Geology: Rock Classification Flashcards

Rock Classification Overview

• Rocks are natural, solid aggregates consisting of one or more minerals.
• Classification is primarily based on the formation process of the rocks.

Igneous Rocks

• Form when magma or lava cools and hardens.
• Can develop deep within Earth or on its surface.
• Large mineral crystals occur when magma cools slowly underground (examples: gabbro, granite).
• Small crystals form when lava cools rapidly at the Earth’s surface (examples: rhyolite, basalt).

Sedimentary Rocks

• Result from the cementation of sediments under pressure.
• Sediments are formed from weathered rocks that collect in loose layers.
• Over time, more layers stack and compress those below them.
• Bottom sediments eventually become cemented together, forming rock.
• Common types include sandstone, conglomerate, and shale.
• Fossils are commonly found within sedimentary rocks.

Metamorphic Rocks

• Created through changes in texture and mineral content due to Earth processes.
• Form under conditions of high pressure, high temperature, or through hot fluid interactions.

Rock Cycle

• Describes the continuous transformation of rocks from one type to another through various geological processes.
• Melting and cooling processes lead to igneous rocks.
• Weathering, erosion, and cementation are responsible for the formation of sedimentary rocks.
• Heat and pressure contribute to the creation of metamorphic rocks.