Gravel averages 100 pounds per cubic foot or 20 cubic feet per ton. That's depth x width x length. So if you want to cover something 6 inches deep, you can cover 40 square feet of surface.
I need to know how thick the layer of gravel is meant to be.
That depends on the size of the gravel and how thick a layer you want to end up with.
In the state of Florida, one ton of gravel will cost you about $9.61. However, it will vary depending on the store in which you buy the gravel.
That's not enough information. You need to know the width of the trench, and how much volume 1 ton of gravel is equivalent to.
One ton of absolutely anything weighs one ton.
Well, 2.2 pounds equals one kilogram and there's 2000 pounds in a ton, therefore one ton of gravel equals 909.09 kilograms
Based on sand and gravel calculator found on L.R. Faulk Construction Co. site, 1 ton of gravel (clean rock) will equal approximately 7.3 sq. ft x 6 inches deep, or 5.2 sq. ft x 3 inches deep. A ton of gravel will cover approximately 15 square yards (135 square feet) at 3 inches deep.
About one half
A load of gravel will vary in cost by area and company. Gravel is sold by the ton. Each different type of gravel is a different price. The price varies from $15 a ton to over $100 a ton. Delivery charges are also added if the gravel is delivered.
In West Virginia, the price of gravel is $17 to $23 dollars per ton. Limestone is one of their industries there.
Its really hard to guage, as it wont be at 2" everywhere. Anyway a ton should do between 15 - 18 square mts.
Knowing that 1 cubic foot is pretty much equal to 100 pounds or 0.05 ton, 1 ton of gravel is around 20 cubic feet.