What are some examples of geological discoveries

The geological ages

The earth has changed a lot since its formation: mountains, seas and continents have arisen and passed, 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 decisive events: within a few thousand years the environmental conditions changed drastically.

For the scientists studying 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, the Eons to be named.

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, caustic and poisonous gases. That sounds like a description of hell - and the name of this time comes from the Greek word "Hades" for hell: Hadaikum. It ended about four billion years ago with the first big change: The earth had cooled down so much that the surface became solid - the earth got a crust.

The earth continued to cool, so that liquid water could collect on the crust: seas were formed. And life began in these seas around 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 time: Archean. An important climate change about 2.5 billion years ago marked the transition to the next epoch: primitive living things began to influence the environment. They produced oxygen that was previously almost completely absent from the atmosphere.

The early unicellular life forms became more complex over time, they formed cell nuclei. Later, some began to work together on a long-term basis in associations - this ultimately resulted in the first multicellular organisms. However, they did not yet have solid shells or skeletons, so that hardly any fossils have survived from this period. This epoch owes its name to this time before the fossils were formed: Proterozoic.

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

This age of life has lasted for 550 million years until today. However, life did not develop evenly either: after the explosive spread of life there were two devastating mass extinctions. These mark further important turning points in the history of the earth, so that scientists divide the age of life, the Phanerozoic, into three sections, Eras called, divide.

The oldest era of the Phanerozoic began 550 million years ago with the mass emergence of new species. They are called that Antiquity or Paleozoic. At first life only took place in the oceans. Then the plants colonized the land, later the animal world followed suit: first the amphibians developed, which could already feel their way a little on land, and finally also reptiles, which became independent of water and conquered the land. The ancient world ended about 251 million years ago with the greatest mass extinction of all time: Over 90 percent of all animal and plant species died out, especially in the oceans. The reason has not yet been finally clarified. 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, it broke Earth Middle Ages or Mesozoic at. It is primarily the age of the dinosaurs: giant lizards evolved and ruled life for almost 200 million years. But the Middle Ages also ended with a decisive event: about 65 million years ago a large meteorite hit 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 benefited from this, as they were best able to adapt to climate change. They had already developed in the Mesozoic, but remained in the shadow of the dinosaurs. Now they could spread rapidly, conquer the most varied of habitats and keep developing. Humans also descend from this group. This most recent age continues to this day and therefore becomes the Earth New Age or Cenozoic called.

This rough classification of the earth's history is based on very drastic changes in life: explosive multiplication or mass extinction. In between, however, there were further upheavals due to various other influences - changes in the seas and continents due to continental drift, climate change between ice ages and warm periods, the composition of the air and much more. The new conditions always favored individual species and disadvantaged others. So the three sections of the Phanerozoic (Age of Life) can each be divided into several periods.


It is a sensation for science: In the north of Canada, geologists have come across the oldest rocks ever discovered. They are part of the Nuvvuagittuq greenstone belt on Hudson Bay and are over four billion years old.

An international team of researchers has now dated the rocks in northern Canada to 4.28 billion years. That would make it just 300 million years younger than our solar system. Now the scientists are investigating whether the ancient rocks are a remnant of the very first crust that was once separated from the earth's mantle. Then the discovery could help unravel some of the secrets of the very early history of the earth. Perhaps the rocks reveal something about where and when life began? The researchers also hope to be able to read in the rock how the atmosphere changed and when the first continent of our earth was formed.

Incidentally, the name greenstone belt comes from the color of its metamorphic rock. It is the minerals contained in the rocks that give them a greenish color in some places.

Age ranking of the "veterans"

They are all old and wrinkled. But the chunks of the oldest rocks are separated by millions of years. Until recently, when the rock from the Nuvvuagittuq rock belt was dated an impressive 4.28 billion years ago, another rock in northern Canada was considered the oldest rock on earth: the so-called Acasta gneiss in the northwest of the country. After all, it is 4.03 billion years old. With its old age, the old gneiss surpasses a formation of ribbon iron in Greenland: This now ranks 3rd on the age scale of the rocks. The rocks in Greenland are “only” 3.9 billion years old!


