Natural Disasters
The last mass extinction was bad news for the dinosaurs and good news for the mammals. It happened, about 65 million years ago, when a comet arrived from outer space and blasted a big hole beside what is now the Yucatan Peninsula in Mexico. We can be fairly certain of that because the hole is still there and distinctive debris, from the impact, accumulated as a thin layer in geological deposits.
The debris spread all around the world and can be seen almost everywhere. Below it, there are bones of dinosaurs. Above, the dinosaurs have gone. All that remains of their lineage are their distant cousins … the birds.
Mammals were around before the comet arrived and survived the deadly impact. Living with dinosaurs had been difficult. The big beasts could tear you apart with their fearsome teeth or knock you flat with a swish of their mighty tails. The best tactic was to remain small and insignificant.
All that changed with the coming of the comet. The dinosaurs vanished. The mammals could now grow as big as they liked, subject only to the laws of nature and an adequate food supply.
Sabre-toothed tigers evolved from tiny cats when conditions were favourable and shrank back down when conditions changed. That has happened many times during the 65 million years since the arrival of the comet.
The tiger was a danger to other creatures but not nearly as dangerous as the creature that emerged from the African jungle three million or so years ago. It left the rainforest and roamed the grasslands that were encroaching on its ancestral home.
An ape came down from the trees and began to walk on its hind legs. As one generation gave way to another it became more upright and, by about a million years ago, it looked very much like us.
In time, it became proficient in the use of fire and began to fashion tools. Cousins formed groups and went their separate ways. Some left Africa. The Neanderthals were one and their remains are found in Europe and the Middle East. The Denisovans are another. They lived further to the east.
We (Homo sapiens) came on the scene relatively recently and our arrival was bad news for the cousins. There was something about us that made us very difficult neighbours. We entered their territory and replaced them everywhere on planet Earth.
Forensic experts have construct detailed models of the Neanderthals. Enough skeletal remains survive for us to be confident that they provide a good likeness, right down to hair and skin colour.
The models show that our Neanderthal cousins were strongly built, with light skins, fair hair and prominent brow ridges. Their brains compared favourably in size with our own.
Dress one up in modern clothes and send him off down the street. Few would stop to take a second look. The Neanderthal would blend in. Enough of us have similar features.
Yet, we replaced (or almost replaced) the Neanderthals and the other cousins. There was something dangerous about us and it has not gone away. Our presence on this planet has been bad news for other creatures, great and small.
There are those who believe that the Earth is facing another mass extinction and we (Homo sapiens) are the cause. Each year, the list of species facing extinction grows bigger. Our exploitation of the Earth’s resources is taking a terrible toll and not just on cuddly animals.
The extinction of pandas would be tragic. Let’s not forget the things we cannot see. Tiny microbes, vital to basic life processes, are being poisoned by the ever expanding cocktail of toxic substances produced by our chemical and pharmaceutical industries.
I mentioned that we did not entirely replace the Neanderthals and Denisovans. They live on as part of us. Our ancestors interbred with the cousins.
If are of European ancestry, there is a chance that as much as six percent of the DNA, that makes you human, comes from Neanderthal forebears. If your ancestors lived in South-East-Asia, then there is a similar chance that you are related to the Denisovans. If you are of entirely African ancestry, then the chances are far less.
If you want to know more about your remote ancestry then you can join the half-million people who have participated in National Geographic’s ground-breaking Genographic Project.
They will supply a DNA Ancestry Kit. Amongst other things, you will discover if you have any Neanderthal or Denisovan ancestry. Go to:
https://genographic.nationalgeographic.com
Planet Earth is molten. It was born as a molten ball of rock and has stayed that way because radioactive elements in the planet’s core are decaying and keeping the rock hot. We are living on the surface of a huge nuclear power station.
Fortunately, it is well-behaved. The nuclear processes are jogging along peacefully. There’s no risk of a runaway reaction that would blow us up.
The same can’t be said for the thin layer of rocky crust on which we live. It’s moving around and the different bits are nudging one another in a way that is far from peaceful.
They are called tectonic plates and they push against one another like rafts on an ocean of molten rock. Usually, one plate slips under the other and pushes it up. It’s the sort of act that produces mountain ranges.
Countries, such as Japan, owe their existence to the collision of tectonic plates but it comes at a price. Land is formed but the process is not gradual. Huge pressures build up as the plates push against one another. For years nothing happens. Then something gives. Rock fractures and vast chunks of land snap to new positions. We call the event an earthquake.
