Sedimentary
Definition
Rocks formed from the accumulation and cementation of mineral and organic particles, often in water environments.
Example
Halite (rock salt) forms when seawater evaporates, leaving behind sedimentary deposits.
Layer by Layer
Sedimentary rocks are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. They tell the story of the Earth's past environments. Unlike igneous and metamorphic rocks which form at high heat and pressure, sedimentary rocks form at low temperatures and pressures.
The Process: Lithification
- Weathering: Wind and rain break down existing rocks into sand and mud.
- Transport: Rivers and wind carry the sediment to lakes or oceans.
- Deposition: Layers of sediment pile up over millions of years.
- Lithification: The weight of the layers squeezes out water (compaction) and minerals dissolved in groundwater glue the grains together (cementation) to create solid rock like Sandstone, Limestone, and Shale.
This is the only rock type that contains fossils!