Planet Earth

Crust

thin, rigid outer shell (5–70 km)

Mantle

thick, slowly flowing rock; convection drives plate tectonics

Outer core

liquid iron–nickel; motion generates Earth’s magnetic field

Inner core

solid iron–nickel under immense pressure

Lithosphere

crust + uppermost mantle; rigid; forms tectonic plates

Asthenosphere

warm, ductile mantle; plates float on it

Mantle Convection & Plate Movement

Heat rises, cool material sinks → convection cells. These cells drag plates apart, together, or past each other.

Divergent

Plates move apart → new crust forms (mid‑ocean ridges, rifts)

Convergent

Plates collide → subduction → volcanos, mountains

Transform

Plates slide past each other → earthquakes

Valence Electrons

Outer electrons determine bonding and mineral properties

Covalent

shared electrons; strongest

Ionic

electron transfer; oppositely charged ions attract

Metallic

electrons flow freely (“sea of electrons”)

Mineral Definition

Minerals are naturally occurring, solid, crystalline, with a specific chemical formula

Chemical Formulas

Formula = fixed ratios (e.g., NaCl)

Crystalline

ordered atomic structure; distinct faces

Amorphous (glass)

random atoms; no long‑range order

Halite’s Structure

Na+ and Cl– alternate in a cubic lattice.

Atomic Structure & Crystal Shape

Ion size + charge determine packing → crystal shape

Polymorphs

Same chemistry, different structure

Mineral Formation & Precipitation

• Cooling of melts

• Precipitation from water (e.g., halite)

• Metamorphism (heat + pressure rearrange atoms)

Color

unreliable; impurities vary

Streak

powder color; more reliable

Luster

the light-reflecting qualities of a mineral's surface;

metallic & non‑metallic

Mohs Hardness & Scratch Test

Diamond = 10, talc = 1. Glass = 5.5, fingernail = 2.5

Habit

shape crystals grow in

Cleavage

breaks along planes

Fracture

irregular, glass‑like breaks

Acid

calcite fizzes

Magnet

magnetite (a gray-black magnetic mineral which consists of an oxide of iron and is an important form of iron ore)

Taste

halite (salty)

Silicates (SiO₄)

Most abundant mineral group. O + Si = 74% of crust minerals

Silicate Tetrahedra

SiO₄ forms a tetrahedron; oxygen corners bond to other tetrahedra → chains, sheets, frameworks

Shield

wide, low‑angle; effusive; basaltic

Stratovolcano

steep, explosive; andesitic/rhyolitic

Cinder cone

small, loose fragments.

Pyroclastic Flows

Super‑heated ash + gas cloud; deadliest hazard. Up to 1800°F and 290 mph

Lahars

Mudflows of ash + water; persist long after eruptions

Intrusive

slow cooling → large crystals (phaneritic)

Extrusive

fast cooling → tiny crystals (aphanitic)

Porphyritic

slow then rapid cooling → large + small crystals

Glassy

extremely rapid cooling → no crystals

Felsic

high silica; light color; viscous

Mafic

low silica; dark; runny

Silica, Temperature & Viscosity

More silica → thicker lava. Higher temperature → thinner lava

Magma Density & Buoyancy

Magma rises because it is less dense than surrounding rock

Lithification

Sediment → rock by compaction + cementation

Physical Weathering

frost wedging, root wedging; no chemical change.

Chemical Weathering

dissolution, alteration of minerals

More transport

smaller, rounder grains

Less transport

coarse, angular grains

Clastic

fragments cemented (breccia, conglomerate, sandstone)

Non‑clastic

chemical precipitates (rock salt, chert)

Biogenic

organic remains (coal, coquina)

Breccia

angular clasts → short transport.

Conglomerate

rounded clasts → long transport

Rock salt

halite precipitated

Coal

compacted plant matter.

Metamorphism

new minerals + textures without melting

Foliated

minerals aligned (slate → phyllite → schist → gneiss)

Non‑foliated

no alignment (marble, quartzite)

Protoliths

Original rock before metamorphism.

Examples:

• Sandstone → quartzite

• Limestone → marble

• Shale → slate → phyllite → schist → gneiss

Recrystallization

same mineral, new texture (sandstone → quartzite)

Phase change

same chemistry, new crystal structure (calcite → aragonite)

Metamorphic Grades

Barrovian ladder: Slate → Phyllite → Schist → Gneiss → Migmatite

Prograde

increasing heat/pressure

Retrograde

decreasing heat/pressure (cooling)

Index Minerals

Minerals that only appear at certain metamorphic grades

Example: Garnet → indicates schist‑grade metamorphism.

Regional

large‑scale; high pressure + temperature; mountain building; foliated rocks

Contact

high temperature, low pressure; magma baking rocks; non‑foliated

Shock

extreme pressure from impacts