Maapõhi

Maapõhi, also known as the Earth's crust, is the outermost solid layer of the Earth, comprising the uppermost part of the lithosphere. It is composed primarily of rock and minerals, and its thickness varies significantly across different regions of the planet. The Earth's crust is divided into several tectonic plates that float on the semi-fluid asthenosphere beneath. These plates are in constant motion, driven by convection currents in the mantle, and their interactions are responsible for various geological phenomena such as earthquakes, volcanic activity, and the formation of mountains.

The Earth's crust can be further categorized into two types: oceanic crust and continental crust. Oceanic crust is thinner and denser, typically ranging from 5 to 10 kilometers in thickness, and is primarily composed of basaltic rock. It is found beneath the ocean basins and is constantly being created at mid-ocean ridges and destroyed at subduction zones. Continental crust, on the other hand, is thicker, ranging from 30 to 70 kilometers, and is composed of granitic rock. It forms the continents and is less dense than oceanic crust, which allows it to float higher on the asthenosphere.

The study of the Earth's crust is crucial for understanding the planet's geological history, natural resources, and potential hazards. Geologists use various techniques, such as seismic imaging and drilling, to investigate the structure and composition of the crust. By analyzing the properties of the crust, scientists can gain insights into the processes that shape the Earth's surface and the dynamics of its interior.