Another piece of the puzzle has been found: excavations in the Thuringian Forest bring new insights into the history of the earth at the end of the ancient world.

In the past two weeks they have dug and dug properly, but the effort has paid off: Researchers from the Freiberg Mining Academy uncovered a ten-meter-high rock wall on the outskirts of Oberhof in the Thuringian Forest. Over 100 fossils were found in it - including crabs, mussels and ferns, but also traces of dinosaurs and freshwater sharks.

But what are sharks doing in the Thuringian Forest? The researchers can explain that: almost 300 million years ago there was a large inland lake at this point. At that time, our continents were not yet separated by seas, but united in a supercontinent Pangea - and the Thuringian Forest was then located between North America and Eastern Europe.

For many millions of years, the remains of the inhabitants were deposited on the bottom of the inland lake. But about 250 million years ago the climate changed: It got drier and hotter and the lake dried up. Today only the fossils bear witness to this time.

The largest dinosaur cemetery in the world

The heart of every paleontologist beats faster here: The city of Zhucheng in the east Chinese province of Shandong is known worldwide as the "dinosaur capital". Dino bones have been found in the area again and again since the 1960s. To date there are more than 50 tons, including a spectacular find of thousands of fossils in 2008. Now the excavations find their place in the recently opened Tyrannosaurus Museum.


The fossil of a baby dinosaur was discovered in a lime works in Kelheim, Bavaria. 98 percent of the small predatory dinosaur has been preserved. This makes it the best preserved dinosaur fossil in all of Europe.

The baby dinosaur, which lived millions of years ago and fed on dragonflies, lizards and beetles, measures 72 centimeters. The little predatory dinosaur kept itself in balance with its long tail. That wasn't easy with the weight of his large skull. This dinosaur was probably not older than a year. On the other hand, it survived the next 135 million years that it lay in the earth: Remnants of skin, hair and even feathers can still be seen on the fossil. He couldn't fly, however. For this he lacked flight feathers and the corresponding muscles.

The find is a real sensation for science. For them, the small predatory dinosaur is the most important fossil from Germany since the ancient bird Archeopteryx was discovered.

Find fossils on the Altmühl river

Ancient times, the area of ​​today's Altmühl was on the edge of a tropical sea. The climate was significantly warmer, ichthyosaurs, crabs, crocodiles and the ancient bird "Archeopteryx" cavorted in and around the shallow water. Today the remains of these animals can be found in the form of fossils. One of them is the recently discovered baby dinosaur from Kelheim. A few kilometers upstream, in the Solnhofen limestone, the world-famous specimens of the ancient bird Archeopteryx were discovered. Everyone can now go on a hunt for fossils there: the Museum Solnhofen offers guided tours of the quarry, where visitors can split limestone slabs and look for fossils.

The beginnings of the earth

We would not recognize the earth immediately after its formation. It was an extremely uncomfortable planet: there were neither continents nor oceans, but a seething surface of glowing hot, viscous magma. Why couldn't the earth's crust form for a long time?

A good 4.5 billion years ago comets, asteroids, gas and dust condensed to form our planet. Its own gravity pressed these individual parts together so that they were subjected to strong pressure. This pressure was of course highest in the earth's core, on which the weight of the entire outer layers weighed. As a result of the high pressure, the rock was heated up and melted. Outwardly, the pressure and thus also the temperature became less. Even so, the surface of the earth remained very hot for several hundred million years and could not cool down and solidify.

In order to understand the reason for this, the scientists had to look at the moon: Ancient lunar craters from the time the solar system was formed tell us that the moon was hit by numerous meteorites when it was young. It is therefore assumed that the earth was also exposed to a real rock bombardment from space at the same time. The lumps fell to the earth at high speed - and the impacts were correspondingly violent: Even lumps of a few hundred tons could easily cause an explosion the strength of an atomic bomb!

