The planet Earth is formed by an internal structure (core, crust, mantle), tectonic plates, hydrosphere (seas, oceans) and the atmosphere. It is the third planet in the solar system and, although the fifth in size and mass, it is also the densest of all and the largest of the so-called terrestrial planets.
It is shaped like a bulging sphere in the middle, with a diameter of 12,756 km in Ecuador. It travels at a speed of 105,000 km / h to circle the sun while rotating on its own axis.
Water, oxygen, and energy from the sun combine to create ideal conditions on the only planet capable of supporting life. Its surface is mainly liquid and makes it look blue from space.
It is the only planet in the solar system with an atmosphere that contains a large amount of oxygen. The distance from the sun produces a sustainable amount of heat on the planet.
As an anecdote, until the 16th century it was believed that our planet was the center of the universe.
Structure of planet Earth
Internal structure
The earth is made up of different layers that have different properties.
The bark varies considerably in thickness. It is thinner under the oceans and much thicker on the continents. The inner core and the crust are solid. The outer core and mantle are fluid or semi-liquid.
Some layers are separated by discontinuities or transition zones, such as the Mohorovicic discontinuity, which is located between the crust and the upper mantle.
Most of the land mass is made up of the mantle. Almost all the rest corresponds to the nucleus. The habitable part is only a small portion of the whole.
The core is probably mostly iron and nickel, although other lighter elements may also be present. The temperature at the center of the core can be much hotter than the surface of the sun.
The mantle is probably composed mostly of silicates, magnesium, iron, calcium, and aluminum. The upper mantle has mainly ferrous and magnesium, calcium and aluminum silicates.
All this information is obtained thanks to seismic studies. The samples of the upper mantle are obtained on the surface as lava from volcanoes since it is inaccessible on most of the earth.
The crust is made up mainly of quartz and other silicates.
Tectonic plates
Tectonic plate map.
Unlike the other planets, the Earth's crust is divided into several solid plates, which float independently on the hot mantle below them. These plates receive the scientific name of tectonic plates.
They are characterized by two major processes: expansion and subduction. Expansion occurs when two plates separate from each other and create a new crust by magma gushing from below.
Subduction occurs when two plates collide and the edge of one sinks under the other and ends up being destroyed in the mantle.
There are also transverse movements in some plate boundaries, such as the San Andreas fault in California, USA and collisions between continental plates.
Currently there are 15 major plates, namely: African Plate, Antarctic Plate, Arabian Plate, Australian Plate, Caribbean Plate, Cocos Plate, Eurasian Plate, Philippine Plate, Indian Plate, Juan de Fuca Plate, Nazca Plate, North American Plate, Pacific Plate, Scotia Plate and South American Plate. There are also 43 minor plates.
Earthquakes are much more frequent at plate boundaries. For this reason, locating where earthquakes occur makes it easier to determine plate boundaries.
Three types of edges or boundaries have been identified:
- Convergent, when two plates collide next to each other.
- Divergent, when two plates separate.
- Transforming, when plates slide past each other.
The surface of the earth is quite young. In a relatively short time, about 500 million years, erosion and tectonic movements have destroyed and recreated most of the earth's surface.
In turn, they have eliminated almost all the remains of geological features in the history of that surface, such as impact craters. This means that most of the earth's history has been erased.
Hydrosphere
71% of the earth's surface is covered with water. Earth is the only planet where water exists in liquid form, being essential to life as we know it.
Liquid water is also responsible for most of the erosion and climate of the continents, a process unique in the solar system.
The thermal conditions of the oceans are very important to keep the earth's temperature stable.
The existence of the oceans is attributed to two causes. The first is the earth itself. It is believed that a large amount of water vapor was trapped within the earth during its formation.
Over time, the geological mechanisms of the planet, mainly volcanic activity, released this water vapor into the atmosphere. Once there, this vapor condensed and fell as liquid water.
The second cause is attributed to comets that could hit the earth. After the impact, they deposited large amounts of ice on the planet.
Atmosphere
The Earth's atmosphere is composed of 77% nitrogen, 21% oxygen, and some traces of argon, carbon dioxide, and water.
There was probably much more carbon dioxide when the earth formed, but since then it has almost all been assimilated by carbonaceous rocks, dissolved in the oceans, and consumed by plants.
Tectonic movement and biological processes now maintain a continuous flow of carbon dioxide in the atmosphere.
The small amounts found in the atmosphere are of great importance for maintaining the temperature of the Earth's surface in a process called the greenhouse effect.
This effect increases the average temperature by 35 ° C so that the oceans do not freeze.
The presence of free oxygen is also a remarkable fact from a chemical point of view.
Oxygen is a very reactive gas and under normal circumstances it would combine with other elements quickly. Oxygen in the Earth's atmosphere is produced and maintained through biological processes. Without life, there could be no oxygen.
References
- Fact Monster (2000–2017) “Planet Earth”. Retrieved June 11, 2017 at factmonster.com.
- Jordan, TH (1979). "Structural Geology of the Earth's Interior". Retrieved June 11, 2017 at nih.gov.
- Nine planets (1994 - 2015). "Earth Facts". Retrieved on June 11, 2017 at nineplanets.org.
- Seligman, Courtney (2008). "The Structure of the Terrestrial Planets". Retrieved on June 11, 2017 at cseligman.com.
- The planets (2010 - 2017). "Earth Facts". Retrieved on June 11, 2017 at theplanets.org.
- Williams, David R. (2004). "Earth Fact Sheet". Retrieved June 11, 2017 at nasa.gov.