Rock

Rock is a naturally occurring solid made up of one or more minerals. Rocks make up the earth's crust and form mountains, valleys, and the ground beneath our feet. Some rocks are smooth and shiny, while others are rough, grainy, or layered. Rocks are found everywhere—on land, in oceans, and even on other planets and moons.

Geologists, who are scientists that study the Earth, group rocks into three main types: igneous, sedimentary, and metamorphic. These types are based on how the rocks form. Each kind of rock has its own story and shows how the Earth changes over time.

Igneous rocks are formed when hot, melted rock called magma cools and hardens. If the magma cools deep underground, it forms rocks like granite, which has large crystals. If it erupts from a volcano and cools quickly on the surface, it forms rocks like basalt or obsidian, which are often darker and smoother.

Sedimentary rocks form when small pieces of other rocks, minerals, and even plants or animal remains pile up in layers. Over time, pressure and minerals glue these layers together. Examples of sedimentary rocks include sandstone, shale, and limestone. Fossils are often found in these rocks, helping scientists learn about ancient plants and animals.

Metamorphic rocks are formed when existing rocks are changed by heat, pressure, or both, usually deep inside the Earth. For example, limestone can turn into marble, and shale can become slate. These rocks often have wavy or sparkly textures because their minerals have been rearranged.

Rocks are important for many reasons. They help build soil, store water, and provide materials for buildings, roads, and tools. Studying rocks helps scientists understand how the Earth was formed and how it keeps changing. Every rock you see—whether on a mountain, a beach, or in your backyard—has a long history that tells part of the story of our planet.