So the earth's surface continued to heat up for a long time, stirred up again and again and remained so fluid. Only when the impacts gradually subsided after a few hundred million years did the temperatures on the earth's surface drop. The rock could slowly solidify and form an earth crust that grew thicker and thicker over the course of millions of years. But to this day it is only a very thin layer that floats on a viscous, hot interior of the earth.

How did the water come to earth?

About two thirds of the earth is covered with water - a unique selling point: the earth is the only planet in the solar system on which there is liquid water. Life originated in water, and water is also vital for us humans. But where does the water on earth actually come from?

Scientists suspect that the water comes from comets. These lumps of ice and dust originally formed on the edge of the solar system. But some also got into the interior of the solar system on orbits and became part of the newly emerging planets.

Initially, the young planets were very hot - so hot that the rock melted and formed a liquid ball. And the ice on the comets not only melted, it even evaporated. Because the water vapor was much lighter than the molten rock, it bubbled up towards the surface. There it escaped into the atmosphere through volcanoes.

As the earth slowly cooled, the steam turned back to liquid water. To put it more clearly: It started to rain. Those first downpours must have been stronger than any thunderstorm we can imagine today. And it must have rained for a very long time - tens of thousands of years. Large parts of the young earth's surface were flooded - in some places up to ten kilometers high. This is how the oceans came into being.

And what happened to the water on the other planets? Why are there no oceans there? Mercury doesn't have enough gravity to hold an atmosphere at all - like all gases, water vapor simply escaped into space. The same thing happened on the moon. The solar radiation on Venus is so strong that the water has also evaporated into space. On the other hand, it is too cold on Mars, but there are suspected large deposits of ice beneath the surface. And the gas planets have no solid surface on which seas could form. One suspects an ocean of water on Jupiter's moon Europa, but the surface is frozen. So the earth remains the only celestial body in the solar system with seas.

How did life come about?

The origin of life on earth has long been puzzled. It is known that simple bacteria developed as early as 3.8 billion years ago. But how was that possible - can life just come into being?

A student named Stanley Miller had an idea in 1953: He wanted to simulate the environmental conditions on earth in an experiment around 3.8 billion years ago. To do this, he filled a glass flask with water and some gases that were probably components of the primordial atmosphere: ammonia, methane and hydrogen. In this gas mixture he ignited electrical discharges in order to simulate the lightning bolts of the thunderstorms of that time. The water should replicate the natural water cycle. There was also a heater where the water evaporated and a cooling coil where it condensed again.

Miller ran this experiment for several days and then examined the water. In it he found a certain kind of chemical compound: amino acids, an important part of the cells of all living things. Miller had shown that the building blocks of life can be created from simple gases.

This is why scientists today assume that the gases in the primordial atmosphere also reacted to form organic substances in a similar way. Rain washed them into the sea, and high concentrations could accumulate, especially in shallow waters. Whether through aggressive sunbeams or lightning - the particles must have reacted with each other again and again. A random combination of molecules then had a special property for the first time: It was able to reproduce itself - the beginning of life.

How did our air we breathe come about?

What do people and animals need to live? Food and water, of course, but above all oxygen! We get it from the air we breathe. But that was not always the case: the primordial atmosphere consisted of water vapor and poisonous gases such as carbon dioxide and foul-smelling hydrogen sulfide. We would immediately suffocate in this “air”. But what has changed since then? Why is there oxygen in the atmosphere today? And since when?

If you look back in the history of the earth, you can find traces of living things that must have needed oxygen more than two billion years ago. So there must have been oxygen in the air back then.

Petrified traces of microscopic bacteria, called blue-green algae, are much older. And they have it all: These organisms were the first to use the energy of sunlight for their metabolism. They absorbed water and carbon dioxide from their environment and, with the help of solar energy, converted them into sugar, which they used to store energy. In addition, this chemical reaction produced oxygen - as a waste product, so to speak. However, the bacteria could not do anything with the oxygen and simply released it into the environment.

