Did you know that the Earth's crust is made up of different types of rocks? These rocks constantly change forms in what is known as the rock cycle. The three main types of rocks are igneous, sedimentary, and metamorphic. Igneous rocks are formed from the cooling of molten rock, either underground (intrusive) or on the surface (extrusive). Examples of igneous rocks are granite and basalt. Sedimentary rocks are formed by the deposition and cementation of particles like sand, silt, and fossils. Over time, these layers of sediment become compacted and hardened into rock. Examples of sedimentary rocks are sandstone and limestone. Metamorphic rocks are rocks that have undergone a change due to high heat and pressure. They are typically formed deep within the Earth's crust. Examples of metamorphic rocks are marble and slate. The rock cycle describes how these three types of rocks are constantly being transformed into one another. For example, igneous rocks can be weathered and eroded into sediment, which then gets compacted and cemented into sedimentary rock. This sedimentary rock can then undergo heat and pressure to become metamorphic rock. And finally, any type of rock can be melted back into magma to begin the cycle again. Understanding the rock cycle is essential in the field of geology as it helps scientists interpret the history and processes that have shaped the Earth's surface over millions of years.