Question

Io is much smaller than Venus, yet it is much more volcanically active. Why?

(a) Io is made of denser rock, which traps heat more effectively
(b) Io is not old enough to have cooled completely yet
(c) Io is heated internally by tidal friction *
(d) Io is closer to the Sun than Venus and therefore warmer
(e) Io's interior is full of radioactive elements whose decays keep it warm

Answer 1

Io is highly volcanically active due to tidal heating caused by the immense gravitational pull of the massive Jupiter. This results in internal friction that heats Io's interior, driving its violent volcanism and maintaining a molten state over billions of years.

Step-by-step explanation:

The reason Io is much more volcanically active than its size would suggest is due to tidal heating. Io experiences extreme gravitational pull from Jupiter, which is over 300 times more massive than Earth. This immense gravitational force distorts Io into an elongated shape, with a several-kilometer-high bulge pointing toward Jupiter. The constant flexing as Io orbits Jupiter generates significant internal friction, which heats its interior, causing violent volcanism and maintaining Io's molten interior, despite billions of years of existence.

Maps of Io show more than 100 recently active volcanoes, with huge flows of lava covering about 25% of the moon's surface. The eruptions on Io are primarily of molten silicates, similar to the volcanic activity found on Earth. This geological activity is driven by the same tidal forces that have stripped Io of water and carbon dioxide, making sulfur compounds the most volatile materials remaining on the moon.