Topsoil is actually a living system and the most productive soil layer on earth. It can also be very heavy.
How much does a yard of topsoil weigh?
A cubic yard of topsoil weighs about 2,000 pounds (907 kg).
Topsoil naturally occurs on the surface of the Earth. Usually it is between 2 inches and 8 inches deep, but in some places it can be as deep as 3 feet.
Topsoil can absorb a great deal of water. One acre of topsoil can store up to 9200 tonnes of water.
All of the nutrients required for the successful growth of plants reside in topsoil.
There are different types of topsoil defined by the amounts of clay, silt and sand that they contain.
Worms feeding on it enrich topsoil. They convert the organic materials into nutrients. When worms move through soil they improve aeration and absorption as well.
How Topsoil Is Used
Topsoil is used to create new lawns and gardens, as well as renew old eroded soil with new topsoil.
Plants and grass thrive in topsoil. Plant roots easily absorb the essential nutrients when dissolved in water.
Topsoil is the most effective when combined with existing soil surfaces. This ensures proper drainage and the best environment for the growth of plants.
If topsoil is darker and smells strongly of earth then it is likely to contain the highest level of nutrients.
~ Fun Fact ~
If you pick up a handful of topsoil, you will find it contains more microorganisms in it than there are people on the planet.
Resources
http://americantopsoil.com/FAQ.htm
https://www.hunker.com/13406893/the-average-weight-of-a-cubic-yard-of-soil