It harbours life, moisture, a little air and holds heat quite well. Earth can also become very unmoveable - as rock it is the ultimate stubborn, set in its ways, inpenetrable, uninterested in anything else sort of element. With a lot of effort you can carve it to reflect other things - but at its heart it is still rock, unchanging, innactive, dull to some, beautiful to those preapred to look closley to see the veins that flow through it. The ultimate form of rock is as gemstones - and the diamond is the most prized form of earth, as are precious metals. But earth is also everything else solid - it is trees and plants, bricks and plastic, concrete and metals.
Air is the great carrier and a motivator.
It brings oxygene to the blood, it transmits the heat of the sun. Its lightness and energy bring stimulation to plants making them grow strong, it whips up the water and blows away the clouds. Air brings us scents and odours, sounds and warnings. It feeds the fire and carries the smoke away, it is the bubbles in champagne and the white in the surf. Air can change direction in a flash and change again just as quickly.