Basalt

volcanoes · igneous rock · planetary geology · lava

Most volcanic rock. More than 90% of all volcanic rock on Earth is basalt. That means whenever a volcano erupts, it's probably making basalt.

Cools really fast. Basalt forms when lava cools quickly at the surface. Because it cools so fast, the crystals inside stay tiny, which is why basalt looks smooth and fine-grained.

Dark and heavy. Basalt is rich in magnesium and iron, which makes it dark colored (usually black or dark gray) and quite dense and heavy compared to other rocks.

Everywhere in space. Basalt isn't just on Earth. The Moon, Mars, and Venus are all covered in basalt, making it one of the most common rocks in our whole solar system.

Watched by scientists. Geologists observe basalt eruptions at about 20 volcanoes around Earth every year, giving them chances to study how this rock forms.