How important is volcanic activity?

sure it provides a renewable source of energy but besides the climate change perspective, how important is volcanic activity and couldnt the majority of the earth live without it. im not talking about never having it because ofcourse it formed many of our mountains and islands etc but if all the magma hardened and became unactive and no earthquakes and eruptions. we get most of our heat from the sun, would there be any drastic results (besides the poor freezing people of iceland) or problems theorized with this event? please be detailed