StarTalk Radio

Cosmic Queries – Space Volcanoes: Fire and Ice with Natalie Starkey

December 23, 2025

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  • Most volcanoes in the outer solar system are 'ice volcanoes' or cryovolcanoes, erupting materials like water, ice, and gas rather than molten rock. 
  • The size of a volcano like Olympus Mons on Mars is determined by factors including weak gravity and the lack of plate tectonics, which allows magma plumes to erupt continuously in one spot. 
  • Earth's internal heat, which drives volcanism, is sustained by both residual heat from planetary formation and continuous radioactive decay within the mantle. 
  • Mountains formed by plate tectonics, like the Himalayas, are not volcanic and will never become volcanoes because they result from crustal crumpling without melting. 
  • Attempting to artificially trigger or relieve pressure from a magma chamber to prevent a major volcanic eruption is likely counterproductive, as releasing pressure can sometimes lead to a worse eruption, emphasizing the need to leave nature to its course. 
  • Io is the closest celestial body to being entirely covered in volcanic activity, mirroring what Earth was likely like four billion years ago due to intense tidal heating from Jupiter. 

Segments

Guest Introduction and Background
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(00:00:00)
  • Key Takeaway: Natalie Starkey is a geologist and science communicator specializing in the volcanoes of the Solar System.
  • Summary: Natalie Starkey’s background is in geology, initially inspired by Earth’s volcanoes after reading about a dangerous eruption. She transitioned into space science, analyzing volcanic rocks from space missions, which led to her book, Fire and Ice: The Volcanoes of the Solar System. She also co-created the Hayden Planetarium show, Worlds Beyond Earth.
Defining Fire and Ice Volcanoes
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(00:08:30)
  • Key Takeaway: Most volcanoes in the outer solar system are ice volcanoes (cryovolcanoes), which are more common than the hot, rocky volcanoes found in the inner solar system.
  • Summary: The term ‘ice volcanoes’ is used because most bodies past the asteroid belt feature volcanoes erupting materials like ice, water, or gas, rather than molten rock. Venus is likely still volcanically active today, covered in basaltic lava flows, despite its extremely hot and dense atmosphere making direct observation difficult. Future NASA and ESA missions are planned to investigate Venus to understand why it evolved so differently from Earth.
Mechanism of Ice Volcanoes
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(00:13:07)
  • Key Takeaway: Cryovolcanoes on icy moons like Enceladus are powered by tidal heating from their host planets, causing internal friction and melting subsurface ice into liquid oceans.
  • Summary: Tidal heating, caused by the gravitational pull of Saturn on Enceladus, generates internal friction and heat, which keeps the subsurface ocean liquid. This pressure opens cracks in the ice crust, resulting in plumes of gas, ice particles, and silica grains shooting into space, contributing to Saturn’s E-ring. These plumes indicate active chemistry capable of supporting organic molecules beneath the ice.
Magma Ascent and Earth Volcanoes
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(00:22:48)
  • Key Takeaway: Volcanic activity is defined as material being forced out from a world’s interior due to internal heat, regardless of whether the material is rock (magma/lava) or ice.
  • Summary: Magma (molten rock below the surface) rises because it is more buoyant than the surrounding solid material, a process accelerated by trapped gases that overpressure the system. Explosive eruptions occur when these gases rapidly escape upon reaching the surface, which can blow apart mountains built up slowly by continuous, less explosive eruptions. Volcanic soil, like that around Vesuvius, is highly fertile due to its ability to absorb water and act as a fertilizer.
Supervolcanoes and Planetary Size
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(00:32:31)
  • Key Takeaway: Supervolcanoes like Yellowstone are monitored, but their potential catastrophic eruptions are unlikely to be sudden, as they typically release pressure gradually, and Olympus Mons grew so large because Mars lacks plate tectonics.
