Nuclear Power: How it Works, Part 1

Nuclear Power: How it Works, Part 1

This is not a “nuclear power is good, or nuclear power is bad” post, this is about nuclear power, how it works for those who basically want to know a little bit more, how nuclear reactions progress, what is involved, how we control a chain reaction, and what happens when things go wrong.

So what exactly is nuclear power? We have to go back and dissect this statement to understand what exactly we are doing.

Nuclear power is not nuclear power per se, it is in fact nuclear energy being transferred into electrical energy through a number of energy transformations. But nuclear power is much easier to wrap our heads around, isn’t it!

Energy cannot be made or destroyed only transferred from one form to another. So we transfer the energy that is contained within the nucleus of an atom to electrical energy – simples.

Atomic fission is our baby which drives the power mad world. To release the energy we have to split the atom, to be more precise we have to split an atom of uranium 235 in half.

So let’s look at what we are splitting: basically, it’s the centre of the atom, the nucleus, which is made up of protons and neutrons, in our baby uranium 235 is a big one, 143 neutrons and 92 protons. Now, think of each proton and neutron as a table tennis ball, now stick then together, and hey—presto—a nucleus.

They are not static, but constantly on the move sliding over each other, and because ours is so big it’s unstable, it wobbles in all directions.

There is a lot of energy keeping all the sub atomic particles together, and it’s a slice of this energy that we want. If we split the nucleus then we will release some of the energy that is keeping it all together.

So how can we split such a particle that is smaller than an atom? Simple: with an atomic bullet.

Our bullet is a single neutron, we fire this particle at the huge nucleus and it hits it with such force that it splits it into two and releases energy – heat. However that’s not the only thing that is released, the splitting action also releases 3 other neutrons – or bullets – which then hit other atoms releasing 3 times the amount of heat and 9 more neutrons which then go on to… well, you get the picture, a chain reaction is formed.

To see the effect of the chain reaction please refer to the table to see how quickly the chain reaction moves:

sequences of atoms 1

Why do we want the heat? Well, it boils water, which turns into steam, this is passed down pipes and forces a turbine to turn which is connected to a generator, which turns a coil of wire through a magnetic field thus electricity is generated. All from heat energy and energy transformations.

So, we need to control the reaction, we need to control the amount of heat being generated and the speed in which it is being generated, and we do this in the core reactor of the nuclear power station. Here we have long rods that are the fuel rods, these are highly radioactive and contain all those uranium 235 atoms we need to split. These are lined up like a row of dominoes next to each other and immersed into a huge vat of water. The water acts as a brake for the free neutrons, the physical properties slow down the atomic bullets so we can slow down the reactions.

But more control is needed, so enter the control rods. These have the ability to absorb our bullets thus reducing the number of reactions at any one time, the lower the amount of bullets the lower the amount of fission reactions.

So, we have our dominoes all lined up, neutrons are fired and a small chain reaction is building. The control centre of the power station is monitoring the heat contained within the water, in the reactor core and it’s rising, we need to slow it down. They lower control rods in-between the fuel rods thus absorbing any neutrons that hit it. The higher the need to reduce the reactions the lower the control rods go, if the water starts to cool then the control rods are raised again allowing more fission to take place, this raises the temperature of the water to a critical level and then they are lowered. You get the picture.

So, we have a happy nuclear power plant generating vast amounts of electricity that we are all using, but what happens to the spent fuel rods – which are highly dangerous for over 10,000 years?

This is our nuclear waste and what happens if things go wrong and the core reactor ruptures or even explodes. That is what we will examine in part two…

Bernadette the Yellow Boxfish

Bernadette the Yellow Boxfish

Eat or be eaten is the law.

It’s a hard life for us under the waves, weather you are planktonic, crawling, sliding, rolling, swimming, buried motionless—we all try to do one thing well, and that’s eat.

We all try to do one thing better, and that’s avoid being eaten.

I am a hypocrite. I cannot stand the thought of some big fish with a huge mouth grabbing me head first and sliding me alive down their throat to be digested, yet at the same time I have no problems biting a happy go lucky (not so lucky today) shrimp in half. But that’s the law of the reef for you.

Now I belong to a family of fish that are strange indeed, we are not fast, nope can’t outswim you, in fact were positively slow. We cannot bury ourselves, we cannot hide in-between small rocks or corals to avoid you. We live mostly solitary lives or indeed in low numbers so we have no protection in large shoals. We are not camouflaged, indeed mostly the opposite, we stand out like a sore thumb, you look at 100 fish and who stands out like a lighthouse with a neon sign flashing “Here I am! Eat me!” above our heads.

