Three kilometres of popsicles

The ice core that climate researchers have drilled in the middle of Antarctica reaches exactly 3270.2 metres deep. At the bottom, the ice is almost a million years old. The three-kilometre-long ice core tells climate researchers a lot about the last eight ice ages.

It is a sensation for science: as part of the “Epica” research project, climate researchers have completely drilled through the Antarctic ice sheet. At the Dome Concordia research station, after nine years of drilling, the researchers hit rocks and reached the deepest point of the borehole: at a depth of 3270.2 metres, the air and ice are a whole 900,000 years old. The samples from this ice core will tell all kinds of new stories about the Earth’s climate history. They contain information about the last eight ice and warm periods, for example about the concentration of carbon dioxide in the atmosphere.

The different ice layers are like annual rings of the climate. Every year snow falls on the ice and forms a new layer. The ice sheet therefore consists of many annual layers lying on top of each other. Air bubbles are enclosed in these ancient ice layers, which provide information about the climate history of the Earth. How strongly did the greenhouse gases in the air fluctuate over thousands of years? How did temperatures develop over long periods of time? Answers to these questions are immortalised in the ice layers.

To extract as much information as possible from the three-kilometre-long ice core, it is sawn into pieces and transported to research laboratories. The pieces are kept in cold storage until the ice can be examined more closely in the laboratory.

Climate research in a whisky glass

Many discoveries are due to chance. The French ice scientist Claude Lorius, for example, observed pieces of ice melting in a glass of whisky. As he did so, the scientist noticed air bubbles trapped in the ice. When the bubbles burst as the cubes melted, Lorius came up with an ingenious idea: the air bubbles were witnesses to the composition of the air. Perhaps one could research the climate history of the earth in a similar way, namely by drilling into ancient ice layers.

This idea came to Claude Lorius in 1965, and in the years to come he put his idea into practice. Large-scale research projects on Greenland and in Antarctica examined climate history with the help of ice cores. The results are presentable: The most recent drilling of Dome Concordia in Antarctica now even provided insight into 900,000 years of climate history!

The Earth Ages

Since its formation, the earth has changed a lot: Mountains, oceans and continents have formed and passed away, animal and plant species have spread and become extinct. Most of these changes happened very slowly, over many millions of years. But every now and then there were drastic events: Within a few thousand years, environmental conditions changed drastically.

For the scientists who study the history of the Earth, these drastic changes are like a new chapter in a book: they divide the Earth’s history into different sections called eons.

At the beginning, 4.5 billion years ago, the Earth was completely uninhabitable. It emerged as a hot ball of glowing molten rock surrounded by hot, corrosive and toxic gases. This sounds like a description of hell – and from the Greek word “Hades” for hell also comes the name of this time: Hadaic. It ended about four billion years ago with the first major change: the earth had cooled down so much that the surface became solid – the earth got a crust.

The earth cooled further so that liquid water could collect on the crust: Oceans were formed. And in these seas, life began about 3.8 billion years ago – but initially only in the form of the simplest bacteria. The Greek word for origin or beginning is in the name of this period: Archaic. An important climatic change about 2.5 billion years ago marked the transition to the next epoch: primitive organisms began to influence the environment. They produced oxygen, which until then had been almost non-existent in the atmosphere.

The early unicellular life forms became more complex over time, they formed cell nuclei. Later, some also began to work together permanently in associations – this eventually became the first multicellular organisms. However, they did not yet have solid shells or skeletons, so that hardly any fossils have survived from this period. The epoch owes its name to this period before the emergence of fossils: Proterozoic.

The Proterozoic ended 550 million years ago with an explosion of life: within a short time, an enormous diversity of species developed from the primitive forms of life. These species were much more complexly built – and some also already had hard shells, which were preserved as fossils for the first time. Therefore, for scientists, the history of life only really becomes visible from this point onwards. And this epoch is also named after the Greek term for “visible”: Phanerozoic.

This age of life has lasted for 550 million years until today. However, the development of life did not proceed evenly: After the explosive spread of life, there were two devastating mass extinctions. These mark further important cuts in the Earth’s history, so that scientists divide the age of life, the Phanerozoic, into three sections called eras.

The oldest era of the Phanerozoic began 550 million years ago with the mass emergence of new species. It is called the Palaeozoic Era. At first, life took place only in the oceans. Then plants colonised the land, and later the animal world followed suit: First, amphibians developed, which were already able to venture a little on land, and finally also reptiles, which became independent of the water and conquered the land. The Palaeozoic ended about 251 million years ago with the greatest mass extinction of all time: More than 90 percent of all animal and plant species became extinct, especially in the oceans. The reason for this has not yet been conclusively explained. Scientists suspect that an ice age was to blame, possibly as a result of a meteorite impact.

When the surviving animal and plant species had to get used to their new environment, the Mesozoic era began. It is above all the age of the dinosaurs: giant lizards evolved and dominated life for almost 200 million years. But the Mesozoic also ended with a drastic event: about 65 million years ago, a large meteorite struck the Earth. So much dust and ash was thrown into the air that the sky darkened and the climate changed for a long time. The dinosaurs and many other species became extinct.

Small mammals in particular, which were best able to adapt to climate change, benefited from this. They had already evolved in the Earth’s Middle Ages, but had remained in the shadow of the dinosaurs. Now they were able to spread rapidly, conquer a wide variety of habitats and continue to evolve. Humans are also descended from this group. This most recent age continues to this day and is therefore also called the Earth’s New Era or Cenozoic Era.

