UPCAT SCI ROCKS AND MINERALS

Igneous Rocks formation & types

Formed when magma or lava solidifies. Intrusive = cools slowly below surface (large crystals). Extrusive = cools quickly on surface (amorphous glass).

Sedimentary Rocks key feature

From rock residues accumulating and hardening over time. This is where FOSSILS are found.

Metamorphic Rocks cause

Formed when rocks undergo physical and chemical changes due to intense pressure and temperature.

Relative Dating definition

Arranges geological events and rock layers in a sequence. Does NOT provide actual numerical dates.

Stratigraphy

The method of reading the order or sequence of rock layers (strata).

Law of Superposition

In an undisturbed sequence, a sedimentary rock layer is younger than the one beneath it and older than the one above it.

Original Horizontality

Sediments are initially deposited as flat, horizontal beds. Tilted layers mean tectonic movement happened later.

Lateral Continuity

Layers of sediment initially extend laterally in all directions as continuous sheets until they hit a barrier.

Cross-cutting Relationships

Faults, cracks, or fractures are strictly younger than the rock layers they cut through.

Intrusive Relationships

An igneous magma intrusion that cuts across a rock formation is younger than the rock it cuts.

Inclusions and Components

Trapped rock fragments (clasts) inside a formation must be strictly older than the rock layer containing them.

Minerals definition

Naturally occurring inorganic solids defined by a specific chemical composition and physical properties.

Mineral Hardness

The physical ability of a mineral to resist being scratched.

Mineral Color

The most obvious property of a mineral, but the least diagnostic (least reliable) due to impurities.

Mineral Streak

The color of a mineral in its powdered form; shows the true, unaltered color of the mineral.

Mineral Density

A property that relates directly to the mineral's chemical composition and the pattern of its atom arrangement.

Crystalline Structure

The geometric shape a mineral takes, determined by the regular arrangement of its atoms, molecules, or ions.

Mineral Cleavage

The natural tendency of a mineral to break cleanly along a flat plane.

Mineral Luster

The specific way a mineral's surface reflects light.

Angle of Repose definition

The steepest slope angle where unconfined loose material can stay piled up without collapsing.

Slope Stability Rule

Slope angle less than angle of repose = stable. Slope angle greater than angle of repose = mass wasting (landslide) occurs.

Grain Texture vs Angle of Repose

Smooth and rounded grains = low angle of repose (flatter pile). Fine and sticky materials = high angle of repose (steeper pile).