The Earth is not mostly made of water. In fact, water makes up only a relatively small percentage of the Earth's overall composition. The Earth is primarily composed of rock, with the main elements being iron, oxygen, silicon, magnesium, sulfur, nickel, calcium, and aluminum.
Water, on the other hand, is a vital component of the Earth's surface and plays a crucial role in supporting life. It covers approximately 71% of the Earth's surface in the form of oceans, seas, lakes, and rivers. This abundance of water on the surface is due to several factors:
Early Earth conditions: During the planet's formation, around 4.6 billion years ago, water vapor was present in the Earth's atmosphere. As the Earth cooled, this water vapor condensed and fell as rain, accumulating in depressions on the Earth's surface and forming oceans.
Volcanic activity: Volcanoes release gases, including water vapor, into the atmosphere. Over millions of years, volcanic activity has contributed to the replenishment of water on Earth's surface.
Water cycle: The Earth's water cycle involves the continuous movement of water between the atmosphere, land, and oceans. The cycle includes processes such as evaporation, condensation, precipitation, and runoff, which distribute water across different regions of the planet.
While water is abundant on the Earth's surface, it represents only a tiny fraction of the planet's overall mass. The Earth's interior, beneath the surface, consists of various layers, including the solid inner core, liquid outer core, mantle, and crust, which are predominantly composed of rock-forming minerals and metallic elements.