Minerals, rocks, weathering,

sequencing & energy

Std. 3

Minerals• Must have the following 5

characteristics: – Naturally occurring– Inorganic – Solid– Crystal structure– Definite chemical composition

Identifying Minerals (physical properties)

• Color• Streak• Luster• Density• Hardness• Special Properties

Rock Cycle• Draw

igneous• Extrusive:– Surface– Cooled rapidly– Small crystals– Glassy

• Intrusive– Inside earth– Cooled slowly– Larger crystal

sedimentary• Clastic– Rock fragments– Conglomerate &

sandstone• Organic– Remains of plants &

animals– Coal & limestone

• Chemical– Minerals dissolved in

solution crystalize– Limestone, halite (rock

salt

metamorphic• Foliated– Grains in parallel

bands– Gneiss, slate

• Nonfoliated– No bands– Grains random

Weathering, erosion, deposition• Weathering– break rock down

• Erosion–move it

• Deposition– lay down sediment

EROSION• Water• Moves the most sediment

• Glaciers• U-shaped valley, till, moraines, kettle

lakes• Wind• Sand dunes

• Gravity• Move sediment downhill

• How fossils form– Death, soft parts decay, hard parts left

(teeth, bones)– Sediment covers organism– Sediment becomes rock, preserving parts of

organism

Types of fossils• Mold• Cast• Petrified– Cells replaced by minerals or sediment– Bones, petrified wood

• Carbon films• Trace fossil• Original/preserved remains– Ice, tar, amber

Fossils & the past• Where do fossils form?–Most: Organisms that once lived in or near

shallow water – Sedimentary rock

• Tell us about past environments– Shallow bay, ocean bottom, freshwater

swamp

Relative Age• Age comparison (older vs. younger)• Law of Superposition– Oldest layers at the bottom, youngest at

the top

Determining Relative Age• Extrusion, Intrusion, Fault,

Unconformity, Index fossil

- The Relative Age of Rocks

Energy transfer• Volcanoes– Heat and mechanical energy as magma

flows• Earthquakes– Energy transferred in seismic waves–Mechanical slipping of fault