7/27/2023 0 Comments Key words rock cycles uc approvalFigure 3.3 Magma forming pahoehoe basalt at Kilauea Volcano, Hawaii This happens at between about 800° and 1300☌, depending on the composition and the pressure, onto the surface and cool quickly (within seconds to years) - forming extrusive igneous rock (Figure 3.3). As we’ll see in more detail below, magma is rock that is hot to the point of being entirely molten. In describing the rock cycle, we can start anywhere we like, although it’s convenient to start with magma. Figure 3.2 A schematic view of the rock cycle. On some other planets or their satellites, such as the Moon, the rock cycle is virtually dead because the core is no longer hot enough to drive mantle convection and there is no atmosphere or liquid water. The rock cycle is still active on Earth because our core is hot enough to keep the mantle moving, our atmosphere is relatively thick, and we have liquid water. The rock cycle is driven by two forces: (1) Earth’s internal heat engine, which moves material around in the core and the mantle and leads to slow but significant changes within the crust, and (2) the hydrological cycle, which is the movement of water, ice, and air at the surface, and is powered by the sun. Take a ten question quiz about this page.The rock components of the crust are slowly but constantly being changed from one form to another and the processes involved are summarized in the rock cycle (Figure 3.2).
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