Chapter 19

Section 3

Identify the three types of rocksExplain the properties of each type of rock

based on physical and chemical conditions under which the rocks were formed

Describe the rock cycle and how rocks change form

Explain how the relative and absolute ages of rocks are determined

MineralIgneous rockWeatheringSedimentary rockFossilsMetamorphic rock

Rocks are composed of mineralsThey are naturally occurring, non-living

substances that have a chemical formulaThere are about 3500 minerals in the Earth’s

crustOnly about 20 are easily found in a pure stateSome rocks are composed of more than 1 mineral

Minerals form crystalsThe top nine are found quite easily

Feldspar, pyroxene, mica, dolomite, quartz, amphibole, clay, and calcite

CharacteristicsRocks may be porous, granular, or smoothThey may be soft or hardThey may have different densities or colors

There are three major types of rockIgneous, formed from molten or melted rockSedimentary, formed from the remains of other

rocks or organismsMetamorphic, formed from pressure and

heating

Obsidian Igneous Rock Black, extrusive

igneous rock Obsidian is often

called volcanic glass due to its absent crystals and glassy appearance

Major minerals include feldspar, quartz and mica

Sandstone Sedimentary Rock

Red, banded sample is due to iron oxidation

Sandstone is formed from beach sand-sized quartz grains that are glued together with quartz or calcite

Sandstone is medium-grained and is often associated with water and oil storage

Slate Metamorphic Rock

Gray rock which was originally shale

Slate has a fine-grained texture and is often used as a building material

Slate can be broken into sheets

The deeper the rock, the older the rockNicolas Steno:Steno proposed several laws that are

still important today: the principle of original horizontality the principle of lateral continuity and the law of superposition:

Assuming no change in the position of the rock layers,

The oldest rocks will be on the bottom,And the youngest rocks will be on top

He became a priest

Igneous rocks are the best for radioactive datingMany elements found

in rock may be “dated”K, Ar, Rb, Sr, U, Pb, C

In Metamorphic and Sedimentary rocks the dating only tells you when the rock was changed, not formed

There are a variety of absolute dating methods in use, most of the commonly used ones are based on natural radioactivity.

In radioactive decay an atom changes to another atom as its nucleus gives off a subatomic particle.

The starting atom is called a PARENT and the new one formed is the DAUGHTER, as P changes to D

The rate of daughter production is constant and unique for each element.

When studying a large number of parent atoms, as is usual in nature, the rate is constant.

Igneous rocks are formed from cooling molten rock

Sedimentary rocks are formed by the deposition of pieces of other rocks and the remains of living organisms

Metamorphic rocks form after exposure to heat and/or pressure for an extended time

Rock can be recycled, (the Rock Cycle)

The relative age of rock can be determined using the Principle of SuperpositionUnless the rock layers are disturbed,The layers on the bottom are oldest

Radioactive dating is used todetermine the absolute age of rocks

10. Volcanic fumes are great for your skin9. Crystal, Ruby, Opal…a bunch of names for

your daughter8. If you choose your field of research well,

you could get paid to be at the beach7. Diamonds are a girl's best friend6. Rocks rock

5. Minerals generally are very accepting and non-judgmental

4. Laugh at the people who said you'd never be a rock star

3. You can get paid to date2. "Magma" is a neat word to say. Say it with

me: "magma." See?And the number 1 reason:

1. Papa was a rollin' stone