The moon's far side is too thick for volcanoes
While the side of the moon facing Earth is covered in dark volcanic plains, the hidden half is a rugged fortress of rock too thick for lava to penetrate.
The moon we see at night is defined by its dark, smooth patches known as maria, which early astronomers mistook for lunar seas. These are actually vast plains of solidified basalt from ancient volcanic eruptions that occurred when the moon's interior was still molten. However, on the far side of the moon, these dark markings are almost entirely absent. Data from lunar orbiters reveals that the crust on the hidden side is up to 20 kilometers thicker than the side facing Earth, creating a massive stone lid that prevented magma from ever reaching the surface.
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