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Minerals; the solid face of the planet


Minerals are crystalline solids that constitute almost the entire solid fraction of the planet (geosphere). In a crystalline solid (i.e. crystal), the atoms are not arranged randomly, but in an extremely ordered three-dimensional arrangement, maintained by chemical bonds between the different elements present. In these structures, it is always possible to identify a basic unit (the unit cell) that, by replication in three directions, allows the construction of a crystal of "infinite" dimensions when compared to the size of the cell... these are the minerals as we know them...

The enormous regularity of these structures means that the number of positions to be occupied by different elements is limited, although there is some freedom. Take as an example the mineral blenda (important as a zinc ore) with a cubic unit cell; its chemical formula can be stated as (Fe, Zn) S. In its crystal structure, both iron and zinc are surrounded (or coordinated) by four sulfur atoms, defining a tetrahedron. These positions can be randomly occupied by either iron or zinc, defining the FeS or ZnS ends that mix together to form what is called a solid solution.

Silicates; the fundamental constituents


Oxygen and silicon are the two most abundant elements in the Earth's crust, so it is not surprising that silicates are the most frequent minerals on the Earth's surface. In most silicates, silicon is coordinated by four oxygens, defining a tetrahedron of silica.
This tetrahedron can have common vertices with other neighboring tetrahedrons, as in quartz, or be isolated, as in olivine, an important magnesium iron silicate, common in all basalts.

Feldspars, which are also silicates, are the most abundant mineral group in the Earth's crust and are common in most igneous rocks. Their composition varies by solid solution between the calcium (anortite; CaAl2Si2O8), sodium (albite; NaAlSi3O8), and potassium (microcline; KAlSi3O8) extremes.

The submicroscopic crystalline structure is reflected in the external appearance of the silicates. This is the case in micas and pyroxenes where, respectively, the layered and chain-like arrangement of silica tetrahedrons induces sheet-like and prism-like growth of these minerals.

However, at the Earth's surface one can also often find minerals in which silicon is not part of their structure and composition. This is, for example, the case with hematite, calcite, gypsum, pyrite, apatite, and fluorite.

only External Energy?


If solar energy allows us to perceive many of the phenomena that we observe on the surface of the Earth, we could hardly imagine a process by which solar energy is responsible for earthquakes, especially since these are completely independent of any climatic factor.

Where then do we get the colossal amounts of energy that are released during an earthquake?
In the absence of an energy source external to our Planet, we can only look for an internal energy source.

only External Energy?


If solar energy allows us to understand many of the phenomena that we observe on the surface of the Earth, it is not with this source of energy external to our Planet that we can explain the volcanic phenomena, in which molten rock at temperatures exceeding 1,000 º C can come out of the Earth's interior.

Where then do we get the colossal amounts of energy that are released during a volcanic eruption?

In the absence of an energy source external to our Planet, we can only look for an internal energy source.

Earth; a planet cooling down...

The Earth's core is at a temperature of over 5,000 degrees Celsius. The thermal inequality between the Earth's interior and surface leads to a continuous transfer of heat from the inner layers to the surface layers, which causes our planet to cool down.

Where Internal Energy Comes From

When trying to find the origin of the Earth's internal heat, we come across not one, but several sources. In fact, since the formation of our planet, various processes that took place inside it have contributed, and some still contribute, to the fact that in terms of energy the Earth is not totally dependent on the Sun, as is the case with other planets in the solar system.


Some of this internal energy is nothing more than the residue of the energy released during the process of formation of our planet some 4,550 million years ago. The successive collisions between the dust that made up the nebula at the origin of the solar system led to the release of enormous amounts of thermal energy obtained by transformation of kinetic energy.


The formation of the; core by collapse of the densest elements (essentially iron and nickel) led to the conversion of large amounts of potential energy into thermal energy.


In 1896 Henri Becquerel discovered that some forms of uranium were not stable, continuously changing their atomic structure and giving rise to new elements. This spontaneous transformation, which always occurs at a constant rate, came to be known as radioactivity. The following years saw the discovery of radioactivity in other naturally occurring chemical elements; radium, lead, thorium, argon, potassium, calcium, rubidium, strontium, carbon, and nitrogen are some of the elements that have been shown to be involved in radioactive processes.


During the formation of the Earth, many of these radioactive elements were trapped inside and have been fueling radioactive processes ever since. Because these processes are always associated with the release of energy, radioactivity has been one of the main sources of internal energy of our Planet, becoming a fundamental factor for its dynamic behavior.

Why do VULCANOS explode?

In depth, the overlying rocks exert a load on the magma, strongly compressing the gases in it. `As the magma rises, the load exerted on it is less and less, and so the gases expand. If the rise of magma is very fast, the decompression of the gases is also fast. This phenomenon causes a sudden expansion of the gases contained in the magma, causing huge and dangerous volcanic explosions. This is also the phenomenon which causes the "explosions" associated with opening a bottle of champagne: without the pressure imposed by the stopper, the gases dissolved in the liquid can suddenly expand out of the bottle, dragging the liquid part with them.

In depth, the overlying rocks exert a load on the magma, strongly compressing the gases in it. `As the magma rises, the load exerted on it is less and less.

Gas ascension

By pumping the piston, you are injecting air to the liquid. Observe that in the bottom the bubles are speric, but as they rise they gain velocity (because the weight of the liquid column decreases) and due to it, its shape is flattened.

only External Energy?


Most people have the idea that rocks are something "that has always existed." However, rocks are always forming. At any given moment, our planet, as the dynamic body that it is, continuously generates all kinds of rocks: sedimentary, igneous and metamorphic. They can have all ages.


from earthquakes to the Earth


Crossing borders
The speed of propagation of seismic waves depends on the medium in which they propagate, so when they pass through different materials they may suffer reflections or refractions.

Zoning the interior of our planet
The comparison between seismograms of the same earthquake recorded in different parts of the world allows us to deduce the characteristics of the paths taken, and to get an idea of the interior of our planet by identifying the major internal discontinuities that compose it.

A particular distribuition
The location of earthquakes on the Earth's surface is along narrow and elongated strips that tend to isolate areas practically without earthquakes...

Earthquakes, mysterious phenomena
or just another evidence of the dynamics of our Planet?


The seismic phenomenon we call earthquake, due to the violence and unpredictability with which it manifests itself, has always aroused curiosity and fear. If in the past the mystery surrounding its origin fed the most delirious myths, today its genesis is perfectly explained in the light of theories of physics.
The phenomenon is explained in terms of forces generated as a result of convection movements that occur in the asthenosphere; volcanic eruptions; landslides; cave-ins or mine collapses; or human causes, such as chemical and nuclear explosions.

The continued action of these forces causes deformation in the rocks that continues as long as the elastic limit is not reached. However, after a certain time, the rocks cannot resist further deformation and fracture, releasing in a few seconds a large part of the elastic energy stored for years... that is the earthquake. During the fracturing process, the two faces of the fault undergo rapid displacement in opposite directions to the deforming forces; this phenomenon is called elastic rebound.

This rapid displacement of matter that is the elastic rebound produces mechanical waves that travel in all directions through the interior of the planet... the seismic waves. When the seismic waves hit the Earth's surface, they transfer part of their energy to the materials they find there, shaking them and thus producing the destruction that is so feared.

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