Best way to represent values.

I have several fields that needs to be within a table but not real sure the
best way to represent this data.

The scenario I'm trying to incorporate is a form that has to be filled out
went a well is drilled and then sent to the state. One of the things the form
wants is the different depths various types of underburden was encountered.

So you start with topsoil that goes from 0 feet to X depth, then say at that X
depth clay is encountered to depth Y and then at depth Y gravel is
encountered and water is found.

I had thought just adding some fields called topsoil_start/topsoil_end,
gravel_start/gravel_end, etc. But them I'm left with how to take those values
and give to total depth for each layer and total depth of the well.

But I'm not sure that is the best way to handle this.

Does anyone have some other suggestions?

BTW, thanks to all that submitted some recommended PostgreSQL books. I have
started with Beginning Databases with PostgreSQL. It's been very helpful. I
plan to pursue the other recommendations.

--
You can tuna piano but you can't tune a fish.