Looking up at the Moon today, our neighbor looks cold and dormant. Things, however, are not always what they seem. Scientists are constantly discovering new things about our satellite that paint the Moon’s volcanic activity in a new light. Read on to find out if the Moon still has some life left in it.
Looking Back at an Ancient Moon
Planetary objects are incredibly hot during their formative years, and our Moon is no exception.
At its birth, the entire Moon would have been a molten mess of fire and lava. The Moon’s crust, or outer layer, would have been the first part of the Moon to start to cool off in the cold vacuum of space.
The Moon would have solidified enough around 4 billion years ago to start displaying volcanic activity. Eruptions were so common that there was enough gas for the Moon to form an atmosphere. It held onto that atmosphere for nearly 70 million years until the Moon cooled even further.
During the zenith of its volcanic activity, molten magma would have regularly breached the Moon’s crust and spilled out onto the lunar surface.
Given that lunar surface material can be traced back billions of years, volcanic activity must have slowed considerably around 3 billion years ago.
The End of a Volcanic Era
While still somewhat active for the next two billion years, the Moon’s volcanic activity continued to lessen until it stopped entirely. For many years scientists thought that volcano activity ended over 1 billion years ago, but recent discoveries suggest otherwise.
The Apollo 15 team was the first to discover irregular patches of cooled lava that are now thought to be as young as 50 million years old. These “young” volcanoes are too small to be seen from Earth but add a new layer of complexity to the Moon’s volcanic past.
Some scientists even believe that we’ve not seen the end of volcanic activity on the surface of our cosmic neighbor.
What Do the Moon’s Volcanoes Look Like?
All this volcanic activity from the Moon’s mantle and core did force magma to flow up through the core and out onto the surface of the Moon. Because there’s so much less gravity on the Moon, magma had a lot less difficulty escaping the crust.
As a result, volcanoes on the Moon do not have tall peaks with smoldering cones but are much broader and flatter. Volcanoes are often found in close proximity to one another as Moon-wide volcanic activity gave way to more localized eruptions.
In many cases, lunar magma seeped out of the mantle to form large lakes of lava. These lakes have solidified but confused early scientists like Galileo. Believing they might be water, Galileo named these cooled basins of lava mare after the Latin word for sea.
If you look up at the Moon on a clear night, it’s very easy to see these dried lava oceans as the dark areas on the Moon. These areas even make up the features of the “Man on the Moon.”
Today, nearly all of the rock on the lunar surface is igneous rock, which results from the cooling of lava.
What Caused the Decay of Volcanic Activity?
Our Moon is only about 25% the size of our Earth. Just as any small object cools faster than a large one, the Moon found itself cooling much faster than our Earth. The Moon’s size means it struggled to hold onto an atmosphere. This played a further role in its cooling as heat escaped into space.
Even at its core, the Moon no longer supports temperatures hot enough to keep iron from turning solid.
As the Moon’s core continued to cool, so too did each of its other layers. The mantle, the layer of the Moon responsible for volcanic activity, cooled to the point of near-complete solidification.
Although the mantle likely has a molten section near the Moon’s core, this molten area is likely 600 miles (1000 kilometers) below the surface. There’s no discernable way for this magma to ever make it up to the lunar surface.
After all, the Earth’s mantle is still entirely molten, right up to its crust. At its thickest location, the Earth’s crust is only 60 miles (100 kilometers) thick. That’s 10% of the distance to the Moon’s molten material.
The Largest Volcano in Solar System
When it comes to volcanoes, there’s none larger in the entire Solar System than Olympus Mons on the planet Mars. This volcano towers some 16 miles (25 kilometers) high, making it roughly three times the height of Mount Everest.
Olympus Mons is also a very wide volcano, covering an area similar to the size of the state of Arizona. Its large size is attributed to a lack of tectonic activity on Mars, allowing the volcano to grow over millions of years.
Io – the Volcanic Moon
Although the Moon has lost its volcanic activity, this isn’t the case for every moon in the Solar System. In fact, one of Jupiter’s four biggest moons, Io, is an absolute hotbed of eruptive energy.
Io is slightly larger than our Moon but sits quite a bit further from the Sun in its orbit around Jupiter. Even so, the moon has hundreds of active volcanoes on its surface.
What’s more, these volcanoes don’t behave in any way scientists would expect.
By constantly erupting, the moon’s surface is covered in molten sulfur that gives it a yellowish hue. These sulfur lava flows can reach temperatures of 3,000 degrees Fahrenheit (1650 degrees Celsius), even though the moon itself is on average -202 °F (-130 °C).
What makes Io such a mystery is that scientists can’t figure out why it’s erupting or when eruptions are going to happen. What’s more, volcanoes should exist mainly at the poles and at the equator but are found dotted all over one of its hemispheres.
While there’s some uncertainty surrounding its eruptive past, there are volcanoes all over the Moon’s surface. It’s possible even dinosaurs were able to bear witness to some of the Moon’s volcanic power. Although not currently active on the volcanic front, no one knows what the future holds for the molten activity simmering deep below the lunar surface.