Lesson 2: Formation Environments

Key Idea

Sedimentary rocks form in specific environments found on Earth's surface. Places like lakes, ocean floors, and river deltas allow loose sediment to accumulate in thick layers over millions of years.

The presence of sedimentary rock in a landscape serves as evidence of these past watery environments. It indicates that the area was once a basin where gravity allowed materials to settle and harden.

Key Idea

Igneous rocks form in high-energy environments where temperatures are hot enough to melt rock. These conditions typically exist deep underground or inside active volcanoes.

Unlike surface environments driven by weather, these magmatic environments are powered by the intense thermal energy radiating from Earth's interior. Finding igneous rock serves as evidence of past volcanic activity or deep underground cooling.