismicity. The Black and White symbols refer to the phases of the moon. He was initially convinced there was a realtionship between more seismic activity and the cycles of the moment. This is partly what fuelled the scepticism amongst UK scientists...but hypotheses are there to test.

Perret’s detailed account of the 1930s unrest provide useful context for present-day activity of Soufrière Hills. However, at the time, Perret’s presence on island and his role during the seismic crisis was seen critically by the Admiralty, to put it mildly. They accused him of being a fear-mongering “pseudo scientist” causing “unneccesary expense to the crown”:

“It is difficult to see what good his [Perret’s] presence or prognostications achieve, while the harm they do by keeping the island in a state of apprehension is obvious.”

A less-than-polite assessment of volcanologist Frank Perret sent from the Admiralty to the 'Secretary of State for the Colonies' in 1935. Credit: UK National Archives

Montserratians, on the other hand, seemed to hold Perret in high esteem. Frustrated by the lack of action in the face of the unrest, several members of Montserrat’s community wrote directly to the ‘Secretary of State for the Colonies’, citing Perret and petitioning for more scientific investigations:

“From the records kept by the Government under the direction we believe, of Professor Perret it is felt that an alarming situation is revealed which points to some major pending calamity. Opinion is being expressed that the island is experiencing similar tremors to those which precede volcanic eruptions.”

As the unrest persisted for several years, several members of Montserrat's community wrote directly to the 'Secretary of State for the Colonies' and petitioned for more scientific investigations. Credit: UK National Archives

Signatories of the petition to the Secretary of the State for the Colonies in September 1935. Felt earthquake swarms continued for another year or so. Credit: UK National Archives

The memory of the seismic swarms in the 1930s is alive on Montserrat, and features in songs such as Zunky N’Dem’s ‘Seismicity’.

Seismicity (Zunky 'n Dem)

Seismicity

‘Seismicity, seismicity / A feature of this 20th century
Our forefathers witnessed / And now we see
This land this land / Paran in seismicity

Back in the thirties / Earthquake shook the hills
Upscale on the Richter / Wrecked churches and mills
Coming and coming / More frequent than rain
Affecting the main crops / Limes, cotton and cane

Oo la la
Emerald city seismicity
Emerald city seismicity
We’re living in a seismic city
Full of seismicity
Montserrat is a seismic city
Full of seismicity
Long ground is a seismic city
Full of seismicity
Plymouth is a seismic city
Full of seismicity

We now know

People that count of history / The future will not be a mystery
Truth otherwise hidden will come to light / Any sign of activity is proof of life’

– Extract from Song 'Seismicity' by Zunky 'n Dem