Origin of continents and oceans

1. Which structure has the lithosphere? What phenomena occur on the boundaries of its plates?

The lithosphere is heterogeneous in structure and consists of the earth’s crust and the upper part of the Earth’s mantle. The Earth’s crust is divided into oceanic and continental crust. The continental crust is much thicker than the oceanic crust and consists of a basaltic granite bedding layer. Sedimentary rocks in the oceanic crust are located directly on the “basalt” layer.

The Earth’s crust is not a monolith. It consists of huge lithospheric plates, which slowly move relative to each other along with the upper viscous layer of magma. Plates may diverge, converge or move one along the other.

On the boundaries of lithospheric plates, a new earth crust may be formed from the substance of magma falling on the surface of the Earth along fault lines. It is these areas of boundaries between lithospheric plates that are characterized by instability

and are characterized by frequent earthquakes and volcanic eruptions. These areas are called seismic belts.

2. How are seismic belts placed on Earth? Tell us about earthquakes and eruptions of volcanoes, known to you from radio, television, newspapers. Explain the reasons for these phenomena.

Earthquakes and volcanic eruptions are a terrible and at the same time fascinating sight. On those who have visited the area of ​​the earthquake or observed the eruption of a volcano, these giant forces of nature make a huge impression, which man is not only unable to control, but often can not even predict the time of occurrence and force of these phenomena. Look at the faces of people in KP Bryullov’s painting “The Last Day of Pompeii”. Panic and fear for the lives of their loved ones and their lives, the horror of the inevitable evil that destroys the city and buries under the piles of destroyed buildings of living people.

Earthquakes and volcanic eruptions are associated with the impact on the earth’s crust of the Earth’s internal forces. When the lithospheric plates

move, parts of the cortex gradually accumulate a stress, which leads to a disruption in stability and a sharp shift in the layers of rocks relative to each other. So there are earthquakes.

On the cracks of the earth’s crust, the molten magma rushes to the surface, where it solidifies and forms a cone of a volcano with a crater in the middle. After the eruption, the volcano can permanently cease its activity, and then, under the influence of the internal forces of the Earth, again erupt, exposing the danger to people who live and farm on its slopes or in close proximity to the volcano.

3. How should I work with a map of the structure of the earth’s crust?

Using the map of the structure of the earth’s crust in the atlas, determine the regions of new and modern folding, for which the phenomena of earthquakes and volcanism are characteristic, and then compare with the population density map. You will find that the density of the population in dangerous areas is quite high.

In addition to the age-varying fold belts, the structure of the Earth’s crust can be used to determine the structure of ancient and young platforms, lava covers and reef zones of continents. On the map, you can determine the structure of the oceanic crust. Pay attention to the areas of the oceanic crust raised above sea level, deep-sea trenches and rift zones of mid-oceanic ridges.

4. Where, in your opinion, can new oceans form on the Earth in the distant future? New continents?

Having studied the map of the structure of the earth’s crust, perhaps we can assume that in the rift fault zones on the continents in the distant future, seas and oceans may form, and in the oceanic ranges, islands and continents. But this is a very bold assumption.

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Origin of continents and oceans