1º BILINGUAL SECTION: PARTS OF THE EARTH (PRACTICE YOUR ENGLISH)

The interior structure of the Earth, similar to the outer, is layered. The Earth has an outer silicate solid crust, a highly viscous mantle, a liquid outer core that is much less viscous than the mantle, and a solid inner core. Scientific understanding of Earth's internal structure is based on observations of topography and bathymetry, observations of rock in outcrop, samples brought to the surface from greater depths by volcanic activity, analysis of the seismic waves that pass through the Earth, measurements of the gravity field of the Earth, and experiments with crystalline solids at pressures and temperatures characteristic of the Earth's deep interior.

The deepest layers are composed of heavier materials; they are hotter, denser and under much greater pressure than the outer layers.

The "skin" of Earth, called the crust, is very thin like the skin of a peach. It is so thin, in fact, that we have to magnify a small piece of our sketch of Earth to see any detail at all. There are two types of crust, oceanic and continental. As you might suspect from the names, oceanic crust is usually found under the oceans, and continental crust is found on the continents.The thin oceanic crust is composed of primarily of basalt and the thicker continental crust is composed primarily of granite. The low density of the thick continental crust allows it to "float" in high relief on the much higher density mantle below.

Earth’s mantle is thought to be composed mainly of olivine-rich rock. It has different temperatures at different depths. Rocks in the upper mantle are cool and brittle, while rocks in the lower mantle are hot and soft (but not molten). Rocks in the upper mantle are brittle enough to break under stress and produce earthquakes. However, rocks in the lower mantle are soft and flow when subjected to forces instead of breaking.

Earth’s Core is thought to be composed mainly of an iron and nickel alloy. The core is earth’s source of internal heat because it contains radioactive materials which release heat as they break down into more stable substances.The core is divided into two different zones: outer core that is liquid and the inner core that is solid.