Line of code used to mine the block beneath the turtle?

I am working on a programme in a turtle that gets it to dig a quarry like hole, the problem I found was that the command turtle.dig() digs the block infront of it so the turtle would need a 1 block hole all the way down so it would be able to work. As this makes it less automatic as you can't just lead it over to an area and get it to dig. I was going to abandon the program but I thought that there might me a line of code that solves my problem. So I was wondering is there a command like turtle.digDown() . As it is late at night and I only just thought of the idea I haven't had time to check for myself so if someone could tell me what the line is that would be very much appreciated.

Yes, there is turtle.digDown, as well as turtle.digUp. Next time just check the wiki.

Read the Turtle API section of the ComputerCraft Wiki. Your answer is there.

EDIT: ninja'd by MKlegoman357

Cheers guys, I just completely forgot about the wiki as I came up with the idea while searching through turtle programs

Also look at the excavate program on the turtle located at /rom/programs/turtle/excavate