  • Summary: Earth’s large volcanoes are built up over long periods by continuous eruptions, often near plate boundaries or mantle plumes (like Hawaii). Olympus Mons on Mars grew immense because its stagnant lid allowed a mantle plume to erupt in the same location for potentially billions of years without the crust moving away. A volcano of that size could not form on Earth because the planet’s stronger gravity would cause it to collapse under its own weight.
Planetary Cooling and Magnetic Fields
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(00:44:03)
  • Key Takeaway: Volcanism is a manifestation of a planet cooling down, and Earth maintains its protective magnetic field because its large size retains enough internal heat to keep the outer core molten.
  • Summary: Earth’s internal heat comes from leftover formation energy and ongoing radioactive decay, which keeps the outer core liquid, generating the magnetic field that shields the atmosphere from solar wind. Mars lost its magnetic field because its smaller size caused it to cool faster, solidifying its core. Terraforming Mars would require overcoming the lack of this natural magnetic shielding.
Asteroid and Comet Volcanism
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(00:49:14)
  • Key Takeaway: Volcanic activity occurs on asteroids and dwarf planets like Ceres, and plumes from comets significantly affect the predictability of their orbits.
  • Summary: Ceres, now classified as a dwarf planet, exhibits ice volcanoes. The NASA Psyche mission is investigating an asteroid believed to have had iron volcanoes in the past. Plumes erupting from comets near the Sun can alter their trajectories, making precise orbital predictions challenging, a concern noted during the Rosetta mission landing.
Mountain Formation vs. Volcanoes
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(00:55:35)
  • Key Takeaway: Non-volcanic mountains form from plate tectonics without melting, unlike volcanic mountains.
  • Summary: Normal mountains, such as Mount Everest, are created when colliding tectonic plates crumple up crust without melting, exemplified by the Himalayas. These mountains will never become volcanic. This process involves plates forcing together at a few centimeters per year, continuously pushing the crust upward.
Forcing Volcanic Eruptions
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(00:56:20)
  • Key Takeaway: Drilling to force a volcano is impractical because magma chambers are usually already known via surface volcanoes.
  • Summary: Drilling into molten rock to force an eruption is technically difficult because drilling into hot material causes melting. If a magma chamber is present, it is generally already associated with a known volcano. Instead of forcing eruptions, the heat from subsurface magma is often harnessed for geothermal electricity generation, as seen in Iceland.
Iceland’s Geothermal Energy Use
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(00:57:02)
  • Key Takeaway: Iceland utilizes extensive geothermal energy for electricity and infrastructure due to its volcanic location.
  • Summary: Iceland, situated on a mid-ocean ridge with a mantle plume, is highly volcanic, allowing it to generate electricity using geothermal energy by pumping water down to be heated by subsurface magma. This energy source is used for heating roads to melt ice and supply numerous outdoor swimming pools. Iceland has the highest electricity use per capita globally because this energy source is nearly free and fossil fuel-free.
Tapping Volcanoes for Pressure Release
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(00:58:39)
  • Key Takeaway: Attempting to tap a volcano to delay a major eruption is dangerous and ill-advised.
  • Summary: Releasing pressure from a volcano’s side to delay a singular cone eruption is not recommended because scientists do not fully understand volcanic behavior prediction. Disturbing unstable volcanic domes, like the one on Montserrat, can destabilize the underlying magma chamber and trigger a massive eruption. The safest approach is relocating populations rather than meddling with the pressure cooker.
Planets Entirely Volcanic
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(01:00:18)
  • Key Takeaway: Io is currently the most volcanically active planet, resembling early Earth.
  • Summary: Io is the closest example of a planet entirely covered in volcanic activity, similar to Earth approximately four billion years ago when its surface was likely molten. Io’s continuous activity is driven by tidal energy from being squeezed by the massive planet Jupiter, creating internal friction and heat. The depiction of Earth 100 million years ago (the age of dinosaurs) being covered in volcanoes is inaccurate compared to this geological timescale.