Magnetic rocks

  • Magnetic rocks are those that contain magnetic minerals, mainly magnetite.
  • Its magnetism is related to the proportion of minerals such as hematite and pyrrhotite.
  • Magnetic anomalies can indicate the presence of underlying geological structures.
  • The Earth's magnetic field varies and is related to plate tectonics and the history of the Earth.
Germán Portillo

6 minutes

magnetite magnetic rocks

The magnetic rocks and the magnetism of rocks are related to the magnetism of minerals, which is of great importance for the understanding of magnetic geophysical exploration methods. Most rock-forming minerals exhibit very low magnetic susceptibility, and the reason rocks are magnetic is that the proportion of magnetic minerals they contain is usually small. Only two geochemical groups provide rocks with these minerals and magnetism.

In this article, we'll tell you everything you need to know about magnetic rocks, their characteristics, and the magnetism of minerals.

What are magnetic rocks

magnetic rocks

The iron-titanium-oxygen group has solid solutions of a number of magnetic minerals ranging from magnetite (Fe3O4) to ulvöspinel (Fe2TiO4). Another common type of iron oxide hematite (Fe2O3) is antiferromagnetic and therefore does not cause magnetic abnormalities. The iron-sulfur base provides the magnetic mineral pyrrhotite (FeS1 + x, 0 which has a Curie temperature of 578 ° C.

Although the size, shape, and distribution of magnetite particles in a rock will affect its magnetic properties, it is reasonable to classify a rock's magnetic behavior based on its overall magnetite content. To learn more about the formation of these rocks and their impact on the continental drift, you can explore the topic of the characteristics of magnetic rocks.

Types of magnetic rocks

terrestrial magnetic field

Due to their relatively high magnetite content, basic igneous rocks are often magnetic rocks. The proportion of magnetite in igneous rocks decreases with increasing acidity, so although acidic igneous rocks have different magnetic properties, their magnetic properties are usually lower than those of basic rocks. To better understand these variations, you can consult information on the Earth's magnetic field and its impact on different types of rocks.

The magnetic characteristics of metamorphic rocks are also variable. If the partial pressure of oxygen is low, magnetite will be resorbed and iron and oxygen will combine with other mineral phases as the degree of metamorphism increases. However, relatively high partial pressure of oxygen can lead to the formation of magnetite, which acts as an auxiliary mineral in the metamorphic reaction. To better understand how this phenomenon relates to the change of magnetic poles, is essential.

Generally speaking, the magnetite content and magnetic susceptibility of rocks vary widely, and there can be considerable overlap between different lithologies. When magnetic anomalies are observed in areas covered with sediments, anomalies are generally caused by underlying igneous rocks or metamorphic basements or intrusive sediments.

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Common causes of magnetic anomalies include levees, faults, folds or truncations and lava flows, a large number of basic intrusions, metamorphic basement rocks, and magnetite ore bodies. The magnitude of the magnetic anomaly ranges from tens of nT in the deep metamorphic basement to hundreds of nT in the basic intrusive body, and the magnitude of magnetite minerals can reach several thousand nT.

Magnetic field and importance

magnetic field

After three years of data collection, so far it has been published the highest resolution space map of the Earth's lithospheric magnetic field. The dataset uses a new modeling technique to combine measurement results from ESA's Swarm satellite with historical data from the German CHAMP satellite, which allows scientists to extract tiny magnetic signals from the Earth's outer layers. Red represents areas where the lithospheric magnetic field is positive and blue represents areas where the lithospheric magnetic field is negative.

ESA's Swarm mission leader Rune Floberghagen said in a statement: “It is not easy to understand the crust of our parent star. We cannot simply use it to measure its structure, composition and history.. Measurements from space are very valuable since they are a description of the magnetic structure of the rigid shell of our planet.

At the Swarm Science Conference in Canada this week, the new map showed detailed changes in the field more accurately than previous satellite-based reconstructions, caused by the geological structure of the Earth's crust. For more information on fluctuations in magnetism, you can read about the new map. the magnetosphere and how it affects the characteristics of magnetic rocks.

One of the anomalies occurred in the Central African Republic, centered on Bangui, where the magnetic field is significantly sharper and stronger. The reason for this anomaly is not yet clear, but some scientists speculate that it may be the result of the impact of a meteorite more than 540 million years ago.

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The magnetic field is in a state of permanent flux. Magnetic north shifts and polarity shifts every few hundred thousand years, so the compass points south instead of north.

Magnetic poles

When volcanic activity produces new crust, mainly along the seafloor, iron-rich minerals in solidified magma will face magnetic north, thus capturing the "snapshot" of the magnetic field found when the rock cools.

As the magnetic poles move back and forth over time, solidified minerals form 'fringes' on the seafloor and provide a record of Earth's magnetic history. Swarm's latest map provides us with an unprecedented overview of the ribbons associated with plate tectonics, reflecting off the ridge in the middle of the ocean.

