Layers of igneous rocks. Photo courtesy of National Park Services.
Another type of rock we often see are igneous rocks. Igneous rocks are made when hot, molten rock solidifies after it has crystalized. Igneous means fire in Greek, and has two types of formations. Intrusive is when magma is trapped inside the Earth, and extrusive is magma cooling around the surface of the earth. Extrusive rocks are formed from volcano eruptions. For those lava rocks, hitting the surface air will cool them almost instantly, because of the large difference in temperatures. Many air pockets do get stuck inside the rocks, which does give the bubble-like texture in many of these rocks. For more information, you can visit: https://www.nationalgeographic.org/encyclopedia/igneous-rocks/