Most fatalities occur when buildings collapse. Poorer countries, using old-fashioned construction methods, are badly hit. Technologically advanced countries minimise the danger by constructing buildings engineered to withstand earthquakes. They have achieved considerable success.
See Chapters 2.3 and 2.4.
They come in two varieties: Hotspot and Tectonic. Both are dangerous but the news is not all bad. Some island nations owe their existence to volcanoes and many farming communities depend on their nutrient-rich ash for their crops.
I’ll begin with the Hotspot variety. They are formed when a convective cell of hot magna (molten rock) makes its way up from the Earth’s core and burrows through the outer crust. Magna spews out and a volcano is born.
The convective cells are long-lived. They have been around for hundreds of millions of years and, during that time, the tectonic plates (Chapter 2.2) have migrated over them. Hotspots turn off and on and the result is a string of volcanoes. The Hawaiian chain is the most famous example.
The second type of volcano results from the collision of tectonic plates. One plate pushes its way under the other. Material that was formerly near the surface is transported down to regions of high temperature and pressure. It doesn’t belong there. It frequently vaporises and explosions occur. Again, the result is a volcano.
Eruptions are particularly violent when marine plates are involved. Superheated steam is produced and the resulting explosion can send millions of tonnes of material into the atmosphere.
A famous example is the eruption of Krakatoa in 1883. A series of relatively mild eruptions opened fissures in the walls of the volcano allowing sea water to pour into the magma chamber. The resulting explosion destroyed most of the island and the sound could be heard in Australia, 3500 km away.
The best defence against volcanoes is evacuation. The problem is to predict when they will erupt. Authorities are loath to declare an emergency only to find that nothing happens. People get complacent when too many false warnings are issued.
I recently visited Mt Unzen in Japan. An impressive museum records its volcanic history. In 1792, 15,000 people died when Unzen erupted. It began to rumble again more recently and the entire area was evacuated.
Newsmen and volcanologists gathered to record the expected event. For days, nothing happened. Then Unzen blew its top. A plume of superheated gas and dust spurted high into the sky then came tumbling back down with the speed of an express train.
The newsmen got some superb shots before they were engulfed. They died but their cameras survived the ordeal. Video players, in the museum, enable visitors to see the oncoming dust cloud right up to the moment when the cameras stopped recording.
We used to call them tidal waves. That was misleading. Tsunamis have nothing to do with tides. Tsunamis are caused by underwater avalanches and earthquakes.
Tsu means harbour in Japanese and nami means wave.
When a tsunami is on its way water levels, in harbours, suddenly fall and that sends an unmistakable message to seamen. They heard stories about tsunamis when they were children and know what to expect.
Coastal communities in Japan are acutely aware of the risk from tsunamis. Children are brought up on tales of past events and drilled in what to do when the tsunami sirens sound. Sadly, these warnings are not always heeded.
I’ll come to that later. First a few words about what causes tsunamis. I’ll stick to Japan because I know it well and have friends who went through the horrors of the recent tsunami that wrecked their homes and released deadly material from the Fukushima nuclear plant.
Earthquakes are the main cause of tsunamis. Japan is located on the, aptly-named, Ring of Fire. It is where the Pacific tectonic plates (Chapter 2.2) push up against the Eurasian and other plates. Huge pressures build up and, sooner-or-later, something has to give.
The result is volcanoes and earthquakes. When the earthquakes occur at sea, huge volumes of water are pushed up and down. Mounds of water form and move outwards. At first they are not very impressive. Boats can ride can them without difficulty ... but it doesn’t last.
The mounds contain vast amounts of energy. While they are far out at sea the energy is contained within a big volume of water. When they reach the shallows the energy is compressed into a small volume. A gigantic wave forms and draws in water as it races forward. The sea retreats from the land then returns with devastating fury.
All of us have seen pictures of the recent tsunami that hit Japan. It was caused by the most powerful earthquake ever recorded. Once caught in its raging waters victims had little chance of escape. It made no difference if they could swim or not. Everything was pulverised into small pieces.
All coastal communities have tsunami evacuation plans. People are drilled in what to do. Sadly, these precautions are not always followed. There are harrowing tales of people who failed to act. The most heart-rendering involve children.