So, who am I and why am I still here? Please allow me to introduce myself…

I am Bernadette the sweet, lovely yellow boxfish.

Our little darling babies are the cutest thing you have ever seen, they melt even the stoniest hearts, but I pack a dark secret under my skin. It takes millions of years to evolve, and in doing so we have a wonderful defense mechanism, one that really puts the predator off for life, that’s if it lives, and to be quite honest we are quite proud of our evolutionary trick.

Now, I am not going to tell you if we produce our defense with specialized cells under our skin or indeed if it is produced by a bacteria living in our skin, that’s for you to find out. So what is it? Well a nasty little chemical called pahutoxin and it packs quite a punch and quickly, well it has to or a bite will kill us.

So let me tell you of a tale. I was swimming by a nice head of brain coral when from behind came the jaws of a stone fish, within a second I was inside and stressed to hell. This stress triggered a fantastic chain reaction and in milliseconds my toxin was released. Now it’s a surfactant which means it’s fast moving in water and disrupts fats, oh what are cell membranes made of – lipids! So water moves through a fish 100% of it flows over the gills, so within 3 milliseconds a toxin laden fluid was bathing the breathing apparatus of the predator. But I am only a small fish and the gills of this beast are huge, so it’s a good job pahutoxin is lethal in extremely low concentrations 10 parts per million to be exact, putting it into a human concept knock back a Sambuca but then spit it out into an Olympic swimming pool that’s the dilution factor.

So what does pahutoxin do? It’s what you call a hemolytic agent, heam – blood, lysis – split so it splits the blood, in fact it destroys blood cells that carry oxygen into the body of our predator. My chemical just sits in the gills and with a biological hammer destroys every blood cell that passes by. Before the stone fish had chance to bite down on my fantastic body it was spitting me out and in a terrible state jerking and shuddering until it simply died of oxygen starvation. Did it bother me? No, it’s the law of life on the reef.

Oh no—here comes James. He’s a nice guy, full of himself, but I don’t like the way he displays his spots to me, believe you me I can do much better, so off I pop, slowly of course, and if we meet just admire my beauty, and above all don’t disturb me!

The Deadly Wave Called Sound

The Deadly Wave Called Sound

Sound is brilliant. It’s fun, it’s amazing and guess what? There is a whole world out there that we cannot hear.

Sound is full of energy, it can bounce, it can destroy, it can attract, and it can be used in many applications and by countless of animals.

But what exactly is sound, how can it travel and how can it harm us?

The tiger’s roar – a sound from a fearsome beast indeed and one that is feared in its natural environment. In one province of India, they take over 350 people each year, in another area honey collection is allowed for only 2 weeks per year due to tiger kills. People are taken collecting honey! Personally, I would put up with peanut butter and I hate that! A big cat with a big secret attack weapon. Contained within its roar is a special sound wave called infra sound, and it’s so powerful that it can cause total muscle paralysis. Simply put, the tiger roars at you, the sound wave hits your body and stops your muscles from working, and you cannot get away. Oh, dear. But how can a sound wave do this?

Okay, so – what exactly is a sound wave? Think of a long line of dominos stood on end and one falls. This falling action contains energy, and as it hits the next domino it passes on the energy to that domino, causing it to fall as well, and so on as the energy is passed along the whole line. Sound is the same, instead of dominos, sound waves are molecules which contain the sound energy, these move and hit the next molecule and the energy is passed on and thus sound moves, from one place to another, one molecule at a time.

So we know what sound is and it travels in longitudinal waves. The amount of waves passing a single point in one second is known as the frequency of that wave, measured in Hertz (Hz). So if a wave has a frequency of 1 Hz it means that one wave is passing a point in one second. So we can now group sounds into frequencies – happy days.

Sounds between 20Hz and 20,000Hz are what we can hear, this is the human hearing range. Sounds above 20,000Hz are known as ultrasound, and sounds below 20Hz are known as infrasound, and it’s these frequencies that are the bad boys. We don’t hear infrasound – we feel it. We feel the energy and the oscillations of the wave can literally shake us to death: a silent roar!

infrasound graph

Infrasound at a certain pitch and frequency can induce organisms or organs to simply rupture, and split open, it can blast matter quite literally to pieces. Quite a horrific way to go, and weapons have been developed to this end but most are not used due to their horrific results. Dr. Vladimir Gavreau in the late 1950s developed an infrasound gun after his research teams complained of illness, headaches and bleeding from the eyes at frequencies between 3 and 7 Hz. In one experimental run the whole building started to shake, glass shattered and only for the bravery of one man who ran in, to turn it off did the building survive.

