Political boundaries are often formed by physical boundaries. An example of this is the Rio Grande River that separates the US from Mexico. An ethnographic boundary or a cultural boundary is a boundary line that runs along differences in ethnicity.
Steel has a density of about 490 pounds per cubic foot, which is more than three times the density of concrete, so the generally accepted density of normally reinforced concrete is 150 pounds per cubic foot which results in a cubic yard weighing 4050 pounds, but this depends on the quantity and grade of the rebar used.
The average weight of a sandstone boulder is approximately 150 pounds per cubic foot. Limestone boulders and granite boulders in most cases weigh more. How much does 1 cubic foot of Silverdale limestone weigh â Ask â¦ Typically limestone averages a weight of 171 pounds per cubic foot. However, this number will vary slightly depending on the type of limestone. Individual quarry â¦.