Monday, 2 May 2022

On Thursday 21st of April, the guest speaker at u3a Todmorden's monthly meeting was Chris Freeman, presenting 'What Have Volcanoes Ever Done for Us?'

His interest in volcanoes began when he was an apprentice in the Royal Navy. On board a ship sailing off Tenerife, he was instructed to take a bearing on Mount Teide. Volcanoes have been as an aid to navigation for hundreds of years. Later in his career, by now a Third Mate, Chris took a bearing from a lighthouse in Japan, but noticed another light in the distance. Looking through binoculars providing magnification times 25 he saw the peak of an exploding volcano, which appeared as a white triangle. The volcano was 150 nautical miles away.

Chris had brought a number of pieces of volcanic and other rock for us to look at, including a piece of accretion lava. This piece, when examined, had traces of different lavas which it picked up when it came out of the volcano as it erupted. Chris went on to describe the many and varying characteristics of the some of the other material, using charts, diagrams and slides.

The slides also showed the different types of volcanoes, for example Hawaii's main volcanoes are "shield" volcanoes, which produce lava flows that form gently sloping, shield-like mountains. Tenerife has four composite volcanoes, built up by many layers (strata) of hardened lava and tephra. These volcanoes are classed as acidic, while the ones on Hawaii are classed as alkaline, and produce a much hotter lava.

The audience might not have been exactly grateful for what Chris described as a present from Russia. This is the volcanic dust from the eruption last year of Mount Kamchatka which is currently falling on Britain. Chris showed pictures of layers of snow outside his house from earlier this year. Each of the layers had specks of black dust which fell with the several snow showers over a number of days and, for good measure, there was a picture of an icicle which again contained specks of dust.

Volcanoes, and the tectonic plates near to them, can affect the Earth's magnetic fields, particularly in the seas between Europe and Africa. At certain, seemingly random points, the needle on a compass can move, at times almost 180 degrees and then back. The Space Station circling the earth disconnects all its electrical systems when flying over this part of the planet to avoid what is known as the 'mid ocean ridge anomaly'.

Chris said that volcanoes have both good and bad effects, an example was volcanic glass, also known as obsidian. This material is extremely valuable and now closely guarded. It was once cut into shapes to form weapons, such as spearheads. Nowadays, one of its uses is for scalpels, being much sharper than steel. He showed a slide comparing a steel blade and obsidian magnified 5000 times. The steel one resembled a saw, while the edge of the obsidian was almost smooth, which help wounds heal much more quickly, and prevent infection.

Volcanic eruptions and activity have lasted, and continued, for millennia. The Smithsonian University website shows how many incidents of volcanic activity have occurred – the week commencing 13th April 2022 shows 23 eruptions, and continuation of eruptions, worldwide.

After the wealth of other information, the talk ended with a summary to illustrate its title.

Volcanoes provide hot water for people in a number of countries across the world and geothermal energy from volcanoes can be harnessed and used for electricity.

Some of the lava and rocks from volcanoes certain kinds of volcanic ash can be used for building purposes. In particular, extremely fast setting and hardening mortar and concrete containing volcanic material has been in use for a long time. The fixed nitrogen which results from the lightning associated with volcanic eruptions is crucial for plant life and in helping to counter the effects of global warming.

Damage to property, destruction of crops, ground displacement and deaths of human beings and animals will continue as long as volcanoes continue to erupt. Volcanic eruptions can result in additional threats to health, such as floods, mudslides, power outages, drinking water contamination, and wildfires.

Chris's final words about volcanoes were more than succinct 'You don't want to live near them – but you couldn't live without them'

The next Todmorden U3A Monthly Members Meeting will be on Thursday 19th April 2022 at 1.45 p.m. open to all fully paid-up members at the Central Methodist Hall, Todmorden. Dr Stephen Caunce with give a talk entitled: 'You Always Remember Your Co-op Number: The Amazing Rise of the People's Own Shops'

Not yet a member? You can attend one talk free by requesting an invitation to this zoom event. We're always delighted to welcome new members. Contact details: website at www.u3atod.org.uk or email at info@u3atod.org.uk.

Many thanks to Colin Sanson for this report

 

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