Maybe more frightening are the physiological effects of this wave, which if you are exposed to can induce feelings of disorientation, fear, extreme sorrow, anxiety, revulsion, chills down the spine and pressure on the chest — all at a frequency of 17hz. Some researches believe that this sound is being emitted when we see ghosts, report chills, and other unexplained sightings of the world that exist on another plane!

Who can tell?

But what we do know that in the frequencies below our hearing exists an extremely dangerous energy. Animals use it to migrate, communicate, find prey and avoid predators. They run from earthquakes and volcanos before we know what is happening and the Earth screams (inaudibly) as its skin is ruptured. Infrasound a deadly yet amazing natural form of energy.

Isn’t sound fantastic!

Isaac Newton, William Herschel, Light & Fluorescent Corals

Isaac Newton, William Herschel, Light & Fluorescent Corals

Just recently, I have seen a few articles on night diving or fluorescent coral diving. I really don’t know if this is a new area to the SCUBA lifestyle but I do know that any diver willing to take the night dive will quite simply undertake the dive of their life. It’s fantastic to think that corals, such small animals will provide a wow factor equal or exceeding that with diving with manta rays, whale sharks or any other beast residing in our fantastic ocean.

Any diver taking a blue light down onto a reef at night will be rewarded with corals fluorescing back at them in the most amazing fashion, the polyps quite simply glow, green, red, blue, yellow. It’s quite simply the 8th wonder of the natural world.

So what has William Herschel—the great man who discovered the planet Uranus—got to do with this? Well, it’s all to do with the area of the electromagnetic spectrum called visible light and an experiment he did in the year 1800.

electromagnetic spectrum

Another great—Mr. Newton—nearly 100 years earlier in 1704 first described light as being made up of many colours by passing light through a prism. Herschel then placed thermometers into each colour when he passed light through a prism, each colour had a different temperature, or think of it like this a different energy level.

Why did they have a different energy level? Well, to put it quite simply each colour has a different wavelength and frequency. Frequency is the amount of waves passing a point in one second, the higher the frequency the more waves there are, the higher the energy level. So, when the light came out of the prism it had split into its different wavelengths, and that’s what we see, energy at different wavelengths.

So our coral polyps absorb light at certain wavelengths, then re-emit it. In the process, some energy is lost as heat. So the outgoing light has less energy thus a longer wavelength, than the light being absorbed. The change in wavelength means a change in colour, and what a sight it is.

colour wavelengths

Evolution is a funny thing. Why has this occurred? Well, I would like to tell you but the fact is we don’t really know, and as with most things I don’t think it will be for only one reason, but more likely an interplay to provide the corals with a number of advantages.

The heat lost could aid healing processes to a damaged polyp. The tissues absorb ultraviolet and re-emit it, is it a natural sunscreen to protect the animal and importantly the symbiotic algae contained within the polyp or is it a prey capture system in attracting animals to the polyps stinging tentacles.


I love it when physics and biology come together as they always do. Fantastic isn’t it? You only have to take a look at the fluorescent corals to be amazed at their beauty, truly the 8th wonder to the biological—or should I say natural world.

Samantha the Sexy Serpent Star(fish)

Samantha the Sexy Serpent Star(fish)

Some people call me sexy because of my vivid red colouration, but many of my relatives exhibit all range of colours, and live from the shallows to the deep dark cold abyssal depths. I have never seen many of my cousins but often throw them food down the continental shelf, well you have to do your part don’t you!

Hi I am Samantha (just call me Sam) and I am a red serpent starfish and quite an amazing animal. Robust in nature yet very delicate at the same time.

To be honest I am quite a thug, at feeding times I have no manners and will try and out race anything to get to that big piece of chunky flesh, oh yes and I am quite the sprinter you know. I will do anything to win and once that flesh is within my arms I will rip it to pieces and then stuff so much in that you can actually see my back bulge upwards with the amount of flesh forced inside me, fine dining, pew, who needs that.

