What is solithification?

Answer 1

Most likely, a typographical error.

It may be a confusion of two terms:

1 - solidification (i.e. the process of becoming solid; converse of liquification or, in some instances, gasification); when liquid water turns into ice, it solidifies. When solid wax melts, it liquefies.

2 - lithification (i.e. the process by which sediments and other materials compact and turn into solid rock).