Question:
What are some positive products from volcanoes?
Answer:
Over the long term and geologic time, volcanic eruptions and
related processes have directly and indirectly benefited mankind.
Volcanic materials ultimately break
down and weather to form some of the most
fertile soils
on Earth,
cultivation of which has produced abundant food and fostered civilizations.
People use
volcanic products,
the internal heat associated with young volcanic systems has been
harnessed to produce
geothermal energy,
and
most of the
metallic minerals
mined in the world,
such as copper, gold, silver, lead, and zinc, are associated with magmas
found deep within the roots of extinct volcanoes.
-- From:
Kious and Tilling, 1996, This Dynamic Earth: The Story of Plate
Tectonics: USGS General Interest Publication, and
Tilling, 1985, Volcanoes: USGS General Interest Publication