Another way of measuring
If we condense the 4 550 million years of Earth's History into 365 days of a year. The dinosaurs appeared only on the 10th of december , became extinct just after december 26, while the first hominids would have started to roam Africa when it was only a few hours before the end of the year. With such a late appearance in the evolution of the Earth, Man has to make a huge effort to grasp the importance of the whole period that preceded him.
31 december - a few hours before the end of the year, Man appeared
26 december - extinction of the dinossaurs
10 december - the dinossaurs appeared
an Earth similar to the one we have now-a-days
Still or in motion?
In a society dominated by haste we don't realize what for us are slow speeds...or super slow speeds.
The concept of speed implies the ability to evaluate a displacement made in a given period of time. It is not always easy to differentiate objects that are stationary from others that move at extremely slow speeds; we know that fingernails are continuously growing because we have to cut them ... but we are unable to see their displacement.
Our senses are not able to detect extreme speeds.
We can identify very fast objects, and very slow objects appear to us to be stationary. It is in these extreme speed ranges that most geological phenomena occur.
Meteorite impact - Erosion - Continental Drift - Earthquakes
When we study the Earth, the problem is even more complicated. Time periods are now estimated using the million-year unit. Many of the geological phenomena, even for observations made over various generations, tend to show a static planet. For example, the Himalayas apparently keep the same form over the years.
Popular tradition says that it is firm as a rock and that it remains of stone and lime, images of the properties of rocks extrapolated to situations in which it is necessary to set an example of something eternal and unchangeable. Nothing could be more misleading... Man sometimes doesn't remember that soft water on hard rock is hard enough to transform it.
The accumulation of events, on the scale of a millimeter a year, during the immensity of geological time, makes any situation ephemeral and transitory.
From the sun to the planets
The contraction of the protosolar nebula caused the concentration of almost all its mass in the central region. The gigantic temperatures reached in the centre during this process led to nuclear reactions where hydrogen nuclei fused into helium nuclei and released energy... a star had just been born, giving birth to our Sun
The turbulence of the nebula prevented some of the gas from building up in the newly formed star. Huge rings then formed in orbit around the new star, which gave way to an accretion disk, consisting of 98.5% gas and 1.5% dust. The frequent collisions between these materials led them to cluster together into larger particles, and in only 100,000 years objects larger than 1 km in diameter appeared... the planetesimals.
The thermal differences in the accretion disk meant that in the innermost regions the planetesimals were composed of rocks and metals, while the planetesimals further away from the proto-Sun they contained large amounts of ice. As the planetesimals collided with each other they clumped together, giving rise to the embryos of planets. After a few million years, giant impacts involving bodies of hundreds or thousands of kilometer radius gave rise to the planets of the Solar System, which are of different constitutions reflecting the compositional zoning of the initial accretion disk.
Earth from accretion .... to differentiation
meteorites ... and its by-products
Do only rocks fall from the sky?
The falling of a rock from the sky associated with huge explosions and flashes that sometimes rival the brightness of the Sun itself, build up a terrifying event. Being a phenomenon that contradicted common sense in everyday experiences, a meteorite fall was almost always interpreted as a divine message.
A long way has come since then, which has now allowed us to realize that after all meteorites are nothing more than pieces of asteroids, bits of the Moon or Mars itself, or perhaps even fragments of comets that come from space and end up falling on Earth. All these fragments have their origin in the inevitable collisions during the evolution of the Solar System. The study of meteorites is a unique opportunity to study the most distant past of our Solar System.
Born 4500 million years ago from the agglomeration of dust condensed from the solar nebula, the primitive Earth appeared as an undifferentiated body formed essentially by an alloy of iron with some nickel, mixed with a few grains of olivine and pyroxene (both silicate minerals with iron and magnesium!) In fact, for the temperatures and pressures that existed at the time in the region of the nebula where our planet was formed, these would be the first condensates to appear as it cooled.
When this proto-Earth reached the size of Mars (about half the radius and one tenth the mass of the present Earth) the heat released during successive collisions, as well as that produced by the chain disintegrations of the main radioactive atoms (mainly aluminum, potassium, uranium and thorium) will have been enough to melt, at least partially, the materials that composed it.
Due to the higher density, the iron and nickel alloy existing in this "magma ocean" gathered into droplets that ended up decanting to the innermost regions of the Earth. This process eventually causes the differentiation of our Planet, which is now constituted by a metallic core surrounded by a mantle predominantly made of iron and magnesium silicates.
The birth of the planets of the Solar System was made the expense of the material that formed the solar nebula. When these planets became nearly as large as they are today, the number of meteor impacts decreased dramatically because most of the material from the original nebula was already incorporated into the planets. Deprived of the energy generated during the impacts, the Earth entered a cooling process, which is still continuing, and which leads to its near solidification.
