Columbia subject headings:
Asteroids--Collisions with Earth.
Climatic changes--History.
Human beings--Effect of environment on--History.
Natural disasters--History.
Weather--Effect of volcanic eruptions on.
Harvard subject headings:
Asteroids--Collisions with Earth
Climatic changes--History.
Human beings--Effect of environment on--History.
Natural disasters--History.
Weather--Effect of volcanic eruptions on
Princeton subject headings:
Middle Ages.