His grandfather? Also a speech expert. And then there was his mother, Eliza Grace Symonds Bell, who was deaf—a fact that shaped young Bell’s fascination with sound. Alexander Graham Bell.

They can be cone- or oval-shaped, usually with a bowl-like crater at their summits. When a cinder cone erupts over and over, it can evolve into a stratovolcano. Stratovolcanoes are cone-shaped ...