Earth and the Universe: Formation, Movements, and Relief
1st Item: The Earth and the Universe
1. The Earth, a Planet of the Solar System
The universe contains all celestial bodies in space: stars, planets, satellites, asteroids, and comets. Stars are celestial bodies with their own light and heat, grouped into galaxies. Planets do not have their own light and form planetary systems around a star. The solar system is composed of eight planets and the Sun. The Earth is a planet in the solar system, shaped like a sphere flattened at the poles. Its surface is covered by water and land.
2. The Earth’s Movement
Rotation is the movement that the Earth makes around its polar axis. It has some consequences: the existence of day and night, the geographical coordinates (latitude and longitude) measured through meridians and parallels, and the existence of time zones. Translation is the movement that the Earth makes around the Sun in almost 365 days. This movement results in inequality between days and nights, and the existence of the seasons: spring, summer, autumn, and winter. The seasons are indicated at the equinoxes and solstices, and are opposite in both hemispheres. The Earth has five climatic zones: a warm zone, two temperate zones, and two cold zones. These areas exist due to the variation in the inclination of the Sun’s rays.
3. The Representation of the Earth
To know the Earth, we use a graphical representation called a spherical map. To move the spherical surface to a plane, we use cartographic projections. The most important are the cylindrical, conical, and azimuthal. To represent the Earth, we use a small scale, which informs us about the relationship between the actual distance and the distance shown on the map. The scale can be graphical or numerical. There are several types of maps; the most commonly used are topographic and thematic. The Earth can also be known through aerial photography and remote sensing, which is the collection of information on the Earth’s surface without coming into contact with it.
4. The Knowledge of the Earth
The knowledge of the Earth by European peoples took place progressively in the Modern Age. During this time, America was discovered, the world was circumnavigated, and all the contours of the continents were known. In the Contemporary Age, the interior of continents and polar regions were explored. After the exploration of the Earth, human beings are devoting their efforts to knowing space.
2nd Item: The Relief of the Earth
1. The Interior and History of the Earth
The interior of the Earth is composed of concentric layers: the core, the innermost layer, hot and thick; the mantle, the middle layer of fluid material (magma); and the crust, the upper layer, solid and rigid. The history of the Earth is divided into eras: Archaic, Primary, Secondary, Tertiary, and Quaternary. According to the theory of continental drift, the continents are moving at an ever-increasing rate. The theory of plate tectonics explains this movement: the lithosphere is divided into plates that float on the mantle and move because the Earth’s crust is continuously created and destroyed.
2. The Internal Factors of Relief
Rocks are parts of the crust composed of several minerals. Based on their formation, they are classified into magmatic, sedimentary, and metamorphic. They are related through the so-called rock cycle. Rocks are placed on the surface of the Earth by the action of internal forces related to the tectonics of plates. Plastic rocks result in folds, while rigid rocks result in faults.
3. The External Factors of Relief
Water, wind, ice, and living things produce erosion and sedimentation. Rain, river, and coastal erosion occur in all climatic areas. Wind erosion is important in deserts, glacial erosion in cold areas, and the erosion caused by living beings in areas with increased human presence.
4. Landforms
The mainland has the following forms of relief: mountains, which may be young and joined to form ridges or old and isolated; plateaus; plains; and depressions.
In the undersea, we find the continental shelf, continental slope, abyssal plains, oceanic ridges, and trenches.
Earthquakes and volcanoes are natural hazards that alter the relief. Earthquakes are movements inside the Earth that shake the area and cause huge catastrophes. Volcanoes are cracks in the crust where magma flows, which turns into lava and creates various types of relief.