Where does topsoil originate from?

What are Different types of load in a stream? Hurricane strength is measured on what scale? Life other than earth would be called? What were the first organisms to live on a rock? How do oceans and the atmosphere interact? Does the moon have energy? How do scientists postulate that the phosphorus on earth was created? What type of weather do toucans like? What geographical features and weather patterns are present when a tornado takes place? what climate changes are the result of global warming? Can you see thunder? Will water travel underground through layers of rocks and soil which are impermeable materials.? Is N2O4 ---- 2NO2 a redox reaction? If the region in which you live has not experienced an earthquake in 200 years your earthquake hazard is low? What is the atomic number for calcium? How do the locations of mountains support Wegener's idea how mountains form? How does Earth's core transmit heat? Difference between chestnut and water chestnut? What is the role of man in his environment? Rain is the most common form of what?

Where does topsoil originate from?