The faces of four U.S. presidents were sculpted from rock at Mount Rushmore.
The faces of four U.S. presidents were sculpted from rock at Mount Rushmore.
Photograph by Barnes Ian, Shutterstock

Geology 101

Dig into rocks!

You see Abe Lincoln's face. The Grand Canyon. An awesome ancient pyramid. A geologist sees granite, volcanic rock, limestone, and the Earth over millions of years. In other words, rocks.

You can't throw a rock without ... hitting another rock. They're everywhere. Rock creates and shapes the Earth's landscape. It forms our magnificent mountains, shapes the deepest oceans, and safely separates us from the boiling magma beneath our feet! (Okay, technically magma is uber-hot liquid rock. But you don't want to stand on it.)

Water, wind, earthquakes, cold, and heat scour, fracture, move, or melt rock. Rock is continuously being changed, rebuilt, or recycled by the forces of the Earth.

Granite, limestone, marble, and sandstone are examples of kinds of rock. Geologists divide rocks into three large groups: igneous, metamorphic, and sedimentary. Lava or magma form igneous rock. Changes in pressure or heat create metamorphic rock. Water and wind create sedimentary rock. (Each rock group includes hundreds of different kinds of rocks.)

Like the world's oldest blog, rock reveals millions of years of events and change. It shares how and when the earth's features, like mountains, oceans, or canyons were shaped. In a way, embedded fossils provide a selfie or picture of the environment at the time the rock was formed. Rock: rockin' the Earth for 4.55 billion years!