Occurs when carbon dioxide and water vapor form an invisible blanket around the globe that allows the sun's light to enter, but traps the heat.

The green house effect occurs when carbon dioxide and water vapor form an invisible blanket around the globe that allows the sun's light to enter, but traps the heat. Green house effect is a process that warms the Earth's surface. When the sun's energy reaches the Earth's atmosphere, some of it is reflected back to the space and the rest is absorbed and re-radiated by greenhouse gases. 

It was said to have happened by earthquakes, the shifts in the tectonic plates moved everything