Changes to the Earth and its atmosphere
The Earth has a layered structure, including the corecore: The core is the innermost part of the Earth., mantle [mantle: A zone of hot rock in the interior of the Earth, located between the outer crust and the molten core. ] and crust [crust: The outer layer of the Earth, on top of the mantle. It is between 6 and 48 kilometres thick and includes the continents and the ocean floor. ]. The crust and upper mantle are cracked into large pieces called tectonic plates. These plates move slowly, but can cause earthquakes and volcanoes where they meet.
The Earth’s atmosphere has changed over billions of years, but for the past 200 million years it has been much as it is today.
The Earth is almost a sphere. These are its main layers, starting with the outermost:
Note that the radius of the core is just over half the radius of the Earth. The core itself consists of a solid inner core and a liquid outer core.