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“These magnetic bands are evidence of magnetic pole reversal, and analysis of the magnetic footprint on the seabed can reconstruct past changes in the core's magnetic field. They also help study plate tectonics, "said Dhananjay Ravat of the University of Kentucky.

The new map defines the characteristics of the magnetic field up to approximately 250 kilometers long and will help investigate the geology and temperature of the Earth's lithosphere.

Igneous rocks are also important from the perspective of magnetic rocks, and we must bear in mind that a large amount of iron is found in the Earth's interior.

One of the layers of the atmosphere that protects us is the ionosphere. It is a region that contains a large number of atoms and molecules that are charged with electricity. These charged particles are created thanks to radiation that comes from outer space, mainly from our star the Sun. This radiation hits the neutral atoms and air molecules in the atmosphere and ends up charging them with electricity. The ionosphere is of great importance for humans and, therefore, we are going to dedicate this entire post to it. We are going to explain everything you need to know about the characteristics, operation and importance of the ionosphere. Main Features While the Sun is shining continuously, during its activity it is generating a large amount of electromagnetic radiation. This radiation falls on the layers of our planet, charging the atoms and molecules with electricity. Once all the particles are charged, a layer forms that we call the ionosphere. This layer is located between the mesosphere, the thermosphere and the exosphere. More or less you can see that it begins at a height of about 50 km above the earth's surface. Although it starts at this point, where it becomes more complete and important is above 80 km. In the regions that we are in the upper parts of the ionosphere we can see hundreds of kilometers above the surface that extend tens of thousands of kilometers into space is what we call the magnetosphere. The magnetosphere is the layer of the atmosphere that we call this way because of its behavior due to the Earth's magnetic field (bond) and the action of the Sun on it. The ionosphere and the magnetosphere are related by the charges of the particles. One has electrical charges and the other has magnetic charges. Layers of the ionosphere As we have mentioned before, although the ionosphere begins at 50 km, it has different layers depending on the concentration and composition of the ions that form it. Previously, the ionosphere was thought to be made up of several different layers that were identified by the letters D, E, and F. The F layer was divided into two more detailed regions which were F1 and F2. Today, more knowledge is available of the ionosphere thanks to the development of technology and it is known that these layers are not very different. However, in order not to make people dizzy, the original scheme that was had in the beginning is maintained. We are going to analyze part by part the different layers of the ionosphere to see in detail their composition and importance. Region D This is the lowest part of the entire ionosphere. It reaches altitudes of between 70 and 90 km. Region D has different characteristics than regions E and F. This is because its free electrons almost completely disappear overnight. They tend to disappear as they combine with oxygen ions to form oxygen molecules that are electrically neutral. Region E This is the layer also known as Kennekky-Heaviside. This name has been given in honor of the American engineer Arthur E. Kennelly and the English physicist Oliver Heaviside. This layer extends more or less from 90 km, where layer D ends up to 160 km. It has a clear difference with the D region and is that the ionization remains throughout the night. It should be mentioned that it is also quite reduced. Region F It has an approximate altitude from 160 km to the end. It is the part that has the highest concentration of free electrons since it is the closest to the sun. Therefore, it perceives more radiation. Its degree of ionization does not have many changes during the night, since there is a change in the distribution of the ions. During the day we can see two layers: a smaller layer that is known as F1 that is higher up and, another highly ionized dominant layer that is known as F2. During the night both are fused at the level of the F2 layer, which is known as Appleton. Role and importance of the ionosphere For many, having a layer of the atmosphere that is electrically charged may not mean anything. However, the ionosphere is of great importance for the development of humanity. For example, thanks to this layer we can propagate radio waves to different places on the planet. We can also send the signals between the satellites and the Earth. One of the most important factors why the ionosphere is fundamental for humans is because it protects us from dangerous radiation from outer space. Thanks to the ionosphere we can see beautiful natural phenomena such as the Northern Lights (link). It also protects our planet from the celestial rock masses that enter the atmosphere. The thermosphere helps us protect ourselves and regulate the Earth's temperature by absorbing some of the UV radiation and X-rays that are emitted by the Sun. On the other hand, the exosphere is the first line of defense between the planet and the sun's rays. The temperatures in this much-needed layer are extremely high. At some points we can find 1.500 degrees Celsius. At this temperature, apart from the fact that it is impossible to live, it would burn every human element that passed by. This is what causes a large part of the meteorites that hit our planet to disintegrate and form shooting stars. And it is that when these rocks come into contact with the ionosphere and the high temperature at which it is found in some points, we find the object becomes somewhat incandescent and surrounded by fire until it ends up disintegrating. It really is a very necessary layer for human life to develop as we know it today. For this reason, it is important to know her more thoroughly and study her behavior, since we could not live without her.
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