1. Rocks Are made up of minerals
Ex: Granite > 4 minerals
Essential Minerals: always occur in the rock
Accessory minerals: sometimes occur

2. Classify Rocks By How they Form!
Igneous- Molten Rock cools and hardens
Sedimentary – Made from sediments
Metamorphic – Rocks Changed by heat and pressure

3. High Silica content forms light-colored rocks (FELSIC).

4. While lower (but only by about 25%) Silica content forms darker-colored rocks (MAFIC).

5. THE ROCK CYCLE
Rocks are naturally occurring combinations or coherent aggregates of minerals, fossils or other hard materials. They are classified by the way in which they form. The three rock types are: igneous, sedimentary and metamorphic.
All rocks on Earth are locked into a system of cycling and re-cycling known as the ROCK CYCLE. (*)

6. IGNEOUS ROCKS
IGNEOUS ROCKS are “born of fire”. In other words, they were once molten and upon cooling, the magma (molten rock) crystallized into solid rock. Igneous rocks may form deep inside the Earth or at the Earth’s surface when a volcano erupts. (*)

7. IGNEOUS ROCKS : intrusive
Slow cooling deep beneath the Earth’s surface allows crystals to grow to large size. These crystals are easily visible and distinguish this group of igneous rocks as INTRUSIVE.
Large Crystals
Both large and small crystals = porphyry (some grow before others begin
Texture size or arrangement of crystals
To get Large: Cools below Earth’s surface

8. Igneous - Intrusive
GRANITE is a coarse to medium-grained rock that forms from the cooling of magma deep within the Earth light color - felsic
DIORITE is very similar to granite, but is distinguished in the hand specimen by the absence of visible quartz.
Generally it has a salt and pepper appearance (about ½ black and ½ white).

9. Igneous Rocks
Rapid cooling near or at the Earth’s surface, produces many small crystals. This group of igneous rocks is called EXTRUSIVE
Eruption at surface
Numerous holes at the surface
Small mineral crystals ex: basalt
No mineral crystals ex: obsidian
Top Part of Lava- gases trapped inside of hardened lava = scoria
From lava thrown out
ex: pumice

10. Igneous - Extrusive
Rhyolite is a fine grained, felsic rock that forms from the cooling of lava above Earth’s surface
Basalt a dark fine grained rock formed from thin to massive lava flows (mafic)
Pahoehoe is a type of basalt that forms on the surface of very fluid lava flows

11. Igneous Review Lava  Extrusive Through Volcanoes
Through hydrothermal vents
Magma  Intrusive/Plutonic
- Cools and Crystalizes in Magma Chamber

12. Note: the minerals of igneous rocks are arranged randomly throughout the rock. There are no parallel alignments or fundamental segregations.
(*)

13. SEDIMENTARY ROCKS
SEDIMENTARY ROCKS are composed of particles derived from pre-existing rocks or by the crystallization of minerals that were held in solutions
Weathering : Rocks are broken into pieces by water, wind or ice
Water – enter cracks, expands and breaks rocks down
Rain – acid rain dissolves minerals
Movement in Rivers – Collect on the bottom

14. Formation – Build very slowly
Formation – Build very slowly layers will grow until environment changes
Cementation – minerals acting as cement holding sediments together
Compaction – pieces compact due to weight squeezing them together
Precipitation – water evaporates and minerals are left behind

15. Unusual Formation
Chemical Rocks – made up of chemical sediments or once living things
Organic Rocks – made up of remains of living things

16. Sedimentary Features Layers Only type of rock that contains Fossils!
Ripple Marks – Air or water sand, silt, and clay
Concretion – water comes into contact with fossils and mineral deposits
Geode – hollow rocks with mineral crystals inside

17. Classifying Clastic Rocks (pieces of other rocks):
Conglomerate & Breccias: Large sediments
Sandstones: Small grains
Siltstone : Very Small grains
Shale : Very Small grains Clay pressed together

18. Classifying Non-Clastic Rocks (minerals in water or past life):
- Look at composition: calcite, halite, gypsum or quartz
Limestone - Calcite and seashells
Rocks Salt - Halite
Rock Gypsum - Gypsum
Chert (flint) - Quartz
Coal – Past life