At one school, the kids were lined up in the designated assembly area and told to wait until the emergency services arrived. That didn’t happen. The emergency people had other things on their hands. They couldn’t be everywhere at the same time.
Most of the children died when the waters rushed in. Some were saved by a young teacher who defied her superiors and lead them to higher ground.
At another school, a frantic mother arrived and bundled as many children as she could into her car. The teachers had cars and there was a school bus. None was used. Children and teachers died together.
There is a lesson here: Don’t wait for others to look after you in an emergency. They might never come. Know what has to be done and do it yourself.
My wife and I recently drove down the coastal strip devastated by the recent tsunami. A lot is designated as National Park and very beautiful. The signs of the tsunami are everywhere.
The authorities were widely criticised for being slow to react when the tsunami struck. Now, with typical Japanese efficiency, they are making the entire coastline Tsunami safe.
Gigantic walls are being built in some places. In others, the land is being raised by thirty or more metres. We were reminded of the opencast mines in Australia. Hills are being carted away and deposited in valleys. My photograph gives an idea of what is being done.
Finally, a few words for readers who don’t live in earthquake zones. You might think you are safe from tsunamis. Don’t be so sure. Tsunamis can be caused by underwater landslides. They are rare but they happen.
Tsunamis deposit marine debris on land. There is evidence of such deposits in Scotland and they have been linked with an underwater landslide, off the coast of Norway, towards the end of the last Ice Age.
Marine debris in the Sydney region is believed to result from a tsunami caused by and underwater landslide off the coast of New Zealand.
We call them tropical cyclones in Australia. Further to our north they are known as typhoons. They don’t develop close to the equator or at high latitudes. If you live in Britain or Singapore you won’t encounter one unless it has come in from somewhere else.
Hurricanes are formed when air starts to rise over a hotspot in the ocean. It spirals in from the sides and forces produced by the Earth’s rotation take control. If you have ever walked around on a merry-go-round you will have an idea of what’s involved.
The outcome is that hurricanes in the southern hemisphere rotate clockwise. Those in the northern hemisphere go in the other direction.
Hurricanes don’t form near the equator because the differential forces, caused by the Earth’s rotation, are too small to take effect. They don’t form at high latitudes because sea temperatures are too low.
As the air spirals in towards the eye of the hurricane it speeds up. It does so for the same reason that ice skaters spin faster when they move their limbs in towards their bodies. Angular momentum is conserved in both case.
Hurricanes can be regarded as gigantic heat engines working between a hot sea and a cold upper atmosphere. They draw their energy from the sea and weaken when they reach land.
Damage is caused by devastating winds and flooding. The ferocious winds, that circulate about the eye of the hurricane, mound up sea water and raise sea levels. If a cyclone reaches land at high tide the flooding can be severe.
Finally, there is a myth that water behaves like a hurricane when it goes down a plug hole. It doesn’t. The differential forces, caused by the Earth’s rotation, are far too small. Water goes down clockwise and anticlockwise no matter what hemisphere you are in. Try it yourself.
Tornados can be likened to small-scale hurricanes. Both are cyclonic storms. Both operate between a hot base and cold upper atmosphere. But, the similarity ends there.
Hurricanes are big, slow-moving giants, dependant on the sea for their energy. Tornados develop on land. They form in minutes and travel at frightening speeds, demolishing everything in their path.
Tornados occur in many parts of the world but nowhere is as prone to them as the United States. The conditions are just right. An extensive stretch of hot, low-lying land is required. And it must be close to an extensive mountain range.
How about the Midwest and Rockies?
They sound about right. Much of the Midwest is low-lying and no one would question the grandeur of the Rockies. The high peaks remain snow-capped even in summer.
We have a heat engine!
And it’s one that we are unable to control. There’s no way we can stop hotspots developing on the plains. And, when cold air flows out from the Rockies, the heat engine will burst into life.
The hot air goes up fast. Air is sucked in from the sides. The slightest windshear causes the whole lot to rotate. Similar forces operate as with hurricanes. They are on a smaller scale but no less intense.
There is no defence against the power of a tornado. The devastating storms emerge swiftly and race along at the speed of an express train. Early records say the Plains Indians had underground shelters. Modern versions are used today.
Some enthusiasts chase tornados. Like the volcanologists and newsmen, who flock to active volcanoes, they take spectacular pictures. Some pay with their lives.
