It was to keep the Egyptians and the Israelites encampments separated during the nights, allowing light to the Israelites and not lighting the Egyptians.
Ash and other derbis in Egypt have been chemically matched and dated to Thera. The plume would have had to be thirty miles high to have been seen in Egypt. Pinatuba (recent) in the Philippines was 26 miles high. It also provides the earthquakes/tidal waves for the parting of the Reed/Red Sea.
The separating of the Red Sea lasted all night long and into the morning as the Israelites crossed. A wall of water being to the left and the right for hours while the pillar kept the Egyptians from entering into the seabed after them. Like Ezekiel's visions, it's awful hard to ascribe any kind of natural phenomenom to this.
(Mike Baillie speculates that a comet fragment may have initiated the Thera eruption and provided other fireworks in that period). Wouldn't something that drastic have been recorded in the bible, somewhere?
What if an electromagnetic force excited the uranium nuclear power plant of our earth's core to the point of causing massive volcanic eruptions. One of the ten plagues was meteors, I believe, so maybe something approached the inner solar system with a massive electromagnetic force to excite the dynamic bodies of our solar system, and brough a huge amount of meteors with it. A neutron star only 12 miles in diameter (smaller than a comet) would have a humongous charge and the mass of our sun. I'm not saying there was a neutron star that passed through, but maybe there could be something not quite as exotic as a neutron star that exists close by wreaking havoc every once in a while. It could be small enough to not cause a big uproar if it passed a considerable distance but still have a big effect on the bodies of the solar system electromagnetically.
I bring these things up because I've always wondered how the earth could flood for months with subterrainian waters, stop rotating then start again, flash freeze the mammoths, etc. Not to mention the anomolies in our solar system. Comets come in from the same spot in the Kuiper belt, Uranus is on it's side, Saturn's ring was recently form, there's an exploded planet between Mars and Jupiter. Just hypothesizing. :^)
I read a review to a book (The Electric Universe, I believe) that went something like that. I don't subscribe to that idea. The one I prefer is the release of stress from the melting of the ice from the Ice Age. Also, the Red Sea was land locked during the Ice Age, it may have even dried up like the Persian Gulf.
The explosion and earthquakes associated with Thera (1628BC) may have broken the 'dam' that seperated the Red Sea from the Mediterranean and caused the 'parting of the waters.' The Red Sea may have been somewhat like the Dead Sea is today, at that time.
"Victor Clube, also of the University of Oxford, argued that we are living in the aftermath of the breakup of a giant comet in the inner Solar System. He suggests that this event may have been associated with the most recent Ice Age, which began about 100 000 years ago. According to Clube, it produced a stream of Sun-orbiting material linked with the Taurid meteor stream, which peaks around 30 June in daylight hours but is visible as "shooting stars" in the night skies of November.
Clube calculates that the Earth passes through the thickest part of this belt of debris every 3000 years, and that this happened most recently in 500 AD and before that in 2500 BC. On both occasions, Tunguska-like events would have been common, with one impact in each region the size of England over a period of a hundred years or so. Could this explain the collapse of past civilizations, the "Dark Ages" of Europe, and recurring legends about fire from the skies? Clube and his colleagues have been promoting this idea for ten years, but now they have a solid weight of scientific evidence to support their case. The Tunguska event itself came at just the right time of year to fit the pattern, as an isolated straggler in the stream, but the next main date to watch out for is the year 3000, give or take 200 years. For once, the scientists involved are happy that they will not be here to test their prediction.