19. METAMORPHIC ROCKS
METAMORPHIC ROCKS have changed (meta) their form (morphic). Under the influence of heat, pressure and fluids, pre-existing rocks are modified in form
Original rock is called the parent rock
This is done within the solid state, i.e. without melting.
3 Types of Changes that occur include:
- Change in Chemistry of Rock
- Englargement of crystals
- Rearrangement of mineral grains

20. Classify
Burial Metamorphism – weight of overlying rock, causes a reorientation of mineral grains
Regional Metamorphism – As mountains rise, large amount of magma is forced toward the surface , it hardens into the mountain core
Contact Metamorphism – Small amount of magma intrudes overlying rock
The nearby Rock is altered by heat, solutions, and gases from the magma
*Metamorphism is the MOST intense near the core where heat and pressure cause the formation of new minerals of existing mineral grains

21. Features
Metamorphic rocks composed of minerals that are not elongated or flat, do not exhibit parallel alignments and are called NON-FOLIATED.
Metamorphic rocks that exhibit parallel alignments of minerals are called FOLIATED. In these rocks, the minerals all line up perpendicular to the exerted pressure.

22. Thinking about relationships among the major rock groups
The Rock Cycle
Thinking about relationships among the major rock groups

23. Major Rock Groups Igneous Sedimentary Metamorphic
Formed from a melt (molten rock)
Plutonic (intrusive):slow cooling and crystallization
Volcanic (extrusion): quick cooling at the surface
Sedimentary
Formed at the Earth’s surface
Clastic (Mineral Fragments or grains, clays)
Chemical (crystalline chemical/biochemical precipitates)
Metamorphic
Changed by pressure, temperature and fluids.

24. Fig. 2.9
MAGMA

25. IGNEOUS
Crystallization
MAGMA

26. IGNEOUS
Plutonic
Crystallization
MAGMA

27. Volcanic
IGNEOUS
Plutonic
Crystallization
MAGMA

28. Weathering
Volcanic
IGNEOUS
Plutonic
Crystallization
Uplift
MAGMA

29. SEDIMENT SEDIMENT Volcanic IGNEOUS Plutonic Uplift MAGMA Weathering
Crystallization
Uplift
MAGMA

30. SEDIMENT Volcanic IGNEOUS Plutonic SEDIMENTARY Uplift MAGMA Compaction
Weathering
Cementation
Evaporation
Volcanic
IGNEOUS
Plutonic
SEDIMENTARY
Crystallization
Uplift
MAGMA

31. SEDIMENT Volcanic IGNEOUS Plutonic SEDIMENTARY Uplift MAGMA Compaction
Weathering
Cementation
Evaporation
Volcanic
IGNEOUS
Plutonic
SEDIMENTARY
Crystallization
Uplift
MAGMA

32. SEDIMENT Volcanic IGNEOUS Plutonic SEDIMENTARY METAMORPHIC Burial
Compaction
SEDIMENT
Weathering
Cementation
Evaporation
Volcanic
IGNEOUS
Plutonic
SEDIMENTARY
Increased P&T
METAMORPHIC
Crystallization
Burial
Uplift
MAGMA

33. Can you see any shortcuts?
Compaction
SEDIMENT
Weathering
Cementation
Evaporation
Volcanic
IGNEOUS
Plutonic
Can you see
any shortcuts?
SEDIMENTARY
Increased P&T
METAMORPHIC
Crystallization
Melting
Burial
Uplift
MAGMA

34. SEDIMENT Volcanic IGNEOUS Plutonic SEDIMENTARY METAMORPHIC Burial
Compaction
SEDIMENT
Weathering
Cementation
Evaporation
Volcanic
IGNEOUS
Plutonic
SEDIMENTARY
Increased P&T
METAMORPHIC
Crystallization
Melting
Burial
Uplift
MAGMA

35. In Conclusion…
The rock cycle demonstrates the relationships among the three major rock groups
It is powered by the interior heat of the Earth
As well as earth’s momentum and…
The energy from the sun
It involves processes on the Earth’s surface as well as the Earth’s interior
It connects the “hydrologic cycle” with the “tectonic cycle”.

37. SEDIMENT Volcanic IGNEOUS Plutonic SEDIMENTARY METAMORPHIC Burial
Erosion
SEDIMENT
Weathering
Transport
Deposition
Volcanic
IGNEOUS
Plutonic
SEDIMENTARY
Increased P&T
METAMORPHIC
Crystallization
Melting
Burial
Uplift
MAGMA