Yet at the same time I can be so delicate that I can handle a single grain of sand with my feet and pass it along and play with it, I also care for my babies so much, I love my little darlings and I won’t have them playing in the plankton waiting to be eaten. I care for them in a little sac inside my body, until they crawl out and are independent, bypassing that dangerous planktonic phase. We are so successful in rearing our children that we can crowd out the sand with as many 1,000 of us living in just one meter square of sand or mud.

I have a water vascular system which is like your blood flowing through your veins, this water passes down my arms and using a series of valves I can extend any one of my hundreds of tube feet, each independent of each other, it’s like turning a tap on when I need them and off when they rest. However, if I am introduced to new water too quickly (like an aquarium) this can be damaged beyond repair.

My tube feet are great at finding small bits of food, I can throw an arm between two rocks, extend my feet into the crevice and remove and organic material lying there, great for cleaning out aquariums. However be warned we like meaty foods and will not tolerate bits all of the time, hey would you be happy with scraps. Now what’s meaty that lives in your aquarium, yum, yes fish, and I will take them if I need to! So feed me well! Sexy I am, but as I have said, a bit of a thug so don’t take me too lightly.

I was passing the house of a good mate of mine the other day, she was not in good shape, even with our calcium carbonate armour covering ourselves we can get into a bit of trouble out here, it’s eat or be eaten. Personally I like the eat bit best. She had been in a fight with a fish, cheeky sod had taken a right bite out of her, 3 arms bitten off down to the stump, however all is not lost as she was already starting to grow them back. We got our revenge, I collected that fish’s eggs and we both had a good meal, ha.

On the end of my 5 arms are the sensory tube feet which is how I get around and can feel the water, they tell me to retreat and run they also tell me when food is around. Right now they are screaming amino acids in the water just north of me, some poor fish is wounded, been in a fight I think.

So it’s goodbye from me, because if I don’t get a move on that crab will get their first, and there is nothing like fresh fish!

That big old bar magnet called Earth

That big old bar magnet called Earth

That big old bar magnet called Earth – how it preserves life.

That wonderful thing, the invisible force—we call it magnetism. It’s been in the news just recently with scientists trying to find out exactly what it is, and that’s the question for it’s hard to describe. Take yourself back in time to when you were a kid and remember that wonderful feeling of experiencing something new as you tried to push two magnets together. If you were lucky your magnet could move another through a desk, or stick together through your hand. What was (is) this magical force that pulled two metal bars together, stopped you from putting them together as they just slipped past, it goes straight through you yet you cannot feel it? It allows birds, fish, insects and others to migrate 1,000s of km every year with pinpoint precision. There are equations used to calculate the strength but let’s leave them (keep it fun) and instead let’s look at the biggest bar magnet we know of – the Earth.

Ok, so our Earth is one big bar magnet, but why? It’s all down to that wonderful thing called the core. Right in the centre of our planet there is a solid ball of iron and nickel 1220 kilometres, or 760 miles in diameter, and it’s hot, boy is it hot. There are theories to exactly how it formed but they all have one thing in common, the heavy element of iron simply peculated through the liquid of a very young Earth and formed this concentrated solid region. Now around this solid core exists the liquid outer core made of nickel and iron again but this time it in a liquid state and about 2,300 kilometres, or 1,400 miles thick. Now this liquid spins around the solid core and hey presto it creates our magnetic field. This field pops out of the North Pole and gets attracted around to the South Pole. But it just doesn’t cover the earth is also extends its influence out into space, which is very handy for us.

magnetic fields

Let’s leave the Earth behind and travel to Mars and have a look around. The most striking thing we can see in this alien landscape is how the rocks are formed, and the channels in the planet’s surface. It all points to one conclusion, at one time in its history many many years ago this planet had water flowing over its surface, to do this it had to have had an atmosphere of gases. So what happened, where is it now? One theory is that the planets magnetic field simply turned off, and when this happened the planet was stripped of its atmosphere and water – think about it, oh dear!

Our sun the life giver to our planet, the water and atmosphere stripper of Mars!

This ball of nuclear fusion every second sends out a stream of charged particles called the solar wind, traveling towards Earth at a maximum of 800 kilometres per second. When they arrive at Earth something magical happens which is handy for us. Because they are charged they hit the Earth’s magnetic field which deflects them around and away from Earth. If this did not happen the solar wind would strip the Earth of its atmosphere, water and life. So thank you inner and outer core, you’re doing a dam fine job.