At that time there was plenty of sunlight and carbon dioxide, and the world's oceans were comparatively warm. These were the best conditions for the blue-green algae to multiply and spread. In doing so, they produced more and more oxygen, which accumulated over millions of years, first in the oceans and later in the atmosphere.

The waste product of these bacteria created the conditions for higher forms of life in water and on land. From the bacteria later emerged the chloroplasts, which to this day capture the solar energy in every plant. The principle of so-called photosynthesis has also remained the same: With the help of sunlight, water and carbon dioxide are converted into sugar and oxygen. The sugar serves as a nutrient for the plant, the oxygen is released into the air and inhaled by humans and animals.

What are asteroids, meteorites and comets?

On some nights you can observe a special moment in the sky: it looks like a star is falling from the sky. Superstitious people even think that whoever sees such a shooting star could wish for something. But what is really behind it and where do the shooting stars come from?

In our solar system there are not only the sun, planets and moons. Many small pieces of rock and metal have also been discovered. They are much smaller and not as nicely round as planets, hence they are called minor planets or Asteroids. Like their big siblings, they circle the sun in regular orbits. Most asteroids can be found in the "asteroid belt" between the orbits of Mars and Jupiter.

Every now and then two of these asteroids collide. A crash like this creates a lot of debris and splinters. These fly away from the previous orbit, across the solar system. Some of them get close to the earth, are attracted to it and fall to the earth. These falling chunks are also called meteorite.

On earth they would literally fall like a stone from the sky - if it weren't for the atmosphere. Because the meteorites are so fast that the air cannot move to the side quickly enough. The air in front of the falling rock is compressed and therefore extremely hot. The air begins to glow and the meteorite begins to evaporate. We can then see that as a glowing streak that moves across the sky - a shooting star.

Most meteorites are so small that they burn up completely as they travel through the air. The trail then simply ends in the sky. Larger debris also lose mass on the way, but does not completely evaporate. They reach the ground and strike there.

What these meteorites do to the earth depends on how big they are. Small meteorites a few centimeters in diameter, for example, just leave a dent in a car roof.

The largest known meteorite hit about 65 million years ago. It was several kilometers in diameter and tore a crater 180 kilometers in diameter. The impact threw so much dust into the air that the sun was eclipsed for hundreds of years. As a result, plants and animals all over the world died out - this was the end of the dinosaurs.

Fortunately, such large meteorites are very rare so we don't have to worry. In addition, unlike the dinosaurs, we can observe the sky with telescopes and discover such large asteroids long before the impact.

While a shooting star burns up in a few seconds, another phenomenon remains visible longer: Comets with its tail there are days or weeks in the sky. In the past, people also attributed many properties to them - as divine signs, heralds of calamity or harbingers of happy events. But the truth is a little less spectacular.

Astronomers also call comets "dirty snowballs". They come from the outer solar system, far from the warming power of the sun. It's so cold there that water immediately freezes to ice. This is how lumps of ice and dust form - dirty snowballs.

Even a comet initially travels far away from the sun - until it is deflected by a collision and flies in the direction of the inner solar system. It gets closer to the sun and over time receives more and more light and warmth. This will cause the frozen surface to begin to thaw and even to evaporate. This creates an envelope of water vapor and dust around the comet.

At the same time, the comet gets to feel the “solar wind” - tiny particles that fly out of the sun at high speed. They hit the comet's vapor envelope. This will blow away the comet's vapor envelope, creating an elongated cloud that points away from the sun. When this cloud is then hit by sunlight, it appears as a glowing streak - the comet's tail.

The comet makes an arc around the sun and then moves away again. When it is far enough away from the sun, thawing and evaporation will also stop. The tail disappears and the comet moves like a dirty snowball through the vastness of the outer solar system. Depending on the comet's orbit, it will take many decades or even centuries before it comes close to the sun again.

