${\left({\mathrm{CH}}_3\right)}_3\mathrm{C}-\mathrm{OH}\stackrel{{\mathrm{H}}_2{\mathrm{SO}}_4, \mathrm{\Delta }}{\to }{\left({\mathrm{CH}}_3\right)}_2\mathrm{C}={\mathrm{CH}}_2$
This reaction takes place through

Step 1: First step is the protonation of the hydroxyl group which converts -OH into good leaving group.

Step 2: Second step is ionization which results in the formation of a carbocation.

Step 3: Abstraction of carbocation which results in the formation of alkene.