But were are not finished yet, some of the solar wind particles do make it through, they are attracted to the field lines and follow them to the north and south poles. Here they interact with the gas in the outer atmosphere, and the energy of these interactions create one of the most amazing natural wonders we can hope to observe, the aurora borealis over the north and down south we have the aurora australis. These are commonly known as the northern and southern lights, and going to look at them is high on my bucket list.

The Christmas Tree Worm

The Christmas Tree Worm

Spirobranchus giganteus : Christmas tree worm

When I look at this hobby/obsession, the one thing that stands out from all else and really, really turns me on (no, not the wife) are the amazing array of little beasts that exist with other beasts in symbiotic relationships. Here we have one of the most visually enchanting relationships that is so misunderstood within the trade and hobby that many will be offered for sale only for the worms and no thought given to the coral it inhabits.

What more can you want? Colour is one of the main goals that reef-keepers try to inject into their aquariums. Just look at the variations of vivid colours displayed by the worm crown—the intensity and mix can be breathtaking. Mix this with the attractive retraction behaviour and the covering of the tube opening with the opercula plate (trap door), and we can see why people fall in love with them and not really that dull brown coral they are boring into.

Now, here we have a small problem for that ‘unattractive’ pitted surface is in fact a coral of the genus Porites which is a small polyped stoney coral. So the often sad situation is that seen in selling systems the purchaser will see only the worms, parted with £25 – 75.00 bagged up and off home. Placed in a very nice aquarium with many soft corals and wonderful fish, but not an aquarium designed to sustain sps corals. Over a period of time our coral sadly dies and along with it so do the worms that adorned this wonder of the reef. To keep the worms alive you have to keep the coral alive as well, so you will need an aquarium system that will grow acropora species as well as other sps corals.

Back to our worms, they are filter feeders capturing particles within the crown, particle size of the food can be as small as bacteria which are produced within the aquarium itself. They will benefit from daily feeding of live phytoplankton and liquid animal based foods. Kept in medium to strong flow, you’ll ensure a supply of currents carrying food and the rapid dispersal of waste products.

When choosing a piece look for the number of populated tubes, one with more empty holes that protruding crowns should be left alone. Note the retraction response to shadows, they should retreat to safety within the blink of an eye. Also look at the colouration of the coral, a nice uniform tan colour, not areas of discolouration suggesting partial coral polyp recession, remember: the coral is just as important as the worms.


Phylum                      Cnidaria

Name                          Spirobranchus giganteus

Location                    Global tropical distribution

Feeding                      Live phytoplankton and other liquid food

Size                              Crown from 0.5 – 3cm

Water Flow               Moderate to high

Lighting                      Intense lighting for the sps coral

Difficulty                    For the more advanced sps reef keeper

The Blue Boxfish

The Blue Boxfish

Ostracion meleagris : Blue boxfish

Of the many beautiful boxfish that inhabit the tropical oceans, this has to be the most stunning. Yet it is also one of the most potentially deadly inhabitants of the worlds marine aquariums. That it is often found in pairs that exhibit such differences in colouration makes this beast even more desirable, yet you have just increased the risk to your aquarium by another 100%.

Ostracitoxin is a fish skin toxin that is released when the fish are stressed, and it’s a powerful little sod as well. Every fish will be killed very quickly, and if you took 1ml of the aquarium water and added it to another you would have another wipe out. In the ocean, it is a defense mechanism against predation. A large beast comes for a snack and is repelled before it can take a bite. In the open seas, the toxin is then diluted in the ocean causing no harm—but in our closed systems dilution is not possible. So why take the risk? Many people do and have great results keeping the fish for many many years without all the above gloom and doom.

The answer here is simple: the toxin is only released when stresses occur so our babies should only be kept with peaceful tank mates, in female-male pairs or as a single specimen. We do not want any hint of aggression here. Another source of stress for the beast is poor water quality, so you have to keep an eye on the nitrate level and ensure that you keep the water as best as possible.

In reefs they can cause damage with their grazing behaviour, damaging some corals. Powerful beaks make short work of tubeworms, crustaceans and other beasts. I do know of these fish in reef aquariums but these are the exceptions and most definitely not the rule.

When you see them, look at the body sides to see if the animal is starving or not, good straight sides is what you are looking for—not pinched, as this indicates a fish that is doomed, stressed and in danger of releasing its toxin load. Pairs are easily seen as the female is brown with white spots and the male has blue sides with orange spots and a fawn back with white spots, just great colouration you cannot get better. To keep this vivid coloration at the best and boost it’s health very important with this species feed at least four times a day more if possible with a vitamin enriched variety of meaty foods.


