transitionThe phenomenon that I choose to talk about is the ‘Volcanic Lightning’. But, before I start talking about this, I’m going to touch a little about static electricity.
Have you ever wonder why does your hair stick to a balloon after rubbing it on your hair? Well, the answer to your question is static electricity. Static Electricity is a familiar electricity phenomenon which particles are transferred from one body to another. Therefore, when you rub a balloon against your hair, the balloon will steal electrons from the hair leaving it completely positively charged. Since opposite attracts, when you try to retract the negatively charged balloon from your hair, the positively charged hairs cause it to be attracted to the balloon.
transitionThe phenomenon of volcanic lightning also revolves around this theory.
A volcanic lightning is basically a rare weather phenomenon which is usually related to the production of lightning in a volcanic plume. It is by far the most vivid demonstration of power, beauty and mystery that the Mother Nature has to offer.
This breath-taking phenomenon has happened several times in our decade. Some of the notable eruptions are from the Chaitén, Kirishima and Sakurajima volcanoes. These dirty storms are twice as powerful as a normal supercell thunderstorm.
Before science and technology have developed to where it is now, the ominous lightning flashing above the erupting volcanoes are always considered as a nightmare as it is considered almost impossible to happen. With the advancement that we have achieved now, scientists are a step closer to understanding the phenomenon of volcanic lightning also known as the ‘dirty thunderstorm’.
transitionHowever, the task of unravelling the origin of volcanic lighting has been proven to be tough.
In normal thunderstorms, the cause of lightning is the colliding small bits of ice crystals which is frozen raindrops. This collision generates enough electric charge in a cloud to trigger lightning. However, ash clouds are harder to observe than supercell because it is less predictable.
Volcanic lightning has little to nothing to do with tectonic activity, and everything to do with everyday physics. Unlike lava, volcanic lightning was not formed deep in the volcano. It only started to form in the volcanic plume, which is simply the ash cloud that caused by eruptions. Volcanoes like the ones in Hawaiian are more likely to eject lava fountains than thick plumes of ashes. Therefore, these types of volcanoes would never have volcanic lightning.
transitionUpon further inspection of this remarkable phenomenon, scientists have listed down two possible causes.
One of it is the static electricity which relates to the balloon. The other source of lightning occurs near the stratosphere which locates high above the Earth’s surface where the tiny bits of ice crystals experiences powerful jolts.
transitionFirst off, I will explain how the static electricity causes volcanic lightning
When the tiny particles that make up a volcanic plume are in a volcano, it is tightly packed and is under high pressure. The atmosphere above ground is way less dense than the atmosphere beneath a volcano. This change in density contributes greatly to the occasion of volcanic lightning. As the previously dense particles are ejected with a very high acceleration into the loose atmosphere, they rubbed violently against each other. This generates friction, which causes ash particles gain or loses electrons and becomes electrically charged. Due to a big difference in the mass between electrons and protons, the plume experiences an enormous charge separation as the charged particles were released into the less dense atmosphere in an impressive acceleration with the electrons high above the sky.
The distance between the positively charged particles and the negatively charged particles continues to increase until it becomes too big for air to resist the flow of electricity. Since opposite attracts, there is a strong attractive force between the charged particles. The electrons would eventually jump to a lower potential difference and the movement of the particles released energy and emits a large amount of photon which is the spark that we see.
transitionAsh particles along with ice were the other main culprit for the occurrence of the lightning
In 2013, a team of researchers led by Corrado Cimarelli, a volcanologist at Ludwig Maximilian University in Munich, Germany had filed a report in 23rd February in the Journal of Geophysical Research Letters. In the report, the team of scientists recorded and observed a video of a volcanic lightning at one of World’s eruptive volcanoes, Sakurajima. They had compared the video to the infrasound and electromagnetic data and come across a conclusion that whenever thick clouds of ashes were present in the video, a sudden rise in the static electricity were recorded based on the electromagnetic data. Upon further inspection, it was stated that the particles of the ashes rub together generating the lightning strike. This phenomenon is also called triboelectricity.
The role of ice in this phenomenon was found under a separate study. After a total of 42 years of silence, the Calbuco volcano in Chile has roared to life. The location of where the volcano erupts which happened in April 2015 was tracked by a group of researchers. The result of their analysis was that the bolts were spread out horizontally for about 100km from the eruption, and at a near-stratospheric height which is 20km above the Earth’s surface. Due to the much colder temperature at the heights, scientist speculated since water vapour were present in the ash cloud, ice was formed at the top of thinning ash clouds which triggers lightning like how a thundercloud does. The study was then published on April 12th in the Geophysical Research Letters.
In conclusion Both of the studies brought the scientist a step closer in solving the phenomenon that remained as a mystery for decades. Alexa van Eaton, a physical volcanologist had once make a remark oh how surprising it is that are a lot of different processes inside a volcanic eruption plume system.
transitionThat’s all from me, thank you.