In 1980, Mount St. Helens erupted with incredible force.
Many houses and roads were destroyed, and 57 people lost their lives.
In 1963, an undersea volcano in Iceland began to boil and churn.
A new island, Surtsey, was formed.
Volcanoes erupted repeatedly over several million years.
Mountains that were high enough to reach from the deep sea bottom appeared as the Hawaiian Islands.
CAUSE
EFFECT