the water cycle

• water stored in the mantle is released to the surface at the same rate as water enters the mantle (in equilibrium)
• water on earth originated from three places: the solar nebular (sun's formation), meteorites (from early planets) and comets from deep space
• ground water is a major part of the water cycle with 97% of the water stored underground having been there over 100 years and often more saline and contaminated as a result
• snow forms glaciers and aids in albedo as well as helping to insulate the planet and provide fresh water for ecosystems during the summer months
• permafrost is a layer of ground between the top soil and deeper earth that remains frozen all year, it hold large amounts of greenhouse gases especially methane trapped in the ground
• snow can compress over time to form glaciers that flow down like a river over vast amounts of time carving the landscape, freezing occurs at the top while melting at the bottom
• ice sheets are massive slow glaciers