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The Cravat Compendium
The Rock Cycle
Igneous, Metamorphic, and Sedimentary Rocks!
Have you ever...
...felt the Earth move under your feet?
The ground beneath our feet is only a very thin crust on this Earth compared to the massive interior layers that make up the core. These layers are composed of heavy metals that sank to the center in the Earth's younger days; they are called the upper mantle, lower mantle, outer core, and inner core. The outer layers are not static, and are constantly moving against one another. To simplify a very complex process, its the movement and pressure of the molten iron and nickel outer core over the inner core that generates the magnetic field that protects our planet from solar radiation. The heat generated from this process is responsible for another important feature of our planet: plate tectonics.
As the core releases heat outward, molten rock is pushed towards the surface where it cools and solidifies into new layers of crust. Eventually, all crust will be recycled back into the mantle to generate new crust until the core cools and the planet ceases to be geologically active. This process of heating and cooling in a cycle is called "convection" and is present in many cycles on Earth. The freshly cooled magma that makes new crust is something geologists call "igneous rock." If this new crust is put under enough pressure and heat for long enough it can turn into "metamorphic rock," and if its exposed to weathering and pressue it can turn into what's called "sedimentary rock." At any point in the rock cycle any of the different kinds of rock can be recycled into any of the others or back into the mantle, given the right conditions.
Featured Facts
Mercury, Venus, and Mars are not as geologically active in the way Earth is, as they're all smaller planets so they've lost much of the heat that powers convection.
Convection is also used to descibe any cyclical heating process, like in a convection oven or the water cycle.
The oldest pages of Earth's history are mostly a mystery, as the rock formed in those days has long since been recycled.