Lightning is what happens when electrical charge is picked up from the ground, by a rising current of air, and carried to immense heights. Huge voltage differences develop and the inevitable spark occurs.
You can create the same sort of spark by rubbing various materials together. The famous combination is amber and cat’s fur. But you don’t need amber and there’s no need to torment the cat. Lots of combinations work.
Lightning has caused many fatalities. The victims are usually out in the open. If you are on a mountain during a thunder storm, keep off ridges or you might become a lightning conductor.
And don’t fly kites into thunder clouds. The American statesman and scientist, Benjamin Franklin, did that during one of his famous electrical experiments. Lightning struck and the world lost one of its most brilliant minds.
Wildfires occur all around the world and are particularly dangerous in regions with wet winters and hot dry summers. California and Australia are particularly at risk but they are, by no means, alone.
Fires occur by accident, lit on purpose or caused by lightning. The outcome is always the same. Huge areas are affected and difficult to control.
I have lived in areas at risk and become acutely aware of the dangers. A common mistake is to think that wildfires move slowly. Often they do. But, a change in conditions can cause them to advance rapidly … sometimes at terrifying speeds.
A mist of volatile gases may develop over pine and gumtrees during exceptionally hot conditions. The smallest spark can cause them to ignite and spread destruction far and wide.
Even grass fires can move swiftly.
I recall a tragic case when motorists left their cars to watch a grassfire. The wind suddenly changed and they were engulfed. If they had stayed in their cars the fire would have swept past and they would have been safe.
It takes a while for vehicles to catch fire. That’s something to remember. But don’t think vehicles are totally fireproof. There is a limit to what they can stand.
And don’t think that buildings are safe because they are constructed from steel-and-concrete. Fire storms develop in wildfires. Air is drawn towards hotspots and swirling cells of superhot gas are produced. They hurtle around like superhot tornados.
I once worked at Mount Stromlo Observatory, Canberra. The famous astronomical research institute is situated on a mountain that was once covered in pine trees. The trees burned down some years ago and most of the observatory was destroyed.
Friends showed me around the ruins. I surveyed the blackened scene and shared their amazement. A steel-and-concrete building had been reduced to rubble. It hadn’t burned down … it had blown down.
A tornado-like cell of superheated gas had emerged from the forest, crossed a carpark and smashed into it. A nearby building was badly scorched but otherwise undamaged. The same sort of thing happened in suburbs at the bottom of the mountain. My old house was safe but the house next door had been blown apart and set alight.
Firefighting authorities advise people to have an evacuation plan and follow it. Get well clear of the blaze. Don’t go up onto your roof and watch it as some people do.
My first scuba club bought a zodiac. The famous inflatable boat is excellent for diving but doesn’t come cheaply. We had to make it pay for itself and one way was to provide a rescue service for sports fishermen crossing the sandbars that develop at the mouths of most Australian rivers.
We moved in circles in front of the bar and waited for the fishing boats to approach. The trick was to cross the bar in the slack water between oncoming waves.
Most boats got it right. Some misjudged and we had to go to their rescue. Very occasionally, everything seemed to be going right … then a freak wave appeared.
It didn’t follow the normal pattern. The wave rose up, as if from nowhere, and caught the fishermen by surprise.
If you go up onto a cliff and watch waves milling around in a bay you will get an idea of how freak waves form. From that vantage point they don’t look quite as freakish as before. You will see that waves interact when they meet. Peaks and troughs cancel. Peaks reinforce one another when they come together.
Statistically, it’s only a matter of time before the peaks of a tremendous number of waves come together and a monster wave is produced. Down through the centuries, seamen have talked about them.
Earnest Shackleton’s epic tale of survival in the Antarctic, in 1916, was almost scuppered when he encountered a monster wave as he piloted his lifeboat from Elephant Island to South Georgia.
In 1995, the liner Queen Elizabeth II was hit by a 33 metre (100ft) wave which, in the words of the captain, “came out of the darkness and looked like the White Cliffs of Dover.”.
The lighthouse in the photograph is on Flannan Island off the west coast of Scotland. In 1900, a boat arrived to relieve the lighthouse keepers and found they were missing. Heavy equipment was strewn around the base of the lighthouse, an iron railing was buckled and a boulder, weighing at least a tonne, was found on the steps.
The evidence points to a gigantic wave striking the lighthouse. The keepers were presumably outside at the time and swept away.