Family                          Ostraciidae

Name                            Ostracion meleagris

Location                      Indo-Pacific

Feeding                        Vitamin enriched meaty foods,

Reef Compatibility   Not recommended

Tank Mates                  Peaceful companions

Size                                 16cm

Difficulty                      Only for the experienced

Are we being watched?

Are we being watched?

Are we being watched, or are we doing the watching?

The search for alien life? Or are we the aliens?!

I don’t want you to just read this little humble blog. No, I want you to sit down and take the time to think about and answer the next three questions. So if you have not got a spare 10 minutes now, then please come back later when you have…

Question 1:

(Have you a paper and pen ready? if not then go and retrieve some supplies for you will need them in question 2 and 3 as well.)

OK… You are no longer a human being, you are a blob of jelly with six eyes and 4 mouths, you are an alien life form, far more advanced in technology than ourselves, and of course you are, your planet is 6,500 light years away, yet here you are in orbit looking down on Earth.

Your mission is to look for signs of life on Earth. What would you look for? How would you know life existed here?

Write down your thoughts. Then move on to question 2.

OK, so you should have quite a few indicators that could tell you life exists on this planet…

Question 2:

You are still that blob of jelly in orbit above Earth, the only difference is that it is 10,000 years ago. There are no big cities, and the Earth is quite different.

What would you look for now? How could you tell life existed? What would you look for?

Write down your thoughts. Then move on to question 3.

OK, your list might not be as big now but you have a few indicators that could tell you life exists on this planet…

Question 3:

You are still that blob of jelly in orbit above Earth, the only difference is that it is 1,500,000,000 years ago. On land was just rock—no life yet—and the atmosphere was totally different.

What would you look for now? How could you tell life existed, if indeed it did?

Write down your thoughts, though I know it’s a bit harder now.

The only thing you could hope to find are bacteria or traces of bacteria.

Now, spare a thought for those magnificent scientists working at NASA and ESA for this process is exactly what they are doing. They are sending space craft, landers and rovers on and over the surface of planets, which are years away from ourselves, to try and find signs of life – bacteria – living or even harder to find fossils of bacteria.

Isn’t worth just standing and thinking about what they are doing, how difficult it is, and hey, why not give them a round of applause? They have got a bloody hard job.

Earthquakes and the Earth’s Core

Earthquakes and the Earth’s Core

A very bad fact is that tens of thousands of people lose their lives every year to the most natural of nature’s events: an earthquake.

It’s a natural event, but the harsh and horrible fact is that people live where the effects of earthquakes are felt and then we have a devastating disaster. But the fact remains that earthquakes have happened since the earth’s crust finally cooled down to form a fluid rock outer coating to our amazing planet.

Floating on the liquid inner part of the globe are the tectonic plates – only accepted by science for the past 60 years. Our landmasses, like scales over a fish, they move and bend as the earths inner liquid rock slowly expands and contracts. So the question is “How is the solid earth’s core the force that drives earthquakes?

Well one word: heat, or to give it it’s proper name – thermal energy.

Let’s imagine we have a Lego block of magma (our liquid rock) and follow it on a journey, starting at just above the earth’s core. The unimaginable amount of heat being generated by the earth’s core pumps energy into our block and this heats it up and makes it less dense than its surrounding liquid rock. So our block is lighter and as such it slowly begins to rise upwards towards the outer crust. It hits the inner surface of the crust and is forced along it, here it bonds with the solid rock and as it moves it tries to drag the crust along with it, via friction. Our block then cools, becomes denser and sinks down through to the core again, where the cycle starts all over. This is known as a convection cell.

Now we have a situation of lots of convection cells all moving in different directions, pulling and pushing the earth’s crust all over the place. This force moves the earth’s crust at the rate of 5 cm a year or as fast as your finger nails grow. If you pushed your finger against a wall for a year, your nail would keep on growing. The pressure of your finger on the wall would stop your nail moving outwards and force it to bend upwards in the middle. Time passes and more pressure builds until your nail can take it no more and it snaps in the middle – an earthquake.

The same happens in the earth’s crust, the plates move past each other slowly, but some get stuck on each other. More and more pressure builds up over time as the convection cells try to move them, but the solid rock is jammed. Then in a few seconds the plates jolt and slip past each other and release all the pressure that has been building up of years and years. The energy is released and causes the earth to shake, an earthquake.

So to answer our original question what causes an earthquake: quite simply it’s heat!