The same heat in the earth that melts the rock into magma, heats the water. Sometimes, the only visible evidence of an old volcano is the kind of rock found in the area. Near the area of ancient volcanoes you usually see volcanic rocks. There are many kinds, some with bubbles and some that are very shiny like glass. Some may be made from ash and they are dull and powdery.
Volcanic rocks come in many colors.
They may be very heavy or extremely light in weight. Inc. PageWise makes no representations about the content published on this site. PageWise hereby disclaims all warranties and conditions with regard to this information, and user agrees that all such use is at its own risk. If you are under 18, please do NOT opt-in to receive email offers on this page.