Quarry

function digDown()
  while turtle.detectDown() do
    turtle.digDown()
  end
end

function digForward()
  while turtle.detect() do
    turtle.dig()
  end
  turtle.forward()
end

function digQuarry(depth)
  for i = 1, depth do
    digDown()
    turtle.down()
  end
  for i = 1, depth do
    for j = 1, 4 do
      digForward()
    end
    turtle.turnRight()
  end
  for i = 1, depth do
    turtle.up()
  end
end