Introduction and Classification of Rocks

Rocks

Naturally occurring solid materials made up of one or more minerals.

Mineral Composition

Refers to what specific minerals are present in a rock.

Rock Texture

Refers to the size, shape, and arrangement of mineral grains.

Hand Sample

A small piece of rock removed from its original location and examined closely.

Outcrop

An exposed rock formation that remains attached to its original location.

Three Major Rock Types

Igneous, sedimentary, and metamorphic rocks.

Igneous Rock Formation

Formed from cooled and solidified magma or lava.

Magma

A molten mixture of rock-forming minerals and gases.

Volatiles

Gases present in magma, such as water vapor and carbon dioxide.

Plutonic / Intrusive Rocks

Igneous rocks formed when magma cools slowly beneath Earth's surface.

Granite

An example of an intrusive or plutonic igneous rock.

Volcanic / Extrusive Rocks

Igneous rocks formed when magma reaches the surface and cools quickly.

Basalt and Pumice

Examples of extrusive or volcanic igneous rocks.

Sedimentary Rock Formation

Formed through the compaction and cementation of sediments.

Sedimentation Order

Deposition, layering, compaction, and cementation.

Strata

Layers of accumulated sediments.

Compaction

Sediments are squeezed together by the weight of overlying layers.

Cementation

Dissolved minerals like calcite or silica binding compacted sediments together.

Sedimentary Rock Examples

Sandstone, limestone, shale, and conglomerate.

Metamorphic Rock Formation

Formed when existing rocks transform under heat, pressure, and fluids without melting.

Metamorphic Conditions

High temperature, high pressure, and chemically active fluids.

Metamorphic Rock Examples

Marble, slate, and quartzite.

Weathering and Erosion

Processes that break down pre-existing rocks into sediments.

Melting

The rock cycle process that turns metamorphic rock into magma.

Igneous Formula

Magma or lava plus cooling and crystallization equals an igneous rock.

Sedimentary Formula and Mnemonic

Sediments plus compaction and cementation. Mnemonic D-L-C-C: Deposit, Layer, Compact, Cement.

Metamorphic Formula

Existing rock plus heat, pressure, and fluids equals a metamorphic rock without melting.

Master Rock Cycle Chain

Magma -> Igneous -> Sediments -> Sedimentary -> Metamorphic -> Magma.

Igneous Rock Transformations

Igneous rocks can become sedimentary through weathering and erosion, or metamorphic through heat and pressure.