As I write, the world is gripped by a severe El Nino event. We hear the odd-sounding Spanish term every day. It rolls off the lips of news readers. We have grown used to it. But what the hell does El Nino mean?
In short it means: “Little Boy”.
That’s not very informative so I shall go back five hundred years to the time when the Spanish arrived on the Pacific coast of South America. They were great fishermen then just as they are now.
Most of the time a cold current ran up the coast from the frigid waters of the south. It was rich in nutrients and that produced the right conditions for lots of fish. But, from time-to-time, the current ceased and warm nutrient-poor water flowed in from the equatorial regions. Fish numbers dropped off and that was very disappointing.
The phenomenon tended to occur at Christmas and the fishermen associated it with the coming of El Nino, otherwise known as the Christ Child.
The image at the top comes from NOAA: The US National Oceanic and Atmospheric Administration. It is based on space satellite observations and shows an unusual band of hot water, in red. That typifies a severe El Nino event.
The opposite phenomenon, which occurs when the equatorial waters are unusually cold, is called La Nina (Little Girl) and is less destructive.
The El Nino/La Nina effect produces severe weather conditions, including tornados, blizzards, hurricanes and torrential downpours. It also effects the monsoon belt.
The phenomenon was discovered by a British meteorologist in the nineteenth century. He was working in, what was then, British India and was assigned the task of discovering why the monsoons sometimes fail. His brilliant investigation led to the discovery that the cause was far away in the Pacific Ocean. Terms like Southern Oscillation Event were used to describe it.
In this Chapter I’ll try to put climate change in its historical perspective. Most of what I say will be about the passing of the last ice age and how it changed the course of human history. The map shows the extent of the ice in the northern hemisphere when the last ice age was at its peak.
Ice ages have come and gone in regular cycles during the last three million years. They have been carefully researched and their cause is well understood.
Planet Earth moves around the Sun on an elliptical orbit and its polar axis wobbles like a spinning top. I’ll not attempt to explain the complexity. The main point is that the amount of sunlight, falling on the landmasses of the northern hemisphere, fluctuates back and forth over periods of tens of thousands of years.
When the northern summers receive a reduced amount of radiation, ice gathers and conditions are ripe for another ice age. Geologists have studied the coming and going of the ice sheets and their observations fit the astronomical model.
An ice age has just passed. If the model continues to be a good predictor, the next one will arrive in about thirty thousand years.
That is a big IF.
A dangerous creature has emerged on Planet Earth and that creature is US. We are fouling our nest with the noxious products of our industries. The climate models that were good predictors in the past might not work any longer. The past is far better understood than the future and I’ll stick to that
Ice cores from the glaciers of Greenland and Antarctica indicate that the last Ice Age ended about fifteen thousand years ago. But it did not end abruptly. It ended in fits and bursts and its consequences are still with us.
The first was the melting of the ice sheets that covered much of what is now the United States, Europe and China. Human populations moved north and powerful nations emerged on land that was once the domain of polar bears.
It didn’t happen overnight.
The first setback came when a natural dam broke somewhere on what is now the border of Canada and the USA. Vast amounts of fresh (not salty) water, from melting ice, flowed into the North Atlantic and disrupted a current delivering warm water to northern parts of Europe.
We now know it as the Gulf Stream. Its loss was a disaster for the northern people. Its return has enabled prosperous nations to arise in Britain and other lands that would, otherwise, have a climate similar to Labrador.
That’s the story of our lives. Nothing stays the same.
The melting ice caused sea levels to rise. People roaming the tundra expanse of northern Europe found themselves cut off from their relatives by encroaching seas. Britain became an island and the trip to Scandinavia could no longer be made on foot.
The same happened elsewhere. Geologists have discovered that, in parts of northern Australia, the encroaching seas would have come in so fast that people would have seen their tribal lands inundated in a single lifetime.
I’ll stick to Europe and the recent past.
Historical records show that the Mediterranean lands were much wetter during the early years of the Roman Empire. Conditions were ideal for growing crops. Then, around the year 400, a cold period set in. Some scientists associate this with an Icelandic volcano. Some historians believe it was the driving force that caused Germanic and Slavic peoples to leave their lands and invade the Empire. At any rate, the Western Roman Empire ended soon after.
Global temperatures began to rise around the year 1000 and a period of immense change followe