From bone to stone: fossils

What we know about the life of long past times, we owe a large part to the fossilized remains of living things: the fossils. Such fossils arise when plants or animals are buried under layers of sediment after their death. The soft parts of living beings decompose, hard parts such as teeth, bones or shells are preserved. When thick layers of rock weigh down on these remnants, they are slowly pressed into rock under the increasing pressure.

The younger fossils are usually found in the upper rock layer. The deeper you go into the sedimentary layers, the older the fossils that are stored there. Very old, but still frequently found fossils are, for example, the ammonites. These are the remains of shellfish that lived hundreds of millions of years ago and became extinct about 65 million years ago. Because they only lived for a limited period of time, it is possible to roughly determine the age of the rock in which they were found.

In order to discover a fossil, it is not necessary to drill deep into the earth. When the rock layers rise over the course of millions of years, deeper layers are also pushed upwards and exposed by erosion. In this way, fossils from the lowest layers of the sea floor, as is the case in the limestone Alps, can reach high mountain peaks.

However, plants and animals such as mosquitoes and beetles are not only trapped in rock, but also in the resin of trees. Over time, the sticky tree sap turns into solid amber. In this yellowish-transparent rock, insects or plants that lived millions of years ago can still be seen very well today.

Warm times - cold times

There were times on earth when large areas of land were buried under a thick sheet of ice. The ice masses even penetrated near the equator at times. In alternation with the ice ages, this planet was hit by gigantic heat waves. For millions of years it was so hot that palm trees could even grow on the North Pole. Ice and warm periods have alternated since the earth has existed. Climate change occurred long before humans inhabited the earth. And these natural climate changes left their mark.

During the ice ages, the glaciers expanded. Ice masses grinded the subsoil, planed valleys and pushed masses of debris in front of them. As long as it was cold, large amounts of water remained bound in the ice, which caused the sea level to drop. As soon as the temperatures rose again, the ice melted and the sea level rose again. Valleys and depressions filled with water, became rivers and lakes.

Animals and plants appeared or disappeared with the temperature changes. For example, many different species of dinosaur lived in a particularly warm phase. When it got cooler, many of them died out. Animals such as mammoth, reindeer and bison were typical of the last ice age. With the rising temperatures, they disappeared from the scene or they moved to cooler regions. Reindeer, for example, still have their home in Northern Europe, Siberia and Canada.

Continents on the move

For a long time it was thought that the land masses of the earth would stand rigidly in place. It later turned out that the opposite is the case. The continents of our planet are moving! Like huge ice floes, they drift in different directions, albeit not very quickly. Their speed corresponds roughly to the growth of a fingernail. But why is it that the continents are constantly on the move?

The earth's crust that envelops our planet is brittle and cracked. It resembles a cracked egg shell and is made up of seven large and many smaller plates. Some of them make up the continents, others make up the ocean floor. These plates of the earth's crust float around on a hot, viscous rock slurry and are driven by movements in the earth's interior, more precisely: by currents in the earth's mantle. Experts also say: you are drifting. All of these processes related to the movement of the earth's plates are called plate tectonics, and the movement itself is also known as plate drift.

The earth is particularly active where the individual plates adjoin one another. At some of these plate boundaries, hot rock penetrates upwards from the earth's mantle and cools down. Here new earth crust forms: the two plates grow and are thereby pushed apart. On the other hand, where two plates collide, the lighter one of them - the continental crust - is crumpled up and unfolded to form mountains. The heavier of the two - the oceanic crust - is slowly disappearing into the depths. Due to the heat in the earth's interior, their rock is melted again. As the edge of the plate sinks into the depth, it pulls the rest of the plate behind it and thus additionally drives the plate movement.

Volcanic eruptions, earthquakes, long mountain ranges and deep ocean trenches accumulate along such plate edges. Most of the unrest on the earth's surface brings with it the largest of its plates: it is the Pacific plate, which is moving northwest at a rate of about 10 centimeters per year. Most of the world's active volcanoes can be found at their edges, and violent earthquakes shake the region. Because of the frequent volcanic eruptions and earthquakes, this plate boundary is also called the “Pacific Ring of Fire”.