🪨 The Rock Cycle

The Rock Cycle: Earth's Endless Recycling System

The rock cycle is Earth's recycling program — a continuous process that transforms rocks from one type to another over millions of years. Igneous, sedimentary, and metamorphic rocks are not permanent categories but stages in an ongoing cycle driven by heat, pressure, weathering, and erosion. This interactive explorer lets students trace the pathways between rock types and understand the geological forces that drive each transformation.

Understanding the rock cycle teaches students to think in terms of deep time — the vast geological timescales over which mountains rise, erode, and reform. A pebble on a beach may have once been part of a volcanic eruption, compressed into sedimentary layers, metamorphosed by heat, and weathered back into fragments. Every rock has a history stretching back billions of years.

Three Rock Types, Many Pathways

Igneous rocks form when magma or lava cools and solidifies (granite, obsidian, basalt). Sedimentary rocks form when weathered fragments are compressed and cemented together (sandstone, limestone, shale). Metamorphic rocks form when existing rocks are transformed by heat and pressure (marble from limestone, slate from shale). The cycle has no fixed starting point — any rock type can become any other through the right geological processes.

Connect the rock cycle to real life: concrete is artificial sedimentary rock, brick-making mimics metamorphism through heat, and volcanic glass (obsidian) is natural igneous rock used by ancient peoples for tools. These connections help students see geology not as an abstract science about distant rocks but as the story of the materials that build our world.

Last reviewed: May 2026 · Aligned with NGSS 4-ESS1-1, MS-ESS2-1