From the Big Bang to the stars
Big-Bang the beginning of everything? E =mc2
About 13,8 billion years ago a brutal event, Big-Bang, was at the origin of the creation of the Universe. Of these first moments only theoretical physicists are able to broadcast some images that, due to the grandiosity of the values involved, surpass our imagination. The temperature existing then was in the order of 1032 degrees centigrade (100 000 000 000 000 000 000 000 000 000 000), that is, one thousand trillion times hotter than today's sun, and that, the universe was expanding at an unimaginable speed - doubling in size every 10-35 seconds (0.00000000000000000000000000000000000000000000001 s).
After this violent explosion, the temperature started to drop, and 10-9 seconds after the initial moment, it was already "only" 1015 degrees Celsius. As the cooling continued, the elementary particles began to interact, and 3 minutes after the Big Bang the first stable atomic nucleus was formed.
For the next 300,000 years the universe was made of plasma, which means that the light elements (e.g. hydrogen, helium) were in the form of atomic nuclei mixed with free electrons.
The temperature began to decrease and some electrons began to combine with the atomic nuclei to form ions; at about 3,500 degrees Celsius, the transformation was almost complete. Most of the ions were electrically neutral and the plasma became a gas..
An impossible journey?
Despite the desire that mankind has of knowing the interior of its planet, it has remained inaccessable. As amazing as it sounds, despite having samples of the surface of the Moon,
located at a distance of 384000 Km, brought to Earth, little more than 12 Km is the greatest depth that mankind has been able to get a sample in its own planet.
This apparently strange situation is easily explained when we remember that the temperature at this depth easily passes 300º C ...
Is it possible to touch?
The formation of mountain ranges can drag to the surface, rocks from the crust and even the mantle, which were at a depth of dozens of kilometers...
The magma that ascends in vulcanoes can drag mantle rocks to the surface, which were at a depth of hundreds of Kilometers...
Some of the meteorites that fall on our planet, we believe they have similar compositions to the Core which lies at more than 2900 kilometers depth...
Is it possible to feel?
When we say the litosphere is solid... or that the astenosphere has a viscous behaviour in the geological time, we are refering to the way materials behave in the course of millions of years.
It isn't possible to replicate this behaviour in experiments that last seconds or minutes, since the physical behaviour of materials depends on the observation time, but... we can try...
Descend into the crater of Yocul of Sneffels,
which the shade of Scartaris caresses,
before the kalends of July,
audacious traveler, and you will reach
the center of the earth. I did it.
Arne Saknussemm
(snippet of "Journey to the Center of the Earth" - Jules Verne)
In the last years, new geophysical methods enabled the understanding tridimensional dynamic of the interior of our planet and... a surprise awaited scientists!
Instead of the predominance of treadmill-like concentric convective cells, the upward hot superplumes... and downward cold ones... appear as the main elements of this internal convection.
Solar radiation
After the formation of the Sun, the gigantic storms that existed there lead to the vibration of its particles. This vibration results in the emission of electromagnetic radiation in the form of electromagnetic waves. The radiation emitted by an object, which can transport thermal energy, depends on its temperature. Because of this dependence, any exchange of thermal energy by radiation always transfers heat from a hotter to a colder object.
Unlike other heat transfer processes (...) that rely on atoms, molecules, or electrons to transport heat, radiation occurs directly through space even when there is nothing between the objects. Solar3 radiation is therefore an extremely efficient process in the continuous transfer of energy to the Earth, and one of the main factors responsible for maintaining the size of this planet.
PERIODIC TABLE ... ORGANIZING DIVERSITY
The existence of periodic regularities in the properties of CHEMICAL ELEMENTS led to the development of the Periodic Table of the elements.
The current table contains 118 elements, arranged in horizontal rows (periods) and vertical rows (groups) in ascending order of ATOMIC NUMBER (the number of protons in the nucleus of an atom).
The electronic configuration (the way the elements are arranged in an atom) of the elements helps to explain the periodicity of their physical and chemical properties. The horizontal lines (periods) are arranged so that elements with similar properties are in the same columns (groups or families).
nothing gets done without EnergY
Without energy, nothing happens.
There would be no Sun, the Earth would not have formed, the water in the rivers would not "flow" and... we wouldn't be here.
There are 2 forms of energy that are especially important for understanding how our planet works: Potential Energy and Kinetic Energy.
Potential Energy is obtained whenever any object is forced to move in a different direction than the force acting on it. It is, for example, the energy that is stored when a bow is stretched and then used to make an arrow shoot. But it is also the energy associated with lifting any object, a situation in which the force of gravity must be overcome.