This rough classification of Earth history is oriented towards very drastic changes in life: explosive proliferation or mass extinction. In between, however, there were further upheavals due to various other influences – changes in the oceans and continents due to continental drift, climate change between ice ages and warm periods, composition of the air and much more. Invariably, the new conditions favoured some species and disadvantaged others. Thus, the three sections of the Phanerozoic (Age of Life) can still each be divided into several periods.

Glaciers of the Ice Age

On Earth, warm and cold periods have alternated over the past millions of years. During the warm periods, the ice melted and the glaciers shrank. During the ice ages, on the other hand, the temperature dropped so much that large amounts of new ice were formed. Glaciers were therefore able to spread over large areas.

At that time, large parts of northern Germany and the Alpine foothills were covered by huge glaciers. The extent of the glaciers can still be seen today in the mounds of debris that the glaciers left behind. The debris, consisting of larger and smaller rock particles, was carried away in the glacial ice and deposited at the place where the ice melted again. When whole mounds of debris are accumulated, they are called moraines.

When the great glaciers of the ice ages melted, rivers and streams of meltwater formed at their lower ends. These rivers dug valleys into the ground, which are known today as glacial stream valleys. Hollows or depressions in the landscape filled with water and turned into lakes.

Warm times – cold times

There were times on Earth when large areas of land were buried under a thick sheet of ice. At times, the ice masses even reached as far as the equator. Alternating with the ice ages, gigantic heat waves gripped this planet. For millions of years it was so hot that palm trees could even grow at the North Pole. Ever since the earth has existed, ice ages and warm periods have alternated. So climate changes existed long before humans inhabited the earth. And these natural climate changes left their mark.

During the ice ages, the glaciers spread out. Ice masses ground across the subsoil, planed out valleys and pushed masses of debris in front of them. As long as it was cold, large quantities of water remained bound up in the ice, which caused the sea level to fall. As soon as the temperatures rose again, the ice melted and the sea level also rose again. Valleys and depressions filled with water and became rivers and lakes.

Animals and plants appeared or disappeared with the temperature changes. During a particularly warm phase, for example, many different species of dinosaurs lived. When it became cooler, many of them died out. Typical of the last ice age were animals like the mammoth, reindeer or bison. As temperatures rose, they disappeared from the scene or moved to cooler regions. Reindeer, for example, still have their home in northern Europe, Siberia and Canada.

A shell of gas

Seen from space, it appears like a fine bluish veil that wraps around the Earth: the atmosphere. It is the envelope of air that surrounds our planet. Compared to the diameter of the Earth, this envelope is quite thin: if the Earth were the size of an apple, the atmosphere would be about the thickness of its skin.

Without the atmosphere, there would be no life on this planet, because plants, animals and humans need air to breathe. It protects us from the cold and from harmful radiation from space. It also allows meteorites to burn up before they can hit the earth’s surface. This air envelope is vital for us – but what is it actually made of?

The atmosphere is a mix of different gases. A large part of this gas mixture is nitrogen: at 78 per cent, that’s almost four-fifths of the entire atmosphere. Only 21 percent consists of oxygen, which we need to breathe. The remaining one percent is made up of various trace gases – gases that only occur in the atmosphere in traces. These trace gases include methane, nitrogen oxides and, above all, carbon dioxide, or CO2 for short. Although the proportion of CO2 is quite small, this trace gas has a huge influence on our earth’s climate. This can be seen in the greenhouse effect, which heats up our planet.

The fact that the Earth has an atmosphere at all is due to gravity. It holds the gas molecules on the earth and prevents them from simply flying out into space. In fact, the air becomes thinner and thinner with increasing altitude and thus decreasing gravity. At altitudes as low as 2000 metres above sea level, this can become unpleasantly noticeable for people: They suffer from altitude sickness with shortness of breath, headaches and nausea. Extreme mountaineers who want to climb high peaks like the 8,000-metre peaks of the Himalayas therefore usually take artificial oxygen with them on their tour.

Sensational find in South Africa

Actually, gold and diamonds are mined in the South African gold mine “Witwatersrand Basins”. But geologists from Leipzig have found something there that is worth more to them than any precious metal: they have come across groundwater that is about two billion years old.

But how could it happen that the water inside the Earth became so old? Normally, the Earth’s water moves in an eternal cycle. That is why it cannot age. But the groundwater that the German geologists excavated was enclosed in stone. Sealed off from the outside world for an extremely long time, an ecosystem of its own developed in this groundwater with tiny creatures that manage without light and oxygen.

The researchers could tell how long the water had been lapping down there by its chemical “fingerprint”: depending on the water’s history, the type and quantity of substances dissolved in the water differed. What was particularly striking was the large amount of the noble gas neon. From the exact neon content, the researchers calculated the true age of the water: two billion years – a sensation! This makes the aged groundwater the oldest water on Earth. Because of its high salt content, however, it should be treated with caution. In any case, it should not be drunk!

Big City Swamp Berlin

Many Berliners wade through water when they go down to the basement. The reason for this is the rise in the groundwater level. And the water table in Berlin is higher than it has been for many years. A good hundred years ago, Berliners were still used to wet feet – after all, the city was founded on a marshland. Only the construction of dams like the Ku’Damm made it possible to get through the city dry. But as the city continued to grow, as industry settled and the underground was built, the water table dropped due to the high consumption of water. This trend has long since reversed. Since the fall of communism, Berliners have been using much less water because large industrial companies have had to close. The result: the water level has risen by more than half a metre in just a few years. The capital is literally up to its neck in water. Berlin will soon have to come up with something to prevent it from becoming a swamp again …