Geology of solar terrestrial planets is basalt, a denser volcanic rock that is the primary constituent of the ocean floors. Sedimentary rock is formed from the accumulation of sediment that becomes compacted together. Nearly 75% of the continental surfaces are covered by sedimentary rocks, although they form only about 5% of the crust. The third form of rock material found on Earth is metamorphic rock, which is created from the transformation of pre-existing rock types through high pressures, high temperatures, or both. The most abundant silicate minerals on the Earth's surface include quartz, the feldspars, amphibole, mica, pyroxene, and olivine. Common carbonate minerals include calcite
Tales from the Flat Earth of agate, the second is made of blue steel, and the third gate is made of black fire. There is only one city in the Underearth – Druhim Vanashta, the city of demons. It is made of precious minerals, gems, and metals and is beautiful, though its inhabitants are cruel and wicked. The Flat Earth appears to include temperate, sub-tropical, and tropical zones, including many deserts. Since "polar" regions would be impossible on a flat world, they are not mentioned in the series. There are many seas, but bodies of water large enough to be called "oceans" do not appear