What layer of soil has largest rock particles?

Answer 1

That is a difficult question in that its phrasing leaves the answer uncertain. In terms of soil - there are three classifications of rock particles when defined by particle size. All three have definite size limits. Sand is the largest or coarsest of the three sizes (generally 0.06 mm up to 2mm) while clay is the finest (less than 0.002 mm). The in-between sized particles are called silt (.002 mm to .06 mm). All three are created by the weathering, crushing or chemical breakdown of rock into particles. Normally rock will continue to break down in size over time until a particle is one crystal of one of the various minerals that comprised the original rock formation. So whether the rock particles ultimately become clay, silt or sand is determined by the mineral composition of the originating rock. The coarsest grains of sand often contain more than one crystal of the original mineral and will still become finer over lengthy periods of time. There are also three main types of rock - sedimentary, igneous and metamorphic. But this is the answer to another question so I won't go any further along this topic right now. So I guess the answer to the question is - the surface contains the largest rock particles. That is where we find all three types (as defined by size) - clay, silt and sand. So far we have gone down twelve miles and are still finding some soil, but even so that is a small fraction of the over 3500 miles to go from the outermost surface (ignoring mountains which only add a few miles at most) to the center of the earth. Still, the largest concentration is probably in the first 20-40 feet so the answer remains - the outer surface. Note that the outer surface also includes the sea bed. Sorry - this may not be the exact answer that was sought, but in order to give a better answer, the question must be more precise.

Answer 2

Bed Rock or D Horizon

Answer 3

Gravel